US3171926A

US3171926A - Circuit breaker having a first plurality of series connecnted fuses and a second plurality of fuses in parallel therewith

Info

Publication number: US3171926A
Application number: US94753A
Authority: US
Inventors: Joseph F Schwab
Original assignee: ITE Circuit Breaker Co
Current assignee: ITE Circuit Breaker Co
Priority date: 1961-03-10
Filing date: 1961-03-10
Publication date: 1965-03-02
Anticipated expiration: 1982-03-02

Description

SCHWAB A FIRST PLURALITY OF SERIES March 2, 1965 J. F. CIRCUIT BREAKER HAVING CONNECTED FUSES AND A SECOND PLURALITY OF- FUSES IN PARALLEL THEREWITH 6 Sheets-Sheet 1 Filed March 10, 1961 FI-GQI Ila n1 INVENTOR. Joseph F. Schwcb BY flsreaztwm F4059, fzma/farew ATTORNEYS March 2, 1965 J. F. SCHWAB 3,17 ,926

' CIRCUIT BREAKER'HAVING A FIRST PLURALITY OF SERIES CONNECTED FUSES AND A SECOND FLURALITY OF FUSES IN PARALLEL THEREWITH Filed March 10, 1961 e Sheets-sheaf 2 INVENTOR. Joseph F. Schwub BY ATTORNEYS.

March 2, 1965 J. F. SCHWAB 3,171,926

CIRCUIT BREAKER HAVING A FIRST PLURALITY 0F SERIES CONNECTED FUSES AND A SECOND PLURALITY 0F FUSES IN PARALLEL THEREWITH Filed March 10, 1961 6 Sheets-Sheet 3 FIG. 30 MENTOR 32 32 32 Joseph F.5chwob lOu IOb lOc m 4;; {Ii/k4 ATTORNEYS J. F. SCHWAB 3,171,926 AVING Y 0F SERIES March 2, 1965 6 Sheets-Sheet 4 Filed March 10, 1961 FIG.4

INVENTOR. Joseph F. Schwob ATTORNEYS.

March 2, 1965 J. F. scHwAB 3,171,926

CIRCUIT BREAKER HAVING A FIRST PLURALITY 0F sERIEs CONNECTED FUSES AND A SECOND PLURALITY 0F FUSES IN PARALLEL THEREIWITH 6 Sheets-Sheet 5 Filed March 10, 1961 FIG.8

3M7 NT 11 :1

INVENTOR. Joseph ESchwob 57194; 51m; 510:4 fang ffifln ATTORNEYS.

March 2, 1965 J. F, SCHWAB 3,171,926

CIRCUIT BREAKER HAVING A FIRST PLURALITY OF SERIES CONNECTED FUSES AND A SECOND PLURALITY 0F FUSES IN PARALLEL THEREWITH Filed March 10, 1961 6 Sheets-Sheet 6 INVENTOR. Joseph F. Schwub ATTORNEYS United States Patent 3,171,926 ClRC UlT BREAKER HAVING A FIRST PLURALTTY 0F SERIES QNNECTED FUSE AND? A SECQND TEJURALTTY @F FUSES TN PARALLEL THEIR 1TH loseph F. Schwah, Philadelphia, Pa, assiguor to l-=T-E Circuit-Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 10, 1961, Ser. No. 94,753 Claims. (Cl. Mid-114) My invention relates to circuit breakers and more particularly to circuit breakers having current limiting fuses connected in series therewith to permit higher capacity circuit protection and being further adapted to prevent "the occurrence of single-phasing It is well known in the art to incorporate circuit breakers in a power transmission system in order to protect the system from faults occurring between the circuit breaker and the load. For adequate protection, a circuit breaker must be chosen which has an interrupting capacity equal to the available short circuit current of the system to be protected. It is possible, however, to utilize circuit breakers having an interrupting capacity below the magnitude of the available short circuit current of the system by placing a current limiting fuse in series with the circuit breaker.

The characteristics of the current limiting fuse are such that the current flowing therethrough is limited to a magnitude which is a relatively small percentage of the magnitude of available short circuit current which the system is capable of delivering. For example, the letthrough current of the current limiting fuse may be only 10% of the available short circuit current and may further be less than-30 times the magnitude of the normal, or rated, current of the circuit. Since the magnitude of the maximum let-through current is much greater than the magnitude of the rated current of the'system, the current limiting fuse must be designed to operate within the first quarter of the cycle of the fault current so that the fault current is prevented from rising to the magnitude of the available short circuit current.

The utilization of a current limiting fuse of this type permits the network and load to be designed to. withstand the thermal and magnetic forces generated by the let-through current which is far less than the thermal and magnetic forces which would be developed by the total available short circuit current.

The use of a current limiting fuse also permits-the use of a series connected circuit breaker which has an interrupting capacity which is much less than the interrupting capacity required for the interruption of the available short circuit current without the series connected current limiting fuse.

The current limiting fuse is further designed to include a striker pin which is under control of an energized spring. During the occurrence 'of the fault condition the energized spring releasesits energy causing the striker pin to protrude through one end of the current limiting fuse. The striker pin actuates a microswit-ch which is electrically connected to the circuit breaker operating mechanism thereby causing the circuit breaker cooperating contacts to become disengaged under control of the current limiting fuse. This provides dual interruption during the occurrence of large magnitude current faults, i.e., the blowing of the current limiting fuse and the separation of the breaker cooperating contacts. The tripping arrangement under controlof the current limiting fuse is quite advantageous in plural phase systems. For example, if a large magnitude fault current appears in only one phase of a plural phase system, actuation of the circuit breaker under control of the current limiting 3,l7l,926 Patented Mar. 2, 1965 'ice fuse in the phase carrying the fault current causes the circuit breaker to trip, thereby interrupting the current flow in all phases to prevent the occurrence of a single phasing condition.

Current limiting fuses in metal clad switchgear are mounted so that the operator cannot have access to the fuses when the circuit breaker is in the fully connected position. This prevents physical contact with the fuse by the operator when the circuit breaker is closed into an energized bus. Mounting the fuses in this manner, however, prevents visual inspection to ascertain where the fault has occurred. In order to overcome this disadvantage, it would therefore be necessary to mount the current limiting fuses in a position to permit observation of their condition. This type of mounting, however, would carry the disadvantage of permitting physical contact with the current limiting fuses, thereby creating a dangerous condition for the operator.

My invention permits visual inspection of the condition of the current limiting fuses while the circuit breaker is in the fully connected position While retaining the feature of preventing access to the current limiting fuses when the circuit breaker is in the fully connected position. Each phase of the system has a current limiting fuse which is series connected withthe circuit breaker. The current limiting fuses are mounted at the rear of the breaker placing the circuit breaker between the current limiting fuses and the operator, thereby preventing physical contact with the current limiting fuses when the circuit breaker is in the fully connected position. A second fuse is connected in parallel with the current limiting fuses of each phase. The parallel connected fuses are mounted at the front of the circuit breaker permitting visual inspection of the parallel connected fuses even with the circuit breaker in the fully connected position. Each parallel connected fuse contains a striker pin controlled by an energized spring. The resistivity of the parallel-connected fuses is substantially greater than that of the current limitingfuses causing almost all of the current to pass through the circuit limiting fuses during normal current flow. The striker pins of each parallel connected fuse are positioned to actuate a tripping mechanism which mechanically links the circuit breaker to the parallel connected fuses.

During the occurrence .of a severe fault current condition, the resistivity of the current limiting fuses increases, thereby causing a decreased current flow through the current limiting fuses and an increased current fiow through the parallel connected fuses. At a predetermined time, the parallel connected fuse in the line carrying the fault current blows, thereby actuating the striker pin. The striker pin actuates the tripping mechanism, causing the circuit breaker contacts for all phases to become disengaged, thereby preventing the occurrence of a single phasing condition.

The parallel connected fuses are mounted in an insulated housing. The front cover ofthe insulating housing is formed of a transparent insulating material to permit visual inspection of the parallel connected fuses contained in the insulated housing. The parallel connected fuses are mounted in apositioning and securing means attached to the transparent front cover. This enables the operator to remove the parallel connected fuses simply by removing the transparent front cover, thus avoiding actual physical contact with the fuses when in the connected position, thereby preventing any contact with the fuses when they are connected to an energized bus.

The positioning of the parallel connected fuses at the front of the circuit breaker does not create the hazard of a. flash-over since the parallel connected fuses carry such a minute current during routine operation and also since the insulated housing prevents any flashover between the fuse mountings and the grounded breaker elements.

The tripping mechanism associated with the parallel connected fuses is further designed to prevent racking of the circuit breaker to its fully connected position with the cooperating contacts in an engaged position when any one of the parallel connected fuses are missing or have previously blown.

It is therefore, one object of my invention to provide a novel circuit interrupter having a current limiting fuse.

Another object of my invention is to provide a circuit interrupter having novel means for producing either a time delay or a fast current interruption operation.

Another object of my invention is to provide a circuit breaker for protecting a multi-phase system which includes novel means for preventing the occurrence of a single phasing condition as a result of the tripping operation.

Another object of my invention is to provide a circuit interrupter having a novel indicating means permitting the visual inspection of the condition of the current limiting fuses enabling the current limiting fuses to be placed I out of reach of the operator when the circuit breaker is in its fully connected position.

Another object of my invention is to provide a circuit interrupter having novel means to prevent the racking in of the circuit interrupter in the closed position when one of its fuses is missing or has blown.

These and other objects of the invention will be apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 is a perspective view showing the rear of my novel circuit interrupter.

FIGURE 2 is a perspective view of the front of the circuit interrupter shown in FIGURE 1.

FIGURE 3 is a side plan view of a portion of the circuit interrupter shown in FIGURES 1 and 2.

FIGURE 3a is a schematic view of the circuit interrupter of FIGURE 1.

FIGURE 4 is a perspective view of the parallel connected fuse housing shown in FIGURE 2.

FIGURE 5 is a side plan view of a portion of the fuse indicating means taken along line 55 of FIGURE 7.

FIGURE 6 is a perspective view showing the front cover of the parallel connected fuse housing.

FIGURE 7 is a top plan view of the parallel connected fuse housing shown in FIGURE 3.

FIGURE 8 is a front view of the parallel connected fuse housing and triple mechanism shown in FIGURE 2.

FIGURES 9 and 10 are side plan views of the parallel connected fuse housing and trip mechanism shown in FIGURE 2.

Referring now to the drawings, FIGURES l and 2 show circuit breaker 10 having upper 11 and lower 12. terminals which are positioned to engage the stationary disconnects (not shown) of the circuit to be protected. The upper and lower terminals consist of a plurality of upper 11a and 12a and lower 11b and 12b fingers which are urged towards one another by springs 11c and 120 respectively. This arrangement provides rigid engagement between the primary disconnects (not shown) and upper 11 and lower 12 terminals when circuit breaker It} is in the fully connected position. A set of upper and lower terminals are provided for each phase of the plural phase system to be protected. Although FIGURES l and 2 show a circuit breaker adapted to protect a threephase system, it should be understood that my novel invention will operate equally well in systems having greater or lesser phases and FIGURES l and 2 are, therefore, set forth as merely exemplary.

A current limiting fuse I3 is secured to the rear of circuit breaker 10 by fastening means I4 and IS. The

upper terminal 13a of each current limiting fuse 13 through which fasteners 14 are inserted, also serves as the electrical connection between the main body of current limiting fuse I3 and an L-shaped member 18 (see FIG- URE 3). Each L-shaped member 18 is electrically connected to contact fingers Ila and 11b by U-shaped member 1701. Contact fingers 11a and 11b are pivotally mounted to U-shaped member 17a at 16a and 16b, respectively.

The lower terminals 136 of current limiting fuses 13 are secured to conductive head 19 by fastening means 315. Contact 20 is positioned at the opposite end of conductive member 19 in such a manner as to be engaged by contact 23, which is positioned on movable arm 21. Movable bridge 21 is pivotally connected to L-shaped conductive member 24 at pivot 22. A push-rod 25 under control of an operating mechanism (not shown) moves bridge 21 between an engaged and a disengaged position. The opposite end of L-shaped member 24 is secured to U-shaped member 17b. The configuration of U-sh-ap-ed member 17b and its relationship to lower

terminal fingers

12a and 12b and spring means is identical to the description of upper terminal 11. With movable bridge 21 in the position shown in FIGURE 3, the current path through circuit breaker It) extends from upper contact fingers 11a and 11b, U-shaped member 17a, L-shaped member 18, fuse terminal 13a, current limiting fuse I3, fuse terminal 13b, conductive head 19,

contacts

20 and 23, movable arm 21, L-shaped member 24, U-shaped member 1712 and

lower contact fingers

12a and 12b.

Arc chute 39 is positioned immediately above the cooperating

contacts

20 and 23 of each phase to aid in the extinguishment of an are formed during the tripping operation. A parallel connected fuse housing 34) is secured to the front of a circuit breaker 10 adjacent and in front of arc chutes 39. FIGURE 3:: shows the electrical connections of current limiting fuses 13, each current limiting fuse I3 being connected in series with the cooperating contacts ltia through of one phase. A low magnitude current fuse 32 is connected in parallel with each current limiting fuse 13. During normal operation, very little current flows through fuses 32 since the resistivity of fuses 32 far exceeds that of fuses 13. It is only when current limiting fuses 13 start to blow that the resistivity of current limiting fuses I3 rises to a level sufficient to cause more current to flow through low magnitude current fuses 32, thereby causing fuses 32 to blow.

Fuse housing 39 consists of insulating sides 31 and removable top 31a, which is also formed from an insulating material. Fastening means 31b permit removal of top 31a for inspection and/or repairs of the tripper mechanism in fuse housing 30. The front cover 82 of housing 39 is formed of a transparent insulating material which enables visual inspection of fuses 32 contained therein. In addition to serving as an indicating means for visually determining the condition of current limiting fuses 13, fuses 32 actuate the mechanical tripping mech anism (not shown) of the circuit breaker 10 to prevent the occurrence of a single phasing condition, as will be more fully described.

FIGURE 4 shows the fuse housing 30 with the top 31a and the cover member 82 removed in order to reveal the contents thereof. Rod 48 is inserted in apertures 47 contained in each side wall 31. Tripper bar 46 is secured to rod 48 by blocks 49 and fastening means 50. Block 49 (see FIGURE 5) contains a groove 49a through which rod 48 passes. Fastening means 50 secure tripper bar 46 to blocks 49 in such a manner as to cause tripper bar 46 to rotate about rod 48 in response to any rotation of rod 48. A pair of fuse clips 41 and 41a: are secured to rectangular shaped block 53 in such a manner as to accommodate vertically mounted fuses 32. Each fuse 32 has a striker pin 45 which is arranged to cooperate with an extension 46w on tripper bar 46 in a manner that will be more fully described. A slot 58a, in fuse mounting block 53, is provided adjacent each fuse 32 to permit the movement of the end 52 of trip boot 51 (see FIGURE 5). Trip boot 51 is pivotally mounted between a pair of blocks 59 by pin 53. Trip boot 51 is biased in a clockwise direction by spring means 55 which is connected to trip boot 51 at aperture 56. The opposite end of spring 55 is secured to rear wall 31b of fuse housing 30 at 57. Trip boots 5]. are prevented from rotating in the clockwise direction by the presence of fuses 32 which are secured between fuse clips 41 and 41a. 'Each fuse 32 abuts the end 52 of its associated trip boot 51 as shown in dotted fashion in FIGURE 5.

The front cover 82 of fuse housing 36' which can best be seen in FIGURES 2, 4 and 6 is-formed of a clear plastic material to allow quick and easy inspection of the trigger fuses with the cover positioned to the housing 30. Handles 43 are secured to the outer surface of front cover 82 to permit easy handling of front cover Yoke '84, which is secured to the inner surface of front cover 82 by fastening means 81 (see FIGURE 7), consists of two rectangular shaped blocks 34a 'and84b. Block 84a is secured to front cover 82 by fastening means 81 and block 841) is secured to block 84m by fastening means 86. Apertures87 are provided for the insertion of vetrically mounted fuses 32. Fuses 32 are slidably mounted through apertures 87 topermit proper positioning of the fuses when'front cover 82 is replaced on fuse housing 30. It can be seen fromthe structure of front cover 82 that fuses 32 need never be touched by the operator when they are positioned in or removed from fuse clips 41 and 41a in order to safeguard the operator when fuses 32 are positioned in or removed from fuse clips 41 and'41a. The positioning of fuses 32 in fuse clips41 and 41a prevent the clockwise rotation of trip boot 51 under control of springs 55, as can be seen clearly in'FIGURE 5.

The right-handend of rod 48 passes through right-hand side wall 31 (see FIGURE '4). Latch member 60 is connected to rod 48 in such a manner as to be rotated with the rotation of rod 48. Spring 63, which is connected to latch 60at'aperture 64 and to circuit breaker at point 65 biases latch 60in a counter-clockwise direction. Slot' 66 in latch 60 engages roller 61a which is pivotally mounted to link member-61. Pin' 68- is connected to latch 60 immediately below rod 48 to permit the reset operation of the tripping mechanism, as will be more fully described. A' reset'button 62 is secured to connecting link 61 by fastening means 67 (see FIGURE 10).

Referring now-to FIGURES 8 and 9, upper connecting link 61 has its lower end secured to lower connecting link 69 by fastening and pivoting means 70. Fastening means 70 rigidly secures-upper connecting link 61 to lower connecting'link 69 and is mounted to the cover 10d of circuit breaker 10 in such a manner as to permit

links

61 and 69 to rotate about the axis of fastening and pivoting'means 70. The operation is such that any rotation of upper link 61 about pivot means 70 is imparted to'lower link 69 due to the rigid contact existing between

links

61 and 69. Upper 61 and lower 69 links are biased to rotate in the counterclockwise direction about the axis of pivot means 70 by spring '78 which is connected at one end to lever 72 at point 72a and at the other 'end to the side of circuit breaker 16d at point 1%.

Links

61 and 69, however, cannot be urged to rotate under control of spring. 78 when latch 60 engages the roller 61a of upper link 61 as will be more fully described. The opposite end of lower link 69 carries a pin'71 which is fixedly secured to link 6%. Lever 72 is pivotally mounted to shaft 76. Fastening means 74 and 75 connect shaft 76 to lever 72 in such a manner as to impart any rotation of'lever 72 to shaft 76. Trip finger 77 is rigidly fastened to shaft 76 by fastening means 77:: causing lever 72 and'trip finger 7'7 to be rotated'in unison. Trip finger 77 is 'operatively connected to the 'mechanical tripping mechanism of circuit breaker 10 (not shown) and operates in a manner to be more fully described.

tion is similar to that described above.

The tripping operation of circuit breaker 10 under control of parallel connected fuses 32 is as'follows:

When a severe fault condition occurs in one phase of the system being protected, the current limiting fuse 13 of that-particular phase starts to blow. As the resistivity of the current limiting fuseincreases, a portion of the fault current is channeled through the parallel connected fuse '32 of that particular phase. At a predetermined time, fuse 32 blows, causing striker pin 45 to move vertically upward. The impact of. striker pin 45 against extension 46a of tripper bar 46 (see FIGURES 4 and 9), causes tripper bar 46 to rotate clockwise about rod '48. Rod 48, which is rigidly secured to tripper bar 46 by blocks 49, is also urgedinto clockwise rotation causing latch 60 to rotate in the clockwise direction. The clockwise rotation of latch 66 moves slot 66 of latch 61 out of engagement with roller 61a. It should be noted that the force of striker pin 45 exceeds the biasing force of spring 63 connected to latch 60. Upper linking member 61, which has been un latched from latch 60 is urged into counter-clockwise rotation about fastening pin 70 under the influence of biasing spring 78. Lower linking member 69, which is rigidly secured to upper linking member 61 by fastening means 70, is also urged into counter-clockwise rotation, causing lever 72, which is connected to lower linking member 69 by means of pin 71 to be rotated clockwise about shaft 76.

The clockwise rotation of shaft 76 is imparted to trip finger 77 which actuates the tripping means (not shown) of circuit breaker 10. The operating mechanism (not shown) causes the cooperating contacts of each phase of the circuit breaker to be separated, thereby interrupting the current flow in all three phases. This operation prevents the occurrence of a single phasing condition which would be created if the current limiting fuse 13 in the phase carrying the fault current were to blow without the accompanying tripping operation of the cooperating contacts of all three phases.

After the occurrence of the tripping operation, fuses 32 -may be'replaced simply by removing front cover 82. The

"51 is as follows:

If front cover 82 is replaced on fuse housing 30 with one of the fuses 32- missing, the trip boot 51 associated with the missing fuse is urged into clockwise rotation about pivot pin 53 (see FIGURE 5) by biasing, spring 55. The

' lower end 52 of trip boot 51 abuts'against the lower edge 46b of tripper'bar 46 causing tripper bar' 46 to be urged into clockwise rotation about rod48. Therotation of tripper bar 46 is imparted to rod 48 causing latch 60 to be rotated clockwise about shaft 48. Roller 61a is thereby disengaged from slot 66 in latch 60. The biasing force of springs 55 imparted to trip boot 51 exceeds the biasing force of spring 63 on latch 60 to permit the clockwise rotation of latch 60. The remainder of the tripping opera- It can, therefore, be seen that the tripping boots 51 prevent the closing of the circuit breaker cooperating contacts when anyone or all of the fuses 32 have not been properly replaced. 'In addition, the replacement of a fuse 32 which has blown previously would also prevent the latching of roller 61a by latch 60 causing circuit breaker It) to remain in a tripfree position, thereby preventing the closing of the circuit breaker cooperating contacts until all fuses have been properly inserted.

The resetting operation is as follows:

After the tripping operation has taken place, front cover 82 is removed from housing 36 by pulling handle 80 (see FIGURE 7) in the direction of arrow 190. Fuses 32 are thereby simultaneously removed under control of the pulling force on handle 80 in the direction of arrow 101. To reset the latching mechanism on the right-hand side pressed in the direction of arrow 103. This causes upper linking member 61 to be rotated clockwise about fastening pin 70. The clockwise rotation of upper linking member 61 places the right-hand edge 61d of upper linking member 61 in contact with pin 68, which is mounted to latch 60. At the instant edge 61b of upper linking member 61 comes into contact with pin 68, roller 61a is positioned immediately below slot 66 in latch 60. Further clockwise rotation of upper linking member 61 causes edge 61b to exert a force against pin 68 causing latch member 60 to rotate counter-clockwise about rod 48. Slot 60 then comes into engagement with roller 61a. Biasing spring 63 holds latch 60 in the position shown in FIG- URES 4 and 10, thereby preventing linking

members

61 and 69 to be rotated under the influence of spring 78'. The rotation of lower linking member 69, which occurs with the resetting force 103 exerted against reset button 62, causes trip finger 77 to be engaged with the operating mechanism (not shown) of circuit breaker 10. The cooperating contacts of circuit breaker 10 may now be reset to the engaged position. At this instant, circuit breaker 10 is no longer in the trip-free position permitting the contacts to remain in an engaged position in readiness for subsequent tripping operations which may be actuated by fuses 32, in the manner set forth above.

My invention may be utilized in metal-clad switchgear such as that set forth in copending US. application Serial No. 86,349, filed February 1, 1961 entitled Racking Mechanism, in the name of F. I. Pokorny and G. A. Wilson, and assigned to the same assignee as the instant invention. The racking mechanism of the metal-clad switchgear, which is clearly set forth in the aforementioned U.S. application is so arranged to prevent racking out of the circuit breaker from the connected position to the disconnected position when the circuit breaker cooperating contacts are in an engaged position. The racking mechanism is further arranged to prevent racking in of the circuit breaker from a fully disconnected to a fully connected position when the circuit breaker cooperating contacts are in an engaged position. It can thus be seen that failure to replace all of the fuses 32 in housing 30 will place circuit breaker 10 in a trip-free condition as described above. Thus, even though circuit breaker 16 may be racked into its fully connected position, the circuit breaker cooperating contacts 20 and 23 (see FIGURE 3) may not be moved to their engaged position unless fresh fuses 32 are properly positioned in fuse housing 30. It should also be noted that the resetting of latch 60 as described above, must accompany-the replacement of fresh fuses in housing before the cooperating

contacts

20 and 23 of circuit breaker 10 can be moved to the engaged position.

The characteristics of the current limiting fuses 13 are such that the fuses 13 will not blow unless a severe fault current condition exists. The circuit breaker 10, how ever, is designed to trip in response to over current conditions thus thereby providing an interrupting device which protects the power transmission system against both large and small magnitude fault current conditions. The over current tripping mechanism is well known in the art and a thorough description has not been set forth since this mechanism lends no novelty tomy invention.

It can be seen from the foregoing that I have provided a circuit interrupter having both instantaneous and timedelayed trip operations in which the current limiting fuses are mounted in such a manner as to safeguard operators from any possible danger but which circuit interrupter also permits simple visual observation of the condition of the current limiting fuses by the inclusion of parallel connected fuses which are so positioned as to permit visual inspection thereof.

Although I have here described preferred embodiments of my novel invention, many variations and modifications will now be apparent to those skilled in the art and 1,

therefore, prefer to be limited not by the specific disclosure herein but only by the appending claims.

I claim:

1. In combination a circuit breaker for use in a metalclad compartment having a pair of cooperating contacts, first and second terminals electrically connected to said cooperating contacts both being positioned along the rear wall of said circuit breaker, a first current limiting fuse means removably mounted to the rear wall of said circuit breaker, a second fuse means removably mounted to the front of said circuit breaker, said first fuse means being connected in series relationship with one of said cooperating contacts and said first terminal, said second terminal being connected to the other of said cooperating contacts, said second fuse means being connected in parallel with said first fuse means, mechanical operating means for disengaging said cooperating contacts, tripping means for actuating said operating means, said second fuse means including means to actuate said tripping means upon the occurrence of a fault condition, fuse holding means for receiving said second fuse means connected to said tripping means, and being positioned along the front Wall of said circuit breaker, said fuse holding means including boot means biased to engage the side of said second fuse means and movable to actuate said tripping means when said second fuse means is removed from said holding means.

2. In combination a circuit breaker for use in a metalclad compartment having a pair of cooperating contacts, first and second terminals electrically connected to said cooperating contacts both being positioned along the rear wall of said circuit breaker, a first current limiting fuse means removably mounted to the rear wall of said circuit breaker, a second fuse means removably mounted to the front of said circuit breaker, said first fuse means being connected in series relationship with one of said cooperating contacts and said first terminal, said second terminal being connected to the other of said cooperating contacts, said second fuse means being connected in parallel with said first fuse means, mechanical operating means for disengaging said cooperating contacts, tripping means for actuating said operating means, said second fuse means including means to actuate said tripping means upon the occurrence of a fault condition, the resistivity of said second fuse means being substantially greater than the resistivity of said first fuse means to channel substantially all of the current passing through said parallel combination to pass through said first fuse means during normal operation, fuse holding means for receiving said second fuse means connected to said tripping means, and being positioned along the front wall of said circuit breaker, said fuse holding means including boot means biased to engage the side of said second fuse means and movable to actuate said tripping means when said second fuse means is removed from said holding means.

3. In combination a multiphase circuit breaker for use in a metal-clad compartment having a pair of cooperating contacts for each phase, first and second terminals electrically connected to said cooperating contacts both being positioned along the rear wall of said circuit breaker, a first plurality of current limiting fuses, one for each phase, removably mounted to the rear of said circuit breaker, a second plurality of fuses, one for each phase, removably mounted to the front of said circuit I breaker, each of said first fuse-s being connected in series is mit said tripping means to be operated by any one or all of said second fuses upon the occurrence of said fault condition, fuse holding means for receiving said second plurality of fuses connected to said tripping means, and being positioned along thefront wall of said circuit breaker, said fuse holding means including boot means "for each phase, removably mounted to the rear of said circuit breaker, a'second plurality of fuses, one for each phase, removably mounted to'the front of saidc-ircuit breaker, each of said first fuses being connected in series relationship with a cooperating contact and said first terminal of its associated phase, said second terminal being connected to the other of said cooperating contacts, each of said secondfuses being connected in parallel with one of said first fuses, mechanical means for simultaneously disengaging the cooperating contacts of each phase, tripping me-ans for actuating said mechanical means, each of said second fuses including means for operating said tripping means upon the occurrence of a fault condition, meansto'pe'rmit said tripping means to be operated by any one or all of said second fuses upon the occurrence of said fault condition, the resistivity of said second fuses being substantially greater than the resistivity of said first fuses to cause substantially all of the current flowing in each parallel combination to r be channeled through said first fuses during normal operation, fuse holding means for receiving said second plurality of fuses connected to said tripping means, and being positioned along the front wall of said circuit breaker, said fuse holding means including boot means biased to engage the side of said second fuse means and movable to' actuate said tripping means When any one of said sec ond fuses is removed from said holding means.

' 5. In combination a multiphase circuit breaker for use in a metal-clad compartment having. a pair of cooperating contacts for each phase, first and second terminals electrically connected to said cooperating contacts both being positioned along the rear wall of said circuit breaker, a first plurality of fuses, each of said first fuses being serially connected with one pair of said cooperating contacts and positioned along therear wall of said circuit breaker, a second plurality of fuses, each of said second fuses being connected in parallelwith one of said first fuses, a housing for said second fuses mounted to the front Wall of said circuit breaker, an operating mechanism for moving said cooperating contact pairs towards a disengaged position, tripping means for actuating. said operating mechanism mounted in said fuse housing, each of said fuses having means responsive to a fault condition for actuating said tripping means, fuse holding means for receiving said second plurality of fuses connected to said-tripping means, and being positioned along the front wall of said circuit breaker, said fuse holding means including boot means biased to engage the side of said second fuse means and movable to actuate said tripping means when any one of said second fuses is removed from 'saidholding means.

6. In combination a multiphase circuit breaker for use in a metal-clad compartmenthaving. a pair of cooperatting contacts for each phase, first and second terminals for each phase electrically connected to said cooperating contacts both being positioned along the rear Wall of said circuit breaker, a first plurality of fuses, each of said first fuses being serially connected with one pair of said cooperating contacts and positioned along the rear wall of said circuit breaker, a second plurality of fuses,

each of said second fuses being connected in parallel with one of said first fuses, a housing for said second fuses mounted to the front wall of said circuit breaker, an operating mechanism for moving said cooperating contact pairs towards-a disengaged position, first tripping means for actuating said operating mechanism mounted in said fuse housing, each of said fuses having means responsive to a fault condition for actuating said tripping means, second tripping means mounted in said housing for operating said first tripping means when any one or all of said second fuses are not replaced in said fuse housing to prevent said cooperating contact pairs to be moved to an engaged position.

7. In combination a multiphase circuit breaker for use in a metal-clad compartment having a pair of cooperating contacts for each phase, first and second terminals electrically connected to said cooperating contacts both being positioned along the rear Wall of said circuit breaker, a first plurality of fuses, each of said first fuses being serially connected with one pair of said cooperating contacts and positioned along the rear Wall of said circuit breaker, a second plurality of fuses, each of said second fuses being connected in parallel with one of said first fuses, a housing for said second fuses mounted along the front wall of said circuit breaker, an operating mechanism for moving said cooperating contact pairs towards a disengaged position, tripping means for actuating said operating mechanism mounted in said fuse housing, each of said fuses having means responsive to a fault condition for'actuating said tripping means, cover means for said'fu'se housing, a yoke secured to said cover means for positioning and securing said second fuses, said cover means yoke removing said second fuses from said housing when said cover means is removed therefrom and inserting said fuses in said housing when said cover means is replaced.

8. In combination a circuit breaker for use in a metalclad compartment having a pair of cooperating contacts, first and second'terminals electrically connected to said cooperating contacts both being positioned along the rear Wall of saidcircuit breaker, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means for receiving said second fuse means, said housing being mounted to the front wall of said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts and said first terminal, and positioned along the rear Wall of said circuit breaker, said second terminal being connected to the other of said cooperating contacts,

said second fuse eans being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted 1 to rotate in response to operation of said second fuse means, operating means for moving said cooperating contacts towards 'a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement With said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to'be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts.

9. In combination a circuit breaker for use in a metalclad compartment having a pair of cooperating contacts,

"first and second terminals electrically connected to said cooperating contacts both being positioned along the rear Wall of said circuit breaker, first fuse means mounted to said circuit breaker rear wall for limiting the amount of fault current passing through said circuit breaker, 'second fuse means, a housing means for receiving said second fuse means mounted Within said housing, said housing being mounted to the front wall of said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts and said first terminal, said second terminal being connected to the other of said cooperating contacts, said second fuse means being connected in electrical parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means and being adapted to rotate in response to operation of said second fuse means, operating means for moving said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means.

10. In combination a circuit breaker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing means adapted to receive said second fuse means mounted within said housing, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, said second fuse means being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted to rotate in response to operation of said second fuse means, operating means for moving said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means.

11, In combination a circuit breaker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means adapted to receive said second fuse means, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, said second fuse means being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted to rotate said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means l9 be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means, said housing and said cover being formed of insulating material.

12. In combination a circuit braker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means adapted to receive said second fuse means, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, with second fuse means being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted-to actuate said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said openating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means, the resistivity of said second fuse means being substantially greater than the resistivity of said first fuse means to cause substantially all of the current flowing through said parallel combination to be channeled through said first fuse means during normal operation.

13. In combination a circuit breaker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means adapted to receive said second fuse means, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, with second fuse means being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted to actuate said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means, the resistivity of said second fuse means being substantially greater than the resistivity of said first fuse means to cause substantially all the current flowing through said parallel combination to be channeled through said first fuse means during normal operation, said first fuse means being adapted to increase its resistivity in response to a fault current condition to divert the flow of fault current from said first fuse means to said second fuse means.

14. In combination a circuit breaker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means adapted to receive said second fuse means, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, with second fuse means being connected in parallel with said first fuse means, trip means pivotally mounted in said housing adjacent said second fuse means adapted to actuate said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from move ment towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means, the resistivity of said second fuse means being substantially greater than the resistivity of said first fuse means to cause substatially all of the current flowing through said parallel combination to be channeled through said first fuse means during normal operation, alternate arc plates of said arc plate assembly having their slots positioned to one side of said longitudinal axis and the remaining are plates of said assembly having their slots positioned to the side of said longitudinal axis opposite the said one side to provide maximum elongation of an arc existing in the region defined by said slots.

15. In combination a circuit breaker having a pair of cooperating contacts, first fuse means mounted to said circuit breaker for limiting the amount of fault current passing through said circuit breaker, second fuse means, a housing including means adapted to receive said second fuse means, said housing being mounted to said circuit breaker, said first fuse means being serially connected to one of said cooperating contacts, with second fuse means being connected in parallel with said first fuse means, trip means pivotaly mounted in said housing adjacent said second fuse means adapted to actuate said cooperating contacts towards a disengaged position, pivotally mounted linking means for operatively connecting said operating mechanism to said trip means, said linking means being biased towards engagement with said operating mechanism, latch means connected to said trip means for restraining said linking means from movement towards said operating means, said second fuse means including pin means for rotating said trip means causing said latch means to be disengaged from said linking means in response to a fault current condition to disengage said cooperating contacts, said housing having a transparent cover means for visual inspection of said second fuse means, a yoke secured to said cover for positioning and securing said second fuse means, second trip means mounted in said housing adjacent said fuse receiving means for actuating said operating mechanism to prevent said cooperating contacts from being engaged when said second fuse means is removed from said fuse receiving means, the resistivity of said second fuse means being substantially greater than the resistivity of said first fuse means to cause substantially all of the current flowing through said parallel combination to be channeled through said first fuse means during normal operation, said first fuse means being adapted to increase its resistivity in response to a fault current condition to divert the flow of fault current from said first fuse means to said second fuse means, alternate arc plates of said are plate assembly having their slots positioned to one side of said longitudinal axis and the remaining are plates of said assembly having their slots positioned to the side of said longitudinal axis opposite the said one side to provide maximum elongation of an arc existing in the region defined by said slots.

References Cited by the Examiner UNITED STATES PATENTS 2,824,929 2/58 Edmunds 200-116 2,911,502 11/59 Edsall 200-416 2,919,328 12/59 Kozacka 200116 2,924,688 2/ Edmunds 2001 16 2,928,997 3/60 Edmunds 200-1l6 2,950,370 8/60 Swain 200116 3,009,036 11/61 Dorfman et al. 200-114 FOREIGN PATENTS 220,420 2/ 59 Australia. 604,748 7/ 48 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

RICHARD M. WOOD, Examiner.