US 3512118 A
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M. G. LEONARD HIGH VOLTAGE ELECTRICAL CONNECTOR 'May 12, 1 970 4 Sheets-Sheet 1 Filed Feb. 2, 1968 FIG. IA.
INVENTOR Merril I (5. Leonard.
Z ATTORNEY y 1970 M. G. LEONARD 3,512,118
HIGH VOLTAGE ELECTRICAL CONNECTOR Filed Feb. 2, 1968 4 Sheets-Sheet 2 FIG. 2.
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y 1970 M. e. LEONARD 3,512,118
HIGH VOLTAGE ELECTRICAL CONNECTOR Filed Feb. 2, 1968 4 Sheets-Sheet 3 FIG. 4. 8% FIG. 5.
32 Q 32 o Q I8 72 '8 x I @2 Q 92 I I6 j 26 98 gg Q F'I l l 40 l l I 60 l 38* I 74 M'. cs. LEONARD HIGH VOLTAGE ELECTRICAL CONNECTOR May 12; 1970 Filed Feb. 2, 1968 4 Sheets-Sheet 4 OOOOm OOOO wmDu 027:2: .rzwmmDo OOO (S3a3dwv) maaano nw-u- 131 United States Patent US. Cl. 339-60 5 Claims ABSTRACT OF THE DISCLOSURE A connector comprising a first plug-in portion and a second stationary portion for connecting one part of a high voltage circuit to another part of a high voltage circuit. The removable or plug-in portion of the connector comprising a first terminal for connecting a high voltage conductor thereto and a second terminal for making contact with the fixed part of the connector and means for removably connecting a current limiting fuse in series relationship with the first and second terminals of the plug-in portion of the connector. The second or fixed part of the connector includes a protruding insulating member and the removable part of the connector includes a hollow insulation member which fits over said protruding insulation member when the connector is assembled with a loose fit and clamping means around the collar portion of the first or plug-in portion of the connector permits quick clamping of the hollow member to the protruding portion of the second member of the connector to obtain a tight interface fit between the protruding portion of the second member of the connector and the hollow portion of the first member of the connector to force out air trapped between faces of the two members of the connector. The hollow portion of the plug-in member has an electrical contact member therein which mates with a spring contact member carried by the protruding portion of the stationary member of the connector to make electrical contact between the first or plug-in member and the second or stationary member of the connector, and means for quickly latching the removable or plug-in member of the connector in circuit making relationship with the second or stationary member of the connector. Arc quenching material is provided for both the plug-in and stationary members of the connector, to assist in quenching any are which might develop during opening and closing of the contacts carried by the plug-in and the stationary members of the connector.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to high voltage connectors and more particularly to a high voltage connector for connecting a high voltage cable to a high voltage terminal of a transformer, or like electrical apparatus.
Description of the prior art The prior art discloses plug-in connectors comprising a first plug-in or removable member and a second fixed member. However, in the prior art the fit between the protruding portion of the fixed member of the connector and the inside of the hollow plug-in or removable portion is so tight that the plug-in portion of the connector must be stretched over the protruding portion of the connector to make a tight seal and at the same time to make electrical contact internally between the two parts of the connecor. In this operation it is difficult to obtain high speed closing of the contacts, yet high speed closing is most important; especially, if the closing operation is attempted while a fault exists on the high voltage line.
As the contacts approach, or make momentary contact, an arc may occur that may generate sufiicient pressure to blow the two parts of the connector apart and possibly destroy the connector and injure the operator. In some of the prior art devices of the plug-in type, a fuse that is not current limiting; hereafter called a conventional fuse has been placed in series with the high voltage line and the contact carried by the plug-in portion of the connector. This conventional fuse has not solved the problem of plugging the plug-in portion of the connector into the stationary portion with a fault on the line, since this type fuse will not break the circuit until the current cycle passes through zero. Even though the fuse might melt, the arc will continue to carry current until the current cycle passes through zero. This means that the maximum available current may be carried before the circuit is opened. This is objectionable since this maximum current generates sufiicient gas to cause the gas bubble which starts at the point of arcing between the electrical contact for the stationary portion of the connector and the removable portion to generate enough energy to destroy the connector. These disadvantages of the prior art plugin type connectors have been corrected by this invention.
Summary of the invention This invention provides a high voltage connector comprising a first or plug-in member and a second or stationary member.
The stationary member comprises a molded insulation member which may be made of filled epoxy or some other suitable material having a metal flange molded therein for stationarily mounting the stationary portion of the member. A rubber insert extends from the molded stationary member. An electrical conductor extends up through the molded stationary member and terminates in a spring contact in the rubber protruding portion of the member. A material which generates gas when exposed to an arc, which gas assists in extinguishing any are which may be generated, is also provided in the end of the protruding rubber portion of the stationary memher.
The first or plug-in portion of the connector comprises a molded rubber member having an electrical terminal molded therein to which is connected a high voltage cable. Another terminal member is provided, spaced from the first terminal member, which is connected to the cable and a fuse clip is attached to this second terminal member. A current limiting fuse is connected in series between the terminal member which is connected to the cable and the second terminal member of the plug-in member. The terminal which is connected to the current limiting fuse extends into a hollow portion of the first member. The hollow portion of the plug-in member has a. slightly larger diameter than the protruding portion of the second or fixed member of the connector so that it may be placed over the protruding member of the second member very rapidly to make electrical contact between the contact member mounted inside the hollow member and the spring contact member mounted inside of the protruding member. This arrangement permits the plug-in member to be rapidly placed on the stationary member and if there should be a fault on the line, and an arc is formed as current starts to flow into the fault, then the current limiting fuse will blow and clear the fault before enough energy has been released at the point of arcing to destroy the connector. This will permit clearing of the fault, and after a new fuse has been installed, the plug-in portion of the connector may be reassembled to the stationary portion to complete the electrical circuit without the destruction of equipment or damage to service people. The current limiting fuse may be replaced in the first or plug-in portion of the connector by means 3 of a handle that is provided exterior of the plug-in portion of the connector.
It is emphasized that the fuse must be a current limiting fuse for if a conventional fuse is used the circuit will not be interrupted until the current has reached the maximum of the cycle because with conventional fuses the arc continues to carry the current until the current cycle passes through zero. With a current limiting fuse of the type used herein the current is interrupted at some point less than a half cycle and only a predetermined amount of current is let through before the circuit is broken.
Description of preferred embodiments FIG. 1A is a side elevation, with parts broken away, showing one embodiment of the plug-in portion of the connector provided by this invention;
FIG. 1B is a side elevation, with parts broken away, showing one embodiment of the second or stationary portion of the plug-in connector provided by this invention;
FIG. 2 is a side view with parts broken away showing the plug-in member of FIG. 1A and the stationary member of FIG. 1B in assembled position, before the clamping band has been tightened;
FIG. 3 is a partial sectional view showing the connectors assembled as in FIG. 2 after the clamping band has been tightened;
FIG. 4 shows a second embodiment of the high voltage connector comprising a plug-in member and a stationary member as provided by this invention;
FIG. 5 is a side elevation showing how two of the connectors as provided by this invention may be utilized to connect the high voltage winding of a transformer in circuit relationship with a high voltage cable;
FIG. 6 is a detailed plan view of the quick acting clamp used to clamp the plug-in member of the connector to the stationary member of the connector when the two are assembled;
FIG. 7 is a section taken along line VII-VII of FIG. IE to show the spring contacts carried by the second or fixed member of the connector;
FIG. 8 is a diagram illustrating how the current limiting fuse used in this invention interrupts the current before the maximum half cycle current is reached; and
FIG. 9 is a diagram illustrating the asymmetrical and symmetrical current of a current cycle and the current let through by the current limiting fuse used in this invention.
Description of the preferred embodiment Throughout the various figures of the drawings which will follow, like reference characters refer to like elements in all figures.
Referring specifically to FIG. 1A of the drawing this figure shows a plug-in member 10 of a high voltage connector as provided by this invention. The plug-in member 10 comprises a molded member having a portion 12 with another offset portion 14 extending substantially at right angles from the portion 12. The member 10 may be molded from a rubber composition or any other suitable insulating material. The portion 12 has a hollow therein for receiving a current limiting fuse as will be described hereinafter. The portion 12 also has mounted therein an electrical contact 16 to which is attached a high voltage electrical cable 18. The offset hollow portion 14 of the plug-in member 10 has positioned therein an electrical contact member 20. The electrical contact member 20 is attached to a fuse clip 22, which fuse clip extends into a hollow portion 24 of the plug-in member 10. The fuse clip 22 is lined up with the electrical contact member 16 to which the high voltage cable 18 is attached. A current limiting fuse 26 is positioned in the hollow 24 in the plug-in member 10 and the fuse 26 is held in circuit making relationship in series with the contact 20* and the contact 16 by the fuse clip 22. The current limiting fuse 26 has a link 28 thereon which engages another link 30'. A handle 32, operated with a hook stick, is attached to the link 30 for withdrawing the fuse from the hollow portion 24 of the plug-in member 10. A new fuse may be inserted into the circuit by attaching the new fuse tothe handle 32 by means of links such as 28 and 30* and then the handle may be used to reinsert the new fuse 26 through an opening 3 4 into the hollow 24 and in circuit engagement with the contact 1 6 and the fuse clip 22.
The offset portion 14 of the plug-in member 10 has a tapered hollow opening 36 therein. The electrical contact member 20 is substantially centered in the hollow opening 3 6. The electrical contact member 20 has attached to the lower end thereof a material 38 which when exposed to an arc generates gas which aids in snuffing out the electrical arc. Surrounding the offset portion 14 of the plug-in member 10 is a clamping band 40. This clamping band 40 is tightened and loosened by means of a handle 41 and a quick acting cam arrangement 42 which provides a means for quickly tightening the band. The function of this band 40 will be described more in detail hereinafter.
In FIG. 1B is shown a second or stationary member of the high voltage connector as provided by this invention. The stationary member 50 shown in FIG. 1B comprises a cast member 52, which may be cast of filled epoxy or other suitable material. The cast member 52 has an electrical conductor 54 extending up through the center thereof. This conductor 54 serves to connect to a load circuit (not shown). The upper end of the conductor 54 is threaded at 56, and attached thereto by the threads 56 is an electrical contact member 58 comprising four spring like members 60, which extend upwardly from the threaded portion 56. Surrounding the contact member 58 and the spring fingers 60 extending therefrom is a protruding insulation member 62. This protruding insulation member may be made of rubber or any other suitable electrical insulating material. A sleeve of material 64 which generates a gas when exposed to an electrical arc is fitted in the upper end of the protruding insulating member 62 beyond the spring fingers 60.
The gas generating material illustrated at 38 and 64 may be either of the materials disclosed in US. Pat. 3,059,081 or US. Pat. 3,027,352 It is recognized that either of these materials when exposed to an arc will generate a volume of gas and the deionization effect of the gas in conjunction with the gas blast effect, will tend to extinguish the arc.
It is emphasized that the external diameter of the protruding insulating member 62 is slightly less than the internal diameter of the hollow 36 in the plug-in member 10. This free fit or small clearance between the protruding member 62 of the stationary member 50 and the hollow portion 36 of the plug-in member 10 permits the plug-in member 10 to be plugged into the stationary member 50 so that the electrical contact 20 of the plugin member 10 makes good electrical contact with the spring fingers 60 of the contact 58 of the member 50. This free fit or small clearance between the stationary member 50 and the plug-in member 10 permits rapid plug-in of the member 10' intothe member 50 with a minimum of force.
This is an important advantage of this connector since with the prior art connectors the hollow portion of the plug-in member must be stretched over the protruding portion of the stationary member and thus requires substantial force or effort to make good electrical contact between the protruding or stationary member and the plug-in member. If it is attempted to plug the plug-in member into the stationary member with a fault on the circuit, this stretching effort may interfere with quick contact-closing, resulting in a flashing or sputtering at the contacts. The are that then occurs may produce enough explosive energy to blow up the plug-in member 10 and increase the danger of injuring service personnel that might be making the connection.
Referring to FIG. 2 which shows the member 1 assembled or plugged into the member 50 to make circuit connection between the cable 18 and a load which is connected to the conductor 54. FIG. 2 illustrates the relative position of the surfaces 62 and 36 before the clamping band 40 has been tightened. As soon as the plug-in member has been completely plugged into the member 50 so that the contact of the member 10 makes complete electrical contact with the spring fingers 60 of the contact member 58, the lever 41 is lowered to tighten the band 40 and tightly squeeze the innerface 36 of offset portion 14 of the member 10 against the outer face of the protruding member 62 of the element 50. This tightening action of the band 40 also moves a hook 70 under a loop 72 which is attached to a mounting flange 74 for the stationary member 50. This hook 70 and loop 72 fixedly attaches the plug-in member 10 to the fixed member 50. The mounting flange 74 is molded intofthe fixed member 50 and serves to mount the fixed member, for example, on a transformer casing 76, by Welding, or the like.
The squeezing action or clamping action of the band 40 against the hollow member 14 also squeezes out air which might be trapped between the inner faces 36 of the hollow member 14 and the outer face of the protruding portion 62, of the stationary member 50'. The band 40 has a particular concave curvature, as seen in FIGS. 1A, 2 and 3, that will squeeze out air from between face 36 and the protruding portion 62 at its center first and progressively toward the ends of the band 40. It is important that air between these surfaces be removed, since an air film between these surfaces would reduce level.
tightened about the hollow portion 14 of the member 10 there is a close fit between the innerface 36 of the hollow portion 14 and the outer face of the portion 62 of the stationary member 50 and the plug-in member 10 is fixedly attached to the stationary member 50 by the loop 72 and hook 70.
If the plug-in member should be plugged into the fixed member 50 while there is a fault on the circuit. and an arc should start, the current limiting fuse 26 would blow and disconnect the cable 18 from the stationary member 50. This operation by the current limiting fuse 26 to break the circuit from the cable 18 to the stationary member 50 would occur in less than onehalf cycle of the current.
FIG. 8 is a diagram of one complete cycle of current illustrating how the current limiting fuse 26 operates to break the circuit. As seen from this FIG. 8, since the current will be interrupted very rapidly the arc will not have a chance to feed the gas bubble developed between the contacts 60 and 20 with enough energy to cause the gas bubble to explode the connector or blow the plug-in member 10 off the stationary member 50 and possibly injure the service personnel.
Referring to FIG. 8, the reference character 80 represents a complete cycle of current. I represents the peak let through current, that is the maximum current let through by the fuse 26. I represents the available peak fault current. T represents the melting time of the fuse 26. T represents the arcing time of the fuse. T represents the total interrupting (clearing) time of the fuse. It is pointed out that with a conventional fuse that the total interrupting time for the fuse is a complete half cycle. This is true because with the conventional fuse after the arc starts, current continues to be carried by the ionized air in the arc stream until the current cycle passes through Zero, which may be a complete half cycle. This also means that the maximum current flows before the circuit is interrupted. With a current limiting fuse, as used in As seen from FIG. 3 after the band 40 has been this invention, this condition does not exist. As seen from FIG. 8, the current limiting fuse interrupts high fault currents before the first loop of the fault current has reached its natural crest value. A current limiting fuse performs its function by producing arc voltages which exceed the system voltage by a significant amount and thereby forcing current to zero. The fuse operates in less than one-half cycle to provide maximum protection; The current limiting fuse as used in this invention is claimed in US. Pat. No. 3,134,874. It is seen from FIG. 8 that the total interrupting time for the current limiting fuse 26 is approximately one-half the time which would be required by a conventional melt type fuse to interrupt the circuit and the energy supplied to the gas bubble is much less than half as much as would be applied using a conventional fuse.
The operating characteristics of the current limiting fuse used in this invention is further illustrated by FIG. 9 of the drawings. On FIG.9 of the drawings the vertical axis illustrates let through current of the fuse in amperes and the horizontal axis illustrates available RMI symmetrical current in amperes. The lines labeled asymmetrical and symmetrical indicates the maximum current available in a current cycle. The line labeled illustrates the difference between the let through current for a current limiting fuse with 10,000 amperes available current and the let through current for a conventional fuse for 10,000 amperes of available current. It is seen that for 10,000 amperes of available current the current limiting fuse will let through approximately 280 amperes before opening the circuit. However, with a conventional fuse, the conventional fuse will let through the maximum current, or 10,000 amperes, before the circuit is interrupted. This FIG. 8 illustrates the advantages of using a current limiting fuse to protect the connector over that of using a conventional fuse.
Referring to FIG. 5 of the drawing, this figure illustrates how two of the plug-in type connectors as provided by this invention may be used to connect a transformer in circuit with a high voltage cable 18. The transformer 90 comprises a tank 92 having oil dielectric 94 therein with a core and coil assembly 91 immersed in the oil dielectric 94. The core and coil assembly 96 comprises a magnetic core with a high voltage winding 97 and a low voltage winding 98 inductively connected to the core. The high voltage winding 97 is connected in series with the high voltage cable 18 by means of two plug-in type connectors as described hereinbefore with respect to FIGS. 1 and 2. The low voltage windings of the transformer are connected to three low voltage terminals. FIG. 5 only illustrates one type of circuit connection using connectors of this invention. It is understood that the connectors of this invention may also be used in other circuits, such as through type and radial type circuits.
FIG. 4 illustrates a second embodiment of the invention. The main difference being that the two sections, the stationary portion of the connector and the plug-in portion of the connector are in line with each other but in all other respects the connector of FIG. 4 is essentially the same as the connector shown in FIGS. 1 and 2. One difference in the connector of FIG. 4 from that of the connector shown in FIGS. 1 and 2 is that in order to replace the fuse 26 in the embodiment shown in FIG. 4 the plug-in connector 10 must be removed from the stationary connector and the electrical contact must be removed from the plug-in member 10 in order to remove the blown fuse 26 and to insert a new fuse 26.
FIG. 6 is a plan view of the band 40, illustrating how the band 40 can be adjusted for different size connectors by means of a bolt 99 and compressible spring 100.
From the foregoing description taken in connection with the accompanying drawings it is seen that this invention has provided an improved plug-in type connector for connecting a high voltage cable into circuit relationship with a load; wherein, if it is attempted to plug the plug-in portion of the connector into the stationary portion of the connector with a fault on the system the connection can be made quickly because of the clearance between the outer dimension of the stationary member ofthe connector and the inside dimension of the hollow portion of the plug-in connector; and the plug-in portion of the connector may be latched to the stationary portion of the connector. If an arc persists after the plug-in portion of the connector has been placed in position on the stationary portion of the connector, then the current limiting fuse will blow before enough gas has been generated to destroy the connector. This will open the circuit so that the connection can be broken and the fault removed, the fuse replaced and the connection remade without destroying the connector or causing personal body injury to service personnel.
This type of operation is not possible with the prior-art connectors which require tight contact and preferably an interference fit between the stationary member and the plug-in member. The friction caused by this tight fit impedes the closing movement of the contacts, which increases the chance for the occurrence of a'destructive arc. Furthermore, this destruction is not averted by placing aconventional fuse in series with the cable and plug-in bushing, because such a fuse is so slow that the destructive action would have been complete before this conventional fuse would blow.
1. A connector for a high voltage circuit comprising a plug-in member and a stationary member, said stationary member comprising a protruding insulation portion having an electrical contact therein, said plug-in member having a hollow electrical insulation portion having an electrical contact therein, the inside diameter of said hollow portion of said plug-in member being greater than the outside diameter of said protruding portion of said stationary member to permit rapid placing of said hollow portion of said plug-in member over said protruding portion of said stationary member with a loose fit to permit quick electrical connection between the electrical contact of said stationary member and the electrical contact in said hollow portion of said plug-in member, quickly 'contractable means for contracting the sides'of said hollow portion of said plug-in member against said stationary member, and means for quickly contracting said contractablc means.
2. A connector as specified in claim 1 wherein said hollow portion of said plug-in member is surrounded by with a quickly contractable band for clamping the inner surface of said hollow portion of said plug-in member tightly to the outer surface of said protruding portion of said stationary member.
3. A connector as specified in claim 2 comprising means associated with the means for quickly contracting said clamping means for fixedly holding said plug-in member in circuit making relationship to said stationary member.
4. The connector as specified in claim 1 wherein the electrical contact member carried bysaid protruding portion of said second member makes spring contact with the electrical contact carried by the hollow portion of said plug-in member.
5. The apparatus of claim 1 wherein the means for contracting the side of said hollow portion of said plug-in member against said stationary member comprises a spring loaded band surrounding said plug-in member.
References Cited UNITED STATES PATENTS 2,124,182 7/1938 Braun 339-91 3,170,752 2/1965 Van Horssen 339217 3,328,744 6/1967 Fiske 339-61 3,408,615 10/1968 Sewell 33994 MARVIN A. CHAMPION, Primary Examiner I. H. MCGLYNN, Assistant Examiner US. Cl. X.R.
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