CA2199628A1 - Light weight genset - Google Patents

Abstract

A machine comprising a stator and a rotor, where the stator includes at least one winding and the rotor comprises a body of soft magnetic material with a plurality of permanent magnets in a surface disposed proximate to the stator, with intervening consequence poles, where the surface area of the permanent magnets proximate to the stator is greater than the surface area of the consequence poles proximate to the stator. Also disclosed is a stator comprising a soft magnetic core with respective three-phase star windings corresponding to different predetermined voltage outputs with the corresponding phases of the respective three-phase windings grouped together as a unit and wound about the core such that the corresponding phases of the respective three-phase windings are in continuous thermal contact with each other. Also disclosed is the use of a variable frequency invertor responsive to a DC signal generated in the stator winding, and a control signal indicative of current drawn by a load on the device for generating an AC
signal, where the frequency of the AC signal is selectively varied in accordance with current drawn by the load. In another embodiment, the rotor comprises a hollow cylinder with magnets mounted on the internal surface of the cylinder with the stator concentrically disposed within the cylinder. Also disclosed is a governor for selectively controlling the engine throttle in accordance with the generator output signal.

Description

~ WO 96/09679 2 1 9 q 6 2 8 PCT/US95/11361 10 TITLE: LIGHT WEIGHT GENSET

BACKGROUND OF INVENTION

The present invention relates to lightweight portable electrical gen~ ol~.

In general, portable DC g~ ol~ are known. Portable g~ latOl~ collllllonly col"l"ise a co"~/~;"lional diesel or gasoline pow~ d engine having a crankshaft coupled to a generator. The generator includes a stationary stator, and a rotor disposed for rotation with the engine shaft. The rotor ge"t;,~Les a magnPtir field. As the mqgnrtir field h,l~,c~l~ wh,dil,g~ on the stator, electrical current is intluced The induced current is typically applied to a bridge rectifier, solllrlilllPs regulqtP~, and provided as an output. Examples of such prior art g~ tol~ include the Generac G1000 (950 watts and 49 pounds), the Honda EX1000 (1000 watts and 57 pounds) and the Yamaha EF1000 (1000 watts and 55 pounds). While typically not found inportable units, an AC output can be provided by applying the DC signal to an inverter.

While referred to as portable, the prior art generator units tend to be heavy and unwieldy, or are incapable of providing s~ qi.-rd power suffiriPnt for typical uses. Further, the prior art units typically provide either a relatively low ~ll~lagc, high voltage (e.g., 115 volts) output, or a relatively low voltage, high a~ lage output (e.g., 12 or 24 volts, at from 25 to 200 amperes) and weigh from appro~imqtPly 40 to 65 pounds, dry weight. In many i..~ res, however, it is desirable to have both high voltage low current outputs, e.g., to run lights or power tools, and a low voltage high amperage output for, e.g., charging batteries or jump starting a car from a unit that is easily carried by one person using a shoulder strap.
SUMMARY OF THE INVENTION.

The present invention provides a truly lightweight generator capable of providing su~tqinPd power sllfftri~nt for typical uses. In accoldà.lc~ with one aspect of the present invention, a light 40 weight generator is implemrnt~od employing a rotor utilizing high energy product permanent mqgn-otc.

Wo 96/09679 2 1 9 9 6 2 8 PcrluS9S/11361 In accolda-lce with another aspect of the present invention, the rotor is mount~d directly on the engine shaft. The rotor is suffiriently close coupled to the engine that an air gap between the stator and rotor is ...A;.,lAi..~d without bearings other than those normally employed in the engine.

In accold~1ce with another aspect of the present invention, the rotor is of multiple pole design with half of the poles col.~;cli.-g of high density magnets and the other half of the poles co~ lg .... .. . .. . . .... .
of con~equ~nre poles, Ih~.efole obLaillillg ...~ .. use of the high density m~gnPt~.

In accordallce with another aspect of the present invention, a multi-winding stator is employed 10 to provide both low voltage high amperage output, e.g., for battery cl1drgillg, and a high voltage low amperage output, e.g., for ope~alil1g lights and power tools.

In accordance with another aspect of the present invention, two alternative low voltage high amperage outputs may be provided, e.g., 12 volts and 24 volts.
In accordance with another aspect of the present invention, the ratio of the generator power output to rotor weight is in excess of 150 or 200, preferably in excess of 500, more l,ler~lably in excess of 700, and most preferably in excess of 800 watts per pound.

20 BRIEF DESCRIPTION OF THE DRAWING.

The present invention will hele;l.an~l be described in conjun.;lion with the figures of the appended drawing wherein like design~tions denote like elements and:

FIGURE 1 is a pictorial illustration of the light weight portable genset in acco~dance with aspect of the present invention;

FIGURE 2 is a partial sectional side view of the genset of FIGURE 1;

FIGURE 3 is an exploded pictorial view of the engine, frame and mounting plate of the genset of FIGURE 1;

FIGURE 4 is an exploded view of the generator unit of the genset of FIGURE 1;

21 9962~
--WO 96/09679 PCr/US95/11361 FIGURE 5 is a partially cut-away pictorial view of the gene-~lor unit housing and control ~ circuitry board;

FIGURE SA is an inside view of an ~lt~n~tive version of the generator unit housing;

FIGURE 6 is a srh~ ic diagram of the stator wh.dings;

FIGURE 7A is a block sc~ lir of the stator windings and control ch~;uilly;

FIGURE 7B is a block srhr.. -~ir. of the control ci-.;~ of the genset of FIGURE 1;

FIGURE 7C is a srh~m~tic diagram of the control circuitry;

FIGURES 8A, 8B, 8C and 8D are front, side sectional, and exploded front views of a 15 rotor in accord~ce with one aspect of the present invention;

FIGURE 9 is a block srhrm~tic of a control circuit inr.hlrlin~ an inverter;

FIGURE 9A discloses suitable regulators for the current of FIGURE 9.
FIGURE 10 is a s( hr~ ic of the pre-phase regulator, single phase bridge at signal supply of the circuit FIGURE 9.

FIGURE 11 is a srh~ iC of a suitable inverter control section.
FIGURES llA - llF are a srhPm~tic memory map and flow chart of the inverter operation.

FIGURE 12 is a sch~ lir, diagram of a basic power converter.

Paragraph FIGURE 13 is a diagram of the output wave form of the inverter of FIGURE
9 employing the basic power converter FIGURE 12.

FIGURE 14 is an output wave form closely 5im~ ting a sign wave.

FIGURES 15 and 15A are s~ irs of alternative auxiliary coil circuits utilized ingcl~.alhlg a wave form of FIGURE 14.

FIGURE 16 is a 5~ diagram of a power collvcl~ion circuit suitable for gell~,là~illg S the wave form of FIGURE 14.

FIGURE 17 is a srh~mqtic of an alternative power conversion circuit for gcll~.athlg the wave form of FIGURE 14.

FIGURES 18A and 18B are sCI~r~ ir illustrations of a throttle control in lc~ecli~/e states .

FIGURES l9A and l91B are an exploded side sectional view of an alternative generator assembly using an external rotor, and a top view of the external rotor, respectively.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT.

Referring to FIGURES 1 and 2, a lightweight portable generator in accG~ ce with the present invention comprises an engine 12, a high output mini~hlre generator unit 14, and a mounting frame 16.
As best seen in FIGURES 2 and 3, engine 12 suitably includes a shaft 200 ç~tt-nr~ing outwardly from a shoulder 42. Engine 12 may be any small high RPM engine with a high hG~ wc;l to weight ratio capable of turning a shaft. In the plcl~l.ed embodiment, engine 12 is a 2.0 hol~o~,.cr, two-cycle internal c~)lll~u~lion engine, having a displ ~r~m~nt of 3 cubic inches and weighing 7 1/2 pounds, such as a Tecum~çll TC300.

Referring now to FIGURES 1, 2 and 3, frame 16 provides a lightweight common mount for engine 12 and generator unit 14. Frame 16 is suitably formed of a lightweight rigid, electrically and thermally con~ ctive material such as, for example, alu,.~ u In the preferred embodiment, an ~IIl,,,i,,,l,,, sheet is bent to provide foot 162, upright 164 and handle 166 portions of frame 16.
The alulllhlulll sheet is bent at a predçtçrminPd distance from one end to form foot 162, and pel~en.lir~ r upright section 164. Handle 166 suitably comprises a first portion 167 bent from upright 164 to overlay foot 162; an upright section 168; and a forwardly facing lip 169 preferably angled, which cooperate to form a channel 170 into which an operator's finger may fit, to facilitate carrying the unit.

If desired, nandle 166 may be adapted to ~fco.. ~ r a strap or a light. For example, rc~.~ec~i~/e ~,lulcs 172 are formed through the lip of handle 166 at either side through which suitable clips of a strap 18 are received. Respective ~cllules 172A are formed through the lip of ~ handle 166 for the llluullling of a flood light.

As will hclcinarlcl be des-lil,~, engine 12 and gcn~,-a~or unit 14 are llloulll~ on opposing sides of frame upright 164. As best seen in FIGURES 2 and 3, engine 12 is mnunt~d to upright 164, overlying foot 162.

10A llwullling plate 204 is hl~ ,osed between engine 12 and frame upright 164 to provide structural strength to upright 164, and provide a medium for llluullling engine 12 and the stator 210 to frame 16. To f~ ilitqts ...~u..l;..g of engine 12 and stator 210, plate 204 suitably includes first and second sets of ~.~,luies 309 and 310. Apertures 309 are suitably disposed in registry with corresponding a~ lUlCs 311 (suitably coulll~,~.ul,k) in frame upright 164, and threaded bores 313 15in motor flange 202. Engine 12 is suitably fixed to upright 164 by a pl'f,d~ t~ . .,.i.,-d number (e.g.
4) of screws 308 (FIGURE 3) which are journaled through ~,lules 311 in upright 164, and a~,~,Lu~es 309 in llwullling plate 204, and are threaded into bores 313 motor flange 202. As shown in FIGURE 3 ...ou~.l;..g plate 204 can, if desired, be eYtrn~lPd upward to the bend of frame 16 between upright 164 and handle 166 to add mrc'nqnifql strength to upright section 168 for 20 lllolllllillg an optional flood light. If desired, a lllounlillg block 206, suitably a soft rubber block to absorb vibration, may be hll~,lJoscd between foot 162, and motor 12, at the distal end of foot 162. If desired, lccL~ lar aperture 172(b) may be provided in foot 162 to acc-lllll,odate an optional lock kit. As previously fl;C~ sei~ ,Lules 310 are suitably threaded to f~cilit~te ln~-u..l;..g of the g~ or stator 210. Accordil1gly, plate 204 is suitably formed of a rigid material 25snffiriently thick to a~co---,--of'~t- threaded à~/C~lUlCS 310, such as, e.g. a 10-gauge plate.

Referring now to FIGURES 2, 3 and 4, generator unit 14 preferably coll-plises a stator 210, a rotor 220, a fan shaft extension 230, a fan 240 and electronic control cil.;uilly 250, all disposed within a housing 260 and top plate 282.
Stator 210 is disposed conc~;,lllically with engine shaft 200, offset by a predetermined distance from frame upright 164. More specifir~lly, stator 210 is fixedly .,..-u"lrd to frame upright 164 (and hence engine 12), and ~onccllllici~y with engine shaft 200 m~int~inrd, by ~ ,eclivc bolts 212.
An offset from upright 164 is m~inr~inrd by lc~.~ecliv-e spacers 214. Bolts 212 extend through W 0 96/09679 21 9~6~8 PC~rrUS95/11361 bores in stator 210, spacers 214, a~ uies 315 in frame 164, and are threaded into holes 310 in plate 204. As previously noted, plate 204 provides the structural inlC~ y for ..~.~u.~ g stator 210.

As will be more fully ~i~cu~ed7 in conju"clion with FIGURES 6 and 7A, Stator 2105 prcr~,ably includes a polarity of three-phase windings to generate first and second low-voltage, high-amperage outputs, e.g., a high-voltage, low-current output, pl~fi,ldl)ly wound with the c~;liv-e coils of each phase grouped together, and con ;ull~ ly wound about a lqminqtç. core as a unit to provide particularly advantageous heat dissipation châlaclclis~ics.

Referring briefly to FIGURE 6, stator 210 suitably cull.~ es two 3-phase willdillgs, and a single-phase control coil that is wound together with the first phase of each 3-phase winding. More specifically, stator 210 includes a first and second 3-phase star wh~ding, 602 and 604, and single phase central winding 605 (wound together with the first phase windings). First winding 602 suitably provides a high voltage, low current output and is formed of a relatively small (li~mpter~
e.g., 24 gauge wire. Winding 604 suitably provides re;,yeclive low-voltage (e.g. 12 and 24 volt), high current output. Each phase of winding 604 suitably includes a first portion 606, defined by a tap to provide a first low voltage (e.g. 12-volt) high current output, and a second portion 608, from which a second low-voltage, (e.g., 24-volt), high-current output is taken. Windings 606 and 608 are formed of multiple 24 gauge wires in parallel preferably within a common insulative sleeve. The effective ~ ç~ of winding 606 wire is apploxilllàlcly twice that of winding 608, e.g. 15 gauge and 18 gauge wire"ci",eclively The ~e~,e.;liv-e coils of each phase of wi"di"gs 602 and 604 include a preclt~-...;..P~ number of turns corresponding to the voltage output associated with that particular coil. The cl-m~ qtive turns of coils 606 and 608 provide a second low-voltage, highcurrent output, e.g., 24-volts. For example, in the plcrcllcd ellll)odi",c"L, 12-volt coil 606 inr~ P~ 5 turns, 24-volt coil 608 includes an additional 4 turns (for an crrc~live total of 9) and high-voltage (e.g. 115 watts) coil 602 includes a total of 29 turns in each phase.

In physical assembly, the ,~ e.;live coils collcspondillg to the high-voltage, and first and second low-voltages of each phase (and the control winding in the first phase) are grouped together as a unit and concullc.llly wound about a l~min~te core together, as a unit. In this manner, the le;,~ecliv-e coils are wound in close proximity, in thermal contact in effect, sharing the same space.
This a,langcn.c..L is particularly advantageous in a number of respects: a single stator generates a plurality of voltages; ~ .. wattage output can be obtained from any of the coils; and, the coils not in use operate as a heat sink for the working winding. The close proximity of the Wo 96/09679 PCr/US9S/11361 esl,ecli~/e coils errccli~ly makes the entire mass of the skein available to ~iccirate the heat g~ ldled by the WO~ g winding.

Rotor 220 is ....J--~ d on engine shaft 200 in coaxial di~o~ilion with stator 210, selJalaled S from stator 210 by a relatively small p~cdc~ hled air gap 242, e.g. in the range of .020 to .060 inch, and p,er~.àbly .030 inch. Specifir~lly, engine shaft 200 is received in a central axial bore in rotor 220. A key 402 (FIGURE 4) ensures a positive rotation of stator 220 with shaft 200. A
spacer 404 is .li~,osed on shaft 200 to axially align rotor 220 with stator 210.
Rotor 220 is ~.ef."ably a p .. ~ magnet rotor, of sllffiri~ntly light weight that it can be m~int~inrd in axial alignmrnt with, and rotated in close pro~ y to stator 210, (i.e. with air gap 242 of less than approximately .060 inch), without the neces~ily of any bealh-gs in addition to those conventionally inrl~ded within engine 12. Rotor 220 suitably ~.,anirc~ls a generator output power to rotor weight ratio in watts per pound of in excess of 150 or 200, preferably in excess of 500, more p.cr~.ably in excess of 700, and most pler~lably in excess of 800. The preferred embodiment lllanir~ in l"a--ir~ a generator output power to rotor weight ratio in the range of 800 to 900 in watts per pound. For example, for a 2-kilowatt unit, rotor 220 would suitably weigh no more than approximately 2.40 pounds. Similarly, for a 900-watt unit rotor 220 preferably weighs no more than 1.06 pounds. As will be more fully ~liccllcsed in conjunction with FIGURE
20 8, in the plcr~llcd emborlimlont~ this is achieved econ~mir~lly by employing high energy product m~gn~tc, and c~l-ce.~ re poles.

Fan eYt~n~ion 230, di~,osed in axial alignm~nt with shaft 200, is employed to couple fan 240 to shaft 200. F-trncjon 230 suitably c~ ises a generally cylindrical body 231, with lc,;.~e~ e reduced ~ ,.. t~-~ ends 232 and 234 (best seen in FIGURE 2), and includes a centrally-disposed axial bore 236. Reduced-r~ ter end 232 is received within the central bore of rotor 220 with the step to body 231 abutting the front surface of rotor 220. Fan 240 is mounted for rotation with shaft 200, to genclal~ air movement to cool the various elements of generator unit 14, and particularly, stator 210 and electronic-controlled cilcllilly 250. Fan 240 suitably includes a plurality of blades, e.g. 5, mounted about a hub 408. Hub 408 suitably includes a central bore 410 generally conrull-lil-g in cross-section to end 236 of extension 230, e.g. includes a flat 412 co~ ,onding to flat 406. Fan 240 is mt~untrd on extension 230 for rotation with shafts 200; fan 240 is suitably forlned of a relatively lightweight plastic such as, for example, Celcon. End 234 of extension 230 is received within central bore 410 of fan 240. Extension end flat 406 cooperates with flat 412 in bore 410 to ensure positive rotation of fan 240 with shaft 230.

Rotor 220, extension 230, and fan 240 are secured as a unit to engine shaft 200 by bolt 414, and a tensioning ...~ ;c... such as a washer 416 and a split washer 418. Bolt 414 is journaled through washers 416 and 418, and through the central bore of fan shaft extension 230, and threadedly engages an axial bore 420 in the end of engine shaft 200. The ~n~jolling l..~cl tends to prevent bolt 414 from ~ .. g~gi.. e with shaft 200.

Housing 260 and a top plate 282 coop~late to enclose stator 210, rotor 220, fan 240 and control circuit 250. Top plate 282 extends p~ ellrl;~ ul~rly from frame upright 164, suitably affixed to upright 164 by, e.g., bolts, rivets or welding. Housing 260 is suitably affixed, e.g., bolted, to top 282, and frame 16. As will h~ af~tl be more fully ~ ssed, housing 260 is formed of a relatively lightweight thermally and electrically conductive material and is suitably employed as an electrical ground for circuitry 250, as well as a thermal heat sink to f~cilit~te cooling.

Referring now to FIGURES 3, 4 and 5, housing 260, top 282 and frame upright 164 cooperate to, in effect, define a closed ~lluclure with pre-defined ~tlLul~i, (e.g. grills) in pledele~ od positions to define an airflow path to f~rilit~te cooling of the elemrnt~ of generator ~4. Specifir~lly~ a grill 320 (best seen in FIGURES 3 and 4) is formed in frame upright 164. Housing 260 includes a face 422 and ,espe~;live sides 424 and 426 (best seen in FIGURES 4 and 5) and a bottom 428. A first grill 430 and second smaller series of al~llul~s 432 are formed at predrl~ ...i..~d positions through face 422.
Additional sets of a~llul~s 434 and 436 are suitably formed through side wall 424 and, if desired, a~)~llules 436A are formed through side wall 426. Grill 430 is disl,osed in a general ~lignmrnt with fan 240. In operation, fan 240 draws air into the enclosure through grill 430, creating a 25 positive pre;.~uie in the interior of the enclosure, and forcing air to exit through grill 320 in upright 164 and aprllul~,s 432, 434, 436 and 436A. Apertures 432, 434, and 436 are strategically placed to cause airflow over specific heat-stl~ilive COIll~ulU;lll~. Additionally, the action of fan 240 itself causes an airflow in a radial direction off of the tips of fan 240. Particularly heat sensitive components are pIef~ldbly disposed in the radial airflow grll~lalrd by fan 240, e.g., a heat sink 30 500 for heat-sensitive electronic colll~)o~ is disposed radially offset from, but axially aligned.
Heat sink 500 can be of various shapes and dispositions (see FIGURE 5A). The use of a fan directly coupled to motor shaft 200 is particularly advantageous in that airflow varies as a function of need. The higher the rpm of the engine, the more power is generated, and conrol..i~ Iy, more heat is generated by the colll~ol1elll~. However, as the engine rpm increases, the airflow generated 35 by fan 240 also hl~ ases to acc~mmo~l~te the additional heat generated.

- ' - 21 99628 Control circuilly 250 rectifies the signals from the stator coils. Control CilcuiLly 250 may coll,plise any suitable rectifir~tion circuits to convert the signals from stator 210 to ~lo~ e DC
signals. Referring to FIGURES 5, and SA, control circuitry 250 suitably co~ lises a first full wave bridge rectifier 706 (high-voltage, low-current) coop~.ding with a heat sink 500 (SOOA in FIGURE SA); a fuse 501; a suitable switch 704; and a second rectifier 700 (high voltage, low current). Control cilcuilly 250 suitably cooperates with a suitable conventional duplex receptacle (outlet) 702; three-pole double throw switch 704, and positive and negative post termin~lc 703 and 705. The colll~ol~.ll~ of control circuitry 250 and COOp~,lalhlg cl~ .lC can be variously disposed within housing 250. Alternative dis~o~iLions are shown in FIGURES S and SA.
Referring to FIGURE SA, rectifier 706 and fuse 501 may suitably be disposed on face 422.
Rectifier 706 suitably u~ lises a diode bridge with the diodes sized to wilh~ d a short-circuit output greater than that capable of being produced within the power limitations of engine 12. Fuse 501 protects the diodes of rectifier 706 from a reverse polarity connecticn at terminals 703 and 705, during, e.g. a battery charging operation.

Outlet 702 and terminal posts 703 and 705 suitably extend through, and switch 704 ml~unttod on sidewall 424. Tçnnin~lc 703 and 705, can, however, be disposed elsewhere on housing 260, as desired, to ~Cc~ A~le the particular configuration and disposition of Colll~ollcllls employed in control circuit 250. For example, while positive terminal 703 is shown at the top of wall 424 in FIGURE SA, and negative terminal 705 shown lower in the wall, relative positions can be reversed (see FIGURES 1 and 5).

Rectifier 700 can be mounted on sidewall 424, ort if desired, can be formed as a separate assembly llluullled on the back of outlet 702.

As will be h~lcillafltr be di~u~e~l, positive terminal 703 is electrically isolated from wall 424 by suitable insulative washers 504. Negative terminal 705 is electrically (and ~ ic~lly) conn-oct~d to side wall 424. As will be ~licc~lcce~l housing 260 serves as both electrical ground and heat sink to various r~ c of circuit 250.

Referring now to FIGURE 7A, high-voltage low-current winding 602 is suitably connected to 3-phase bridge 700. The output of rectifier 700 is co..l.eclcd to duplex receptacle 702. The respective low-voltage, high-current outputs of winding 604, i.e. from windings 606 and 608, are 35 applied to the respective throw tennin~lc of 3-pole double throw switch 704. The poles of switch WO 96/09679 PCr/USsS/11361 614 are co~ c~ed to control circuit 250 (rectifier 706; FIGURE 5A), which provide low-voltage, high-current output at terminql~ 703 and 705.

In operation, engine 12 rotates shaft 200, and rotor 220 and fan 240 rotate co.-~o;l~.lly.
Rotation of rotor 220 causes current to be induced in the coils of the stator 210.

The l.,s~,eclive outputs of stator 210 are sele~,Lively applied to control circuit 250, which suitably rectifies the signals to provide the desired low-voltage, high~ p~ .ge output signals at positive and negative output t~nnin~l~ 703 and 705 for uses such as clla~ lg bd~ ies, and high-voltage, low-current at duplex recept~le 702 for powering conventional power tools, lights, and the like.

FIGURES 7A and 7B, control circuitry 250 may also comprise, if desired, various circuits to provide certain protection functions, in addition to, or in lieu of fuse 501. The protection circuits are advantageously disposed on a printed circuit board 250A (FIGURE 5). With specific ~f~.el~ce to FIGURES 7B and 7C, in such control circuit rectifier 706 is preferably SCR-controlled, i.e., colll~)lises a positive diode block 708, and a negative diode block 710 formed of silicon-controlled rectifiers (SCR's) coopcl~lil.g with a suitable control circuit 712. Control circuit 712, in tum, cooperates with lc~ ecli~e sensing circuits such as, for example, a reverse-polarity sensor 714, and enable and disable sensors 716 and 718.

Reverse polarity sensor 714 suitably disables control cil-;uilly 712 (and hence rectifier 706) if it senses a reverse polarity voltage in excess of a pre-detennin~d level, i.e., in excess of 0.6 negative volt across output terrnin~l~ 703 and 705. Thus, the unit is disabled if, e.g. Ieads from temninals 703 and 705 are coupled to wrong polarity battery temlinals during a ch~gillg operation.

Enable sensor 716 and disable sensor 718 sense the voltage across output te~rnin~l~ 703 and 705, e.g., from a battery, and enables control circuit 712 only if a voltage in excess of a pre-~leterrnin~d threshold, e.g., 150 millivolts. In this manner, the unit is disabled if the output 30 t.orrnin~l~ are discol~llecled from a battery, to avoid sparks or short-circuits across inadvertent connections.

If desired, a lllolllcnl~l~ switch S1 can be provided to override the protection features for the purpose of supplying power to a battery that is completely without charge or supplying power to 35 a load with no battery.

~ Wo 96/09679 PCT/US95/11361 Referring now to FIGURE 7C, the negative block of rectifier 706 suitably u"l.~lises 3 SCR's receptive of control signals from control circuit 712. Control circuit 712 selectively enables SCR's 704 to perrnit current to flow to the negative pole of the ~ ~,h~;uilly. Control circuit 706 suitably Cu111~11i;~CS rc;,l,ecliYe llallsi~lol~ Ql and Q4, respective 5 lc~i~lol~ R2 and R3, and a ~ r~ lly contact switch S1. Tlallsi~Lor Q4 is selectively forward biased by the sensing ChcUi~ as will be explained. In the absence of a sensed reverse polarity, when llallSi~lOl Q4 is forward biased, Q1 is turned on through divider chain l~si~lol~ R2 and R3, enabling SCR's 704.

10Reverse polarity sensor 714 disables control circuit 712 upon sensing a reverse polarity COnl~f'cl ion at output tçrminqlc 703 and 705 . In the pltftll-,d embotlimrnt~ reverse polarity sensor 714 cc,lll~,ises Ic~ ecliYe resi~lol~ R4, R5, R6 and Rll, a diode CR7, and lc~ecliYe transistors Q2 and Q3. A relatively small reverse polarity voltage across terminals 703 and 705, e.g., by virtue of a reverse polarity connection to a battery to be charged, causes diode CR7 to be forward 15 biased. When diode CR7 is forward biased in excess of a predc~e~...i..tod level, e.g., 600 millivolts, a base drive is provided across divider chain R5 and R6, turning on transistor Q3.
Transistor Q3 is collector coupled to the base of llansi~lor Q2. When ~ lol Q3 is turned on, it disables llansi~lor Q2 and, col-ro...;l;,l.lly, ll~lsi~lol Ql in control circuit 712 to disable rectifier 706.
Enable sensor 716, in effect, enables control circuit 712 only after terminals 703 and 705 are collnecled to a battery, to avoid sp~ iug or inadvertent short circuits. Enable sensor 716 suitably comprises a Cd~dcilOl C2, ~c~ecli~e resislul~ Rl, R10 and R16, a diode CR5, and a Zener diode CR4. When diode CR5 is forward biased above pre~lrtrrminr(l threshold, e.g., 600 millivolts, the 25 voltage is applied to the cathode of Zener diode CR4. When the voltage o~lcollles the Zener voltage of the diode, voltage is then applied across a voltage divider colll~ illg resistor R10, and resistor R9 in control circuit 712, to provide a bias voltage for transistor Q4 in control circuit 712.
This, in turn enables transistor Ql and, hence, rectifier 706. Should the voltage at terminal 703 drop below 600 millivolts, as would be in the case of a short circuit, Llansi~lur Q4 is turned off, 30turning off llai~si~lol Ql, and disabling SCRs CRl, CR2 and CR3 of rectifier 706. Resistor R1 and C~paritQr C2 comprise a filter for noise ;~ y.

Disable sensor (over-voltage sensor) 718 senses a rise in voltage when current flow drops and Ic~ol~h~ely disables rectifier 706. This effectively disables the high current output when terminals 703 and 705 are disco~ cled Disable sensor 718 comprises respective Zener diodes Zl and Z2, 21 9~628 capacitor C1, resi~lol~ R7 and R12, and transistor Q5. Zener diode Z2 is selectively switched in and out of the circuit depending upon which of the re~ec~ e low-voltage, high-current windings has been selected, e.g., the 12- or 24-volts. When voltage is applied across diode CR5 to the cathode of Zener diode Z1 or Z2, the Zener voltages, e.g., 22 volts for Zener Z2 and 18 volts for 5 Zener Z1, is applied across the divider co.,.~ il.g ~e~i~lo-~ R7 and R12, turning on transistor Q5.
This, in turn, disables transistor Q4 and control circuit 712, disabling SCR block 710.

In accoldal1ce with another aspect of the present invention, to facilitate a light weight unit, housing 280 serves as both an electrical ground and as a heat sink for various of the circuit components. Referring now to FIGURES 7B, 7C, 4, and 5, the anodes of SCR's 704 of block 710 are conl.ecLed directly to housing 260. Specifically, the anodes of SCR's 704 are electrically and thPrrn~lly comle-,~ed to housing 260, e.g., to wall 422. Negative terminal 705 is electrically and ~"~rl~ ir~lly connected to housing 260, i.e. wall 424 of housing 260, and thus electrically coll,.e.;led through the housing to the anodes of SCR's 704. Terminal 705 suitably includes a post extending through wall 424 (Fig 1 and 4). Housing 260 thus serves both as electrical ground and heat sink. The cathodes of positive diodes in block 708 are electrically and thermally connected to heat sink 500 (500A in FIGURE 5A) and thcr~r u..- to terminal 703. The post of terminal 703 extends through an aperture 502 in wall 424 of housing 260, electrically isolated by insulative washers 504. By employing housing 260 as both electrical ground and a heat sink, the necessity of a separate heat sink for one set of diodes is avoidcd.

As previously noted, rotor 220 is preferably a pe~ magnet rotor of a sufficiently light weight that it can be m~int~inPd in axially alignmPnt with, and rotated relative to, stator 210 without the necessily of any bearings in addition to those conventionally included within engine 12. In the preferred embodiment, this is achieved by employing high energy product magnets, and con.cequen~e poles.
Referring to FIGURES 8, 8A, 8B, and 8C, rotor 220 plcr~ bly co",l"ists a generally disc-shaped core 80û bearing a polarity of high energy product Magnets 802 to dispose on the ch~;ull-rel~ ial surface thereof. Magnets 802 are plere,~bly disposed within the insets 803 in the ch~;u"~reicl~lial surface, with the intervening portions of core 800 cu",~,isi"g con.ceqnPnre poles 802.

Magnets 802 include an outer face 808, and an inner face 810. (810A in FIGURE 8A) Magnets 802 is disposed within inset 803 with inner surface 810 (in 810A) seated on a COIl~llllillg surface 805 (805A) of core 800, offset from the adjacent conceq~lenre poles 806 by a pre-35 ~let~rminPd gap 812.

~ 21 99628 WO 96/09679 PCr/US95/11361 Magnets 802 p.~,f l~bly co.l.~lise high energy product magnets having a flux density of ~ at least on the order of five kilogauss, suitably formed of a rare earth alloy such as neodymium iron boron, or 5al11aliUIII cobalt. Such rare earth materials tend to be extremely expensive, and, acco,di,-gly, it is desi,able to 1~ the amount of material used. However, at the same time, 5 it is desirable to genclaLe relatively high flux tl~n~iti~s. In the plcrc.lcd embodiment, m~gnrtc 802 are relatively thin, e.g. on the order of 1/10 of an inch thick, but present a relatively large area, e.g. 3/4 of an inch by ~-oxill~cly one inch, to ...;..;,..;,~ the amount of high energy product magnet used.

In accordâl1ce with one aspect of the present invention, the overall size of the device, and amount of high energy product m~gnrtic material used, is ...;..;...;,Pd for a given total flux.
Specifically, the area of magnet face 808 is greater than the area of the face 806 of con~equrnre poles by approx;...~ y the ratio of the flux density produced by the pe~ magnet to the allowed flux density of the con~equPnre pole. Thus, by maximizing the area of the pelll,ane 15 magnet relative to the con~eq~l~nre pole, a smaller dia llelel core is required for a given total flux.
A smaller ~ mrtçr core results in less weight and less m~gnrtir material being required for a given total flux.

Inner faces 810 (FIGURE 8C) and co--~ondil.g inset surface 805 of inset 803 are preferably 20 cuNed along a radius cQnr~-.l.ic with magnet outer surfaces 808 and the outer surfaces of con~eqnenre poles 806. Respective gaps 812 are m~int~inrd between each magnet 802 and adjacent con~equ~nre pole 806. Gap 812 is plcrclably sig-~ir.r-..lly larger than air gap 242 (FIGURE 2) between rotor and stator, e.g., five or six times greater, to ensure that the majority of magnetic energy is directed into the stator rather than across gap 812.
Magnets 802 are suitably secured to core 800 with glue. If desired, rotor 220 can be wrapped in a non-metallic material, e.g. fiberglass tape, to secure magnets 802 against centrifugal forces g~ .alcd by rotation.

Magnet inner face 810, 810A and corresponding inset surface 805 and 805A may be any configuration, so long as they conform to each other. For example, lefcllh~g to FIGURE 8D, inner face 810A of magnet 802 and mating surface 805A on core 800, may be planar. In such case, it has been .l~ d that it is desirable to include a notch 814, c~le~ i,.g radially below surface 805(a) in the vicinity of magnet con~equ~nre pole air gaps 812. Notch 814 has been found to increase the amount of flux directed into the stator from rotor 220.

WO 96/09679 2 1 9 9 6 2 8 PcrluS9~/11361 If desired, generator unit 14 can be m~lifiPd to generate AC signals. Referring to FIGURE
9, a 115 volt AC signal can be provided by: replacing high voltage low current winding 602 with a higher voltage winding 902, e.g. 150 volt whldil,g; replacing three-phase bridge 700 with an analogous circuit 904 rated for the higher voltage; and applying the DC signal to a suitable inverter 5 906.

Three-phase regulator 904 generates an output voltage on DC rail 905A, 905B at a level, e.g., 150 volts DC, suffiriPnt to gen~,~al~ the desired AC voltage. DC rail 905A, 905B is suitably floating with respect to system ground (i.e. housing 260), to facilitate gluull.lillg inverter 906 in 10 accordance with UL ~ u~da~(L~..

Inverter 906 ge"el~tes an output signal 915 at outlet 702 that simulates a sine wave of predetermined rl~ u.,.lcy. Inverter 906 is prl,f~lably a variable frequency inverter, and suitably includes a control section 908 and power conversion section 910. In general, control section 908 15 generates ~.wilchh~g control signals to power conversion section 910, which responsively applies the DC rail voltage to the lt..l,eclive termin~l~ (L1, L2) of outlet 702. The application of the DC
rail signals genelàtes an output signal 915 with a predeterminPd wav~rol... sim~ ting (e.g. having the same RMS value as) the desired AC signal (e.g 120v 60 Hz in the U.S.; v 50 Hz in Europe). Stable supply voltages ( e.g. 15v, 5v) for inverter control section 910 are suitably derived from control winding 605 by a bridge rectifier 912 and regulator 914.

The use of a variable fie.lu~.lcy inverter is particularly advantageous in a number of respects. Since the AC signal is developed synthPtir~lly by inverter 906, it is in~PpPnrl~Prlt of the rpm of engine 12. Accordi"gly, inverter 906 can be adjusted to provide full power at various 25 pre~lrl~ ,..in~d frequPnriPs, e.g., 60 Hertz in the United States, and 50 Hertz in most Eulopean countries.
Further, by varying the frequency of the output as a function of load current draw to a~co.... o-l~te ~Allavldilla-y transient ~Pm~ntlc from loads, unit 10 is made capable of ~ g with much larger devices than would typically be the case. Particularly, it has been determined 30 that the current required to start a large motor, such as, for example, the refrigeration cu~ lessor on an air conditioner, is much greater than the current required to m~int~in operation of the motor once it has been started. When the load, e.g. motor, draws a current higher than the rated output of the system, the DC rail voltage applied to inverter 906 tends to drop. It has been determined that by reducing the frequency of the AC output signal as a function of, e.g. proportionately with, 35 the reduction in voltage, unit 10 can be used to start, and ,..i.i..l;.i.. in operation, motors that would --WO 96/09679 2 1 9 9 6 2 8 PCTtUS95/11361 typically require a much larger gcll~,.àlOl. Lowering the frequency at the applied signal effectively lowers the O~C~d~illg RPM of the motor, e.g. co~ lessor, to be started. This lowers the load on the motor and theleforc decreases the current required to start the motor. The frequency can then ~be illcleased, h~cl~sillg the motor RPM to the dP~ign~d ~p~lalillg speed. For example, when the 5 voltage drops below a pre-dcl~ ...;l.~d level, e.g. a~lo~ill.àtely 110 volts, frequency is decleased, pl~,fe~ably linearly tracking voltage down to about 30 hertz and 50 volts. Once the motor is running, the current drawn by the motor reduces, the DC rail voltage rises, and the normal o~.dling rlcy,len~ is l~ lllRd. For example, 2 kilowatt generator in accorlallce with the present invention is capable of starting and ...~;..l~;.~;.~g a 13,000 btu air conditioner which, previously, in 10order to ~c~ te the starting loads, required a 4 or 5 kilowatt generator.

Conversely, since the speed of engine 12 can be lowered without reducing frequency, the speed of engine 12 can be varied as a function of output drawn. Thus if only a fraction of the system capacity is being drawn, the engine can be throttled hack or made to idle. More 15specific~lly, a voltage feedl,ack control can be employed to govern the speed of the engine. The speed of the engine is thus varied as a function of load, providing decreased noise and increased fuel ecollc,ll.y.

As previously noted, regulator 904 gen~ales the DC rail signal to inverter 906. Referring 20to FIGURE 10, a suitable regulator 904 colll~ ts: a rectifier bridge 1002; a leveling capacitor C21; a colll~aldlor 1004; and an optoisolator 1006. Rectifier bridge 1002 is suitably formed of ,ecli./e diodes D28, D29 and D30 and rei,l,ccli~e SCR's TH1, TH2, and TH3. Comparator 1004 suitably collll~liscs l~ ,ccLive Llal~i~Lol~ Q13 and Q15, and a voltage divider formed of resistors R21 and R23.
The output leads (J6, J7, and J8) from 3-phase alLcllla~or coil 902 provide 3-phase input signals to bridge 1002. Such allcllldLol output signals are of variable voltage and frequency in accoldà.lce with the RPM of the engine. Comparator 1004 selectively activates opto-isolator 1006, to turn on SCR's TH1, TH2, and TH3 to generate a regulated output across DC rails 905A and 30 905B.

In essence, colll~alaLor 1004 provides active feedback to m~int~in the rail voltage at the pled~t~....;..~d level, e.g., 150 volts. Indicia of the rail voltage is derived, and compared against a lcr~.cnce voltage (a stable regulated DC voltage provided by regulator 914). When the rail drops Wo 96/09679 2 1 9 9 6 2 8 PCr/US95/11361 below the d~ign ~ecl voltage, e.g., 150 volts, co...~ a'or 1004 activates opto-isolator 1006 to turn on SCRs TH1-TH3.

Stable supply voltages ( e.g. l5v, Sv) are suitably derived from control winding 605 by bridge rectifier 912 and regulator 914. Bridge 912 suitably co,-,~ es a conventional single phase diode bridge. Regulator 914 suitably comprises rei,~c~,live co"ve,l~ional regular devices Vrl and Vr2, such as Motorola 78LXX series pass three lead regulator devices to provide stable, regulated DC outputs at ~plo~liate levels ( e.g Vrl 15v, Vr2 5v) for inverter control 908 (15v), SCR's THl, TH2, and TH3 (Sv), and for deriving a stable ~cr~ ce signal for colll2àldtor 1004 (Sv).
As previously noted, control section 908 generates s~ cl hlg control signals to power conversion section 910. Referring to FIGURE 11, inverter control section 908 suitably comprises:
a suitable microcc,lllpul~. 1102; a suitable digital-to-analog ("D to A") converter 1104; a suitable crystal 1106 of pred~ ...i..rd resonant frequency, e.g. 4 m.og~h~rtz; suitable feedback signal interface circuits 1108 and 1115; and suitable colll~illàlorial logic 1110.

Microcolll~,ule, 1102 is suitably a conventional microcomputer, such as, for example, a Ziolog Z86E04, inr.~ 1ing internal random access memory (RAM), cow~le~ and registers ( which can be implçm~nttod in the RAM in acco~dallce with standard terhni~ es), and additionally, 20 re;,~eclive internal co"l~alalol~ capable of genelàlillg hll~llul~ls, and respective port legi~ for controlling the output signals at various output terrnin~l~ (pin) with the miclocolll~ulel. (For convenience of ~Ç~ ce, coll.,i,lJolldillg port l~gisl~l~ will s...llr~ s be referred to ~y"u"y"~ously.) More particularly, mi~,oco",l.ul~. 1102 suitably includes two internal comparators, the first COIll~alillg the voltage applied at pin 8 to that applied at pin 10, and the second COIII~ the voltage applied at pin 9 to the voltage applied at pin 10 (the voltage at pin 10 is a collllllon l~r~lellce signal). As will be explained, the COIulllOll r~f~lence signal is suitably a controlled ramp voltage gen~laled by D to A converter 1104.

Micloco"l~ l 1102 genelales a count (AtoD, FIGURE llA) which is reflected at pins 14 and 15-18. D to A converter 1104, suitably an R2R resistor ladder conilc~,led to pins 1-4 and 15-18 of microcolll~ulel 1102, generates a ramp le~,e,lce signal reflecting that count. The voltage across the R2R ladder is filtered and applied as the common collll.alalor reference signal at microcolll~,ulel pin 10. As will be described, comparisons of various parameters, (e.g. indicia of output signal 915 voltage (pin 8), indicia of supply voltage or o~el-;u,lelll condition (pin 9)) against the ramp signal are employed to generate digital indicia of the parameters or specified functions;

Wo 96/09679 PCr/US95/11361 the ;...~ nro~ value of count AtoD when the p~ and rcr~,lence voltage are equal is - indicative of the value of the paldlll~tel voltage. The c~,llll.alisons are also employed to selectively initiate inl~,ll,~l filnrtion~.

S Microcn~ u~l 1102 is suitably illl. llulJI driven; various illl~llu~ll signals are genclaled to effect l)led~ d funrtion~. For example, hll~llu~ are g~ A in lesponse to: a colll~alison of the D to A ramp lefc.~,.lce signal to the indicia of output signal 915 from interface 1108 (swilcllillg cycle frequency adju~ ); a colll~Jalison of the D to A ramp l~f~"~,.lce signal to the indicia of output current, current sense signal (ISEN) (o~ ;ulclll protection) and indicia of the supply voltage (below power ~la,lsi~or gate threshold protection); and a collll.alison of counts from an internal clock to l~ ,ecli~e control pal~llel~ (pulsewidth of ~wilcllillg pulses generated at pins 12 and 13 and ~ between pulses).

In addition, microcu...~ el 1102 suitably cooperates with combinatorial logic 1110 to 15 gellelate l~ e~ e swilclli,lg signals LHRL (Left High, Right Low) and RHLL (Right High, Left Low) to power conversion section 910, in re~ollse to which power conversion section 910 effects controlled application of the DC rail to output tenninql~ L1 and L2. More specifirq-lly~
microcc""l,lLcl 1102 g~,n~,ldlcs, at pins 12 and 13, l~spe~ e alternative pulses of controlled pulsewidth, relative timing, and repetition rate. These pulses are gated with current sense (ISEN) 20 rce.ll,ack signal, to gcll.,lale ~wilcllillg signals LHRL and RHLL. Miclocollllmlcl 1102 and coll,billatoliâl logic 1110, may also gel~lale, if desired, further ~wilcl,illg signals HIV (BOOST) and CHARGE, and GOV to power coll~el~ion section 910 to effect advantageous shaping of output signal 915. The operation of microcc,lll~ul~r 1102 will be more fully described in colljull(;lion with Figures llA- llF.
Indicia of the voltage of output signal 915, suitable for co,llpalison to the ramp leÇ~.~..ce signal gell~latcd by A to D converter 1104, is provided by feedl,ack signal interface circuit 1108.
Feedback signal interface circuit 1108 suitably comprises: a single phase diode bridge 1112 connected to output terminql~ L1 and L2; a suitable low pass filter circuit 1114 (e.g., resistors R29 and R30, and capacitor C7); a Zener diode Z1; and second low pass filter circuit 1116 (e.g., resistors R8 and R14, and capacitor C18). Output signal 915, as provided at output terminals L1 and L2 is applied to bridge 1112, to generate an average DC signal. The DC signal is filtered, smoothed and limited by filters 1114 and 1116, and Zener diode Z1, and applied to a voltage divider (R8, R14) to generate a signal proportional to the average voltage of output 915. The signal is applied at pin 8 of micro-co"lpul~l 1102, for C~ alisOII against the ,cfe,c"ce ramp.

Signals indicative of under threshold voltage supply levels and over current conditions are provided by second fe~Jl,;lcL- hlL.,lrace circuit 1115. More specifi~lly, the 15 volt supply voltage generated by regulator VR1 of supply of 914 is applied across a voltage divider formed of Zener diode Z5 and resistor R26 to g~ ale a signal hl~licd~ive of the supply voltage level. This signal S is applied to pin 9 of micloco~ ,ulçl 1102 for co~ alison against the lcI;~.I"lce ramp. In addition, a signal (ISEN) indicative of the current level of the output signal ge,lc,dt~d by power converter 910 is applied through an isolation diode D1 to 1009 of "licrQc~ ul~ ~ 1102. In essence, if the supply voltage level drops below a pre~( t~ ...;..~d ...i,~ .., or the output current exceeds a pre-det~""i"ed m~im--m, an h~le,lu~l is ~,~,R,aled to disable power converter 910, and protect its 10 colll~o~ from damage.

Power co"~ ion section 910, in resyollsc to swilellillg control signals LHRL and RHLL, (and further ~wilcllillg signals HIV (BOOST) and CHARGE, if utilized) from control section 908, selectively applies the DC rail voltage to the respective tçrmin~lc (L1, L2) of outlet 702 to genclalcs an output signal 915 with a predcl~ .. ;.l~d waveform. Referring to Figure 12, a suitable basic power conversion circuit 910A co"l~lises: rei~yecli~e high-side isolated power switch circuits 1202 and 1204; le~.yeclive low-side non-isolated power switch circuits 1206 and 1208; and a current sensor amplifier 1210.

High-side isolated power switch circuits 1202 and 1204 and low-side non-isolated power switch circuits 1206 and 1208 each include a power transistor (Q1, Q2, Q3, and Q4, lc~eclively) and a suitable firing circuit for turning the power transistor on and off in acco,.làllce with ~wilchillg signals LHRL and RHLL. Power switch circuits 1202-1208 are illklco~ cled in an H-configuration: High-side isolated power switch circuits 1202 and 1204 define controlled current paths to output tçnnin~l.c Ll and L2, le~yeclively, electrically co"l,ecled together at a high-side t~nnin~l 1203 (e.g. the drains of power transistors Q1 and Q2 are con"e.;led at terminal 1203); and low-side non-isolated power switch circuits 1206 and 1208 define controlled current paths to output tçnnin~lc L1 and L2, l~i~yeclivcly~ electrically co~ cl~d together at a low-side ttonnin~l 1207 (e.g.
the sources of power transistors Q3 and Q4 are connecled at terminal 1207). In the basic configuration of Figure 12, highside terminal 1203 is com1e.;led to positive rail 905A and low-side tçnnin~l 1207 is conn~ctçd, through an isolation diode D7, to negative rail 905B.

Power switch circuits 1202-1208 effectively operate as an electronically controlled double pole, double pole switch, selectively co""Pc';,-g the DC rail to tPnnin~lc L1 and L2 in response to switching control signals LHRL and RHLL. More specifically, switching signal LHRL is ---Wo 96/09679 pcTrus95lll36 applied to high-side isolated driver 1202 and low-side non-isolated driver 1208, and ~wilchi~g signal RHLL is applied to high-side isolated driver 1204 and low-side non-isolated driver 1206.
When LHRL is of a pre~ ...;..f-d state, (e.g. low), high side terminal L1 is co~ c~1 to positive DC rail 905A by driver 1202, and low side t~rmin~l L2 is connP~ d to negative DC rail 905B by 5 driver 1208. Conversely, when RHLL is of a plcdf~ Pd state, (e.g. low), high side tçrmin~l L1 is c...~.~F~l~l to negdlive DC rail 905B by driver 1204, and low side te~min~l L2 is co~...r~l~d to positive DC rail 905A by driver 1206. By ~l~frn~fly ge.le.dlillg swilcl,i"g signals LHRL and RHLL, a simnl~fd sine wave, shown in Figure 13, can be produced, having an RMS value controlled by the period of time ("Dead Time") between turning off one pair of drivers ( time T1) 10 and the turning on of the ol)posi"g pair (time T2). Control of the dead time in relationship to the voltage levels provides an RMS value a~"u~ fly equal to that of the desired sine wave.

It is desirable that the firing circuits of isolated drivers 1202 and 1204 quickly the associated power l~dl~SisLo. Q1, Q2 into a sdluldled state when the ~ccoci~tfd swilcl,i"g signal 15 LHRL, RHLL changes state to ...;.,;..~ power dissipation during the ~wilchi,lg interval. A
particularly ecQnn...ir~l firing circuit that provides advantageous turn on and turn off characteristic Culll~JriseS: a resistor R13 (R19); an NPN lld,~ Lor Q9 (Q10); a diode D2 (D3); a capacitor C4 (C2); and ,~e~ e resistor R9 (R15) and R6 (R10). If desired, .ei,~e~ e capacitors C8 (C10) and C6 (C9) may be co~ f~ d between the drain and source and gate and source of power 20 l~d"~i~lor Q1 (Q2) to prevent any high frequency oscillations, and a Zener diode Z4 (Z7) connfcted between the drain and source of power l,a,~i~lor Q1 (Q2) to limit the gate voltage to no more than a predel~.",i"ed value, e.g. 15v.

In the pref~ d embodiment control signals LHRL and RHLL are at a low level when 25 ~ctl-~ted and a high level when l~ul~ d When the ~ccoci~t~d control signal LHRL (RHLL) is nnn~rtl-~t.od, i.e. high, l,~ lor Q9 (Q10) is rendered conductive. This, in effect, grounds the gate of power l,ansi~lor Q1 (Q2) and renders it nû,lcond~lctive. However, a current path is created from the 15 volt supply through diode D2 (D3) and resistor R6 (R10); approximately 15v is thus dropped across resistor R6 (R10). With l~ lor Q9 (Q10) conductive, capacitor C4 (C2) is 30 effectively in parallel with resistor R6 (R10) and is therefore charged to a level (apprnxim~tloly 15v) sO~ wllal in excess of the threshold gate voltage (e.g. 8v) necessa,y to place power transistor Q1 (Q2) into saturation.

When the associated control signal LHRL (RHLL) changes to an actuated state, i.e. goes 35 low, transistor Q9 (Q10) is rendered nonrQnd~ctive. This, in effect, places the gate of power transistor Q1 (Q2) at 15v and renders it conductive. When power transistor Q1 (Q2) is rendered con~ ctive, the device exhibits very little resi~t~n~e, and the source voltage approaches the voltage of the drain (e.g., 150 volts) the ne~;~ive tennin~l of capacitor C4 (C2) thus assumes a voltage ~ g the rail voltage (150 volts). Since capacitor C4 (C2) is already charged to 5 approximately 15 volts, the positive side of the capa~;ilor is at a voltage approaching the rail voltage plus the charge voltage, i.e., 165 volts. This, in effect, reverse biases diode D2 (D3), rendering the diode non-con~ tive and effectively blocking the 15 volts ply. However, since capacilol C4 (C2) is charged to a level above the set saturation threshold gate voltage of power transistor Q1 accordillgly, ~ sisLor Q1 continues to conduct. The level of the source voltage (15 volts) and the 10 level to which ca~a~ C4 (C2) is initially charged, is chosen to initially place power transistor Q1 (Q2) into a hard full conduction. However, once diode D2 is blocked, capacitor C2 begins to discharge through resistor R9 (R10). The time constant of capacitor C4 (C2) and resistor R9 (R10) is chosen such that the charge on capacilor C4 (hence the gate voltage) a~lroa.,llcs (is only slightly above) the threshold value of power transistor Q1 (Q2) at the point in time when the associated 15 control signal LHRL (RHLL) changes state. In those systems where the frequency varies, the time con~t~nt is chosen such that the gate voltage is ap~ ac}lillg (slightly higher than) the threshold value at the lowest frequency at which the system is int~n~ d to operate. When the associated control signal RHRL (RHLL)initially resumes a non a~tll~tlod state, i.e., goes high, transistor Q9 (Q10) is again rendered con~ rtive, ~lOUll~illg the gate of, and turning off, power ~lansi~lor Q1 20 (Q2) and the cycle is repeated. By dischalgillg CàpaCilOl C4 (C9) to a point a~Jpluachillg the threshold voltage (el;...;~ g excess charge), the turn off speed of power llansislor Q1 (Q2) is h~lcased.

The recdback signal indicative of output current level (ISEN) provided to feedback interface circuit 1115, is g~ dled by current sensing amplifier 1210. Amplifier 1210 simply comprises a resister R3, and an amplifier coll,lulisillg transistor Q13. Resister R3 develops a voltage indicative of the current through power transistors Q1-Q4 if the voltage across resister R3 exceeds a pre-~ ....;...od lirnit, ll~lsi~lol Q13 is rendered conductive effectively pulling the ISEN signal to ground. As previously noted, the ISEN signal is applied as a gating control to co",bi"alorial logic 1110 (nand gates U7A, U7B, and U7C; FIGURE 11) effectively h~hibiling those gates. In addition, it crrt~livcly pulls the voltage at 1009 to zero, effecting generation of an interrupt, âS will be t1i~c~-~sed.

A closer approximation to a desired sine wave output can be achieved by shaping the waveform of output signal 915. This may be accomplished by genelalil,g an auxiliary signal and W096/09679 PCr/US95/11361 controllably applying it through the a- Iivdled high side power ~ or to the associated output termin~l. The resultant waveforrn is shown in Figure 14.

- An auxiliary (boost) signal can be ge.~,aled in any nurnber of ways. For example, the S boost sinal can be ~ cd by an auxiliary winding added in stator 210. Referring to Figures 14, 15, l5A, and 16, an 7~lf~hif)nql winding 903 may be wound on stator 210 con.;ul,~,.llly with will~lillg 902, in e~senti~lly the same space. Winding 903 cooperates with a con~,..lional three-phase diode bridge 1502 to ge..e.dle an i..~ r~li~te positive rail 90SC of pl~ t~-...;..~d voltage (e.g., 70v). To ~,ene,~àte the sim~ d sign wave waveform of Figure 14, the active ~errninql (L1, L2) is crrc-;livcly C J f cled to i~ ",P~ e positive rail 905c, and positive rail 905a, in seq~l~nre.

The i.ll~....P.~ ç rail voltage can be alternative to the positive rail voltage provided by wi..di..g 902, or it can be additive. For example, rerc.ling to Figure 15, the ;lllr....~ le positive rail and positive rail voltages can be in~ nrl~..lly developed, e.g., winding 903 gel.clales the 15 ;-~ te rail voltage, and winding 902 g~ alcS the entirety of the positive rail voltage, lly indcpc--dently from winding 903. If desired, however, windings 903 and 902 can be utilized to co~,.a~ ly gelle.ale the desired voltage at positive rail 905a. Referring briefly to Figure 15A, in such an a.l~l~~ ,.ll winding 903 would include a pre~irl~-..,;..~d number of windi--gs coll~,ondi,lg to the desired voltage and ;-l~ le rail 905c, and diode bridge 1502 would be il.l~.~osed between regulator 904 and negative rail 905B. A winding 902A, coll~ Jollding to winding 902, but including a pled~ t~ ~ ...;. .ed number of turns co. lc~ollding to the dirr~.~ncc between the desired voltage at ;..l4-...~ e rail 905c and the voltage, e.g., 150 volts, at positive rail 905a is provided.

Referring to Figure 16, the ;~ e voltage (70v) rail 905c is co~ cled high side t~rmin~l 1203 of basic power converter 910A (i.e., to the drains of power lla~ lol~ (FET's) Ql and Q2 in high side isolated power ~wilches 1202 and 1204), through a suitable isolation diode D4.
The high voltage (e.g. 150v) positive rail is selectively coupled to high side terrnin~l 1203 of basic power co..~ ion circuit 910A through a booster circuit 1600. Booster circuit 1600is~ 1l1ially i(lentic~l to high side isolated power swil~hil.g circuits 1202 and 1204, including an FET Q5, and an associated firing circuit. Booster circuit 1600, however, is rc~l)ol~ /e to control signal HIV
(BOOST) from control section 908 (from NAND gate U7C in Figure 11, corresponding to the signal at pin 11 of microcolll~ l 1102). The drain of booster circuit FET Q5 is comlecled to high voltage positive rail 905A. The source of the power transistor is connected through an isolation 2i 99628 WO 96/09679 PC'r/US95111361 diode D3 to the drains of the power ll~~ L-"~ Q1 and Q2 in high side power ~wilcl~ g circuits 1202 and 1204. A reverse polarity flyback diode D6 may be provided if desired.

The auxiliary (BOOST) voltage can also be g.,ll~,.aled without the addition of an auxiliary 5 winding from, for example, the energy gen.,ldted during the output signal dead time. This is accomplished by, an in effect, storing the energy g~.~ldted during the output signal dead time (which olh~;lwise would be wasted) in a capacitor, and controllably dischdl~;illg the capacitor to gellelde the booster pulse. Specifir~lly, rl,f~llhlg briefly to FIGURE 11, a separate control signal (CHARGE) inverted from the HIV (BOOST) control signal, i.e., active during those periods from 10 the trailing edge of a booster pulse (T3) to the leading edge of the booster pulse in the next successive half-cycle. The CHARGE signal is applied to a controlled storage/discharge circuit 1710 which effects cha ghlg and di~clla~gillg of a cal~a~;ilol to generate the booster pulse. Circuit 1710 suitably colll~ es an NPN ll~ulsi~lor Q16, an FET Q6 and a capacitor C19. The CHARGE
control signal is applied to the base of transistor Q16. When the charge signal is activated (e.g., low), FET Q6 is rendered conductive, trre~;~ively co.~.~P~ g capacitor C19 to positive rail 905C.
(The use of the dead time energy to generate the booster pulse permits a lower rail voltage to be employed.) When the HIV (BOOST) control signal is -qrt~lqt~P(l and hence control signal CHARGE
de-~tllqtPcl, FET Q6 is rendered non-conductive, and capacilol C19 additively discharges to the high side tPrminql 1203 of basic power convertor 910A to provide the boost pulse.
As previously mentioned, llliCIOC~....l.u~rl 1102 gen~lales a count (pins 1-4 and 15-18) from which the ramp r~f~,lence signal is generated by D to A col.~ el 1104 and generates ~wi~ g pulses (pins 11-13) to colllbhldlorial logic 1110 from which the ~wilullillg control signals to power conversion section 910 are derived (to control application of the DC rail to output tPrrninqlc L1 and L2 by power conversion section 910). The ~wilcllillg cycle frequency is adjusted in accordance with a co--l~,alison of the indicia of output signal 915 from interface 1108 (pin 8) to the r~rel~llce ratnp (pin 10); and the pulsewidth of ~wilchillg pulses and deq~1timp between pulses) q-~lju~t~Pd in accoldallce with a colll~llison of counts from an internal clock to l~ e.;live control palalllt~ . Power conversion is disabled in response to ovel~;ull~lll or inadequate supply voltage conditions reflected at pin 9.

More specifiç-qlly, referring to FIGURES 11 and llA, miclocu~ uler 1102 -..~i..l;.i...~ a number of internal ~egi~ and cuulll~ an analog to digital count (ATOD); l~ ,e.;li~e internal timers, timer 1 and timer 2; a cycle COUNT (COUNT); ~e~ecli~e re~ lel~ (RVALU and 35 GVALU) for storing indicia of the output voltage, and gate voltage (supply voltage), respectively;

~WO 96/09679 PCr/US95/11361 a count indicative of a half cycle of the output r~ u~ (CPS); a count h.dicalive of the trailing edge (T1 on FIGURE 14) of the jwi~cl.i.lg pulses (PWM) a count (BASE) indicative of the time base of the output frequency; an FET output enable flag (DUMMY); and a register (FETMASK) indicative of-the switch pulse output pattern desired at pins 11-13) h~ uyl enable register (INIT) 5 having a bit co..~,yohdillg to each hll.,lluyl; and r~,.,ye~;liye port register P0 and P2 co~ ,pondillg to pins 11-13 and pins 1-4 and 15-18 l~yec~ ely. In addition, where a stepped output signal is employed, counts indicative of the leading edge (TB) of the step (FIRST) and trailing edge (T4) (SECND) of the step, steps are also defined. If desired, the plocessor may also include an hlltlluyl priority register to df~,sifo,..~ the relative priorities of the ~e.,yecliye interrupt.
Referring to FIGURES 11 and 1 lA-1 lF, mi~;-oco,,,yul~l 1102 suitably effects a these operations through a contin--ol-~ primary loop (simple lact;~ cl~) progl~ll with a pre~letPnninPd number, e.g., 4 of hll~"luyL driven ,ubylOglall~,. The basic loop program implements the operation of D to A
converter 1104. The various other functions are hll~,luy~ driven.
Referring now to FIGURE 1 lB, when power is first applied to mi~roc~ u~, 1102, the various timers, legi:iL~l~i, and ports are init~ 7pd (step 11). After initi~li7~tion~ microc~.,.,yu~tr 1102 suitably effects a continuous primary loop i~.",le .,- .~ g the operation of D to A collv~,Ler 1904, and generation of the l.,f,_,e.lce ramp. D to A coll~ l 1104 in effect, g~,lc,d~es a controlled 20 ramp voltage from 0 to 5 volts. More specifically, A to D count ATOD, is hl~ ed (step 1912), and then tested to dr~ I;IIf. whether a rollover has occurred; count ATOD suitably runs from zero to 256,, then rolls over to zero (step 1914). ~s--mi~ a rollover has not occurred, the ATOD count is loaded to the port P2 coll~yon~ g to pins 1-4 and 15-18 (C~ ed to ATOD
coll~ell~l 1904) (step 1916), and ATOD is again hlcl~ ~..f -.lPd (step 1912 I..pe~te~l). If a rollover 25 occurs, the contents of inl~,lu~.t enable register INIT is mof1ified to enable re~ye~;live hlt~,luyls (step 1918)~ lt;lluyl IRQ0 (the over-current/insufficient supply voltage hll.,lluyt and hll~.~uyt IRQ2 (the output voltage hll~,lluyl). As will be explained, over-current hll."luyl IRQ0 and output voltage illl~,lu~l IRQ2 are y~ d to occur only once per ramp cycle to avoid spurious readings.

The in~ffirj~nt supply voltage level and over current protection function is initiated by inlt;llU~II IRQ0. IRQ0 is g~ ed when the voltage at pin 9 (supply voltage/FET gate voltage and ISEN over current signal) is equal to the reference ramp. Except in over current conditions (when ISEN drives pin 9 to ground, i.e., 0 volts), the count is indicative of the supply voltage (e.g., n-~min~lly 15 volts) applied to the gates of FET's Ql-Q4 of power collvellel 910. Referring to FIGURE 11C, when hl~e~llul~l IRQ0 is generated, the value of count ATOD is averaged with the contPnt~ of register GVALU, and the average loaded into register GVALU to ~ qin indicia of the running average of the supply voltage level (step 1920). A ~ in~ion is then made as to whether or not the GVALU is within legal lirnits, e.g., the supply voltage is at least equal to the ...;..;~..~.. logic high voltage seen by the power lla,~ or gates (step 1922).
s DC~F ~ e upon whether or not the content of GVALU is within legal limits, the FET
enable flag (DUMMY) is either cleared, to disable power cu~ 910 (step 1924) or set to enable power col,~ lor 910 (step 1926). The content of il,l~,l,u~,l enable register (INIT) is then a~ljucted to disable h~ up~ IRQ0 (Step 1928) and a return from the inle.lupt is effected (step 1930). (As previously noted, inle:llupl enable register INIT is set to re-enable h~kl~upl IRQ0 at the begi....il~g of the next ramp cycle (step 1918).

A IIRaSUI~.ll.,lll of the average rectified output voltage is effected in response to h~lellu~t IRQ2, generated each time that the l~f~ ce ramp exceeds the indicia of output voltage provided at pin of microcol"l.ulel 1102. Referring to FIGURE llD, when h,l~",ul,l IRQ2 is g~llelaled, the ATOD count-(ATOD) is added into register RVALU, and the sum divided by two, to generate in register RVALU, count indicative of the running average of the output voltage (step 1932). The input enable register (INIT) is adjusted to disable IRQ2 for the remqin-ler of the ramp cycle (step 1934); hll~llu~l IRQ2 is re-enabled at the be~ g of the next ramp cycle (step 1918). A return 20 from the hll~llul)l is then effected (step 1936).

The state of the s-vilclli"g signals gen~ld~ed at pins 11-13 of miclocolll~uler 1102 is controlled by varying the content of switch control output register (FETMASK). The FET state is varied on a periodic basis in accol.l~lce with the pre-dete~ i..rd frequency reflected by the contents of the first interval timer, timer 1. For example, for an output frequency of 60 hertz, an hll~,llu~l IRQ4 is g~,n~lated, e.g., every 8.2 milli~econ-l~. Referring to FIGURE IIE, when timers 1 hllellu~t, IRQ4, is gen~,laled, FET output enable flag (DUMMY) is tested (step 1938). If the flag in~ tes that the FETs have been disabled, e.g., because of an over current or supply voltage deficiency condition, switch control output register FETMASK is cleared, to turn off (disable) the FETs of power coll~lk, 910 (step 1940), and a return from illlcll~l is effected (step 1942).

A~ ming that the FETs are not disabled, the cycle COUNT (COUNT) is illClCIll~ tod (step 1944) then tested against lc~e~;lh~e p~alnct~l~ to d- t~ illP, and set the ~plopliate state of the power convertor FETs. The cycle COUNT is initially tested against count PWM (step 1946) 35 indicative of the trailing edge of the switch pulse (Tl in FIGURE 13). If the cycle COUNT has ~WO 96/09679 PCr/US95/11361 reached pulse width count PWM, FETs Ql-04 in power convertor 910 are turned off, e.g., the port register (PO COllb~yO~ ;~ to pins 11 through 13 is cleared) (step 1948).

- The cycle COUNT is then tested against count (CPS) i.. di~ of one-half cycle of the 5 output signal frequency (step 1950). If the cycle COUNT has reached half-cycle COUNT CPS, the status of the le~e~ /e pairs of FETs in power convertor 910, i.e., LHRL and RHLL, are ~ (the bits in switch control output register FETMASK are complim~nt~d) (step 1952), and the cont~-nt.c of FETMASK loaded into port register PO COll~ Ol~illg to pins 11 through 13 (step 1954). The cycle COUNT is then cleared (step 1956), and a return from h,l~,.,upl effected (step 10 1958). If the cycle COUNT is less than the half-cycle pal~ll~,te~ CPS, a return from il~L~llu~Jl is effected (step 1958).

If the system is employing the basic power convertor 910 FIGURE 12, and the cycle COUNT is found to be less than the pulse width pa~ t~,l PWM, a return from i,,le,,u~ul is 15 effected. If ho..~,.,., a closer sim~ tiQrl of the sine wave is int.onrl.od i.e., plural steps are provided in the output signal such as illu~ ed in FIGURE 14, e.g., power conversion circuits of figure 16 or 17 are employed, the cycle COUNT is tested against the edges of the high voltage pulse to control generation of the ~wil,_hi,.g signal at pin 11 from which the HIV (BOOST) and CHARGE control signals g~..e.aled. Specifi~lly, the cycle COUNT is initially tested against count 20 SECND co--. i",ol~d,ng to the trailing SECND edge of the high voltage pulse (T4 in FIGURE 14) (step 1960) if the cycle COUNT is greater or equal to trailing edge count SECND, the co.,~ ollding booster circuit is effectively disabled, e.g., the bit in port register PO collci,l,ol~ g to pin 11 is cleared (step 1962) and a return from hllcrl~l effected (step 1964).
If the cycle COUNT is less than trailing count SECND, the cycle COUNT is then tested against the count co--~ u--dillg to the leading edge (T3 in FIGURE 14) of the high voltage pulse (step 1956).

If the cycle COUNT (already dr~ d to be less than at corresponding to trailing edge T4) is greater than or equal to the count (FIRST) co~ ondh,g to the leading edge of high voltage pulse, booster circuit 1600 is enabled, e.g., the bit in port register PO co,-~,onding to pin 11 is set (step 1968) and a return from hll, ~lu~J~ effected (step 1970).

WO 96/09679 PCr/US95/11361 If the cycle COUNT is less than the count co,.ci,~oll~li.lg to the leading edge of the booster pulse, a return from i~ luyl is effected (step 1972). Additional steps are employed in the output signal, intervening tests of the cycle COUNT against the trailing and leading edges of those pulses would suitably be effected between the test against the first step pulse trailing edge (step 1960) and 5 first step pulse leading edge (step 1966).

The frequency, and other pa~ t~,rs of the output signal are adjusted in accold~1ce with the lllf~uled values of output voltage on a periodic basis, suitably every two cycles of the nominal output rr~uellfy~ e.g., 32.256 milli~eco..~s, (ayylo~ tl ly 32.32 milli.ceconfl~ for 60 hertz). In 10 essence, the fi~.lu~"l~ pulse width and dead time p~a,llet~.~ (the time dirr.,re.l-;c between trailing edge T1 and half-cycle point T2) are varied to ~cGo.. -~date transient heavy loads (i.e., motor start-up). In essence, if the output voltage falls below a pre-detenninfd ...i.-i...~.-, the frequency is decreased and output wave shape p~alll~t~l~ adjusted to provide additional power to the load.
Upon generation of periodic hl~flluyl IRQ5, FET output enable flag (DUMMY) is tested (step 1974). If the output is not e.labled, FETs turned offduring (step 1975) and a return from interrupt effected.

mir~ that the FET output is enabled, the output voltage indicia RVALU is tested against a pre~lct.. i.. fd .. i.. i... value collc~yol ding to the voltage detc~ h~ed to be unacceptably low, e.g., 108 volts AC (the UL low voltage figure). (Step 1976) if the output voltage is less than or equal to the ~--i--;---~-- voltage, it is ~c~ lf~d that the unit is encountering an extra-ordinary load, e.g., a culll~ sor motor under start-up conditions. Acco,dillgly, the frequency of the output signal is hlf rc~ lly decl~sed down to a pre-de~e....;..f d minim--m value (e.g., 30 hertz), and output waveform pal~llct~,l varied accordillgly to m~ximi7f~ current to the 25 load.

More ~I~e~-;r.~lly, a count indicative of the time base for the clesign~ted output frequency (during initi~li7~tion to a count (e.g., 4) coll~olldil-g to the desired output frequency, e.g., 60 hertz), is hlclf ..~ .~Pd by one (step 1978) to effectively decrease the output frequency. The 30 frequency is checked against the pre-de~f ...;..~ .. value, (e.g., 30 hertz) and ~ -ming that the frequency is within the acccyl~ble range, the pulse width and dead time are adjusted to reflect the change in frequency, e.g., are adjusted so that ratios are ...~ f'd (step 1982). For example, the count (FIRST) collc~,olldillg to the leading edge of the high voltage pulse is set equal to the adjusted BASE count; the count (SECND) col,es~ol1ding to the trailing edge of the high voltage 35 pulse is then set to five times the leading edge count (FIRST); the count in (PWM) col,c~onding ~WO 96/09679 PCrtUS95/11361 to the trailing edge (T1) of the pedestal pulse is set equal to seven times the BASE count and, the count (CPS) corresponding to the half-cycle is set equal to eight times the adjusted BASE count.
After the output wave form p~UllC~Cl~ are adjusted (step 1982), a return from inl~.~u~ is effected (step 1984).
s As noted above, ...i.~ .. frequency (e.g., 30 hertz) is e~bli:.l,ed. Acco,din~;ly, if r~ P-.~ g the BASE count would cause the r,c.lu~,., ;y to drop below the .. i.-i.. ,.. , the BASE
count is reset to the count co.~ ,onding to that ...;..;..,~.. (step 1986) prior to err~ -g adju~
of the output wave form pala-".,t~.~ (step 1982).
Once the extra-ordir~y load con~lhiQn abates, i.e., the inertia of start-up is ovclco...e, an i-.~;rease in output voltage will be ~-.a. ir~i,led due to the change in output frequency and ~. a~ a~e.
Ab~ is ACC...~.Pd once the ~ncd~u-cd value RVALU reaches a pl.dPt~ d value (e.g., 122 volts). Accordi-,gly, ~ ..ling that the lllc~ulcd value of output voltage RVALU is greater than 15 the ...i"i"...,., voltage (e.g., 108 volts) the ~--~a~u.ed output voltage (RVALU) is tested against the pre-dete min~d ..,~xi,,.,,,.. voltage deemed to indicate recovery from the extra-ordinary load con~ ion (e.g., 122 volts) (step 1988). The frequency is then i,--,.cased on i"~ ,."~ntal basis until it is brought up to the desired output frequency (e.g., 60 hertz).

More spccir,cally, if the .llcdsu,cd output value is greater than pre-d~e~ Pd .. i.. ;.. ~
(e.g., 108 volts), and less than the pre-d~l~." h,ed ".~xi.""", (recovery) voltage, a return from hll~llu~l (step 1984) is effected. (Adjust pa,a."e~ step 1982 is effected, but since the BASE
count is not adjusted, the values do not change.) If, ho~ el, the ",~asu,ed value is greater than the pre~i~ te ".il.~d mq~imllm (recovery) voltage (e.g., 122 volts), the frequency BASE count (BASE) is dec,e."~.lted (step 1990), errt;~;lively hlc,tâsi"g the output frequency. The frequency is then tested against the desired Ç~ue,.~, i.e., the BASE count is tested against a count co"es~ol1di"g to the desired frequency (e.g., 60 hertz) (step 1992). A~ ..i.-g that the frequency is within range, the output wave form 30 palalllC~e~S are adjusted to account for the change in frequency (step 1982) and a return from illl~.lU~Jl effected (step 1984). If dcc,~ illg causes the BASE count to co"esl,ond to a frequency greater than a desired frequency, the BASE count is set to that co,~ ,ollding to the desired frequency (step 1994) prior to ~rrecli,lg the adjusting palaulelel~ (step 1982).

- 219~628 Wo 96l09679 Pcrlussslll36 As previously noted, since the speed of engine 12 can be lowered without reducing r~ u~ncy, engine 12 can be throttled back, or made to idle under chu~ res where if only a fraction of the system capacity is being drawn. Referring briefly to FIGURE 11, mic.oco...l.ul~ ~
1102 suitably gen~,lates at pin 15 a control signal for a load dernand governor. When the signal 5 at pin 15 is high, 1~ si~lo, Q12 is rendered conductive, ~-lu~;.,g an ele~ o...~..- ~ic go~elllor coup~La~ g with the throttle of engine 12. Referring to FIGURES 18A and 18B throttle control signal GOV is suitably g~.le.dt~d, as a r.~ , ;on of the average load output voltage (e.g., RVALU).
In steady state (FIGURE 18A), the engine is suitably throttled back. However, when the output voltage decreases the pre clct~ ...;..~ value, the governor signal is g~ .dt~ d to throttle-up, and 10 increase the RPM of engine 12. A particularly advantageous load demand governor control co ~-~,is~s a c~li"~l.;r~l magnet 1800, mq~gn~ti7Pd through the length, suitably formed of Alnico, coope.à~ g with a non-magn~tiC push rod 1802, for example, formed of nylon, and a winding 1801 wound around a suitable core, e.g., formed of cast nylon. Push rod 1802 coop~làles with throttle lever arm 1803. A spring 1806 biases throttle arm 1803 into an idle position.
When the signal at pin 15 is g~ .ated, and l,~i~lor Q12 rendered con~ ctive, a current path is formed through winding 1801 causing magn~ti~ interaction with cylin~lrirql magnet 1800.
The mqgn~tic interaction between coil 1801 and magnet 1800, causes magnet 1800 to move for~,vard (FIGURE 18B) against the bias of spring 1806, throttling up (i...;.easi..g the RPM) of 20 engine 12.

The control signal g~ .aIed at pin 15 of mic.oco...~,~le. 1102 is suitably pulse-width mocllllqtlo~ The wider the pulse width, the more power to coil 1801, and conro...ilit..lly, the greater the ...ov~",~.,l of magnet 18, push rod 1802, and throttle arm 1803. If desired, a fly-back diode 1804 can be provided across coil 1801.

In some i~ res, weight and size advantages can be obtained by employing an external rotor disposed to rotate around the pc.i"~cl~r of an int~rnqlly disposed stator. Referring to FIGURES l9(a) and l9(b) an external rotor suitably 1100 comprises a cylindrical casing 1102 30 formed of soft m~nrtir material, having an internal cavity 1104. Altern~ing permanent magnets 802 and con~e~uenre poles 1106 are disposed in the interior side wall of casing 1102. If desired, ,e~ e fins (fan blades) 1108 can be formed on the exterior side walls of cup 1102, to facilitate cooling. Likewise, the top of cup 1102 is sul.~ lly open, including ~~ e~ e cross-arms 1110 and a central hub 1112 to provide for connection to motor shaft 200. If desired, cross arms 1110 35 can also be configured as fan blades, to facilitate cooling interior ch~u--bel 1104.

2 1 9'~628 ~WO 96/09679 PCr/US95111361 A stator 1114 suitably co~ g a l~min~te core 1116, and ~ ,e~ /e Whl~ lg:~ 1118.
Windings 1118 are suitably the type previously desclibed. Core 1116 inrlu-les a central axial through-bore.

5Stator 1114 is secured to engine 202 by a mount 1122. Mount 1122 inr.lyd~s a central axial stem, 1124, with an internal bore 1126.

In assembly, mount 1122 is bolted to engine 202 with engine shaft 200 journaled through bore 1126. Bore 1126 is so..-~..lld~ larger in ~ t~ ~ than is motor shaft 200, so that motor shaft 10200 can rotate freely therein. Stator 1114 is ~ ,os~ on mount 1122, with stem 1124 received in central bore 1322 of stator 1114. Stem 1124 suitably effects an i.ltelr~"elIce fit with bore 1322 hough, adhesive can also be used, if desired.

Rotor 1100 is disposed over stator 1114 and fastened to engine shaft 200. Stator 1114 is 15received within the interior of cavity 1104. Hub 1112 includes a central bore 1128 disposed in registry with a threaded axial bore 1130 in motor shaft 200. A bolt 1302 is received through bore 1128 and ~ng~gC-d in threaded bore 1130 to fasten rotary 1100 to shaft 200 for rotation lI.erewil}-.

FYtlqrn~l rotor 1100 and internal stator 1114 provide for a particularly compact gel~ldlOI
20unit. In some i~ s, the entire assembly can be disposed in the fly-wheel and m~nl~to area of a small engine, such that g~ ,la~Ol is provided with no parent external co,..l on~.l.l~. In ~ 1iti~
the assembly can be i.lcollJolded into a pull cable starter. As shown in FIGURE l9(a), a pull cable assembly and suitably inrln~ing a ratchet and overriding spring-type clutch and pulley 1328, is secured to, and in axial ~lignm~nt with rotor 1100, over hub 1112. When the rope is pulled, 25 and pulley rotated, ccnrc....;~ rotation of rotor 1100 is effected.

It will be understood that while various of the conductors and connections are shown in the drawing as single lines, they are not so shown in a limiting sense, and may comprise plural co~ ions or cQl-..~r~ as understood in the art. Similarly, various power connections and 30 various control lines and the like various c~ had been omitted from the drawing for the sake of clarity. Further, the above description is of p.ef~l.ed exemplary emb~l1imrntc of the invention, and the invention is not limited to the specific forms shown. Modifications may be made in the design and alldn6~ nl of the el~mPnt~ in the scope of the invention, as e~plessed in the claims.

Claims (107)

In the Claims:

1. A machine comprising a stator and a rotor, the stator including at least one winding, and the rotor comprising a body of soft-magnetic material with a plurality of permanent magnets in a surface disposed proximate to the stator, separated from the stator by a predetermined gap distance, such that relative motion of the rotor and stator causes magnetic flux from the magnets to interact with and induce current in the stator winding, wherein the permanent magnets are high energy product magnets with a predetermined surface area, and the magnets are mounted in insets formed in the rotor surface proximate to the stator, the rotor surface proximate to the stator includes portions between the insets to form respective consequence poles, each consequence pole having a predetermined surface area, and the magnets are disposed within the insets, separated from adjacent consequence poles by a predetermined distance, improved wherein:
the surface area of the permanent magnets proximate to the stator is greater than the surface area of the consequence poles proximate to the stator.

2. The machine of claim 1 wherein the surface area of the permanent magnets proximate to the stator is greater than the surface area of the consequence poles proximate to the stator by the ratio of the flux density produced by the permanent magnet to the allowed flux density of the consequence pole.

3. The machine of claim 1 wherein the magnets have a flux density of at least on the order 5 kilogauss.

4. The machine of claim 1 wherein:
the insets are symmetrically disposed in the rotor surface proximate to the stator;
the consequence poles are symmetrically disposed in the rotor surface proximate to the stator;
the magnets are centrally disposed within the insets.

5. The machine of claim 1 wherein the distance separating the magnets from the consequence poles is greater than the distance separating the rotor surface from the stator.

6. The machine of claim 5 wherein the distance separating the magnets from the consequence poles is at least five times greater than the distance separating the rotor surface from the stator.

7. The machine of claim 1 further comprising an engine to rotate the rotor.

8. The machine of claim 1 wherein the stator is generally annular with a central aperture and the rotor is concentrically disposed for rotation within the aperture.

9. The machine of claim 1 wherein the rotor comprises a hollow cylinder with the magnets mounted on an internal surface of the cylinder. and the stator is concentrically disposed within the cylinder.

10. The machine of claim 9 wherein the stator includes a central aperture, and the rotor is adapted for mounting on a shaft journaled through the stator central aperture.

11. The machine of claim 1 wherein the stator includes a plurality of windings.

12. The machine of claim 1 wherein the stator includes a first winding for generating a relatively high voltage low amperage signal and a second winding for generating a relatively low voltage high amperage signal.

13. The machine of claim 1 wherein the stator includes:
a soft magnetic core;
a first 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a first predetermined voltage output; and a second 3-phase star winding, each phase of the second winding including a predetermined number of turns corresponding to a second predetermined voltage output;
the corresponding phases of the respective 3-phase windings grouped together as a unit and wound about the core such that the corresponding phases of the respective 3-phase windings coils are wound in continuous thermal contact with each other.

14. The machine of claim 13 wherein the first predetermined output voltage is on the order of 110 volts, and the second predetermined output voltage is on the order of 12 volts.

15. The machine of claim 13 wherein each phase of at least one winding includesa first portion defined by a tap to provide a third predetermined voltage output.

16. The machine of claim 15 further comprising:
a switch, for selectively effecting a connection to one of the second or third predetermined voltage outputs: and a rectification circuit, receptive of signals from the switch for generating DC signals.

17. The machine of claim 15 wherein the first predetermined output voltage is on the order of 110 volts, the second predetermined output voltage is on the order of 24 volts, and the third predetermined output voltage is on the order of 12 volts.

18. The machine of claim 1 further comprising a rectification circuit. responsive to signals from the stator winding, for generating DC signals.

19. The machine of claim 18 wherein the machine includes respective output terminals; and means for disabling the rectification circuit in response to a reverse polarity voltage in excess of a pre-determined level, across the output terminals.

20. The machine of claim 19 wherein the machine further includes:
means for enabling the rectification circuit in response to voltage in excess of a pre-determined level, across the output terminals.

21. The machine of claim 12 further comprising:
a first rectification circuit, responsive to signals from the first stator winding, for generating a relatively high voltage low amperage DC signal; and a second rectification circuit, responsive to signals from the second stator winding, for generating a relatively low voltage high amperage DC signal.

22. The machine of claim 21 wherein:
the second winding includes a first portion defined by a tap to provide a third predetermined voltage output;
and the machine further comprises:
a switch, for selectively effecting a connection between the second rectification circuit and one of the second or third predetermined voltage outputs.

23. The machine of claim 18 wherein:
said rotor, stator, and rectification circuit, are disposed within a housing;
the housing is formed at least in part of electrically and thermally conductive material;
the rectification circuit includes heat generating components connected to ground potential;

at least one of the rectification circuit components being electrically and thermally connected to the housing, such that the housing serves as a heat sink for the components and electrical ground for the ratification circuit.

24. The machine of claim 18 wherein:
the machine further includes a fan mounted for rotation with the rotor;
said rotor, stator, rectification circuit, and fan are disposed within a housing, rotation of the fan creating a positive pressure within the housing;
the rectification circuit includes heat generating components; and the housing includes respective apertures disposed in predetermined position relative to the heat generating components, creating an air flow over the components through the apertures to cool the components.

25. The machine of claim 18 further comprising an invertor, responsive to the DC signal, for generating an AC signal.

26. The machine of claim 25 wherein the invertor comprises a variable frequency invertor, responsive to indicia of the current drawn from the invertor, for generating an AC signal having a frequency in accordance with the current drawn.

27. The machine of claim 25 wherein the invertor comprises a variable frequency invertor, responsive to indicia of the DC voltage level, for generating an AC signal having a frequency in accordance with the DC voltage.

28. The machine of claim 1 configured as a generator for generating a predetermined power output, wherein the ratio of the power output to the weight of the rotor is greater than 150 watts per pound.

29. The machine of claim 1 configured as a generator for generating a predetermined power output, wherein the ratio of the power output to the weight of the rotor is greater than 200 watts per pound.

30. The machine of claim 1 configured as a generator for generating a predetermined power output, wherein the ratio of the power output to the weight of the rotor is greater than 500 watts per pound.

31. The machine of claim 1 configured as a generator for generating a predetermined power output, wherein the ratio of the power output to the weight d the rotor is greater than 700 watts per pound.

32. The machine of claim 1 configured as a generator for generating a predetermined power output, wherein the ratio of the power output to the weight of the rotor is greater than 800 watts per pound.

33. A generator for generating a predetermined power output, comprising a rotor and a stator including a stator winding, wherein:
the rotor comprises a body of soft-magnetic material with a plurality d permanent magnets in a surface disposed proximate to the stator, separated from the stator by a predetermined gap distance, such that relative motion of the rotor and stator causes magnetic flux from the magnets to interact with and induce current in the stator winding;
the ratio of the power output to the weight of the rotor is greater than 150 watts per pound;
and the stator includes:
a soft-magnetic core;
a first 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a first predetermined voltage output; and a second 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a second predetermined voltage output;
the corresponding phases of the respective 3-phase windings grouped together as a unit and wound about the core such that the corresponding phases of the respective 3-phase windings are in continuous thermal contact with each other.

34. The generator of claim 33 wherein the first predetermined output voltage is on the order of 110 volts, and the second predetermined output voltage is on the order of 12 volts.

35. The generator of claim 33 wherein each phase of at least one winding includes a first portion defined By a tap to provide a third predetermined voltage output.

36. The generator of claim 35 further comprising:
a switch, for selectively effecting a connection to one of the second or third predetermined voltage outputs; and a rectification circuit, receptive of signals from the switch for generating DC signals.

37. The generator of claim 35 wherein the first predetermined output voltage is on the order of 110 volts, the second predetermined output voltage is on the order of 24 volts, the third predetermined output voltage is on the order of 12 volts.

38. The generator of claim 33 further comprising a rectifier, responsive to the first predetermined voltage output signal, and an invertor cooperating with the rectifier, for generating an AC signal.

39. The generator of claim 38 wherein the invertor comprises a variable frequency invertor, responsive to indicia d current drawn from the invertor, for generating an AC signal having a frequency in accordance with the current drawn.

40. The generator of claim 38 wherein the invertor comprises a variable frequency invertor, responsive to indicia of the rectifier output signal, for generating an AC signal having a frequency in accordance with the voltage of the rectifier output signal.

41. A generator for generating an AC signal to a load, the generator comprising: a stator including at least one winding, a rotor disposed relative to the stator such that relative motion of the rotor and stator causes magnetic flux from the rotor to interact with and induce current in the stator winding, a rectifier circuit, responsive to current in the stator winding, for generating a DC signal;
and a variable frequency invertor, responsive to the DC signal and a control signal indicative of current drawn by the load, for generating the AC signal, the frequency of the AC signal being selectively varied in accordance with current drawn by the load.

42. The generator of claim 41 wherein the control signal indicative of current drawn by the load comprises indicia of the voltage level of the DC signal.

43. A generator comprising a stator including at least one winding, and a rotor disposed relative to the stator such that relative motion of the rotor and stator causes magnetic flux from the rotor to interact with and induce current in the stator winding, improved wherein the stator comprises:
a soft-magnetic core;

a first winding, including a predetermined number of turns corresponding to a first predetermined voltage output; and a second winding, including a predetermined number of turns corresponding to a second predetermined voltage output;
the respective windings being grouped together as a unit and wound about the core such that the respective winding coils are wound in continuous close thermal contact with each other.

44. The generator of claim 43 wherein:
the rotor comprises a body of soft-magnetic material with a plurality of permanent magnets in a surface disposed proximate to the stator.

45. The generator of claim 44 wherein the magnets are high energy product magnets.

46. The generator of claim 44 wherein:
the magnets have a predetermined surface area;
the magnets are mounted in insets formed in the rotor surface proximate to the stator;
the rotor surface proximate to the stator includes portions between the insets to form respective consequence poles each consequence pole having a predetermined surface area;
the magnets are disposed within the insets separated from adjacent consequence poles by a predetermined distance; and the surface area of the magnets is proximate the stator greater than the surface area of the consequence poles proximate the stator.

47. The generator of claim 44 wherein the surface area of the permanent magnets proximate the stator is greater than the surface area of the consequence poles proximate the stator by the ratio of the flux density produced by the permanent magnet to the allowed flux density of the consequence pole.

48. The generator of claim 47 wherein the magnets have a flux density of at least on the order 5 kilogauss.

49. The generator of claim 46 wherein:

the insets are symmetrically disposed in the rotor surface proximate to the stator;

the consequence poles are symmetrically disposed in the rotor surface proximate to the stator;
the magnets are centrally disposed within the insets.

50. The generator of claim 46 wherein the distance separating the magnets from the consequence poles is greater than the distance separating the rotor surface from the stator.

51. The generator of claim 50 wherein the distance separating the magnets from the consequence poles is at least five times greater than the distance separating the rotor surface from the stator.

52. The generator of claim 43 wherein:
the first winding is a 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to the first predetermined voltage output; and the second winding is a 3-phase star winding, each phase of the second winding including a predetermined number of turns corresponding to the second predetermined voltage output;
the corresponding phases of the respective 3-phase windings being grouped together as a unit and wound about the core such that the corresponding phases of the respective 3-phase windings are in thermal contact with each other.

53. The generator of claim 52 wherein the first predetermined output voltage is on the order of 110 volts, and the second predetermined output voltage is on the order of 12 volts.

54. The generator of claim 52 wherein each phase of at least one winding includes a first portion defined by a tap to provide a third predetermined voltage output.

55. The generator of claim 54 further comprising:

a switch, for selectively effecting a connection to one of the second or third predetermined voltage outputs; and a rectification circuit, receptive of signals from the switch for generating DC signals.

56. The generator of claim 54 wherein the first predetermined output voltage is on the order of 110 volts, the second predetermined output voltage is on the order of 24 volts, the third predetermined output voltage is on the order of 12 volts.

57. A generator comprising a stator and a rotor, the stator including at least one winding, and the rotor comprising a body of soft-magnetic material with a plurality of permanent magnets in a surface disposed proximate to the stator, separated from the stator by a predetermined gap distance, such that relative motion of the rotor and stator causes magnetic flux from the magnets to interact with and induce current in the stator winding, improved wherein:
the rotor comprises a hollow cylinder with the magnets mounted on the internal surface of the cylinder;
the stator is concentrically disposed within the cylinder; and the rotor is mounted for rotation about the stator.

58. The generator of claim 57 wherein:
the magnets are high energy product magnets with a predetermined surface area;
the magnets are mounted in insets formed in the internal surface of the cylinder;
the internal surface of the cylinder includes portions between the insets to form respective consequence poles, each consequence pole having a predetermined surface area;
the magnets are disposed within the insets, separated from adjacent consequence poles by a predetermined distance; and the surface area of the permanent magnets is greater than the surface area of the consequence poles.

59. The generator of claim 57 wherein the stator includes a central aperture, and the rotor is adapted for mounting on a shaft journaled through the stator central aperture.

60. The generator of claim 57 wherein the stator includes a plurality of windings.

61. The generator of claim 57 wherein the stator includes a first winding for generating a relatively high voltage low amperage signal and a second winding for generating a relatively low voltage high amperage signal.

62. The generator of claim 57 wherein the stator includes:

a soft-magnetic core;
a first 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a first predetermined voltage output;
a second 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a second predetermined voltage output;
the corresponding phases of the respective 3-phase windings grouped together as a unit and wound about the core such that the corresponding phases of the respective 3-phase windings are in thermal contact with each other.

63. The generator of claim 62 wherein each phase of at least one winding includes a first portion defined by a tap to provide a third predetermined voltage output.

64. The generator of claim 57 further comprising a rectification circuit, responsive to signals from the stator winding, for generating DC signals.

65. The generator of claim 64 wherein:
the generator further includes a fan mounted for rotation with the rotor;
said rotor, stator, rectification circuit, and fan are creating a positive pressure within the housing;
the rectification circuit includes heat generating components; and the housing includes respective apertures disposed in predetermined position relative to the heat generating components, creating an air flow over the components through the apertures to cool the components.

66. The generator of claim 65 wherein the fan comprises fan blades disposed on the exterior of the cylinder.

67. The generator of claim 57 wherein the rotor further includes fan blades disposed on the exterior of the cylinder.

68. A method for extending the operating capability of an AC generator, comprising the steps of generating a DC signal;
applying the DC signal to a variable frequency invertor to generate an AC signal;

generating a control signal to the invertor to vary the frequency of the AC signal in accordance with current drawn from the generator, to thereby accommodate extraordinary transient demands from loads.

69. A light weight portable genset comprising:
an engine with a rotatable output shaft;
a generator, comprising a rotor and a stator;
the stator including at least one winding and a central aperture, the stator being fixedly mounted concentric with the engine shaft;
the rotor comprising a body of soft-magnetic material with a plurality of permanent magnets, each having a predetermined surface area, mounted in insets formed in a surface of the rotor disposed proximate to the stator, separated from the stator by a predetermined gap distance, such that relative motion of the rotor and stator causes magnetic flux from the magnets to interact with and induce current in the stator winding, the rotor surface proximate to the stator induces portions between the insets to form respective consequence poles, each consequence pole having a predetermined surface area:
the surface area of the magnets being greater than the surface area of the consequence poles;
the rotor being mounted on the engine shaft sufficiently close coupled to the engine that the predetermined gap distance between rotor and stator is maintained during rotation of the rotor without bearings external to the engine.

70. The generator of claim 69, wherein the stator includes a plurality of windings.

71. The generator of claim 69, wherein the stator includes a first winding for generating a relatively high voltage low amperage signal and a second winding for generating a relatively low voltage high amperage signal.

72. The generator of claim 69, wherein the stator includes:
a soft-magnetic core;
a first 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a first predetermined voltage output; and a second 3-phase star winding, each phase of the first winding including a predetermined number of turns corresponding to a second predetermined voltage output;

the corresponding phases of the respective 3-phase windings grouped together as a unit and wound about the core such that the corresponding phases of the respective 3-phase windings are in thermal contact with each other.

73. The generator of claim 72 wherein the first predetermined output voltage is on the order of 110 volts, and the second predetermined output voltage is on the order d 12 volts.

74. The generator of claim 72 wherein each phase of at least one winding includes a first portion defined by a tap to provide a third predetermined voltage output.

75. The generator of claim 74 further comprising:
a switch, for selectively effecting a connection to one of the second or third predetermined voltage outputs; and a rectification circuit, receptive of signals from the switch for generating DC signals.

76. The generator of claim 74 wherein the first predetermined output voltage is on the order of 110 volts, the second predetermined output voltage is on the order of 24 volts, the third predetermined output voltage is on the order of 12 volts.

77. The generator of claim 69, further comprising a rectification circuit, responsive to signals from the stator winding, for generating DC signals.

78. The generator of claim 77 wherein:
said rotor, stator, and rectification circuit, are disposed within a housing; the housing is formed at least in part of electrically and thermally conductive material;
the ratification circuit includes heat generating components connected to ground potential;
at least one of the rectification circuit components being electrically and thermally connected to the housing, such that the housing serves as a heat sink for the components and electrical ground for the rectification circuit.
the rectification circuit includes heat generating components connected to ground potential;
at least one of the recertification circuit components being electrically and thermally connected to the housing such that the housing serves as a heat sink for the components and electrical ground for the recertification circuit.

79. The generator of claim 77 wherein:
the generator further includes a fan mounted for rotation with the rotor;

said rotor, stator, rectification circuit, and fan are disposed within a housing, rotation d the fan creating a positive pressure within the housing;
the rectification circuit induces heat generating components; and the housing includes respective apertures disposed in predetermined position relative to the heat generating components, creating an air flow over the components through the apertures to cool the components.

80. The generator of claim 77 further comprising an invertor. responsive to the DC signal, for generating an AC signal.

81. The generator of claim 80 wherein the invertor comprises a variable frequency invertor, responsive to indicia of current drawn from the invertor, for generating an AC signal having a frequency in accordance with the current drawn.

82. The generator of claim 80 wherein the invertor comprises a variable frequency invertor, responsive to indicia of the DC voltage level, for generating an AC signal having a frequency in accordance with the DC voltage.

83. The light weight portable genset of claim 69, further including a connection mechanism for a carrying strap.

84. The light weight portable genset of claim 69, wherein the permanent magnets are high energy product magnets.

85. The light weight portable genset of claim 69, wherein:
the magnets are disposed separated from adjacent consequence poles by a predetermined distance greater than the distance separating the rotor surface from the stator.

86. The light weight portable genset of claim 85 further including:
a mounting frame having a foot portion and a transverse portion with first and second opposing sides:
an aperture formed in the frame transverse portion; and wherein: the engine is mounted on one side of the frame transverse portion overlying the foot, with the engine shaft extending through the aperture; and the stator is mounted on the opposite side of the transverse portion concentric with the engine shaft;
and the rotor is mounted on the shaft laterally aligned with the stator.

87. The light weight portable genset of claim 86 wherein the mounting frame is formed of a single sheet of material.

88. The light weight portable genset of claim 86 wherein the mounting frame includes a handle portion.

89. The light weight portable genset of claim 89 wherein the handle portion is adapted for connection to a shoulder strap.

90. The light weight portable genset of claim 86 wherein the mounting frame is adapted for connection to a carrying strap.

91. The light weight portable genset of claim 86 wherein:
the stator is generally annular with a central cavity; and the rotor is coaxially disposed within the cavity.

92. The light weight portable genset of claim 86 wherein:
the stator is generally cylindrical with a central axial bore;
the engine shaft extends through the bore;
the rotor includes a generally cylindrical central axial cavity and a hub; and the rotor is mounted to the engine shaft at the hub, with the stator coaxially disposed inside the rotor cavity.

93. The light weight portable genset of claim 69, further including: a mounting frame having a foot portion and a transverse portion with first and second opposing sides;
an aperture formed in the frame transverse portion; and wherein:
the engine is mounted on one side d the frame transverse portion overlying the foot, with the engine shaft extending through the aperture; and the stator is mounted on the opposite side of the transverse portion concentric with the engine shaft; and the rotor is mounted on the shaft laterally aligned with the stator.

94. The light weight portable genset of claim 93 wherein the permanent magnets are high energy product magnets.

95. The light weight portable genset of claim 93 wherein the mounting frame is formed of a single sheet of material.

96. The light weight portable genset of claim 93 wherein the mounting frame includes a handle portion.

97. The light weight portable genset of claim 96 wherein the handle portion is adapted for connection to a shoulder strap.

98. The light weight portable genset of claim 93 wherein the mounting frame is adapted for connection to a carrying strap.

99. The light weight portable genset of claim 93 wherein:
the stator is generally annular with a central cavity; and the rotor is coaxially disposed within the cavity.

100. The light weight portable genset of claim 93 wherein:
the stator is generally cylindrical with a central axial bore;
the engine shaft extends through the bore;
the rotor includes a generally cylindrical central axial cavity and a hub; and the rotor is mounted to the engine shaft at the hub, with the stator coaxially disposed inside the rotor cavity.

101. A compact generator, comprising:
an internal stator, comprising:
a core with respective windings; and a central axial throughbore within the core;
an external rotor disposed to rotate around the perimeter of the stator, the rotor comprising:

a cylindrical casing formed of soft-magnetic material, the casing having an internal cavity and an internal side wall; and a plurality of alternating permanent magnets and consequence poles, disposed in the interior side wall of the casing;
an engine mount having a central axial stem with an internal bore, wherein the stator is disposed on the mount with the central axial stem received the central axial throughbore so that the central axial stem effects an interference m with the central axial throughbore;an engine shaft journaled the internal bore, wherein the internal bore is somewhat larger in diameter than the engine shaft, so that the engine shaft is rotatable therein, and wherein the rotor is fastened to the engine shaft.

102. The compact generator of claim 101, further comprising fins formed on exterior side walls of the rotor casing to facilitate cooling.

103. A genset for generating an output signal to a load, the generator comprising:
an engine with a rotatable output shaft, the engine rotating the shaft at a rotational speed in accordance with a throttle control;generator, comprising a rotor and a stator, with the rotor disposed relative to the stator such that relative motion of the rotor and stator causes magnetic flux from the rotor to interact with and induce current in the stator winding, a rectifier circuit, responsive to signals from the stator winding, for generating a DC
signal; a invertor, responsive to the DC signal, for generating an output signal of predermined frequency; and a governor for selectively controlling the engine throttle in accordance with the genset output signal.

104. The genset of claim 103 wherein the governor comprises:
a sensor for generating indicia of load demand;
means for selectively generating a throttle control signal; and an electromagnetic actuator mechanically coupled to the engine throttle, and responsive to the throttle control signal, for selectively varying the setting d the throttle.

105. The genset of claim 104 wherein the electromagnetic actuator comprises:
a cylindrical magnet, magnetized through its length;
a non-magnetic push rod cooperating with the cylindrical magnet and the engine throttle;
an actuator winding wound around the push rod;

wherein the throttle control signal is selectively applied to the actuator winding to generate a magnetic interaction between the winding and the magnet and cause movement of the magnet and pushrod to vary the setting d the throttle.

106. The genset of claim 105 wherein the throttle control signal is pulse width modulated and the width of the pulse determines the power of the electrical signal supplied to the winding.

107. The genset of claim 105, further comprising a fly-back diode provided across the winding.