US3136921A - Circuit breakers - Google Patents

Description

H. D. DORFMAN ETAL 3,136,921

June 9.,V 1964 CIRCUIT BREAKERS 3 Sheets-Sheet l Filed Dec. 10, 1957 June 9, 1964 H. D. DORFMAN ETAL 3,136,921

CIRCUIT BREAKERS 3 Sheets-Sheet 2 Filed Deo. 10, 1957 Fig.3.

Fig.4.

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| NVENTORS Hiller D. Dorfman 8 Robert H. Flick BY Ef ATTRNEY June 9, 1954 H, D. DQRMAN ETAL. 3,136,921

CIRCUIT BREAKERS 3 Sheets-Sheet 3 Filed D60. 10, 1957 Fig. 5.

United States Patent() 3,136,921 CIRCUIT BREAKERS `Hiller D. Dorfman, Beaver, and Robert H. Flick,

This invention relates to circuit breakers and more particularly to circuit breakers embodying current limiting means.

An object of the invention is to provide ak circuit interruptingkdevice embodying an automatic circuit breaker and an electromagnetic current limiter which introduces ya high resistance in the circuit through the breaker when rthe contacts open to reduce the current required to be interrupted by the breaker.

Another object of the invention is to provide a circuit interrupting device embodying a circuit breaker responsive to overload circuits to interrupt the circuit and an electromagnetic current limiter operable in response to excessive currents before said circuit breaker opens to draw an arc and thereby introduce a high resistance in the circuit and reduce the current required to be interrupted by the circuit breaker.

Another object of the invention is to provide a circuit interrupting device including a circuit breaker and a highspeed electromagnetic current limiting device having contacts connected in series with the contacts of the circuit breaker which open in advance of opening of the circuit breaker contacts to reduce the current the circuit breaker is required to open.

The invention, both as to structure and operation, tgether with additional objects and advantages thereof, will be best understood. from the following detailed description thereof when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE 1 is a vertical sectional view of a circuit breaker embodying the principles of the invention;

FIG. 2 is a vertical sectional view showing the trip device for the circuit breaker;

FIG. 3 is a top plan View showing the current limiting device; v

FIG. 4 is an elevational view partly in section of the current limiting device;

FIG. 5 is a top plan view of a modification of the current limiting device; and

FIG. 6 is an elevational view partly in section of the current limiter shown in FIG. 5.

Referring to FIG. l of the drawings, the circuit breaker comprises generally a base 11 and cover 13 both of molded insulating material, a stationary contact 15, a movable Contact 17, an operating mechanism 19 and a trip device 21. The circuit breaker is of the three-pole type and is provided with a set of stationary and movable contacts in each compartment of the housing comprising the base 11 and cover 13.

Each of thefstationary contacts is rigidly mounted on the inner end of a conducting strip 23, the other end y of which is connected to a terminal 24 and the movable contact 17 for each pole is mounted on a contact arm 25. Each of the contact arms 25 is supported on a movable switch arm 27. The movable switch arms 27 are rigidly secured to a tie bar 29 which is common to all of the poles of the breaker. The operating mechanism 19, which includes themovable switch arms 27, is supported in a frame 31 rigidly secured to the base 11 of the housing.

The operating mechanism 19 comprises a releasable cradle 33 pivotally supported on the frame 31 and connected to the switch arm 27 for the center pole by a i n 3,135,921 Patented June 9, 1964 ice toggle comprising toggle links 35 and 37. The toggle 'links 35 and 37 are pivotally connected together by a knee pivot pin 39. The toggle link 35 is pivotally connected to the releasable cradle 33 by a pivot pin 41 and the toggle link 37 is pivotally connected to the movable switch member Z7 for the center pole by a pivot pin 43.

The toggle 35-37 is manually operated to open and close the contacts by means of a generally U-shaped operating lever 45 pivoted on the frame 31 and having a handle member 47 mounted thereon and extending out through an opening 49 in the cover 13. Two overcenter operating springs 51, only one of which is shown, are connected under tension between the knee pin 39 of the .toggle and the outer portion of the operating lever 45.

The contacts 15-4-17 are opened manually in a Well known manner by manipulation of the handle 47 to the oit position which causes, through the overcenter springs 51, collapse of the toggle 35-37 and opening movement of the switch arms 27 for all of the poles.

The contacts are closed yby reversed movement of the handle 47 from the off to the on position. During this movement the overcenter springs 51 straighten the toggle 35-37 and closes the contacts with a snap action.

The circuit breaker is tripped open by operation of the trip device 21 which releases the cradle 33. When the cradle 33 is released, the overcenter springs 51 act through the toggle 35 to rotate the cradle 33 counterclockwise to carrythe pin 41 over to the left of the line of force of the overcenter springs 51. This causes collapse of the toggle 35-37 and movement of the switch arms 27 to the open position.

The trip device 21 comprises a base 53 (FIGS. 1 and 2) mounted on a yU-shaped bracket 55 rigidly mounted by means of screws 57 to the base 11 of the breaker. A sealed cover 59 is provided to enclose the trip device. The screws 57 also serve to secure to the base 11, one end of a conductor k61 which has its other end suitably connected to a terminal 63 (FIG. l). The inner end of the conductor 61 is connected to the movable contact arm 25 by a ilexible conductor 65. Pivotally mounted (by means not shown) on the base 53 of the trip device, is a trip bar 67 which extendsr across all of the poles of the breaker.

The conductor 61, to the right of the base 53 (FIG. 2) of the trip device, formsk a loop 69 to the righthand leg of which is secured by means of rivets 71 a bimetal element 73 which extends upwardly adjacent the trip bar 67. The leg of the loop 69 to which the bimetal element 73 is secured forms a heater portion for heating the end of the birnetal element 73, which is secured thereto, by

conduction. T hetrip bar 67 is provided with a latch 75 which normally engages a latch mechanism shown generally at 77 and holds it in operative positions thereby releasably restraining the cradle 33.

When the bimetal element 73 is heated a predetermined amount in responseto an overload current, it delects toward the right causing the free upper end thereof to engage an adjusting screw 79 in a projection of the trip bar 67 and rotate the trip bar clockwise. This causes the latch to release the latch mechanism 77 which, in turn, releases the cradle 33 to etiect automatic opening of the breaker in the previously described manner.

The circuit breaker is also tripped open instantaneously in response to fault currents or short-circuit currents by means of a tripping elcctromagnet 81 (FIG. 2). The tripping magnet 81 comprises a fixed magnet yoke 83 supported on a bracket 85 mounted on the rivets 71, and a movable armature 87 secured to one end of a trip rod 89 slidably mounted in an extension 91 of the bracket 85. The trip rod 89 together with the armature 87 is biased upwardly to unattracted positions by a compression spring 93 and at its upper end the trip rod 9 is provided with a head 95 for engaging and actuating the trip bar 67.

When an overload above a predetermined value of, for example, 1000% of normal rated current or a short circuit current occurs, the electromagnetic trip means 81 is energized and attracts the armature 87 causing the head 95 of the rod 89 to engage and rock the trip bar 67 clockwise to effect instantaneous tripping of the breaker.

Before the breaker can be closed following an automatic tripping operation, it is necessary to reset and relatch the mechanism. This is effected by movement of the handle 47 to the off position. During this movement a projection 97 on the operating lever 45 engages and moves the cradle 33 back to its normal latched position. Thereafter the breaker is closed in the previously described manner.

iCurrent limiting means is provided in each pole of the breaker. The current limiting means functions in response to very high currents to limit the current the circuit breaker is required to interrupt thereby increasing the interrupting capacity for a circuit breaker of a given ratin Thge current limiter, shown generally at 191 (FIGS. 1, 3 and 4), is supported between spaced plates 103 and comprises a stationary contact 105 mounted on the inner end of a conductor 167. The conductor 107 is supported between the plates 103 by lateral projections 169 extending into facing recesses in the plates. The conductor 107 extends out through the adjacent end wall of the base 11 of the interrupter and terminates in a'terminal portion 111. A moving contact 113 is mounted on one end of a movable U-shaped switch arm 115 having its other end pivoted in notches formed in one leg 117 of an angular member 119 of magnetic material and forming part of an electromagnetic 120. The other leg 121 of the angular member 119 is provided with lateral extensions 123 which extend into recesses in the spaced plates 1113 to support the member 119. Mounted on the leg 121 is a magnet core 125 having an energizing coil 127 Wound thereon but insulated therefrom by an insulating tube 129. One end of the coil is rigidly secured to a terminal 131 secured to the terminal 24 (FIG. l) to which the end of the conductor 23 is secured. The other end of the coil 127 is connected by means of a flexible conductor 133 to the movable switch arm 115. An armature 135 is mounted on the switch arm 115 and a spring 137 biases the switch arm to the normally closed position. An arc control device 13S, comprising a plurality of slotted plates 139, is provided for controlling the arc drawn between the contacts 1115-113.

The current limiter is so constructed that it does not respond to currents much below the interrupting capacity of the breaker. On the occurrence of a fault current at or near the interrupting capacity of the breaker the electromagnet 12@ of the current limiter 101 operates at high-speed to open the contacts 105--113 before the circuit breaker contacts -1'7 open. When the contacts 1135-113 of the current limiter 191 separate, an arc is drawn in the arc control device 138. The device 138 is so designed that the arc is not immediately extinguished, but hangs on, thus introducing a high resistance in the circuit breaker and thereby reducing the current required to be interrupted by the circuit breaker. The result is that the effective interrupting capacity of the breaker is greatly increased.

After the current is interrupted by opening of the breaker contacts deenergizing the electromagnet 120 of the current limiter, the spring 137 acts to close the contacts 10S-113.

FIGS. 5 and 6 illustrate a modication of the current limiter shown in FIG. 4, the structure and operation of which is generally the same as that just described. This current limiter remains open after it functions and must be manually reset. f

The stationary contact 165 of the FIG. 6 modification is mounted on a conductor 141 which has integral therewith a terminal 143 connected to the terminal 24 to which the conducting strip 23 (FIG. l) is connected. The coil of the electromagnet is connected to a terminal 145 and by the flexible conductor to the moving switch arm 115. An overcenter spring, which is not shown, but the centerline of which is indicated at 147, is connected under tension between a spring stud 149 on the leg 117 of the magnetic member 119 and a struck out portion 151 of the switch arm 115. A resetting plunger 153 is slidably mounted in a support and guide member 155 mounted between the side plates 103, and has a nger piece 157 extending out through an opening in the cover 13 of the housing to permit manual resetting of the device.

The operation of the current limiting device shown in FiG. 6 is the same as that shown in FIG. 4 except that when the switch arm 115 operates in response to excessive fault currents to the open position, the line of force of the overcenter spring 147 moves above the pivot of the switch arm and holds the switch arm in the open position after the current is interrupted by opening of the breaker contacts. The device is reset by pushing inwardly on the nger piece 157 which moves the switch arm to the closed position and in so doing moves the line of force of the overcenter spring 147 below the pivot of the switch arm 115 where it then biases the switch arm closed.

Having described the invention in accordance with the provisions of the patent statutes, it is to be understood that various changes and modilications may be made therein without departing from the spirit of the invention.

We claim as our invention:

1. A circuit-interrupting device comprising a circuitbreaker, said circuit-breaker comprising a pair of circuitbreaker contacts and means manually operable to open and close said circuit-breaker contacts, means releasable to eifect opening of said circuit-breaker contacts, trip means automatically operable in response to overload currents to effect release of said releasable means, a current limiting device comprising current-limiting contacts connected in electrical series relation with said circuitbreaker contacts, said current-limiting device comprising an electro-responsive device automatically operable only in response to excessive currents to open said currentlimiting contacts to thereby draw an arc between said current-limiting contacts to thereby introduce a resistance in the circuit through the circuit interrupting device, and means for maintaining said arc until said circuitbreaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt.

2. A unitary circuit interrupting device comprising an insulating housing, a control mechanism supported within said housing and comprising a circuit-breaker and a current limiting device, said circuit-breaker comprising a pair of circuit-breaker contacts and manually operable means operable from outside of said housing to open and close said circuit-breaker contacts, means releasable to eiect opening of said circuit-breaker contacts, trip means operable automatically in response to overload currents to efrect release of said releasable means, said current limiting device comprising current-limiting contacts connected in series relation with said circuit-breaker contacts, said current limiting device comprising an electro-responsive device automatically operable only in response to excessive currents to open said current-limiting contacts to draw an arc between said current-limiting contacts to thereby introduce a resistance in the circuit interrupting device, and means for maintaining said arc until said circuit-breaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt,

3. A circuit interrupting device comprising a circuitbreaker having relatively movable contacts and means releasable to effect opening of said circuit-breaker contacts, trip means operable in response to overload currents to release said releasable means, current limiting means comprising a stationary contact, a movable switch arm having a movable contact thereon, said stationary and said movable current-limiting contacts being ycon-k nected in electrical `series with said circuit-breaker contacts, an overcenter spring normally biasing said switch arm closed, electroresponsive means operable in response to excessive currents to move said switch arm to an open position to draw an arc between said currentlimiting contacts `before said circuit-breaker contacts open, arc control means for maintaining said arc until said circuit-breaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt, and said overcenter spring in the open'position of said switch arm biasing said switch arm open.

4. A circuit interrupting device 'comprisingy a circuit breaker 'having relatively movable contacts and means releasable to eiect opening of said circuit-breaker contacts, trip means operable in response to overload currents to release said releasable means, current limiting means comprising a stationary contact, a movable switch arm having a movable contact thereon, said stationary and said movable current-limiting contacts being connected in electrical series with said circuit-breaker contacts, an overcenter spring normally biasing said switch arm closed, electroresponsive means operable in response to excessive currents to move said switch arm to an open position before said circuit-breaker contacts open to thereby draw an arc between said current-limiting contacts before said circuit-breaker contacts open, are control means for maintaining said arc until said circuit-breaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt, said overcenter spring in the yopen position of said switch arm biasing said switch arm open, and manual means operable to close saidfswitch arm.

5. A circuit interrupter comprising a circuit-breaker having relatively movable contacts and means releasable to eiect opening of said circuit-breaker contacts, trip means automatically operable in response to overload currents to cause release of said releasable means, and

yan electr'oresponsive device automaticallyoperable only in response to excessive currents to draw an arc inthe circuit of the breaker before said circuit-breaker contacts open and tok maintain said arc until said circuitbreaker contacts open to tnereby reduce the current that said circuit-breaker contacts will interrupt.

6. A circuit interrupter comprising a circuit-breaker having relatively movable contacts and means releasable to effect opening of said circuit-breaker contacts,V trip means automatically operabley in response to overload currents to cause release of said releasable means, and an electroresponsive device having separable contacts f automatically operable only in response to excessive currents to draw an arc in the circuit of the breaker before said circuit-breaker' contacts open and to maintain said arc until said circuit-,breaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt.

7. A circuit interrupter comprising a' circuit-breaker having relatively 'movable circuit-breaker contacts and means releasable yto eiect separation of said circuitbreaker contacts, trip means automatically operable in response to overload currents'to cause release of said releasable means, electroresponsive current limiting means connected in series relation in the circuit throughy said breaker contacts, said current limiting means comprising separable contacts for drawing an arc therebetween, and electromagnetic means automatically operable only in response to excessive currentsy in said circuit to effect high-speed separation of said separable contacts to draw an arc rbetween said separable contacts before said relatively movable circuit-breaker contacts open, and an arc retaining device for holding said arc until said relatively movable circuit-breaker contacts open to thereby reduce the current that said circuit-breaker contacts will interrupt.

- References `Cited in the tile `of this patent UNITED STATES PATENTS p 1,479,465 rGreenwood s Jan. 1, 1924 2,177,774 Jackson Oct. 31, 1939 V2,617,861 Ridgley Nov 11, 1952 2,819,429 Skeats Jan. 7, 1958 2,828,392 Leopold Mar. 25, 1,958 2,920,164 Edsall Jan. 5, 1960k FOREIGN PATENTSv 366,966 Great Britain Feb. 12,v 1932 562,729 Great Britain July y13, 1944

Claims (1)

1. 6. A CIRCUIT INTERRUPTER COMPRISING A CIRCUIT-BREAKER HAVING RELATIVELY MOVABLE CONTACTS AND MEANS RELEASABLE TO EFFECT OPENING OF SAID CIRCUIT-BREAKER CONTACTS, TRIP MEANS AUTOMATICALLY OPERABLE IN RESPONSE TO OVERLOAD CURRENTS TO CAUSE RELEASE OF SAID RELEASABLE MEANS, AND AN ELECTRORESPONSIVE DEVICE HAVING SEPARABLE CONTACTS AUTOMATICALLY OPERABLE ONLY IN RESPONSE TO EXCESSIVE CURRENTS TO DRAW AN ARC IN THE CIRCUIT OF THE BREAKER BEFORE SAID CIRCUIT-BREAKER CONTACTS OPEN AND TO THEREBY REDUCE THE CURRENT THAT SAID CIRCUIT-BREAKER CONTACTS WILL INTERRUPT.

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