US3029363A - Ballast and system for gaseous discharge lamps - Google Patents

Description

April 10, 1962.

L. MAUERER LINE INPUT FIG. I

LINE INPUT I FIG. 2

INVENTORI LEOPOLD MAUERER ATTORNEYS! 3,029,363 BALLAST AND SYSTEM FQR GASEOUS DISCHARGE LAMPS Leopold Mauerer, Qconomowoc, Wis, assignor to Jefferson Electric Company, a corporation of Delaware Filed Aug. 11, 1958, Ser. No. 754,495 5 Claims. (Cl. 315-232) This invention relates to improvements in ballasts for lamps of the gaseous discharge positive column type and to systems including same.

it is an object of this invention to provide a lamp ballast which is more economical to produce, utilizes less material, and is of smaller size with lower losses, than the conventional lead-lag ballast.

The invention is particularly applicable to that type of lamp known as the instant-start lamp.

Considerations of cost make it desirable to provide a ballast utilizing the minimum amount of copper and of iron; in other words, the number of turns utilized in the ballast windings is desirably kept to a minimum. As a result, it is desirable to provide a transformer, either of the insulated or autotransformer type, in which the secondary has as few turns as possible. The minimum number of turns, insofar as operating conditions are concerned, is determined by a certain ballasting ratio, this ratio being the ratio of the open circuit voltage induced in the transformer secondary to the voltage drop across the lamps. The difference between these voltages represents the voltage drop due to the reactance, or other impedance which provides the desired ballasting action. For instance, in a system embodying two 96Tl2 lamps connected in series, each of which has a normal operating voltage of 196 volts, it has been found that to secure a steady operation, there must be sufficient ballast in the circuit as to require an induced voltage of approxi-.

mately 600 volts.

However, each of these lamps requires a starting voltage of 625 volts, with the result that when two lamps are connected in series circuit, a total of 1250 volts must. be applied thereto. Thus, unless some special means areprovided to apply the required starting voltage, the size of the ballast will be primarily determined by the starting voltage, and not by the ballasting ratio.

The present invention provides a means whereby the proper starting voltage may be applied to the lamps without the necessity of increasing the number of turns in the transformers beyond that which is dictated by the ballasting ratio.

According to my invention, I provide a shunt circuit across the. lamp load, which shunt circuit includes a reactance or". the opposite type from the reactance utilized for ballasting. For instance, the ballasting reactance may he inductive reactance due to leakage in the transformer. In such an event the reactance of the shunt circuit will be a capacitive reactance.

in order to keep the size of the condenser, which provides the capacitive reactance, as small as possible, the condenser is tuned to the third harmonic of the input frequency, and the size of the condenser is such that the voltage drop across the same will be equal to or greater than the required starting voltage.

After the lamps have been ignited the power supplied by the third harmonic is relatively small; hence, there will be only negligible power loss during operating conditions due to the third harmonic current.

Furthermore, since the condenser is tuned to the third harmonic, its impedance at the fundamental frequency will be three times as great as its impedance at the third harmonic frequency with the result that very little current of the fundamental frequency will flow through the condenser.

ire Staes ice If desired the condenser may be tuned to higher bar I With reference now to the drawings in which like reference numerals designate like parts:

FIG. 1 is a diagram illustrating an embodiment of my invention and HG. 2 is a similar diagram showing a modified form thereof.

In FIG. 1 the reference numeral ll) indicates generally a leakage reactance transformer having a primary winding 11 and a secondary 12, both of which are mounted on a suitable core 13. The windings are preferably connected in autotransformer relationship for reasons of economy, although the invention is equally applicable to an insulated type transformer. The windings are suitably spaced from each other to provide the desired leakage reactance, and a magnetic shunt 14 may be employed Where necessary. Two fluorescent lamps '15 are connected in series across the secondary terminals 16. Also, a condenser 17 is shunted across the terminals 16.

During operating conditions, the voltage applied by the secondary to the lamps 15 is suficient to keep them in operation, and the reactance inherent in the transformer design provides the desired ballasting effect. Only a small proportion of the current flows in the shunt circuit through condenser17.

Under starting conditions, that is, when the primary circuit is initially closed and before an arc has struclc across the lamps, the'voltage induced by the secondary I is not sufi'icient to ignite the lamps, since in this particular mately three times the operating voltage. For this reason, the condenser 17 is shunted across the terminals 16 and the size of the condenser is such that the impedanceoflered thereby at the third harmonic of the frequency applied to the primary 11, will cause a voltage drop across the condenser and across the lamps which is sufiicient to start the same.

It will be understood that the primary 11 is to-be connected to a standard commercial power source or the like. only a fundamental 60 cycle current, but also harmonic currents of lesser magnitude. Using high magnetic density in the ballast primary circuit increases the third and other harmonics.

In,the modification shown in FIG. 2, the transformer- 20' is an autotransformer having a primary Winding 21 and a secondary winding 22, together with a suitable core, not shown. Here the windings may be closely coupled and a separate reactance 23 may be provided. In other respects this embodiment is substantially the same as that shown in FIG. 1, there being two lamps 15 connected in series across the output terminals 16 of the transformer, and the condenser 17 is also connected acrossthe terminals 16. In both embodiments, a low value impedance 24 may be connected in the lamp circuit, between one of the lamps 15 and one of the terminals '16. This impedance can either be a resistance or a reactance, and serves to reduce any current distortion occasioned by the condenser 17.

In operation, the PEG. 2 embodiment is substantially the same as the FIG. 1 embodiment.

It will be seen, therefore, that I have shown and described herein a means by which a starting voltage, substantially higher than the open circuit voltage of the transformer output, can be applied to a fluorescent lamp The current of such a power source includes not" By approaeeaees 3 priate modification of the circuit elements, the invention can be applied to loads of varying sizes.

As a specific example, referring to FIG. 1, the leakage reactance transformer has a turn ratio of 4.1 to l. and a leakage reactance of approximately 2.85 henries. When the primary is connected to 118 volt line, the transformer will induce an open circuit voltage of 600 volts. During the lamp operation, the transformer delivers 388 volts to the lamps at .425 ampere.

The lamps are 96-T12 instant start lamps having a resistance during operation of approximately 456 ohms each, making a total resistance of 912 ohms. During operating conditions the voltage drop in each lamp is approximately 194 volts, making a total resistive voltage drop of 388 volts.

The condenser 17 has a capacity of approximately .273 microfarad.

The resistance and other resistive losses of the circuit including the transformer 10 and the condenser 17, referred to herein as the resonant circuit, is 60 ohms.

Under these conditions it will be seen that at the frequency of the third harmonic, 180 cycles, the impedance of the reactance 23 will be approximately 3220 ohms, and the impedance of the condenser will be approximately 3220 ohms.

Under starting conditions, that is, before the lamps have been ignited, the current in the resonant circuit which includes the condenser 17 is .500 amp., and the voltage drop across the terminals 16 is approximately 1600 volts. This is considerably in excess of the starting voltage of 625 volts for each lamp with result that the lamps will ignite immediately.

The impedance of the condenser alone does not govern the voltage developed thereacross, the voltage depends upon the current flowing therethrough, as well as the impedance thereof. The current through the condenser depends upon the total impedance of the series circuit which, at resonance, is the ohmic resistance of the circuit; the general formula being where e=the voltage across the condenser, E=the open circuit voltage of the transformer, Xc=the reactance of the condenser, and z=the impedance of the circuit. In other words, the voltage drop across said condenser is determined by the open circuit voltage of said high reactance transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit at resonance.

This application is a continuation-in-part of my earlier application Serial No. 269,163 filed January 31, 1952, now abandoned.

Although I have shown and described herein only preferred embodiments of my invention, it will be apparent that various modifications and changes may be made therein without departing from the spirit of my invention as defined in the appended claims.

I claim:

1. In combination, a source of alternating current, a high reactance transformer having a primary and a secondary, a lamp load of the gaseous discharge positive column type, connected across said secondary and ballasted thereby, said primary being connected across said source, the turn ratio of said high reactance transformer being such that the open circuit voltage induced in said secondary winding is less than the starting voltage of said lamp load, and a condenser connected across said secondary in parallel with said lamp load and having a reactance substantially equal to the reactance of said secondary at a harmonic frequency of said source so as to provide a series resonant circuit tuned to said harmonic frequency, the reactance of said condenser being sufliciently great with respect to the resistance of said lamp load that said series resonant circuit will not oscillate at said harmonic frequency after said lamp load has been ignited, and said condenser reactance at said harmonic frequency being sufficiently great with respect to the harmonic current traversing same that the voltage drop across said condenser as determined by the open circuit voltage of said high reactance transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit will exceed the starting voltage of said lamp load.

2. A lighting system comprising an alternating current source of given frequency, a transformer having a primary and a secondary, said primary being connected across said source, and a lamp load of the gaseous discharge positive column type connected across said secondary, the turn ratio of said transformer being such that the open circuit voltage induced in said secondary winding is less than the starting voltage of said lamp load, said lamp load and said secondary comprising a load circuit designed for operation at the frequency of said source, means providing inductive reactance in said load circuit sufficient to ballast said lamp load, and a condenser connected across said lamp load in parallel circuit therewith and in series circuit wtih said secondary and said inductive reactance means, the net reactance of said condenser and of said inductance reactance means at a harmonic of said given frequency being substantially less than the net reactance thereof at said given frequency so as to permit the flow of a harmonic current through said condenser, the reactance of said condenser at said harmonic frequency being sufiiciently great with respect to the harmonic current traversing same that the voltage drop across said condenser as determined by the open circuit voltage of said transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit will exceed the starting voltage of said lamp load, and said condenser reactance being sufiiciently great with respect to the resistance of said lamp load as to avoid oscillation of the circuit including said condenser after ignition of said lamp load.

3. A lamp system comprising, in combination, a source of alternating current of a given fundamental frequency, a high reactance transformer having a primary winding connected across said source and a secondary winding, a load including a lamp of the gaseous discharge positive column type connected to the output terminals of said transformer so that substantially the entire secondary voltage of said transformer is applied to said load during starting, the turn ratio of said high reactance transformer being such that the open circuit voltage induced therein is less than the starting voltage of said lamp, and a condenser connected acrcss said terminals so as to be in parallel circuit with said load, said condenser and said high reactance transformer providing a series resonant circuit tuned with respect to a harmonic of said given fundamental frequency applied to said primary, said condenser having a reactance sufliciently great with respect to the resistance of said lamp that said series resonant circuit will not oscillate at said harmonic frequency after current flow through said lamp has been established, and said condenser reactance at said harmonic frequency being sufficiently great with respect to the harmonic current traversing same that the voltage drop across said condenser as determined by the open circuit voltage of said high reactance transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit will exceed the starting voltage of said lamp.

4. -A lamp system comprising, in combination, a transformer having a primary and a secondary, an alternating current source of a given frequency connected to said primary, a lamp load of the gaseous discharge positive column type energized from said transformer, the turn ratio of said transformer being such that the open circuit voltage induced therein is less than the starting voltage of said lamp load, reactance means sufficient to provide proper ballasting for said lamp load when operating at said given frequency and including an inductive reactance, and a shunt circuit connected across said transformer secondary and said inductive reactance, said shunt circuit including a condenser, said condenser'and said inductive reactance providing a tuned circuit with respect to a harmonic of the given frequency of said source so that the impedance of said tuned circuit at said harmonic frequency is less than its impedance at the frequency of said source so as to permit the flow of a harmonic current in said shunt circuit, the reactance of said condenser at said harmonic frequency being sufliciently great with respect to the harmonic current traversing same that the voltage drop across said condenser as determined by the open circuit voltage of said transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit will exceed the starting voltage of said lamp load, and said condenser reactance at said harmonic frequency being sufficiently great with respect to the resistance of said lamp load as to prevent oscillation of said tuned circuit at said harmonic frequency after said lamp load has been ignited.

5. A lighting system comprising an alternating current source of given frequency, a transformer having a primary and a secondary, said primary being connected across said source, and a load including a lamp of the gaseous discharge positive column type connected across said secondary, the turn ratio of said transformer being such that the open circuit voltage induced in said secondary winding is less than the starting voltage of said lamp, said load and said secondary comprising a load circuit designed for operation at the frequency of said source, means providing reactance in said load circuit sufficient to ballast said lamp, and including inductive reactance means, and a condenser connected across said load in parallel circuit therewith and in series circuit with said secondary and said inductive reactance means, the net reactance of said condenser and of said inductive reactance means at a harmonic of. said given frequency being substantialiy less than the net reactance thereof at said given frequency so as to permit the fiow of a harmonic current through said condenser, the reactance of said condenser at said harmonic frequency being sulficiently great with respect to the harmonic current traversing same that the voltage drop across said condenser as determined by the open circuit harmonic voltage of said transformer multiplied by the ratio of the condenser reactance to the total impedance of the circuit will exceed the starting voltage of said lamp, and the ratio of the reactance of said condenser at third harmonic frequency with respect to the reactance of said lamp being greater than unity.

Dosio Mar. 18, 1947 Bird Nov. 8, 1949 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,029.363 April 10, 1962 Leopold Mauerer appears in the abov id Letters Patent sho It is hereby certified that error a numbered patuld read as ent requiring correction and that the sa corrected below.

Column 4, line 22. for "wtih" r'ead with line 24, for "inductance" read inductive column 6, line 21, for "reactance" read resistance Signed and sealed this 24th day of July 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Commissioner of Patents Attesting Officer

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