US2354162A - Circuit breaker - Google Patents

Description

J. WEBER CIRCUIT BREAKER Filed March 19, 1942 @j 45 55 4 7 6 7 97 hau/afl of? July 18, 1944.

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Patented July 18, 1944 UNITED sTATEs` PATENT OFFICE CIRCUIT BREAKER Joe Weber, Irwin, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 19, 1942, Serial No. 435,367

21 Claims. (Cl. goo-88) This invention relates to circuit breakers and, more particularly, to circuit breakers of the type which are operated instantaneously on heavy overloads or short circuits and after a time delay on persistent overloads of lesser magnitude.

An object of the invention is\to provide a circuit breaker having an improved current responsive trip device wherein a resistance connected in series with an electromagnet for tripping the breaker is controlled by a thermal element to control energization of the electromagnet and tripping of the breaker.

Another object of. the invention is to provide a circuit breaker with an improved trip device wherein a thermal element deects, when heated in response to overload currents, to reduce a resistance connected in series with the Winding of the trip magnet, thereby causing increased energization of the magnet to trip the breaker.

Another object of the invention is to provide a circuit breaker having an improved trip device wherein the deection of a thermal element in response to excessive current controls a. variable regulator or a resistance tol increase the energization of a trip electromagnet and eil'ect tripping oi the breaker.

Another object of the invention is to provide an improved circuit breaker wherein a trip magnet is energized under the control of a variable regulator or a resistance, which is varied by a bimetal elementin accordance with the magnitude and duration of the overload current.

Another object of the invention is to provide a circuit breaker in accordance with the preceding paragraphs wherein means is provided for adjustably determining the initial resistance of the resistor to vary the operating point of the trip magnet.

Another object oi' the invention is to provide a circuit breaker with an improved trip device wherein a regulator or a resistance connected in series with a trip magnet is controlled by a therv mal element to effect tripping of the breaker after a time delay on overloads below a predetermined value, and in which the magnet is effective to trip the breaker instantaneously on overloads above the predetermined value.

Another object of the invention is the provision of a circuit breaker with an improved trip device embodying a thermally responsive ele ment heated in response to overload current of the circuit, and having means for varying the speed of response of the device in accordance with the magnitude of the overload current.

Another object oi the invention is to provide a circuit breaker with an improved trip device which is simple in construction, reliable and efficient in operation, and inexpensive to manufacture.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following description of several embodiments thereof when read in conjunction with the accompanying drawing, in which:

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

Figs. 2 and 3 are fragmentary views oi a circuit breaker embodying modiiled forms of the invention.

The circuit breaker illustrated in Fig. 1, with the exception of the trip device, is essentially the same as that disclosed in United States Patent No. 1,802,758, issued to H. D. Dorfman on April 28, 1931, and assigned to the assignee of the lnstant invention, and only a brief description of the structure of the circuit breaker will be given herein. For the specific details of construction, reference may be had to the patent referred to. i

The circuit breaker comprises, generally, a base 1 and a cover 9 of molded insulating material, end terminals Il, a stationary contact I3, a movable contact l5, operating mechanism indicated generally at il, a current-responsive trip device indicated at i9, and an arc extinguisher 2|.

The movablecontact I5'is secured to a resilient contact arm 21 which, in turn, is secured by suitable means to a channel-shaped frame 29 pivotally supported by means of a pivot pin 30 on a, U-shaped main frame 3i.

The operating mechanism I'l comprises a U-shaped operating lever 33 having an operating handle 35 secured to the outer end thereof and projecting through an opening 36 in the cover 9, a cradle 31, a toggle comprising a pair of toggle links 39 and 4I, and a pair of overcenter springs 43 (only one of which is shown). The' operating lever is pivotally mounted on pivot pins 34 supported in the sides of the frame 3|, and the cradle 3l is pivoted on a pin 38 also supported in the frame 3|. One end of the toggle link 39 is pivotally connected to the cradle 3l by a pin 40, and the toggle link Il is pivotally connected to the free end of the channel-shaped member 2G by means of a pin 42. The toggle linlrs 39 and 4| are pivotally connected together by a knee pivot pin 44. The overcenter springs 43 are tensioned between the knee pin 44 of the toggle 39-4i and the outer end of the operating lever 33. The cradle 31 is provided with a latch end 45 with which a pivoted latch member lil is adapted to cooperate to releasably restrain the cradle 31 in the position shown. The operating member 33 is provided with an extension which is adapted to cooperate with the cradle in order to relatch the cradle by manual movement of the handle 35 to the oil position after the breaker has been tripped open.

When the latch member 41 is operated by the trip device i in a manner to be presentLy described, the cradle 31 is released and rotated in a clockwise direction by the overcenter springs 43. During this rotation, the line of action of the springs 43 changes to cause collapse of the toggle SE--i and opening oi the contacts |-|3.

Before the contacts may be closed, it is necessary to relatch the cradle 31 with the latch member 4l. This is effected by moving the operating handle i5 in a counterclockwlse direction, during which movement the extension 49 of the operating lever 33 engages and rotates the cradle 31 in the same direction to reengage the latch portion 45 of the cradle with the latch 59. The contacts can now be closed by moving the handle .t5 and the operating lever 33 to the extreme right-band position. This movement changes the line of action of the overcenter spring so as to straighten the toggle 39-4l and thus effect closing ci" the contacts.

'.llhe breaker may be opened manually by moving the handle 35 toward the left. During this movement, the line of action of the overcenter springs 43 is moved to the left oi' the pivot pin causing the springs to exert a force on the it e of the toggle 39-4i in a direction to cause collapse of the toggle, which results in movement of the movable contact |5 to open position. The contact-s are closed in the previously described manner.

The trip device I9 includes the latch member pivotally mounted on a pivot 5| supported on ears 53 (only one being shown) formed on the support member 55. A spring 51 biases the latch member in latching direction. On the free end of the latch member 41 is mounted an armature 50 adapted to be attracted by an electromagnet 5i mounted on the support bracket 55. The electroniagnet comprises a winding 53 and a core me' ber and is adapted to be energized in response to tbe current of the circuit. Also mounted on the support bracket 55 by means of an insulating button 91 is a variable regulator oi' any suitable type, such as a carbon pile 61, e. bimetallic member 69 is supported on an anguiar bracket li secured to the conductor 20 by means of a screw 13, and extends outwardly therefrom adjacent one end of the resistance 61. An adjusting screw 15 having an insulating button "Vl mounted on one end thereof bearing against the end of the carbon pile is locked in place on the bimetal element 69 by means of a lock nut 19. The purpose oi the screw 15 is to communicate the deflecting movement of the bimetallic member @El to the carbon pile 51 and also to provide a convenient means for adjusting the initial compression of the carbon pile. The conductor 20,

which is formed as an extension of the terminal il, is connected by means of a shunt conductor of predetermined electrical resistance to the conductor 93, and the conductor Il is connected to the channel frame 29 by means of a flexible shunt conductor 95.

The circuit of the breaker extends from the left-hand terminal through the conductor 2l, the resistance shunt conductor 3|, the conductor 93, flexible shunt conductor B5, channel member 29, resilient contact arm 21, movable contact I5, the stationary contact I3, the conductor 25 to the other terminal The bimetal element B9, the winding 63 of the magnet 6| and the carbon pile 61 are electrically connected in series relation in a shunt circuit as follows: Prom the terminal through the conductor 20, angie bracket 1|, bimetallic element 59, a flexible wire 51, winding 63 of the electromagnet 9|, a wire 89, through the carbon pile 51 and a wire 5| to the conductor 83, thus completing a shunt circuit in parallel with the shunt member 3|.

When normal rated current flows through the circuit of the breaker, the resistance of the carbon pile 61 is of such value that current llow through the bimetallic element 33 and the magnet winding 63 is negligible, and, therefore,.i5 insufficient to energize the winding 53 to cause operation of the latch member 41. Upon the occurrence of a persistent overload current, the resistance of the shunt conductor 8| forces an increased flow of current through the bimetni 59, the winding of the electromagnet 6| and the resistance 61. This results in heating the bimetal an amount determined by the value and duration of the overload current, and causes the bimetal to deflect in a. direction to increase the compression of the carbon pile 61. The resistance of the carbon pile is thereby lowered, resulting in an increased flow of current through the winding 5l and the bimetal element 69. The increase in the value of current flowing through the bimetal element due to the decrease in resistance of the carbon pile 61 causes the bimetal to be heated at an increased rate, thereby producing a cumulative effect to increase the rate and extent of deflection of the bimetal element. Thus the time delay action of the trip device is less than the ordinary thermal trip device, and the time delay decreases at an accelerated rate as the magnitude of the overload current increases. When the current flow through the electromagnet reaches a predetermined magnitude, the electromagnet attracts the armature 60 and causes the operating mechanism to open the contacts in the previously described manner..

By rotating the adjusting screw 15. the initial pressure on the carbon pile 61 may be increased or decreased, thus decreasing or increasing the initial resistance. This provides a convenient means for varying the operating point of the trip device. Upon the occurrence of overloads above a predetermined value or short-circuits, the excessive current energizes the magnet 6| sufficiently to cause instantaneous operation o! the trip member 41 to release the operating mechanism. Obviously, by mounting the carbon pile 51 on the support 55 a greater or lesser distance from the base 1, the change in pressure on the carbon pile for a given deflection of the bimetal element may be varied.

According to the modification of the invention shown in Fig. 2, the bimetai element 69 may be provided with an auxiliary armature member 93 securely mounted on the bimetal adjacentl the core member 65. The purpose of the auxiliary armature 93 is to provide for quicker tripping of the breaker for a given amount of heating of the bimetal on intermediate overload currents below the previously mentioned predetermined value. When the bimetal element is heated in response to an overload current, it defiects toward the right and simultaneously increases the pressure on the carbon pile 61 and at the same time moves the armature 93 closer to the core oi' the magnet. This causes the electromagnet to exert a stronger pull on the armature 93 which tends to still further deiect the bimetal and thereby further decrease the resistance of the carbon pile. The rate of heating of the bimetal element is increased due to the decrease in resistance of the carbon pile and the increased pull of the magnet on the armature 93 due to the increased current ow through its winding and the decrease in air gap between the armature 83 and core 65 produces cumulative effects all tending to decrease the time delay action of the device in accordance with the magnitude oi' the current. The result is to increase the iiow of current through the winding 63 and to `increase the magnetic flux, and thus eiect quicker tripping of the breaker for a given value of overload current than in the case of the original embodiment.

According to the modication of the invention illustrated in Fig. 3, the magnet winding 63 and the carbon pile 61 are electrically connected in parallel, and both are connected in series with the bimetal element 89 which is disposed to denect, when heated, away from the carbon pile. Thus, under normal circuit conditions, the pressure exerted on the carbon pile by the bimetal element is at its maximum, and the resistance of the carbon pile is at its minimum, thereby limiting the value of current flowing through the winding 63. As the bimetal 69 is heated and deiiects away from the carbon pile 61, the pressure thereon is reduced, thus increasing the resistance and causing an increased flow of current through the magnet winding 63. When the magnitude of the current flowing through the electromagnet reaches or exceeds a predetermined value, the electromagnet efl'ects tripping of the breaker in the previously described manner.

Having described several embodiments of the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made therein without departing fromsome of the essential features of the invention. It is, therefore, desired that the language of the appended claims be given as reasonably broad interpretation as the prior art permits.

I claim as my invention:

1, A circuit breaker comprising an operating mechanism for operating the breaker, a trip device comprising an electromagnet operable to cause operation of the breaker, a resistor electrically connected in series with said electromagnet, and a current-responsive member connected in series relation with said electromagnet and said resistor, said current-responsive member being operable in response to certain circuit conditions to decrease the resistance of the resistor and cause the electromagnet to trip the breaker.

2. A circuit breaker comprising an operating mechanism for causing automatic operation of the breaker, a trip device comprising an electromagnet operable to cause operation of said mechanism, a variable resistor for controlling the energization of said electromagnet, and thermally responsive means operable when heated in response to overload currents for varying the resistance of said resistor in accordance with the magnitude and duration o! the overload current to vary the energization of the electromagnet.

3. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, an electromagnet operable when energized a predetermined amount to cause opening of the contacts, a variable resistor for controlling the energization of said electromagnet, and a bimetallic element operable in response to overload currents to cause the resistor to increase the energization of'the electromagnet and thereby eil'ect opening of the contacts.

4. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device comprising an electromagnet operable when energized by overload currents above a predetermined value to cause instantaneous opening of the contacts, a variable resistor connected in the circuit of the electromagnet for controlling the energization ci said magnet, and a bimetal element operable when heated by overload currents below said predetermined value to cause the resistor to increase the energization of the electromagnet in accordance with the magnitude and duration of the overload current.

5. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device comprising electroresponsive means operable when energized a predetermined amount to cause opening of the contacts, a variable regulator for controlling the energization of the electroresponsive means, and thermally responsive means operable in response to overload currents for actuating the regulator in accordance with the magnitude and duration of the overload current.

6. A circuit breaker comprising relatively movable contacts, operating mechanism therefor, electroresponsive means operable when energized a predetermined amount to cause opening of the contacts, a variable regulator for controlling the energization of the electroresponsive means, thermally responsive means operable when heated in rsponse to overload currents to actuate the regulator to increase the energization of the electroresponsive means an amount determined by the magnitude and duration of the overload current, and means for adjusting the regulator to vary the operating point of the electroresponsive means.

7. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts. a trip device comprising an electromagnet operable when energized a predetermined amount to cause opening of said contacts, a variable resistor for controlling the energization of the electromagnet, a bimetallic member operable when heated in response to overload currents for actuating the resistor to cause increased energization of the electromagnet ln accordance with the magnitude and duration of the overload current, and means for adjusting the resistor to vary the initial resistance thereoi.

8. A circuit breaker comprising relatively movable contacts, operating mechanism for said contactsa trip device comprising an electromagnet operable when energized to cause opening of the contacts, a variable resistor for controlling the energization of said electromagnet, auxiliary magnetic means operable to vary the magnetic reluctance of said electromagnet, and a bimetallic element operable when heated in response to overload currents for simultaneously actuating the resistor' to eiect increased energization oi the electromagnet and for actuating the auxiliary magnetic means to reduce the magnetic reluctance.

9. A circuit breaker comprising operating mechanism for causing automatic Operation of the breaker, a trip device comprising an electromagnet operable to cause said mechanism to operate the breaker, a variable resistor for controlling the energization of said electromagnet, and a bimetallic element operable when heated in response to overload currents to increase the resist-ance of said resistor and cause increased energization of the electromagnet.

l0. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device comprising an electromagnet operable when energized a predetermined arnount to cause opening of said contacts, a variable resistor for controlling the energization of said electromagnet, a bimetallic element operatively associated with said resistor and operable in response to overload currents to increase the resistance of said resistor to thereby increase the energization of the electromagnet, and adjustable means for adjustably determining the initial resistance of said resistor to vary the operating point of the electromagnet.

ll. A circuit breaker comprising relatively movable contacts, operating mechanism biased to cause opening of said contacts, latch means for restraining said loperating mechanism and operable to cause opening of said contacts, an electromagnet operable when energized a predetermined amount ior operating said latch means, a variable resistor for controlling the amount oi energization of said electromagnet, and a bimetallic element operable when heated in response to overload currents to decrease the resistance of the resistor thereby increasing the energization ci the electromagnet.

l2. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, an armature operable to cause opening or" said contacts, an electromagnet operable when energized a predetermined amount for operating said armature, a variable resistor comprising a carbon pile for controlling the amount of energization of said electromagnet, a bimetallic element operable when heated in response to current for actuating said carbon pile to reduce the resistance thereof to thereby increase the energization of the electromagnet and cause said electromagnet to operate the armature.

13. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, an armature operable to cause opening of the contacts, an electromagnet operable when energized a predetermined amount to operate said armature, a variable resistor comprising a carbon pile for varying the energization of said electromagnet, a bimetallic element operable when heated in response to current to reduce the resistanceoi said carbon pile to thereby increase the energization of the electromagnet and cause said electrcmagnet to operate the armature. and adjustable means i'or determining the initial resistance of the carbon pile to vary the operating point of the electromagnet.

i4. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts. an electromagnet including a movable armature operable to cause opening of the contacts, said electromagnet being operable when energized a predetermined amount to operate the armature, a. variable resistor comprising a carbon pile operable to vary the energization of the magnet, an auxiliary armature operable to vary the reluctance of the magnet, and a bimetallic element operable when heated in response to current to simultaneously operate the carbon pile and the auxiliary armature to simultaneously increase the energization of the electromagnet and reduce the magnetic reluctance.

15. A circuit breaker comprising relatively movable contacts, operating mechanism therefor, an electromagnet including an armature operable to cause opening of said contacts, a variable resistor for controlling the energization of said electromagnet, an auxiliary amature operable to vary the magnetic air gap of the electromagnet, and a bimetallic element operable when heated in response to current to actuate the variable resistor and the auxiliary armature to simultaneously increase the energization o! the electromagnet and reduce the magnetic air 88D- 16. A circuit breaker comprising relatively movable contacts, operating mechanism therefor, a trip device operable to cause opening of the contacts, said trip device comprising a bimetal element heated in response to the current of the circuit and operable to cause operation of the trip device, a variable resistance connected in series relation with said bimetal element in the circuit controlled by the breaker, said bimetal element deilecting when heated to reduce the resistance of the variable resistance thereby increasing the heating of the bimetal element.

17. A circuit breaker comprising an operating mechanism for operating the breaker, a trip device comprising an electromagnet operable to cause operation of the breaker, a variable resistance electrically connected in the energizing circuit of said electromagnet, a bimetal element at all times connected in series relation with said variable resistance and heated in response to the current of the circuit of the electromagnet, and means including said bimetal element for varying the resistance of said variable resistance.

18. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device comprising an electromagnet operable when energized by overload currents above a predetermined value to cause instantaneous opening of the contacts, a variable resistor connected in the circuit of the electromagnet for controlling energization of said magnet. and a bimetal element connected in series with a parallel connection of said variable resistor and the electromagnet, said bimetal element being heated in response to the current in the circuits of the electromagnet and said variable resistor, said element being deiiectable in response to predetermined heating of said element to operate the resistor and vary the resistance of said variable resistor.

19. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, a trip device including an electromagnet having an armature operable to cause opening of the contacts, a variable resistance for controlling the energization of said electromagnet, a bimetal element deecting when heated in response to overload currents in a direction to actuate the variable resistance to thereby cause increased energization of the electromagnet, and an auxiliary armature movable toward the electromagnet upon deflection of the bimetal element, said auxiliary armature exerting a force on the bimetal element tending to deect said element in the same direction as the heating action.

20. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts, an electromagnet including a movable amature operable to cause opening of the contacts, said electromagnet being operable when energized a predetermined amount to operate the l0 amature, a variable resistor comprising a carbon pile operable to vary the energization of the electromagnety an auxiliary armature operable to effect increased energization of the electromagnet, and a bimetal element operable when heated ln response to current to simultaneously Yby the bimetal element and operable by the electromagnet to e'ect additional increase in the 15 energization of said magnet,

JOE WEBER.

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