US3665350A - Electric circuit breaker with electromagnetically assisted closing means - Google Patents

Abstract

Discloses an electric circuit breaker that includes electromagnetic assist means for opposing the magnetic contactrepulsion forces developed when a high current flows through the circuit breaker. The electromagnetic assist means comprises flexible conductive means in series with the contacts of the breaker for carrying the inter-contact current through a loopshaped path where a magnetic closing force is developed on the contacts. Only a minor portion of the total inter-contact current is conducted through the loop-shaped path. For carrying the remaining and major portion of the current, additional flexible conductive means is connected in series with the contacts and in parallel with the loop-shaped path, and this additional conductive means follows a path separate from and independent of the loop-shaped path. Sufficient closing force is obtained from the minor portion of the total current that passes through the loop-shaped path to hold the contacts engaged during the highest current surges for which the breaker is rated.

Description

United States Patent Klint I Q [151 3,665,350 [451 May 23, 1972 [541' ELECTRIC CIRCUIT BREAKER WITH ELECTROMAGNETICALLY ASSISTED c osmc MEANS Primary Examiner-Harold Broome Attorney-J. Welsey Haubner and William Freedman [57] ABSTRACT Discloses an electric circuit breaker that includes electromagnetic assist means for opposing the magnetic contact-repulsion forces developed when a high current flows through the circuit breaker. The electromagnetic assist means comprises flexible conductive means in series with the contacts of the breaker for carrying the inter-contact current through a loopshaped path where a magnetic closing force is developed on the contacts. Only a minor portion of the total inter-contact current is conducted through the loop-shaped path. For carrying the remaining and major portion of the current, additional flexible conductive means is connected in series with the contacts and in parallel with the loop-shaped path, and this additional conductive me'ans follows a path separate from and independent of the loop-shaped path. Sufiicient closing force is obtained from the minor portion of the total current that passes through the loop-shaped path to hold the contacts engaged during the highest current surges for which the breaker is rated.

4 Claims, 2 Drawing Figures l6 a" Md 0 a l 26 100 20/ l u u I 204 74 u n F .r 7r 3 70 a: 50 V J4 44 as 42 Q 40 [ff-m 42a Patented May 23, 1972 3,665,350

INVENTOR. ROBERT 1 AL/NT,

r J e A TTORIVE) v 1 ELECTRIC CIRCUIT BREAKER WITH ELECTROMAGNETICALLY ASSISTED CLOSING MEANS.

CROSS-REFERENCE TO RELATED APPLICATION -This application is related to application Ser. No. 865,046- Barkan et al., filed Oct. 9, 1969 and assigned to the assignee of the present invention, which application is incorporated by reference in the present application.

BACKGROUND This invention relates to an electric circuit breaker that ineludes electromagnetic means for opposing the magnetic contact-repulsion forces developed when a high current flows through the circuit breaker. This type of circuit breaker is referred to hereinafter as a circuit breakerwith electromagnetically-assisted closing means.

A circuit breaker with electromagnetically assisted closing means is disclosed and claimed in the aforesaid Barkan et al application, and the present-application discloses and claims an improvement thereof. The circuit breaker of the Barkan et al., application comprises a first contact and a second contact movable into engagement with said first contact to close the circuit breaker and movable out of engagement with said first contact to open the circuit breaker. The electromagnetic assist means develops a magnetic closing force on the movable contact which varies directly in accordance with the current through thecontacts. This assist means comprises conductive means in series with said contacts for carrying the intercontact current through a loop-shaped path that comprises a pair of series-connected anns between which a repulsive magnetic DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The circuit breaker shown in FIG. 1 is in many respects similar to that shown and claimed in the aforesaid Barkan et al application. Accordingly, the same reference numerals are used for the parts of FIG. 1 as are used for corresponding parts in the Barkan et al application; and reference may be had to said Barkan et al application for a detailed description of such parts. Generally speaking, where the parts have been fully described in the Barkan et al., application, they will not be satisfactory for circuit breakers of low and moderate current SUMMARY An object of the present invention is to provide a high current circuit breaker with electromagnetically assistedclosing means in which the volume of the braid in the loop region is limited to a relatively low value despite the high current rating of the circuit breaker.

In carrying out the invention in one form, I conduct only a minor part of the total current that passes through the contacts through the loop-shaped path. For carrying the remaining and major portion of the current, additional braid is connected in series with the contacts and in parallel with the loop- I shaped path, and this additional braid follows a path separate from and independent of the loop-shaped path. Sufficient closing force is'obtained from the minor portion of the total current that passes through the loop-shaped path to hold the contacts in engagement during the highest current surges for which the circuit breaker is rated.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a side elevational view of a circuit breaker embodying one form of the invention, the circuit breaker being.

shown in its fully closed position.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

described in the present application except insofar as necessary to provide an understanding of the present invention. Emphasis in the present description will be placed on those features that are not shown in the Barkan et al application.

In the circuit breaker of FIG. 1 the electromagnetic-assist means 60 comprises a flexible conductor 62 of a loop-shaped form connected in series with contacts ll, 12. One end of the flexible conductor 62 is suitably connected to contact rod 17 at 63, and the opposite end is connected at 64 to a terminal stud 65, preferably of copper. Flexible conductor 62 is preferably of copper braid and may be thought of as compris ing two series-connected arms 67 and 68. The arm 67 and stud 65 are fixed to a stationary supporting frame 70. This supporting frame 70 is preferably of a low conductivity metal so that no appreciable part of the current flows therethrough. Most of the braid 62 is physically connected to other parts of the electromagnetic assist means 60, as will soon be explained.

The electromagnetic-assist means 60 further comprises a toggle comprising two toggle links 74 and 75 pivotally joined together at a knee 76. Upper toggle link 74 has its upper end pivotally connected to contact rod 17 by a pivot pin 77. Lower toggle link 75 has its lower end pivotally mounted at 78 on a toggle support lever 80. Toggle support lever 80 has one end pivotally mounted on a fixed pivot 82 carried by frame 70. The opposite, or free, end of toggle support lever 80 is restrained in its position of FIG. 1 by a releasable latch 83 that cooperates with a latch roller 85 carried by lever 80. A suitable stop 86 prevents counterclockwise motion of lever 80 past its position of FIG. 1. The latch 83 is pivoted on a stationary pivot 87 carried by frame 70.

Returning now to the flexible conductor 62, the lower portion of this conductor is mechanically connected to the toggle support lever 80, and the arm 68 is mechanically-connected to the two toggle links 74 and 75. Current flowing at any given instant through the loop-shaped conductor 62 passes in opposite' directions through the two arms 67 and 68, developing magnetic fields around the two arms that interact in a known manner to produce a repulsive magnetic force F that urges the arms apart. This repulsive magnetic force varies directly with the square of the current passing through the loop-shaped conductor. The effect of this repulsive magnetic force is to urge the toggle 74, 75 toward an in-line or extended position, thus developing a force on the contact rod 17 that acts in an upward closing direction. The geometry of the toggle 74, 75 is preferably such that the electromagnetic repulsion force between the .two arms 67 and 68 is multiplied by a factor of 2 or 3. Thus, when high currents flow through contacts l1, 12 to produce a contact separating force, a larger than proportional closing force is developed by the magnetic-assist means 60 to oppose the contact-separating force. Toggle linkage 74, 75 is a highly eflicient arrangement for producing this desirable force-multiplying effect.

In the circuit breaker of the Barkan et al., application which uses the braid 62, all the current that passes through the contacts also passes through braid 62. As pointed out hereinabove, this is satisfactory for circuit-breakers of low or moderate current ratings, but it has a serious disadvantage for high current ratings,- e. g., those with a steady state current rating of 2,000 amperes or greater. This disadvantage is that the volume of the braid required to carry the high current is too great to permit a reasonable size loop to be formed in a loopshaped path.

I overcome this problem by using the loop-shaped braid 62 for carrying only a minor portion of the current through the contacts. For carrying the major portion of the current, I provide additional segments of flexible braid 200 and 201 in series with the contacts 11, 12 and in parallel with the loopshaped braid 62. This additionalbraid 200 and 201 extends between the stud 65 and the movable contact rod 17 via a path which is separate andindependentfrom the loop-shaped path followed by braid 62. Current flowing through additional braid 200, 201 develops no closing force on the movable contact rod 17. It is to be understood that the flexibility of the braid segments 200 and 201 allows contact rod 17 to move between open and closed positions with no substantial restraint from these braids.

The braid segment 201 is electrically connected at its right hand end to a stud 204, which in turn is electrically connected to the stud 65 by a conductor 206 which extends around a portion of frame 70 externally thereof. This relationship can be seen in FIG. 2.

For properly distributing the current through the various braids 200, 201 and 62, I match the impedances of these braids so that only a minor portion (i.e., less than half) of the total current flows through braid 62. The remaining and major portion of the total current is divided between the braids 200 and 201.

Because only a minor portion of the total current flows through the loopshaped braided conductor 62, the cross sectiorlal area of this conductor 62 can be kept relatively small; and the loop therein can therefore be made relatively sharp and can thus be accommodated in a relatively small space.

Although only a minor portion of the total current flows through the loop-shaped conductor 62, sufiicient closing force is developed thereby on movable contact rod 17 to hold the contacts ll, 12 in engagement against the highest current surges that the circuit breaker is rated to carry. It is to be understood, of course, that this closing force is developed only when the toggle support lever 80 is restrained in its position of FIG. 1 by latch 83. Current through the other braids 200 and 201 develops no significant closing force on contact rod 17.

Although in a preferred form of my invention, a major portion (i.e., greater than 50 percent) of the total current is carried by the braids 200 and 201, it is to be understood that my invention in its broader aspects comprehends an arrangement in which a somewhat smaller percent of the total current is through these braids 200 and 201. In any case, however, an appreciable portion, i.e., greater than one-third of the total current, should be carried by means (200, 201) paralleling the loop-shaped conductor 62 of the magnetic assist means 60.

Suitable local insulation such as shown at 211 is preferably provided to confine the current to the braids 68, 200, and 201 and thus to minimize the passage of current through frame 70.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changesand modifications maybe made without departing from my invention in its broader aspects; and I, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: l

1. An electric circuit breaker comprising:

a. a first contact,

b. a second'contact movable into engagement with said first contact to close said circuit breaker and movable out of between which a repulsive magnetic force is developed that urges said arms apart when current traverses said loop-shaped path, and means for converting said repulsive force into said magnetic closing force on said movable contact,

e. andadditional conductive means in series with said contacts and in parallel with said first conductive means for carrying another portion of the intercontact current to and from said movable contact via a path that is spaced from and independent of said loop-shaped path, said additional conductive means carrying at least one-third of the total current through said circuit breaker.

The circuit breaker of claim 1 in which:

a. said first conductive means comprises first flexible conductive braid in a region where said series connected arms are joined for permitting relative movability of said arms,

. said additional conductive means comprising additional flexible conductive braid that is spaced from said first braid,

c. said additional braid being capable of flexing in response to movement of said movable contact and arranged so that current flowing therethrough develops no substantial closing force on said movable contact.

3. The circuit breaker of claim 1 in which said first conductive means carries a minor portion of the intercontact current and said additional conductive means carries a major portion of the intercontact current.

4. The circuit breaker of claim 1 in which said additional conductive means is constructed and arranged so that current flowing therethrough develops no substantial closing force on said movable contact.

Claims (4)

1. An electric circuit breaker comprising: a. a first contact, b. a second contact movable into engagement with said first contact to close said circuit breaker and movable out of engagement with said first contact to open the circuit breaker and the circuit therethrough, c. electromagnetic assist means for developing a magnetic closing force on said movable contact which varies directly in accordance with current through said contacts, d. said electromagnetic assist means comprising first conductive means in series with said contacts for carrying a portion of the intercontact current through a loop-shaped path that comprises a pair of series-connected arms between which a repulsive magnetic force is developed that urges said arms apart when current traverses said loop-shaped path, and means for converting said repulsive force into said magnetic closing force on said movable contact, e. and additional conductive means in series with said contacts and in parallel with said first conductive means for carrying another portion of the intercontact current to and from said movable contact via a path that is spaced from and independent of said loop-shaped path, said additional conductive means carrying at least one-third of the total current through said circuit breaker.

2. The circuit breaker of claim 1 in which: a. said first conductive means comprises first flexible conductive braid in a region where said series connected arms are joined for permitting relative movability of said arms, b. said additional conductive means comprising additional flexible conductive braid that is spaced from said first braid, c. said additional braid being capable of flexing in response to movement of said movable contact and arranged so that current flowing therethrough develops no substantial closing force on said movable contact.

3. The circuit breaker of claim 1 in which said first conductive means carries a minor portion of the intercontact current and said additional conductive means carries a major portion of the intercontact current.

4. The circuit breaker of claim 1 in which said additional conductive means is constructed and arranged so that current flowing therethrough develops no substantial closing force on said movable contact.

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