US3309573A

US3309573A - Repeating circuit interrupter

Info

Publication number: US3309573A
Application number: US437762A
Authority: US
Inventors: Date Kazuo Henry
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1965-03-08
Filing date: 1965-03-08
Publication date: 1967-03-14
Anticipated expiration: 1984-03-14

Description

March 14, 1967 K, DATE REPEATING CIRCUIT INTERRUPTER Filed 'March 8, 1965 INVENTOR. Kazaa H, Da/ 9 United States Patent O 3,309,573 REPEATING CIRCUIT INTERRUPTER Kazuo Henry Date, South Milwaukee, Wis., assignor to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Mar. 8, 1965, Ser. No. 437,762 9 Claims. (Cl. 317-22) This invention relates to repeating circuit interrupters and, more particularly, to the class of circuit interrupters commonly known as reclosers.

A recloser may be characterized as a circuit protective device having fault measuring means, interrupting switches, lswitch opening and reclosing means and an operation counting and lockout mechanism. n More speciically, reclosers are commonly provided with means connected to the line being protected and which is responsive to overload currents to initiate a switch opening operation, switch reclosing means operable after each opening operation, normally inactive time delay means, and operation counting and lockout means which is operative to initiate time delayed switch opening after a series of rapid opening operations and for preventing closure after a predetermined number of opening operations. The fault sensing, operation counting and time delay means of reclosers often consist of electronic circuitry which is energized by a low voltage D.C. source. In the event that such electronic circuitry or its low voltage power source should fail wheny the circuit interrupters contacts are closed, the operation of a backup circuit interrupter would be required whereby service would 'be interrupted in a substantially greater portion of the line than the location of the fault would normally require.

It is an object of the invention to provide new and improved repeating circuit interrupter or recloser.

A further object of the invention is to provide an electronically controlled repeating circuit interrupter with means for initiating an opening operation in the event of a failure in the electronic control or its low voltage power source. j

These yand other objects and advantages of the instant invention will become more apparent from the detailed description thereof taken with the accompanying drawing which schematically illustrates a repeating circuit interrupter incorporating the instant invention.

In general terms, the invention comprises a repeating circuit interrupter having an electronic control for initiating an opening operation upon the occurrence of an abnormal circuit condition and independent control means responsive to overload current and operable to produce a time delayed switch opening operation in the event of a failure in the electronic control or its low voltage power source.

Referring now to the drawing, the schematically illustrated repeating circuit interrupter is shown to include interrupter switches 10, overload responsive means 12, switch opening means 14, Aauxiliary switch opening means 15, switch reclosing means 16, and operation counting and lockout means 17. The over-current responsive means 12 is operative to actuate the switch opening means 14 upon the occurrence of an overload in the system being protected so that the interrupting switches will each be moved to its open position. Upon this event, the reclosing means 16'is made operable to return the interrupting switches to their closed position. The operation counting and lockout means 17, which includes stepping relay 18, is operable to initiate time delayed opening or reclosing operations if the fault does not clear after an initial series of rapid operations and, finally, to prevent reclosure of the main contacts 10 if the fault does not clear after a predetermined number of such delayed operations. The auxiliary switch opening means 3,309,573 Patented Mar. 14, 1967 ICC 15 is provided to open the main contacts 10 upon failure of the overcurrent responsive means 12 or its low voltage power source 19-20.

The `apparatus schematically illustrated in the drawing is generally disposed in a metallic housing (not shown) which supports a set of incoming porcelain bushings 21, connection to the phase wires A, B and C, and a set of outgoing porcelain bushings 22.

The overcurrent responsive means 12 is shown coupled to phase A by means of current transformer 23 and a full wave rectifier 24. As those skilled in the art will appreciate, the overcurrent responsive means 12 is similarly connected by means of current transformers and full wave rectitiers, to each of the other phases B and C. The overcurrent responsive means 12 consists of electronic circuitry (not shown) and includes an overcurrent sensing portion 26, a timing portion 27 and an output portion 28. The various portions of the overcurrent responsive means 12 are merely shown in symbolic form, it being suicient for an understanding of the present invention to state that the overcurrent sensing portion 26 is operable when the rectified current at the output of rectier 24 exceeds a minimum value, to provide a signal to the timing portion. Upon the receipt of this signal, the timing portion 27 initiates a timing operation and, after a predetermined interval, provides a signal to the output portion 28, which then initiates a switch opening operation in a manner to be described. For a more detailed description of the overcurrent sensing portion y26, the timing portion 27 and the output portion 28, reference is made to copending Application Serial n.

No. 325,215 filed November 21, 1963, and assigned to the assignee of the instant invention.r

The switch opening means 14 is shown to includean electromagnetic tripper 30 having a coil 36 which is connected by conductor 37 to the negative powerrsupply terminal 19 and by lconductors 38, 3940 and 42y and contacts 43. Contacts 43, which are mechanically connected tothe output portion 28 of the overcurrent responsive rneans 12, are normally open so that coil 36 remains de-energized under normal operating conditions.

Upon the occurrence of a fault in one of the phases A, B 0r C, output portion 28 will be made operative to close contacts 43, thereby energizing coil 36. Upon this event, the trip rod 52 of tripper 30 is moved into engagementwith the lower end of a trip lever 53 to pivot said lever in a counterclockwise direction against the inuencei of spring 54. As a result, the lower end of trip lever 53 is moved into engagement with a rocking lever 56 carried on the end of a trip shaft 58. This rotates trip shaft 58 clockwise ,to effect tripping of the recloser in the manner to be described in the ensuing paragraphs.

The mechanical portion of the recloser to be described next is merely schematically illustrated in the drawingfor the sake of brevity. A more complete description of the assembly appears in U.S. Patent 2,804,521 issuedr to A. Van Ryan et al., and assigned to the assignee of the instant invention.

The interrupting switch 10 of each phase is carried by associated bell cranks 60', 61 and `62 which are adapted to pivot on fixed pins 64, and 66, respectively. Each lbell crank is further pivotally connected at pivots designated 67 to a common power bar 68 to which a switch opening spring 69 is attached. Under normal circuit conditions, when the Irecloser is closed, as shown in the` drawing, the opening spring `69 tends to shift the power bar -68 to the right and thereby rotate bell crank 60, 61 and 62 simultaneously in a clockwise direction to open the various switches 10 by a force transmitted from the bell cranks through insulating switch links 70. Such opening action is, however, normally prevented 'by a collapsible general latch means or toggle linkage assembly 71. When the toggle linkage assembly 71 is in a rigid condition, it restrains the power bar 68 and, accordingly, the switches from being operated by the opening spring 69.

When the `repeating circuit interruptor is closed as shown in the drawing, the toggle linkage -assembly 71 effects a rigid connection between the bell crank 60 and a rocking lever 73, the latter of which is normally latched and participates in a switch resetting operation to be explained. The toggle linkage assembly 71 comprises a long link 74 pivotally connected near its mid-point by a pin 76 to a triangularly shaped link 77 which, in turn, is pivotally connected to the rocking lever 73 at 78. The tendency is for the elongated link 74 to rotate in a clockwise direction under the influence of opening spring 69 acting on the power bar `62%, but this is normally prevented by a semicircular latch member 80 that acts as `a stop for link 74. Member 80 is affixed to trip shaft 58 which, in turn, is rotatably mounted on triangular link 77.

The semi-circular member 80 is also provided with an ear 82 which is normal-ly biased toward a stop pin 83 by a small spring 84 anchored to the triangular link 77. The tip 86 of the long link 74 bears in low frictional relation on the outer periphery of the semicircular member 80, so that clockwise rotation of the trip shaft 58, due to the operation of the tripper 30, as described earlier, will cause clockwise rotation of member 80 against the force of the spring 84 to allow the tip 86 of member 74 to move past the flattened portion of member 80 so that the toggle links 74 and 77 are free to rotate. Upon this event, bell cranks 60, 61 and 62 rotate clockwise through a limited angle opening the main switches 10. The opening of the main switches 10 in this manner interrupts the cur- -rent flowing in phases A, B and C, so that the output from the overcurrent responsive means 12 ceases. Upon this event, contacts 43 will open to de-energize the circuit to trip coil 36.

The rocking lever 73, referred to earlier, is carried on a rocking shaft 87 that remains inactive until the interrupting switches 10 are fully open. This results fro-rn the latching of rocking lever 73 by a latch arm 88 that is biased by a spring 89 in a clockwise direction around a fixed pivot pin 90 and against a stop pin 91. When the main switches 10 reach their fully open positions, however, the center bell crank 61 swings clockwise and en gages the l-atch lever 88 freeing the rocking lever 73. The rocking lever 73 then rotates counterclockwise under the influence of a spring 92 to cause the toggle assembly 71 to be -reset in a rigid condition in preparation for the power bar 60 being moved to the left so that the various main interrupting switches may again be reclose-d sirnultaneously.

During the brief interval immediately `following the opening of the main interrupting switches 10 and during the time toggle assembly 71 is set, the rotation of the rocking lever 73 also elevates a resetting of magnetic plunger 93 to which it is attached -by an insulating link 94 and which is a portion of the reclosing means 16. The resetting plunger 93 resides in a dashpot 95 surrounded by a reclosing solenoid coil 96 that Ais -controlled by a switch 98 which is operable upon the rotation of the rock shaft 87 through a toggle linkage assembly 99 to which it is connected by a vertical link 100. The toggle linkage 99 includes a first link 102 which is connected at one end to link 100 and at its other to a fixed pin 103. In addition, the second link 104 is also connected at one end to fixed pin 103 while an overcenter spring 106 connects the free ends of each of the toggle links 102 and 104. An arm 108 aixed to the end of rock shaft 87 connects the latter to toggle link 104 by means of a pin and slot 109.

It will be recalled that the rocking lever 73 and the rock shaft S7 are held inactive by the latch arm 83 until the main interrupting switches 10 reach their fully open position, at which time the 'bell crank 61 strikes the latch arm 88, thereby releasing the rocking lever 73 and the rock shaft 87 for counterclockwise rotation under the influence of spring 92. As the rock shaft 87 rotates, arm 10S rocks counterclockwise to swing link 104 in a clockwise direction around the fixed pivot point 103. After link 104 moves overcenter relative to link 102, spring 106 will urge link 102 counterclockwise to rotate the bell cranks 110 and thereby close contacts 111.

Pivotal movement of link 102 is initially prevented, however, by a reclosing time delay assembly 112 which includes an elongate rod 113 mounted for rotation about its longitudinal axis and which has a transversely extending arm 11S for engaging the upper edge of link 102.

The reclosing time delay assembly 112 also includes a solenoid 120 and a time delay relay bank 121 and a switch 122 which is coupled to the rocking lever 73 and which is in open position when said rocking lever is in its unpivoted position shown in FIG. 1.

Conductors

123 and 124, respectively, connect the solenoid 120 to the time delay relay bank 121 and to the negative supply terminal 19 through the switch 122. The other side of the time delay relay bank 121 is, in turn, connected to the positive power supply terminal 20 by conductor 41 and the step switch 147 which is a part of the stepping relay 18.

Before continuing the discussion of the mechanical .portion of the recloser, the operation of the stepping relay 18 will be mentioned briefly. This device accomplishes operation counting and lockout of the recloser in conjunction with

step switches

146 and 147. In addition, operation of the step switches 146 and 147 is effective to change the time delay for the `opening and reclosing operations, respectively.

Prior to the rst opening operation, step switches 146 and 147 are each on tap a. The stepping relay 18 is' connected to conductors 37 and 38 in parallel with coil 36.

When contacts'43 are closed by output portion 28 upon the occurrence of a fault, therefore, the circuit between the negative and positive terminals 19 and 20 will be completed through stepping relay 18, which then operates

switches

146 and 147 to their taps b. k

It will be rec-alled that when the main contacts 10 are in their closed positions, switch 122 will be opened su that solenoid 120 and time delay relay bank i121 will be de-energized. However, when the main switches 10 reach their fully open positions, the rock shaft `87 will be released for rotation in a counterclockwise direction, whereupon switch 122 will be closed to complete the circuit through the time delay relay bank 121. The time delay relay in bank 121 that is connected to tap b will close contacts 121b after a time delay to complete the circuit through solenoid .120. Upon this event, solenoid 120 will pivot arm 136 counterclockwise against the action of spring 13S to rotate elongate rod 113 counterclockwise and to move its end out of engagementwith link 102. This frees link 102 for pivotal movement counterclockwise under the influence of overcenter spring 106 to close contacts 110 and completethe circuit through reclosing solenoid coil 96 between phases A and C.

When the reclosing coil 96 is energized, the resetting magnetic plunger 93 is attracted downwardly, whereupon the rocking lever 73 is rotated in a clockwise direction. This recloses the main interrupting switches 10, extends the opening spring 69 to store energy for the next opening operation, and opens switch 122, thereby de-energizing solenoid and the time delay relay bank 121. Rock shaft 87 also pivots arim 108 clockwise, thereby rotating the toggle linkage 99 to its position shown in FIG. 1 to open the contracts 111 and de-energize coil 96. This completes one opening and reclosing operaiton of the re` closer, which is now poised for another operation.

iFor a more complete description of the time delay relay' bank 121, reference is again made to copending appli-- cation Serial No. 325,215 filed November 2l, 1963, and assigned to the assignee of the instant invention.

Should the fault clear after one opening and reclosing operation, the step switches 146 and 147 will be recycled to their taps a, by means which is not shown but which is well known in the art. However, should the fault persist, the output portion 28 will again be energized after a short time delay to close contacts 43. This will again energize trip coil 36 and stepping relay 18, so that

switches

146 and 147 will each be moved to their taps c to energize the time delay relay connected to tap c of switch 147, whereupon contacts 121C will close after a time delay to energize solenoid coil 120 and institute a second reclosing operation. Similarly, should the fault persist after the second reclosing operation, trip coil 36 would be energized after a time delay dictated bythe time delay circuit connected to tap c of the timing circuit 27 to again open the main switches 10. After the third opening operation, stepping relay 18 will move each of the

switches

146 and 147 to their positions d, whereupon solenoid 120 will be energized through contacts 121d after a time delay to again elfect the closure of the main cont-acts 10.

If the fault continues after the third reclosing operation, switch 43 will be reclosed after a time delay dictated by the time delay circuit connected to tap d of timing circuit 27. This will again energize the trip coil 36 to open the main switches 10. In addition, stepping relay 18 will be energized to move each of the

switches

146 and 147 to their contacts e.

It can be seen that because each of the contacts e of

switches

146 and 147 areropen circuited, solenoid 121) will not be energized even though switch 122 closes when the main contacts open.k The end 115 of blocking shaft 113 will therefore remain in engage-ment with the toggle link 102 and the reclosing coil 96 will remain de-ener- Igized and the main contacts 10 will remain in open position. In this manner, the repeating circuit interrupter is locked in open position after a predetermined number of opening and closing operations and will remain so until the stepping relay 18 is recycled to its initial position by means not shown but which are well known in the art.

It can be seen from the foregoing discussion that a switch opening operation depends upon the operability of the electronic circuitry containedy in the overcurrent sensing portion 26, the timing portion 27 and the output p0rtion 28 of the overcurrent responsive means 12 plus the availability of the low voltage source 19-20. In the event that the overcurrent responsive means 12 or the low voltage D.C. source 19-20 should fail, the trip coil 36 would not beenergizedand, accordingly, the main switches 10 would not open even though a fault would occur in one of the phases A, B or C. For this reason, the auxiliary switch opening assembly is provided.

The auxiliary switch opening means 15 includes a series overload responsive relay 153 connected in each phase and each of which includes a coil 154 connected in series with its respective phase conductor A, B or C. Each of the series coils 154 surrounds a time delay dashpot cylinder 155 in which resides a magnetic plunger 156. An elongate link :158 is connected at its lower end to each of the magnetic plungers 156 and carries a pair of pins 159 intermediate its ends for embracing one arm of an L-shaped lever 160, which is pivotally mounted at 161 and which is engageable at its other end with a pin 162 carried by a common trip bar .164.

If any of the series coils 154 is traversed by minimum trip current, that is, the current which will cause operation of the overload sensing means 12, it attracts its associated magnetic plunger 156 downwardly into the time delay dashpot 155, yand against the spring 166 coupled to the upper end of the link 158. The time delay of each of the dashpots 155 is set so that it will be longer than the time delay of any of the time delay circuits connected to the taps a, b, c or d of time delay circuit 27. Under normal operating conditions, therefore, the overcurrent sensing portion 12 will operate to open circuit the main switches 10 before the plunger 156 can be attracted downwardly into the dashpot cylinder 55. The opening of the main switches 10 will de-energize the series coils 157 so that the spring 166 can return the plungers 156 to their initial positions in the event of -any slight downward movement.

In the event that any of the portions of the overcurrent sensing means 12 should be inoperative or upon the failure of the low voltage source 19-20, the main contacts 10 will not be opened by the trip coil 36. As a result, the coil 154 in the faulted phase will continue to attract its plunger 156 downwardly, causing a downward movement of the attached vertical link 158. This, in turn, causes clockwise rotation of the L-shaped lever 160 to move its upper end into engagement with one of the pins 162 carried by the common trip bar 164, driving said trip bar to the right as viewed in the drawing. As the trip bar 164 moves to the right, its extreme right end will engage a short lever 166 of the lockout latch assembly 178. The lockout latch assembly 170l includes a latch link 171 whose tip 172. normally bears on the shoulder 173 of a lockout latch lever 174 which is carried on the same shaft 175 as the short lever 166.

When the link 164 -strikes the lever 166, the lockout latch lever 174 is rotated clockwise against a holding spring 177 and thereby releases latch link tip 172 so that link 171 may be rotated clockwise by spring 178. This causes the translation to the right of a long link 180 to pivot clockwise a vertical link 181 mounted on rod 113. As a result, a second link' 182, pinned to the lower end of link 181, is moved toward the left and into engagement with the upper end of trip lever 53. This pivots rocker, arm 56 and trip shaft 58 clockwise to trip the main switches 10 in the manner previously described. In addition, a pin 183 extending laterally from the upper end of link 181 moves into engagement with an arm 184 aflixed to blocking shaft 73 to hold the end portion 115 in en- Y gagernent with the toggle link 102 and thereby'to prevent the energization of the closing coil 96.

In addition, manual lockout of the repeating circuit interrupter may be accomplished by rotating a manual operating handle 185 clockwise so as to cause an arm 186 carried by a common shaft 187 to pry the lockout lever 174 clockwise against the holding spring 177 and thereby to effect opening of the main switches 10 in the manner described hereinabove. v

The repeating circuit interrupter may be manually reclosed after the mechanical lockout operation just discussed by pivoting the operating handle 185 counterclockwise to its initial position shown in the drawing, which in turn rotates the latch link 171 counterclockwise until its tip 172 is again latched on the shoulder 173 of a lockout lever 174.

While only a single embodiment of the instant invention has been shown and described, other modifications will be apparent to those skilled in the art and, accordingly, it is not intended to be limited thereby but only by the scope ofthe appended claims.

I claim:

1. A protective device for an electrical system including interrupting contacts for opencircuiting said system, electroresponsive means for opening said interrupting contacts, electronic control circuit means coupled to said system and normally operative upon the occurrence of an overload condition to actuate said electroresponsive means to initiate a switch opening operation, low volt-age power supply means for energizing said electronic control circuit means, an electromotive control means coupled to said system independently of said electronic circuit means and being operatively associated with said electroresponsive means, said electromotive control means being operable in response to an overload in `said system and being independent of said low voltage power supply means and said electroresponsive means to effect the opening of said switch means, and time delay means for delaying the operation of said electromotive control means and having a time delay period longer than that normally required for said electronic circuit means to initiate a switch opening operation.

2. A repeating circuit interrupter for protecting an electrical system, switch means in circuit with said system, rst switch opening means including electronic circuit means coupled to said system and normally being operable upon the occurrence of an overload condition to initiate a switch opening operation, switch closing means operable after each opening operation to close said switch means, operation counting means operable after a predetermined number of opening operations to prevent the operation of said switch closing means, and second switch opening means coupled to said system independently of said electronic circuit means and said operation counting means and being operatively associated with said switch means, said second switch opening means being operable upon the occurrence of an overload in said system to eiect the opening of said switch means and to prevent the operation of said switch closing means, and time delay means for delaying the operation of said second switch opening means and having a time delay period longer than that normally required for said electronic circuit means to initiate a switch opening operation.

3. The repeating circuit interrupter set forth in claim 2 wherein said rst switch opening means includes electroresponsive switch opening means and low voltage power supply means, said electronic circuit means being operable to complete an energizing circuit to said electroresponsive means upon the occurrence of an overload condition, said second switch opening means being operable independently of said low voltage power supply means. g

4. A repeating circuit interrupter for protecting an electrical system, switch means in circuit with said system, electronic circuit means coupled to said system for sensing overload currents therein `and including time delay means, said electronic circuit means normally being operable upon the occurrence of an overload condition to initiate a switch opening operation, switch closing means operable yafter each opening operation to close said switch means, operation counting means operable after a predetermined number of opening operations to prevent the operation of said switch closing means, and electroresponsive switch opening means coupled to said system independently of said electronic circuit means and said operation counting means and operatively associated with said switch means, said electroresponsive switch opening means being operable upon the occurrence of an overload in said system to elect the opening of said switch means and to prevent the operation of said switch closing means, and time delay means for delaying the operation of said electroresponsive means and having a time delay period longer than the time delay period of said electronic circuit means. y 5. A repeating circuit interrupter for protecting an electrical system, switch means in circuit with said system, electronic circuit means coupled to said system for sensing overload currents therein and including time delay circuit means, low voltage power supply means, switch holding means for normally holding said switch means in closed position, rst electroresponsive means coupled to said switch holding means, said electronic circuit means normally being operable upon the occurrence of an abnormal circuit condition to effect the completion of an energizing circuit between said rst electroresponsive means. and said power supply means, said rst electroresponsive means being operative when energized to release said switch holding means, and second electroresponsive means coupled to said system and said switch holding means independently of said electronic circuit means and being operable upon the occurrence of an overload in said system to eiiect the release of said switch holding means, and time delay means for delaying the operation of said second electroresponsive means and having a time delay period longer than the time delay period of said electronic circuit means.

6. A repeating circuit interrupter for protecting an electrical system, switch means inl circuit with said system, electronic circuit means coupled to said system for sensing overload currents therein and including time delay circuit means, low voltage power supply means coupled to said electronic circuit means for supplying energizing power thereto, said electronic circuit means normally being operable upon the occurrence of an overload condition to initiate a switch opening operation, switch closing means operable after each opening operation to close said switch means, operation counting means operable after a predetermined number of opening operations to prevent the operation of said switch closing means, and electromagnetic means independent of said electronic circuit means and said operation counting means and including a coil in series with said system and operable upon the occurrrence of an overload in said system to effect the opening of said switch means and to prevent the operation of said switch closing means, and time delay means for delaying the operation of said electromagnetic means and having a time delay period longer than the time delay period of said electronic circuit means.

7. A repeating circuit interrupter for protecting an electrical system, switch means in circuit with said system, electronic circuit means coupled to said system for sensing overload currents therein and including time delay circuit means, low voltage DC. power supply means, latch means for normally holding said switch means in closed position, electroresponsive means coupled to said latch means, said electronic circuit means normally being operable upon the occurrence of an overload condition to couple said electroresponsive means to said power supply means, said electroresponsive means being operative when energized to release said latch means, .and electromagnetic means including a coil in series with said system and a plunger operatively associated with said latch means and movable toward said coil upon the occurrence of an overload in said system to effect the release of said latch means, and time delay means for delaying the movement of said plunger and having 'a time delay period longer than the time delay period of said electronic circuit means.

8. A repeating circuit interrupter for protecting an electrical system, switch means in circuit with said system, switch opening means urging said switch means toward an open position, electronic circuit means coupled to said system for sensing overload currents therein and including time delay circuit means, low voltage D.C. power supply means, latch means for normally holding said main switch means in closed position, electroresponsive means coupled to said latch means, said electronic circuit means normally being operable upon the occurrence of an overload condition to couple said electroresponsive means to said power supply means, said electroresponsive means being operative when energized to release said switch means for movement toward its open position by said switch opening means, switch closing means operable after each opening operation to close said switch means and to reset said latch means, operation counting means operable after a predetermined number of opening operations to prevent the operation of said switch closing means, and electromagentic means independent of said electronic circuit means and said operation counting means and including a coil in series with said system and a plunger operatively associated with said latch means and movable toward said coil upon the occurrence of an overload in said system to effect the release of said latch means and to prevent the operation of said switch closing means and time delay means for delaying the movement of said plunger and having a time delay period longer than the time delay period of said electronic circuit means.

9. A polyphase repeating circuit interrupter for protecting an electrical system, a plurality lof switch means, one of said switch means being in circuit with each of the phases of said system, electronic circuit means including time delay means coupled to each phase in said system for sensing overload currents therein, said electronic circuit means normally being operable upon the occurrence of an overload condition to initiate the simultaneous opening of each of said switch means, switch closing means operable after each opening-operation to close each of said switch means simultaneously, operation counting means operable after a predetermined number of opening operations to prevent the operation of said switch closing means, and a plurality of electroresponsive means each being coupled to one phase of said system `independently of said electronic circuit means and said operati-on counting means, each of said electroresponsive means being 10 operatively associated with said switch means and each being operable upon the occurrence of an overload in its associated phase of said system t-o elect the simultaneous opening lof said switch means and to prevent the opera- References Cited by the Examiner UNITED STATES PATENTS 3,177,402 4/ 1965 Muchnick et al 317-33 3,229,164 1/1966 McCartney et al. 317-33 X 3,259,803 7/ 1966 Battista 317-31 MILTON O. HIRSHFIELD, Primary Examiner. R. V. LUPO, Assistant Examiner.

Claims

1. A PROTECTIVE DEVICE FOR AN ELECTRICAL SYSTEM INCLUDING INTERRUPTING CONTACTS FOR OPENCIRCUITING SAID SYSTEM, ELECTRORESPONSIVE MEANS FOR OPENING SAID INTERRUPTING CONTACTS, ELECTRONIC CONTROL CIRCUIT MEANS COUPLED TO SAID SYSTEM AND NORMALLY OPERATIVE UPON THE OCCURRENCE OF AN OVERLOAD CONDITION TO ACTUATE SAID ELECTRORESPONSIVE MEANS TO INITIATE A SWITCH OPENING OPERATION, LOW VOLTAGE POWER SUPPLY MEANS FOR ENERGIZING SAID ELECTRONIC CONTROL CIRCUIT MEANS, AN ELECTROMOTIVE CONTROL MEANS COUPLED TO SAID SYSTEM INDEPENDENTLY OF SAID ELECTRONIC CIRCUIT MEANS AND BEING OPERATIVELY ASSOCIATED WITH SAID ELECTRORESPONSIVE MEANS, SAID ELECTROMOTIVE CONTROL MEANS BEING OPERABLE IN RESPONSE TO AN OVERLOAD IN SAID SYSTEM AND BEING INDEPENDENT OF SAID LOW VOLTAGE POWER SUPPLY MEANS AND SAID ELECTRORESPONSIVE MEANS TO EFFECT THE OPENING OF SAID SWITCH MEANS, AND TIME DELAY MEANS FOR DELAYING THE OPERATION OF SAID ELECTROMOTIVE CONTROL MEANS AND HAVING A TIME DELAY PERIOD LONGER THAN THAT NORMALLY REQUIRED FOR SAID ELECTRONIC CIRCUIT MEANS TO INITIATE A SWITCH OPENING OPERATION.