US2924686A - Fusible switch comprising a circuit breaker and current limiting fuse - Google Patents

Description

Feb. 9, 1960 w, EDMUNDS I 2,924,686

FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSE Filed Dec. 23, 1955 I 5 Sheets-Sheet 1 IN VEN TOR. Ill/UM #11010 [an/rm Feb. 9, 1960 w. H. EDMUNDS FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSE 3 Sheets-Sheet 2 Filed D60. 23, 1955 Arracwzfs 3 Sheets-Sheet 3 Feb. 9, 1960 w. H. EDMUNDS FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSE Filed Dec. 25, 1955 INVENTOR. M/u/n/v/meaza EDMI/Nw 9% Arrap/m' s United States Patent FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSE William Harold Edmunds, Havertown, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application December 23, 1955, Serial No. 555,073

4 Claims. (Cl. 200-114) My invention relates to fusible switches and more particularly to a fusible switch comprising the series connection of a circuit breaker and a current limiting fuse.

In my copending application Serial No. 461,378 filed October 11, 1954, I describe .a circuit breaker having overload features connected in series with a current limiting device, these two devices being electrically and mechanically coordinated.

In the instant invention I provide the same type of connection as indicated above but the circuit breaker is not provided with the overload features and merely operates to interrupt normal load curent. That is to say, the circuit breaker will merely operate as a switch. In series with this circuit breaker or switch I provide a current limiting fuse of the type described in the above mentioned application Serial No. 461,378 whereby op eration of the current limiting fuse energizes a striker pin which can be effective to operate the tripper bar of the circuit breaker which in turn operates the circuit breaker contacts to a disengaged position.

Therefore, upon the occurence of a fault in one phase of a multiple phase system, the current limiting fuse of the faulted phase will operate and, in view of the mechanical coordination between circuit breaker and the fuse, the tripper bar of the circuit breaker will be operated to cause contact disengagement for each phase of the system.

It is therefore apparent, that the application of my novel invention will prevent the serious condition of single phasing upon the occurence of a single phase fault in the system being protected.

Another advantage which is inherent in my novel invent is that various desirable features such as under voltage devices, shunt trip and other features which are presently available for circuit breakers could be provided. Similarly, remote tripping or remote closing of the device is possible. Furthermore, the interrupting capacity of a circuit breaker is available for interrupting higher loads than a corresponding switch would be able to interrupt.

Clearly the above features could not be obtained in presently used fusible switches since a common tripper bar is not provided as in the case of the circuit breaker of my novel invention, nor are the presently used switches provided with the arc extinguishing properties of the circuit breaker.

It is now apparent that in view of the absence of overload sensing devices for the circuit breaker, that this combination is more economical than the circuit breaker and current limiting fuse combination described in my above mentioned copending application Serial No. 461,378. Furthermore, all the advantages of the circuit breaker and current limiting fuse combination are provided with the exception of overload devices for the circuit breaker. However, short circuit protection is afforded by the current limiting fuse whereas in the case 2,924,686 Patented Feb. 9, 1960 fusible switch utilizing a circuit breaker as one com-' ponent whereby devices such as under voltage devices, shunt trip and all other available devices for circuit breakers may be applied to the combination.

My novel combination may be so constructed that the current limiting fuses may be assembled into a common housing and the circuit breaker is assembled into a second housing, these two assemblies being connectible by means of disconnect contacts. I then so position the circuit breaker tripper bar that it will be biased to disengage the circuit breaker contacts when the fuse assembly is not in place.

It is therefore seen that when the fuses are disconnected from the circuit breaker that the circuit breaker contacts, if not in the disengaged position, will be automatically disengaged.

In the case of presently used fusible switches this safety feature is not provided and it is possible to remove one or more fuses while the switch is closed, thereby leading to possible danger to the operating personnel.

Another principal advantage of this type'of construction for a fusible switch is that by removing the current limiting fuse housing the load is positively disconnected from the source, thereby adding another important safety feature to the fusible switch of my invention.

Accordingly, another object of my invention is to provide means whereby disconnecting the fuse will automatically trip the circuit breaker.

A still further object of my invention is to provide a fusible switch utilizing a series connected circuit breaker and current limiting fuse whereby the load will be positively disconnected from the source when the current limiting fuse housing is being moved.

Another object of my invention is to provide a fusible switch wherein current limiting fuses are contained in a first assembly, a circuit breaker is contained in a second assembly, and the two assemblies are electrically connected and mechanically coordinated whereby disconnecting of the two assemblies automatically disconnects the circuit breaker contacts.

These and other objects of my invention will become apparent from the following description taken in conjunction with the drawings in which:

Figure 1 shows a perspective view of a series connected circuit breaker and current limiting fuse constructed in accordance with my novel invention.

Figure 2 is a cross-sectional side view of the fusible switch of Figure 1.

Figure 3 is a cross-sectional view of a current limiting -fuse which could be utilized as the fuse element of my novel fusible switch.

Figure 4 is an exploded perspective view of a second embodiment of my invention where the circuit breaker and the current limiting fuses which form my novel invention are in separate housings.

Figure 5 is a cross-sectional side view through the fuse housing and a portion of the circuit breaker .of

Figure 4, and specifically shows the connection between is well known in the art.

a current limiting fuse and the tripper bar of the circuit breaker.

Figure 6 is an electrical schematic diagram of the fusible switch of my invention.

Figures 1 and 2 show a fusible switch comprising a circuit breaker whichis mechanically coordinated with a current limiting device. The operating mechanism of the circuit breaker per se may be of any type which By wayof example, I have illust'rateda molded case circuit breaker of the type shown in United States Patent 2,574,093 issued Novemher 6, 1951. The current limiting device which is used in coordination with the circuit breaker may be of the type-shown in United States Patent 2,592,399 issued April 8, 1952, and operates on the principles described therein.

As will be more fully explained hereinafter, coordination between 'the two devices is provided by the striker pin of the fuse and the tripper bar of the circuit breaker.

Referring now to Figures 1 and 2, the circuit breaker and the current limiting device are contained within the molded case housing 10, which has a cover 11 as seen in Figure 2. The circuit breaker is provided with a pair of cooperating contacts 12 and 13 for each pole, only one pole being observable in Figure 2. Stationary con tact 12 is shown as being connected to the terminal 15 and the movable contact 13 is connected to the movable contact arm 14. An arc chute 15a as seen in Figure 1 is provided for each pole to aid in extinguishing the are created by the cooperating contacts 12 and 13 when these contacts are moved to the disengaged position.

It should however be realized that since the interrupting duty of the circuit breaker in my novel fusible switch will not be subjected to heavy interrupting duty that it maynot be necessary that arcextinguishing means be provided.

The circuit breaker of Figures 1 and 2 then has a common tripper bar 16 on which prop latch17 is mounted. As more clearly seen in Figure 2, the prop latch 17 engages the latch surface 18 of the member 19 which is controlled by the operating mechanism 20 of the circuit breaker. When the latch surface 18 is positioned under the latch 17 and thehandle 21 moved to the extreme right as illustrated in Figure 2 the cooperating contacts 12 and 13 are moved to their-engaged position.

However, if the'tripper bar 16 is rotated in a counterclockwise direction, theprop latch 17 will be released the occurrence of a severe short circuit current, the

current limiting device 25 will rupture thereby releasing its striker pin 30 as will be more fully described, so that the strikernpin will be driven forwardto engage the protrusion 23. This willrotate the common tripper bar 16in a'counterclockwisedirection to release the latch 17 and 18 so that the cooperating contacts 12, 13 will be driven to their disengaged .position. "Obviously, the same operation would occurxifxthe. fuse of any other phase operates since it would engage-its corresponding tripper bar protrusion.

Current limiting device 25 may be positioned within the circuit breaker in any desirable manner, as for example by clips which are not shown in thefigure but would be constructed to connect the terminals 32 and 33 to terminals 34 and 35of the current limiting de- -vice"25.'

Thustheele'ctrical circuit of'the one'phase'ofthe ingdevice '25 is provided with a striker pin 30 which is biased to the right by means of spring 39. However, the thin wire 40 prevents the spring 39 from driving the striker pin 30 forward. The circuit interrupter 25 is provided internally with terminal blocks 41 which secure the inner units 42. The inner units 42 are constructed in substantially the same manner as shown 1n United States Patent 2,592,399 issued April 8, 1952, wherein a reduced cross-sectional fusible element is surrounded by quartz crystals so that the rupture of the fusible element will result in a melting of the quartz crystals permitting it to flow between the gap created by the rupture to result in extremely rapid interruption of the arc.

This particular device will operate within less than one-fourth of a cycle so that the let-through current is less than 10% of the available short-circuitcurrent and still not more than thirty times the magnitude of the rated current.

As further seen in Figure 3, the inner unit 42' which contains the main portion of the current limiting device is connected in electrical parallel with the thin wire 40. A quartz filler 44 surrounds both the inner unit 42 and the thin wire 40. Following the rupture of the inner unit 42, all of the current will be diverted to the thin wire 40. Due to the small cross-sectional area of the wire 40, it will rupture substantially instantaneously thereby enabling the spring 39 to release its energy to drive the striker pin30 forward.

It is now possible to consider the operation of my novel fusible switch as shown in Figures 1, 2 and 3. It is understood that in the case of a fault in one of the phases that the wire 40 will be broken. The breaking of the wire 40 will release the stored energy in the biasing spring 39 to thereby drive the striker pin 30 upward to engage the respective protrusion 23 of the common tripper bar 16 to effect release of the latch 17-18 so that the cooperating contacts 12-13 of each phase will be moved to their disengaged position.

That is, even though-a severe short-circuit may exist ononly one pole of a multi-phase line, the current limiting device associated with that pole will'operate. However, after the fuse operation, the mechanical coordination between thisunit and the circuit breaker will result in the opening of all three. poles of a circuit breakernin it is inherent in'the device that the load is positively disconnected from the source by means of the disengaged circuit breaker contacts when fuses are being replaced. It is further understood that the circuit breaker of Figures 1, 2 and 3 could have been provided with various circuit breaker auxiliary equipment such as under-voltage devices, shunt trip, and so on. Similarly, remote tripping or remote closing. could havebeen provided.

A second possible form which my novel invention can take is shown in Figures 4 and 5. As shown specifically in the exploded perspective view of Figure 4, the current limiting devices can be assembled in an individual unit shown generally at 50 for cooperation with a circuit breaker 51 which could have the same type of operating mechanism as the circuit breaker shown in Figures 1 and 2.

The fuse housing '50 rand the circuit breaker 51 tare provided with disconnect contacts of the type described in copending application Serial No. 536,586 filed September 26, 1955 whereby each pair of disconnect contacts 52-53, 54-55 and 5657 cooperate with the circuit breaker contacts 58-59, 6061 and 62-63 respectively.

As shown in Figure 5, which is a section taken through one phase of the device of Figure 4, the contacts 52 and 53 of the fuse housing 50 connect the current limiting fuse 25 which may be of the type shown in Figure 3 in series with a corresponding circuit breaker phase which has the disconnect contacts 5859.

The tripper bar 16 of Figure 5 is shown as having a link 64 which is biased to move to the left by the biasing means 65 thereby maintaining the left hand tip 66 of the link 64 as seen in each of Figures 4 and 5 in engagement with a protrusion 67 of the link 68. Link 68 which is pivotally mounted at pivot point 69 of the fuse housing 50 and the upper portion 70 of the link 67 are biased in a counterclockwise direction about the pivot point 69 by means of the biasing spring 71 to overcome the effect of biasing spring 65 when the fuse assembly is connected to the normal operating position as shown in the solid lines of Figure 5. The extension 72 of the tripper bar 16 prevents counterclockwise rotation of the tripper bar 16 by engaging the notch 73 of the link 64. Upon the occurrence of a fault however, the striker pin 74 of the current limiting fuse 25 will protrude through the aperture 75 to engage the portion 70 of the pivotally mounted link 67 in such a manner as to overcome the force of biasing spring 71 and allow the link 64 to move toward the left by the force of the biasing spring 65. This position is shown in the dotted line view of Figure 5. Clearly, the tripper bar 16 will rotate in a counterclockwise direction and the prop latch will as is shown in conjunction with Figures 1, 2 and 3 allow contact disengagement of the circuit breaker contacts. It is to be noted in conjunction with Figures 4 and 5, that each of the fusible elements 25 corresponding to each phase of the system can operate the tripper bar 16 to cause contact disengagement of circuit breaker contact. Hence, it is seen that in the case of the device of Figures 4 and 5 that single phasing is prevented since a fault when any of the phases will cause operation of the circuit breaker contact to their disengaged position.

Hence, the fusible switch shown in Figures 4 and 5 operates in the same manner as does the fusible switch shown in Figures 1 and 2. However, the distinction here is that the components comprising the circuit breaker and the fusible switch are mounted in separate and interchangeable assemblies thereby providing extreme flexibility for installation and maintenance of the system.

Another important advantage provided by the fusible switch of Figures 4 and 5 is that upon disconnection of the fuse assembly 50 and the circuit breaker 51, that positive disconnection between the fuse terminals and the line is effected to thereby allow safe maintenance of the fuses.

This may be more clearly undertsood with reference to Figure 6 which shows a diagrammatic circuit of the device of Figures 4 and 5.

In Figure 6, the fuse terminals 52, 54 and 56 of Figure 4 are shown as being connected to the load terminals 80, 81 and 82 respectively. The fuse terminals 53, 55 and 57 are then shown as being connected to the circuit breaker terminals 59, 61 and 63 respectively as was the case of Figure 4. The circuit breaker terminals 83, 84 and 85 are then connected to the line terminals 86, 87 and 88 respectively.

Consider now that it is desired to replace a fuse or in some manner work on the fuse assembly 50.

If the fuse assembly is removed, it has been seen that the circuit breaker contacts are automatically moved to the disengaged position and housing 50 must be disconnected to achieve entrance to the individual fuse ele- 6 ments. It is to be noted that the circuit breaker will be opened even if maintenance personnel neglected to operate the circuit breaker prior to attending to work on the housing 50.

While working on the disconnected housing 50 however, it is essential to note that the fuse terminals are completely isolated from line terminals 86, 87 and 88 by virtue of the disengaged circuit breaker contacts at terminals 59, 61 and 63. Hence, maintenance personnel are subjected to no shock hazard when working on the current limiting fuses.

In the foregoing we have described my invention solely in connection with specific illustrative embodiments thereof. Since many variations and modifications of the invention will now be obvious to those skilled in the art, we prefer to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

1. A multiphase fusible switch; said multiphase fusible switch comprising a multiphase circuit breaker and a current limiting fuse for each phase of said multiphase circuit breaker; said circuit breaker being constructed to be non-responsive to electrical overload conditions; said circuit breaker comprising a pair of cooperable contacts for each phase, a common latch means to maintain each pair of said cooperable contacts in an engaged position, means to move said cooperable contacts to a disengaged position responsive to defeat of said latch means and a tripper bar; said tripper bar being operatively connected to said latch means to defeat said latch means responsive to operation of said tripper bar; said current limiting fuses being assembled in a first housing; said circuit breaker being assembled in a second housing; said first and second housings having disconnect contacts arranged to connect one of said current limiting fuses in series with a pair of circuit breaker cooperable contacts for each phase of said multiphase circuit breaker; each of said current limiting fuses being operatively connected to said circuit breaker tripper bar whereby electrical disconnection between said current limiting fuse and said circuit breaker cooperable contacts operates said tripper bar to disengage said cooperable contacts; operation of the current limiting fuse of any phase thereby being operative to defeat said common latch means and disengage the cooperable contacts of each phase.

2. A multiphase fusible switch; said multiphase fusible switch comprising a multiphase circuit breaker and a current limiting fuse for each phase of said multiphase circuit breaker; said circuit breaker being constructed to be non-responsive to electrical overload conditions; said circuit breaker comprising a pair of cooperable contacts for each phase, a common latch means to maintain each pair of said cooperable contacts in an engaged position, means to move said cooperable contacts to a disengaged position responsive to defeat of said latch means and a tripper bar; said tripper bar being operatively connected to said latch means to defeat said latch means responsive to operation of said tripper bar; said current limiting fuses being assembled in a first housing; said circuit breaker being assembled in a second housing; said first and second housings having disconnect contacts arranged to connect one of said current limiting fuses in series with a pair of circuit breaker cooperable contacts for each phase of said multiphase circuit breaker; each of said current limiting fuses being positioned to operate said circuit breaker tripper bar responsive to operation of said current limiting fuses; said current limiting fuse being operatively connected to said circuit breaker tripper bar whereby electrical disconnection between said current limiting fuse and said circuit breaker cooperable contacts operates said tripper bar to disengage said cooperable contacts.

3. A multiphase fusible switch; said multiphase fusible switch comprising a multiphase circuit breaker and a current limiting fuse for each phase of said multiphase 7 circuit breaker; said circuit breaker being constructed to be non-responsive to electrical overload conditions; said circuit breakercompri'sing a pair of cooperable contacts for each, phase, a common latch means to maintain each pair of said cooperable contacts in an'engaged position, means to move said cooperable contacts to a disengaged position responsive to defeat of said latch means and a tripper bar; said tripper bar being operatively connected to said latch means to defeat said latch means responsive to operation of said tripper bar; said current limiting fuses being assembled in a firsthousing; said circuit breaker being assembled in a second housing; said first and second housings having disconnect contacts arranged to connect one of said current limiting fuses inseries with a pair of circuit breaker cooperable contacts for each phase of said multiphase circuit breaker; each of said current limiting fuses being operatively connected to said circuit breaker tripper bar whereby electrical disconnection between said current limiting fuse and said circuit breaker cooperable contacts operates said tripper bar to disengage said cooperable contacts; operation of the current limiting fuse of any phase thereby being operative to defeat said common latch means and. disengage the cooperable contacts'of each phase; said circuit breaker terminals being connected to a power source, said current limiting fuse terminals being connected to a load; disconnection of said first housing from said second housing providing positive disconnection of said current limiting fuse terminals.

I 4. A multiphase fusible switch; said multiphase fusible switch comprising a multiphase circuit breaker and a current limiting fuse for each phase of said multiphase circuit breaker; said circuit breaker being constructed to be non-responsive to electrical overload conditions; said circuit breaker comprising a pair of cooperable contacts for each phase, a common latch means to maintain each pair of said cooperable contacts in an engaged position, means to move said cooperable contacts to a disengaged position responsive to defeat of said latch means and a tripper bar; said tripper bar being operatively connected to said latch means to defeat said latch means responsive to operation of said tripper bar; said current limiting fusestbeing assembled in a first housing; said circuit breaker being assembled in a second housingysaid first and second housings having disconnect contacts arranged to connect one of said current limiting fuses in serieswith a pair of circuit breaker'cooperable contacts for each phase of said multiphase circuit breaker; each of said current limiting fusesbeing positioned to operate said circuit breaker tripper bar responsive to operation of said current limiting fuses; said current limiting. fuse being operatively connected to said circuit breaker tripper bar whereby electrical disconnection between said current limiting fuse and said circuit breaker'cooperable contacts operates said tripper bar to disengage .said cooperable contacts; said circuit breaker terminals being connected to a power source said current limiting fuse terminals being connected to, a load;.disconnection of said'first housing from said second housing providing positive disconnection of said current limiting fuse terminals.

References Cited in the fileof this. patent UNITED STATES PATENTS

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