US2885501A - Fused drawout switchgear - Google Patents

Description

May 5, 1959 J. D. woon E'TAL 2,885,501-

FUSE@ nRAwouT swITcHGEAR Filed June 2l. 1957 2 Sheei.:=.-Sheeil 1 H 1132 I 15K/76 i i I l l INVENTORS JOfEP/r .D- V000 J. D. woon Erm. 2,885,501

FUSED DRAWOUTV SWITCHGEAR May 5, 1959 Filed June 21, 1957 2 Sheets-Sheet 2 INVENTORS Affe/@ww United States Patent O FUSED DRAWOUT SWITCHGEAR `oseph D. Wood, Wayne, and Gustave E. Heberlein, Bryn Mawr, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., 'a corporation of Penn- Sylvania Application June 21, 1957, Serial No. 667,208

6 Claims. (Cl. 200--50) This application relates to drawout type switchgear and more particularly to contactors having current limiting fuses connected in series therewith wherein the current limiting fuses are mounted on the contactor so as to automatically be disconnected from the power source when the contactor is moved to the test position or is entirely withdrawn from the cubicle.

In prior art arrangements wherein current limiting fuses are in series With a contactor, the fuses have been mounted in a separate compartment together with a separate disconnect switch. Since the load current passes through the fuses as well as the contactors, it was necessary to provide husky leads or another set of contacts equal in i capacity to that of the primary contacts. An elaborate system of interlocks was required to prevent opening of the disconnect associated with the fuses unless the contactor was also open and for the arrangement having the husky leads it was necessary to disconnect the leads before the contactor could be withdrawn from the cubicle.

This invention mounts the current limiting fuses to the back of the contactor between the movable primary contacts so that when the contactor is in the operating position at the rear of the cubicle, with the movable and stationary sets of primary contacts engaged, the fuses occupy the heretofore unoccupied space between the upper and lower primary contacts and between the back of the contactor and the back of the cubicle. Replacement of a fuse can only be accomplished by withdrawing the contactor from the cubicle at which time the fuses are positively disconnected from the power source. No additional interlocking is required to safely renew a fuse, only the conventional interlock, to prevent withdrawal of the contactor when it is closed, need be provided.

In addition the current limiting fuses may be equipped with plungers that protrude when the fuse blows, with the plungers being positioned to actuate switches in series with the holding coil of the contactor. In this way the blowing of any one fuse will open the contactor and prevent single phasing.

Accordingly, a primary object of this invention is to connect current limiting fuses in series with a drawout type switchgear without the necessity of providing a separate compartment for the fuses.

Another object of this invention is to connect current limiting fuses in series with a drawout type switchgear Without the necessity of providing additional safety interlocks.

Still another object of this invention is to connect current limiting fuses in series with a drawout type switchgear without the necessity of providing a separate disconnect switch associated with the fuses.

A further object of this invention is to connect current limiting fuses in series with a drawout type switchgear wherein the fuses are mounted to the back of the contactor and positionable in the heretofore unoccupied space between the primary contacts.

A still further object of this invention is to connect current limiting fuses in series with a drawout type switch- Patented May 5, 1959 rice gear wherein the blowing of any one fuse will cause the contactor to trip open.

These and other objects of this invention will become more apparent after reading the following description of the accompanying drawings in which:

Figure l is a longitudinal section of a drawout type switchgear having current limiting devices mounted there- 1n.

Figure 2 is a schematic presentation of the switchgear of Figure 1.

Figure 3 is a longitudinal section of a current limiting device.

Referring to the tigures, drawout type switchgear 10 comprises a contactor 11 which is slidable into and out of cubicle 12 on wheels 13. For the sake of clarity, only a single phase of the switchgear 10 is illustrated in Figure 1. However, it is to be understood that switchgear 10 is a multiphase unit, but preferably a three phase unit, with each phase being substantially identical to the phase illustrated in Figure l.

Lead 14, connected to one phase of the three phase power source 15, passes through the bushing 16 at the back of cubicle 12 and terminates inside cubicle 12 with upper stationary primary contact 17 while lead 18, terminating in lower stationary primary contact 19, passes through bushing 20 to connect to the load 21. Upper movable primary contact 22 is mounted on insulating standoff 23, which projects from the back of contactor 11, by means of conducting bar 24.

Fuse holder 46 is also mounted on bar 24 while another fuse holder 47 is mounted on one end of conductor 57 which passes through insulating bushing 58 secured to the back of contactor 11. The other end of conductor 57 is connected to the stationary contact 50 of cooperating contacts 50 and 51, where current interruption takes place. Movable contact 51 is mounted on conducting member 52 which is pivoted at 53 on one end of lead 54. Lead 54 passes through insulating bushing 55 secured to the back of contact 11 and terminates in lower movable primary contact 56 which is engageable with lower stationary primary contact 19.

Primary contacts 17, 22 and 19, 56 may be of any type well known in the art or be of any type disclosed in copending application Serial No. 552,614, led December 12, 1955, and assigned to the assignee of the instant invention.

Cooperating contacts 50, 51 are operated into and out of engagement by the operating mechanism, generally designated as 60, which comprises toggle links 61 and 62 joined at knee 63. One end of the toggle 64 is secured lto a xed pivot while the other end is pivoted at 65 to insulating bridge member 66 which is rigidly secured to conducting member 52. Toggle link 61 is part of crank 67 which is engaged at 68 by bale 69. rhe operating rod 71 of closing solenoid 70 is secured to bale 69 to control the operation of the cooperating contacts 50, 51 through operating mechanisms 60.

Drawout type switchgear generally have three racking positions designated operating, test and disconnect. ln the operating position the contactor 11 is fully within the cubicle 12 with the primary contacts 17, 22 and 19, 56 engaged as illustrated in Figure 1. In the test position the contactor 11 is moved to the right with respect to Figure 1 a distance sucient to disengage the primary contacts 17, 22 and 19, 56, but, the secondary contacts (not shown), supplying power to the contactor control circuits, are still engaged. While in the disconnect position the contactor is moved further to the right with respect to Figure 1 or even fully withdrawn from the cubicle 12 so that the primary and secondary contacts are fully disengaged and no power whatsoever is being supplied to contactor 11.

A conventional type interlock, generally designated as 72, is provided to assure that all switching between load 21 and three phase power source 15 takes place at cooperating contacts 50, 51 having arc extinguishing means 73 associated therewith, rather than at the primary contacts 17, 22 and 19, 56. Interlock 72 may comprise any one of a vast number of arrangements well known in the art such as the interlock means disclosed in Patent 2,554,510 assigned to the assignee of the instant invention. Cooperating contacts 50, 51 are operatively connected to interlock means 72 by means of link 74 which is secured at one end to pivot 65 of bridge 66 and at the other end to pin 75 which is secured to interlock disc 76 of interlock means 72.

The gap between fuse holders 46 and 47 is lled in by means of current limiting device or fuse 25 which completes one series path from the source through the primary contacts 17, 22 and 19, 56 and cooperating contacts 50, 51 to the load 21. Current limiting device 25 per se forms no part of this invention and may be of the type set forth in Patents 2,321,711; 2,342,310; 2,358,676; 2,592,399.

As seen best in the cross-sectional detailed View of Figure 3, the current limiting device has a hollow cylindrical housing 27 which serves as a main insulating casing for the unit. The metallic cap is provided to fit over one end of the hollow cylindrical insulator 27.

The main portion of the current limiting device 25 is the fusible element 29 which is made of silver or any other metal with a high melting point. The metal cap 30 is provided to iit over the right hand end. The caps 28 and 30 are made of conducting materials and serve as terminals for vthe current limiting device 25 which nest in fuse holders 46 and 47.

Fusible element 29 has extending areas 31, 32, 33 and 34 which protrude over and around the surface of the main casing 27. When the caps 28 and 30 are placed over the hollow insulating cylinder 27, they engage the extremities of the areas 31 and 32-33 and 34, respectively, to thereby grasp these units between the inner surface of the caps and the outer surface of the cylinder 27.

Although it has bene found desirable and practical to construct a fusible element 29 with protrusion or extension areas 31, 32, 33 and 34, etc., it will be understood that any other means may be provided to hold this element within the casing 27 such as the method set forth in the above mentioned patents.

The fusible element 29 is provided with a series of fholes 36 laterally disposed across `the element. Thus, the current will ow from the terminal cap 28 through the protrusions 31, 32 through the portion 35 and thence, through the reduced cross-sectional area 36 to portion 37, through protrusion or areas 33, 34 to lthe conducting cap 30.

When a severe fault current occurs the increased resistance due to the reduced cross-sectional areas 36 located between the holes 36 will cause the fusible element 29 to rupture along the lateral line, distinguished by the holes 36.

The conducting cap or terminal 28 has an opening 38 in the center thereof through which the biased plunger 26 extends. The fusible element 29 has a T- shaped extension 39, 39 at the bottom end thereof and ythe plunger 26 is rigidly secured thereto. The disc 40, positioned within the cap 28 by means of the hollow cylindrical insert 45 and frictionally held therein, has an opening 41 in the center thereof.

The insulating disc spacer 40 acts as a barrier for gas which may be blown within the current limiting device and also serves as a base for the compression spring 42. The compression spring 42 is disposed between the insulating disc spacer 40 and the collar 39. The collar 39 thus acts as a second base for the compression spring 42 and also acts as a closure for the opening 38 in the metallic terminal cap 28 to prevent explosion of gases w'hen the fuse 29 is ruptured.

Thus, on the occurrence of a fault current, the fuse 29 will rupture through the lateral line distinguished by the holes 36' and the compressed spring 42 will thereafter be instrumental in driving the collar 39 and the plunger 26 downward to thereby engage the micro-switch associated with the current limiting device and mounted to the back of contactor 11.

The fusible element 29 is surrounded by a powdered quartz filler (not shown) which is vitreous material. Thus, when the fusible element 29 is ruptured due to excess of heat caused by the fault current, silver vapors will be formed within the housing 27 to aid in the extinguishing of the arc which will gap a portion 35, 37 of the fusible element 29. Since the distance of separation of the two parts 35, 37 of the fusible element 29 is not sutliciently large to prevent restriking of the arc, it is necessary to supply supplemental means to prevent restriking. This is accomplished as follows:

The heat generated by the fusible element 29 is suciently large to vitrify the powdered quartz filler thereby melting same to form a glass barrier between the portions 35 and 37 of the fusible element 29. Hence, a solid glass insulator is formed by this operation to render restriking of the arc impossible.

As noted, the silver vapor formed by the fusible link 29 aids in the extinguishing of the arc. Thus, it is desirable to build up as large a pressure within the current limiting device as possible. This is achieved by means of the collar 39 which following rupture of the element 29, will be urged downward to thereby seal off the opening 38 of the metal cap terminal 28 to thereby enable sulficient pressure of the vapors to extinguish the fault current arc.

In like manner, the insulator disc spacer 40 acts as a barrier for the gas vapors to aid the collar 39' in maintaining a high pressure.

Micro-switch 77, secured to the back of contacter 11, is connected in series with solenoid coil 78. Upon the occurrence of a fault current in any phase, the fusible element 29 of the associated current limiting device 25 is ruptured and the spring mechanism 42 is released to drive the plunger 26 downward with respect to Figure l. The plunger 26 will then open the normally closed microswitch 77 thereby interrupting the energizing circuit for the solenoid coil 78.

The energizing circuit for solenoid coil 78 is illustrated as a series path across one phase of three phase source 15 and comprises the three normally closed micro-switches 77 associated with the current limiting devices 25, a set of normally closed contacts of the Off Switch 81, and a set of normally open contacts 79 associated with a holding coil 80 which is in parallel with the solenoid coil 78. It is apparent that the energizing circuit could be connected to an auxiliary source of power rather than three phase source 15. A normally open On Switch 82 is in parallel with the series combination of contacts 79 and 81.

When the On Switch 82 is depressed this completes an energizing circuit for solenoid coil 78 which, acting through operating mechanism 60, brings about the engagement of 'cooperating contacts 50, 51 as seen in Figure l. Since holding coil 80 is also energized its associated contacts 79 will close thus completing an alternate energizing circuit which will remain closed even after On Switch 82 is opened.

Thereafter, the energizing circuit for solenoid coil 78 may be interrupted by depressing normally closed OE Switch 81 or when any of the micro switches 77 are opened by their associated plungers 26. When solenoid coil 78 is deenergized cooperating contacts 50, 51 will disengage since they are biased open.

To those skilled in the art it should be apparent that pivot 64 need not be permanently xed but instead may be latched in position as part of a trip free arrangement. Similarly, the current limiting device micro switches 77 may be part of a holding coil circuit for a trip latch which holds the closing mechanism 60 in its closed position and thereby allows solenoid coil 78 to be deenergized once the cooperating contacts 50, 51 are brought into engagement. The trip latch may also have conventional time delay and instantaneous trip device associated therewith.

Thus we have added current limiting devices 25 to a draw-out type switchgear in the heretofore unused space between the sets of primary contacts and between the back of the contactor 11 and the back wall of the cubicle 12 thereby eliminating the need to enlarge the cubicle to accommodate the new components. In addition the current limiting devices 2S have been mounted to the contactor 11 thereby eliminating the necessity of providing additional interlocks or a separate disconnect switch for reasons of safety in replacing a blown current limiting device or servicing the contactor.

In the foregoing, we have described our invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of our invention within the scope of the description herein are obvious. Accordingly, we prefer to be bound not by the specilic disclosure herein but only by the appending claims.

We claim:

1. A drawout type circuit interrupter comprising a cubicle and a controller movable into and out of said cubicle; a current limting device secured to the back of said controller and connected in electrical series with said controller, said device being movable into and out of said cubicle in unison with said controller.

2. A drawout type circuit interrupter comprising a cubicle and a contactor movable between an operating position and a disconnect position; said cubicle having a pair of stationary primary contacts positioned therein and secured to a irst wall thereof; said contactor be movable through an opening in a second wall of said cubicle; said second wall being opposite said iirst wall; said contactor having a pair of movable primary contacts secured to the back thereof positioned to be engaged with said stationary primary contacts when said contactor is in said operating position and to be disengaged from said stationary primary contacts when said contactor is in said disconnect position; said contactor including a pair of cooperating contacts operable to an engaged and disengaged position; a current limiting device connected in electrical series between one of said cooperating contacts and one of said movable primary contacts; said current limiting device being secured to the back of said contactor.

3. A drawout type circuit interrupter comprising a cubicle and a contactor movable between an operating position and a disconnect position; said cubicle having a pair of stationary primary contacts positioned therein and secured to a first wall thereof; said contactor be movable through an opening in a second wall of said cubicle; said second wall being opposite said rst Wall; said contactor having a pair of movable primary contacts secured to the back thereof positioned to be engaged with said stationary primary contacts when said contactor is in said operating position and to be disengaged from said stationary primary contacts when said contactor is in said disconnect position; said contactor including a pair of cooperating contacts operable to an engaged and disengaged position; a current limiting device connected in electrical series between one of said cooperating contacts and one of said movable primary contacts; said current limiting device being secured to the back of said contactor, and being positioned in the space between the primary contacts of said pairs of primary contacts and between the back of said contactor and said iirst wall when said contactor is in said operating position.

4. A drawout type circuit interrupter comprising a cubicle and a contactor movable between an operating position and a disconnect position; said cubicle having a pair of stationary primary contacts positioned therein and secured to a first wall thereof; said contactor be movable through an opening in a second wall of said cubicle; said second wall being opposite said first wall; said contactor having a pair of movable primary contacts secured to the back thereof positioned to be engaged with said stationary primary contacts when said contactor is in said operating position and to be disengaged from said stationary primary contacts when said contactor is in said disconnect position; said contactor including a pair of cooperating contacts operable to an engaged and disengaged position; a current limiting device connected in electrical series be tween one of said cooperating contacts and one of said movable primary contacts; said current limiting device being secured to the back of said contactor and being positioned in the space between the primary contacts of said pairs of primary contacts and between the back of said contactor and said first wall when said contactor is in said operating position; interlock means operatively connected to said cooperating contacts to prevent engagement and disengagement of said pairs of movable and stationary primary contacts when said cooperating contacts are in their said engaged position.

5. A drawout type circuit interrupter for the control of a multiphase circuit; said circuit interrupter comprising a cubicle and a contactor movable between an operating and a disconnect position; a pair of stationary contacts and a pair of movable primary contacts for each phase of said multiphase circuit; said pairs of stationary primary contacts being positioned within said cubicle and being secured to a lirst wall thereof; said contactor be movable through an opening in a second wall of said cubicle; said second wall being opposite said iirst wall; said pairs of movable primary contacts being secured to the back of said contactor and being positioned to be engaged with said pairs of stationary primary contacts when said contactor is in said operating position and to be disengaged from said stationary primary contacts when said contactor is in said disconnect position; said contactor including for each phase of said multiphase circuit a pair of cooperating contacts and an operating means therefor; a current limiting device for each phase of said multiphase circuit; said current limiting device being connected in electrical series between one of said movable primary contacts and the cooperating contacts of its associated phase; said current limiting devices being secured to the back of said contactor; each of said current limiting devices including means engageable with said operating means when said current limiting device has blown to thereby automatically disengage all of said pairs of cooperating contacts when any one of said current limiting devices has interrupted the circuit of its associated phase.

6. A drawout type circuit interrupter for the control of a multiphase circuit; said circuit interrupter comprising a cubicle and a contactor movable between an operating and a disconnect position; a pair of stationary contacts and a pair of movable primary contacts for each phase of said multiphase circuit; said pairs of stationary primary contacts being positioned within said cubicle and being secured to a first wall thereof; said contactor be movable through an opening in a second wall of said cubicle; said second wall being opposite said first wall; said pairs of movable primary contacts being secured to the back of said contactor and being positioned to be engaged with said pairs of stationary primary contacts when said contactor is in said operating position and to be disengaged from said stationary primary contacts when said contactor is in said disconnect position; said contactor including for each phase of said multiphase circuit a pair of cooperating contacts and an operating means therefor; interlock means operatively connected to said cooperating contacts to prevent engagement and disengagement of said pairs of movable and stationary primary contacts when said cooperating contacts are in their said engaged position; a

7 8 current limiting device for each phase of said multiing devices has interrupted the circuit of its associated phase circuit; said current limiting device being connected phase. in electrical series between one of said movable primary contacts and the cooperating contacts of its associated References Cited ill the le 0f this Patent phase; said current limiting devices being secured to the 5 back `of said contacter; each of said current limiting de- UNITED STATES PATENTS vices including a plunger biased outwardly to engage said 2,249,662 Matthews July 15, 1941 operating means when said current limiting device has 2,558,074 Claybourne et al June 26, 1951 blown to thereby automatically discngage all of said pairs 2,689,293 Claybourne et al Sept. 14, 1954 of cooperating contacts when any one of said current limit- 10 2,734,966 Schneider a Feb. 14, 1956

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