US2349632A - Automatic reclosing breaker - Google Patents

Description

May 23, 1944. J. w. MAY

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Patented May 23, 1944A AUTOMATIC BECLOSING BBEAKER John W. May, Pittsburgh, Pa., assignor to Wetinghouse Electric Manufacturing Company. East Pittsburgh, Pa., a corporation of Pennsyl- Appuccucn December 19, 1941, serial Nc. 423,631 1o claims. (ci. 11s-294) My invention relates to circuit interrupters, and in particular relates to automatically reciosing circuit breakers.

yl'or certain purposes such, for example, as rural electriflcation, it is desirable to have a circuit interrupter which will automatically open when excessive current flows through the line, and will then automatically reclose itself after a short interval, since in many cases the cause of the short circuit disappears within a time if the line is disconnected from a source of power. It is, however, impossible to be certain that the cause of the excessive current or short circuit will be removed merely by a brief removal of the line from connection to the voltage source, and in such cases it is desirable that the circuit breaker shall again automatically reopen this circuit as soon y as the load current reaches an excessive value.

In someinstances, a second or a third interruption of the connection between the line and the voltage source will be followed by a disappearance of the condition causing excessive current flow, but there are occasional situations in which excessive current will ilow even after a considerable number of reclosures of the circuit breaker connecting the line to the voltage source. Such a repeated opening and reclosure of the circuit interrupter will quickly overheat and ruin the latter, and it is, accordingly, desirable to provide an arrangement by which the circuit breaker shall remain open if the cause of excessive current does not disappear after a few automatic reclosures.

My invention relates to a novel arrangement for thus opening and reclosing a circuit breaker when the line carries excessive current, but will carry out this operation for only a limited number of reclosures and thereafter maintain the circuit breaker open permanently until it is manually reclosed by a power-line attendant.

Circuit interrupters for carrying out the abovementioned function have been devised before, but there are certain special conditions characteristic of rural electrification and other similar fields which make prior art circuit breakers un satisfactory; foi` example, by reason of their excessive cost compared with the service they are expected to render, or their mechanical complexity or their liability to require constant inspection and repair or their short life in service. 'I'he device which I have invented avoids such ditllcultles as have just been enumerated, inasmuch as it has a relatively low first cost, has no complicated gear train escapements, ratchets or similar complex mechanisms, has few moving parts likely to get out of order, and is adapted to employ standard circuit interrupters which have been developed for non-reciosing circuits and which are now marketed in large numbers at very low cost and with high reliability.

One object of my invention, accordingly, is to provide a circuit interrupter which shall reclose automatically, but for only a limited number of times, and shall then remain open circuited.

Another object of my invention is to provide an arrangement of the type mentioned in the preceding paragraph which shall employ for its circuit interrupting function mechanisms which have been developed and successfully used for non-reciosing circuit breaker service.

Stillanother object of my invention is to provide a circuit interrupter of the type mentioned under the first paragraph naming the objects of my invention which shall be inexpensive to manufacture, and which shall employ a minimum of moving parts and other mechanical adjuncts.

Still another object of my invention is to provide an arrangement of the type mentioned in the first paragraph naming the objects of my invention which shall employ two diiierently rated bimetalllc or thermostatic elements for controlling the tripping and reciosing cycles of the circuit breaker.

Still another object of my invention is to provide an arrangement mentioned in the immediately preceding paragraph in which is embodied a tripping coil which is traversed by substantial current only for a period at each tripping operation, and is normally substantially free from load current traverse.

Still another object of my invention is to provide an arrangement of the type mentioned in the nrst paragraph naming the objects of my invention in which the arrangement controlling the opening and reciosing cycle has an inverse timecurrent characteristic and can be altered as to rating very simply by replacement of only two relatively inexpensive and simple bimetalllc elements of the device.

Other objects of my invention will become apparent upon reading the following description taken in connection with the drawing, in which the single iig-ure is a view partly in elevation and partly in section of a circuit interrupter embodying the principles of my invention.

Referring m detail te the drawing. the circuit interrupter is preferably contained within an enclosure or tank l which may be of insulating material or may be of suitable metal. Line terminals for the circuit controlled by the circuit interrupter are mounted at 2 and 3 on the casing l, each line being preferably insulated from the casing if the latter is of metal by insulating washers 4, 5. The terminal 3 is connected by a through-bolt 6, insulated from the casing I if the latter is of metal, with one layer 1 of a thermostatic bimeta1 which carries on itsfree end the holding element 8 of a latch, the other element 9 of which revolves about a stationary pivot II an'd constitutes the trip-free arm of the socalled trip-free mechanism of a circuit breaker actuating arrangement such as that shown in Patent 2,044,157, issued June 16, 1936, to H. D.

Dorfman et al., and assigned to Westinghouse Electric & Manufacturing Company, the assignee of my instant application. The layer I2 assoelated with the above-mentioned layer 1 to constitute a bimetallic thermostatic element is insulated from the layer 1, vexcept at the free end of the bimeta1, as a result of which current owing from the terminal 3 traversed the layer 1 to its free end and then ows back through the layer I2 to the exible lead I3 which conducts current to the moving contact I4 of the circuit breaker mechanism illustrated in the above-mentioned patent. The stationary contact I5 of the circuit breaker mechanism is mounted on circuit breaker base plate of insulating material and current ows thence through the strap I1 to the iixed end I8 of a second bimetallic thermostatic element I3. Current then ows through the sec ond thermostatic element to the free end thereof, thence flowing through a contact button 2| to a second contact button 22 which is normally in contact with the button 2| in the undeflected condition of the bimetallic element now under discussion.

The contact button 22 is mounted in a fixed position on an insulating block 23 which is supported from the wall of the enclosure l. A ilexible lead 28 extends from the contact button 2| to one termina1 of a solenoid 25 which is mounted on the casing I, the other terminal of this solenoid being connected through a lead with the terminal 2. 'I'he contact button 22 is also connected by a suitable lead passing through the wall of the container I to the terminal 2.

The operating mechanism for the movable contact I4 comprises a lever 21 having a stationary pivot 23 and attached to the resilient arm 29 which supports the contact I4. Pivoted to the lever 21 is a 1ink 3| which is, in turn, pivoted to one end of a link 32 of which the other end is pivoted upon the arm 9. 'I'he links 3l and 32 constitute a toggle provided with means which prevents link 3| from moving clockwise further than the position shown in the drawing; in this position the movable contact I4 is pressed into firm engagement with the stationary contact I5.

A handle 33 having a stationary pivot 34 is connected to theknee of the toggle 3|, 32 by a spring 35 which in the position shown in the drawing exerts a force on the knee of the toggle 3| 32 tending to turn link 3| clockwise; the spring 35 thus acts to hold links 3|, 32 in the position shown, thereby stressing the contacts I4, I5 to closed circuit position. 'Ihe handle 33 may, however, be turned counterclockwise about the pivot 34 thereby displacing the upper end of the spring 35 to the left in the drawing to such a degree as to pull the knee of the toggle 3i, 32 likewise over to the left, thereby breaking the toggle and pulling the movable contact I 4 away from the stationary contact I5. The free end of the handle 33 is biased in a clockwise direction in the drawing by a spring 36 which is attached to an insulating projection 31 attached to the strap I1. 'I'he handle 33 carries an arm 33A adapted to engage the trip-free arm 9 under certain conditions later to be explained.

The arm 33 is adapted to be moved from its closed circuit position, as shown in the drawing, and against the bias of the spring 35 by a bell crank lever 38 pivoted at 39 to the container I. The bell crank lever 38 is moved clockwise from the position shown in the drawing by a magnetic core 4I which slides through the axis of the solenoid 25. The core 4I is provided with a handle 42 by which it may be moved manually. There is also provided a rod 43, which slides through a. guide 43 and has its end pivoted to bimeta1 I9. When the latter is heat-deected by being traversed by overload current, it moves the end of the rod 43 downward into latching engagement with core 4| for a purpose described below.

The mode of operation of my above described circuit interrupter is as follows: Assuming the mechanism to be in the position shown in the drawing, the contacts I4, I5 will remain in their indicated closed-circuit position until suicient current ows through the bimeta1 I9 to separate the contacts 2|, 22 whereupon current will ow through the solenoid 25. 'Ihe core 4I will be drawn inward, thereby rotating the bell crank lever 38 in a clockwise direction, displacing the arm 33 in a counterclockwise direction against the bias of spring 36 and causing the spring' 35 to exert a pull upon the toggle 3|, 32 to break the latter, thereby separating the contacts i4, I5 and opening the circuit. The bimeta1 1, I2 will, of course, be heated by this same current but is so proportioned that it is not suiiiciently heated to be substantialy displaced from the position indicated in the drawing by the time allie bimeta1 I9 has moved to open the contacts The Vcore 4| will remain latched by the rod 43, thus holding the arm 33 in the open-circuit position against the bias of the spring 36, until such time as the bimeta1 I9 has had time to cool and close the contacts 2 I, 22. As soon as the contacts 2|, 22 close, the rod 43 disengages core 4I and the spring 36 can pull the circuit breaker arm 33 together with its attendant bell crank lever 38 and core 4I to the closed circuit position shown in the drawing. The contacts I4 and I5 are thus again closed.

If during the open-circuit interval just described, the cause of the flow of excessive current through the circuit breaker has been removed. the circuit breaker will remain in its closed-circuit position. However, if the line is in such a condition that an excessive current still flows through the bimeta1 I9, the latter will b'e heated suiiiciently to open the contacts 2|, 22, thereby reenergizing solenoid 25 to again pull the arm 33 to the open circuit position against the bias of spring 36. The bimeta1 1, I2 is so designed that it is more massive than the bimeta1 I3, and hence does, not lose such heat as was previously stored in it at the time the circuit breaker was rst opened. The bimeta1 1, I2 is, therefore, again heated and caused to store more heat while the circuit breaker remains closed for the short time required to heat the bimetal I9 enough to open contacts 2i, 22. The bimetal 1, I2 is, however, so designed that even after this second heating,it is not deiiected far enough to disengage the latch member 3 from the trip free arm 9.

Cessation of current now through the circuit breaker due to the opening of contacts Il. I for the second time again permits the bimetal I9 to cool, thereby disengaging latch 43 from core 4I so that the spring 36 can again move the circuit breaker to its closed circuit position. If the cause for excessive current-flow in the line has disappeared during this second open circuit interval, the circuit breaker will remain closed. On the other hand. if the cause of excessive current in the linel still persists, the bimetal 1. I2 is so designed that the additional heating due to the ilow of this excessive current for the third time will deiiect its upper end to disengage the latch member 8 from the arm 8. When this happens. the spring 35 exerts such an upward pul1 on the knee of the toggle 3|, 32 as to move the member 3 clockwise about the stationary pivot I I, thereby permitting the arm 21 to rotate about its pivot 28 to open the contacts I4, I5. This clockwise movement of member 9 is arrested when it engages arm 33A. The circuit breaker will thereafter remain in its open circuit position regardless of the cooling of the bimetal 1, I2 and the bimetal I9 until an attendant manually moves the handle I2 to actuate handle 33 to open circuit position through the agency of bell-crank lever 38. When this happens arm 33A engages and engages and moves trip free arm 9 counterclockwise about its pivot II into latching engagement with the latch member 8. Thereafter, the spring 36 is able to move the arm 33, the toggle 3|, 32 and the contacts I4, I5 to their closed circuit position again as soon as the attendant releases handle 42.

It will be recognized that by properly proportioning the heat-storage and other properties of bimetals 1, I2 and I8 the number of openings of the circuit-breaker by bimetal I8 which intervene before bimetal 1, I2 unlatches the trip-free arr'n 8 can be fixed at will.

While I have shown the bimetal I9 as positioned above the surface oi' the oil and the bimetal 1, I2 below the surface of the'oil, it will be recognized that it may, under certain circumstances, be desirable to locate the bimetal I9 likewise below the surface of the oil in the container I. While I have shown a, particular mechanism for moving the contacts Il, I5 to closed-circuit and open-circuit position, it will be recognized that the principles of my invention are by no means limited to the use of this particular mechanism in combination with the bimetal 1, 12 and I9. Any circuit breaker arrangements in which a motor means energized by one bimetal moves to open-circuit position a circuit breaker biased to closed-circuit position, and in which a predetermined amplitude of movement of a second bimetal serves to permit the exertion of forces able to open the circuit breaker against any closed-circuit bias acting thereon are within the purview of my invention. The arrangement in which the second bimetal releases the trip free arm of a toggle mechanism is, however, a very convenient and advantageous form of my invention, which may be used with numerous types of circuit breaker mechanism otherwise dissimilar to the specic form shown in the Dorfman et al. Patent 2,044,157.

Many forms of circuit breaker mechanism having trip free arm-latches are known. and the control of the trip free arm-latch by means of a bimetal which is only moved suiiciently to unlatch the arm after several successive trippings of the circuit breaker within a predetermined limited interval oi' time are within the purview of my invention.

I claim as my invention:

1. In combination with a pair of relatively movable contacts, mechanism having a trip free latch for holding said contacts in closed-circuit in one of its positions, means for biasing said mechanism to closed-circuit position as long as said trip free latch is engaged, means responsive to ilow fora predetermined time of overload current to move said mechanism to the open-circuit position, and a heat storage means actuated to disengage said latch only upon the iiow of overload current for a time greater than said predetermined time.

2. In combination with a pair of relatively movable contacts, mechanism having a trip free latch for holding said contacts in closed circuit in one of its positions, means for biasing said mechanism to closed circuit position as long as said trip free latch is engaged, means responsive to flow for a predetermined time of overload current to move said mechanism to the open circuit position, and a bimetal traversed by current ilowing through said contacts and actuated to disengage said latch after the iiow of overload current for a time greater than said predetermined time.

3. In combination with a pair of relatively movable contacts, mechanism having a trip free latch for holding said contacts in closed circuit lin one of its positions, means for biasing said mechanism to closed circuit position as long as said trip free latch is engaged, means responsive to flow for a. predetermined time of overload current to move said mechanism to the open circuit position, a thermal responsive device traversed by-current flowing through said contacts and provided with means for moving said mechanism to open circuit position against said bias upon development of a predetermined temperature in said thermal responsive means, and a second thermal responsive means adapted to disengage said latch upon the ow through said contacts of an amount of energy substantially greater than that which was required to actuate said rst thermal responsive means.

4. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary contact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted arm and said tripfree arm. a latch for said trip-free arm, a pivoted handle connected by a spring to the knee of said toggle links, means for biasing said handle-- to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a linkage connecting said core to said handle, heat storage means connected in series with said contacts and arranged to short-circuit said solenoid while in its unenergized condition, and a second heat storage means connected in series with said contacts and adapted to maintain said latch in engagement with said trip-free arm in its deenergized condition and to disengage said latch from said tripfree arm when its temperature is raised by a predetermined amount.

5. In a circuit interrupter, a stationary contaot, a movable contact supported on a pivoted arm for engagement with said stationary contact, a ivoted trip-free arm, a pair of toggle links p voted together and having their free -ends respectively pivoted to said pivoted arm and said trip-free arm, a latch for said trip-free arm, a pivoted handle connected by a spring to the knee oi' said toggle links, means for biasing said handle to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a linkage connecting said core to said handle, a thermostatic bimetal connected in series with said contacts and arranged to short-circuit said solenoid while at room temperature but to energize said solenoid when its temperature is raised by a predetermined amount, and a second thermostatic bimetal connected in series with said contacts and arranged when at room temperature to maintain said latch engaged with said trip-free arm and when raised to a predetermined temperature to disengage said latch from said trip-free arm.

6. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary contact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted arm and said trip-free arm, a latch for said trip-free arm, a pivoted vhandle connected by a spring to the knee of said'toggle links, means for biasing said handle to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a bell crankl lever interconnecting said core with said handle, heat storage means connected in series with said contacts and arranged to short-circuit said solenoid while in its unenergized condition, and a second heat storage means adapted to maintain said latch in engagement with said trip-free arm in its deenergized condition and to disengage said latch from said tripfree arm When its temperature is raised by a predetermined amount.

7. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary cona tact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted arm and said trip-free arm, a latch for said trip-free arm, a pivoted handle connected by a spring to the knee of said toggle links, means for biasing said handle to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a bell crank lever interconnecting said core with said handle, heat storage means connected in series with said'contacts and arranged to short-circuit said solenoid while in its unenergized condition, and a thermostatlc bimetal connected in series with said contacts and arranged to maintain said latch in engagement with said trip-free arm while at room ternperature but to disengage said latch from said trip-free arm when its temperature is raised by a. predetermined amount.

8. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary contact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted armand said trip-free arm, a latch for said trip-free arm, a pivoted handle connected by a spring to the knee of said toggle links, means for biasing said handle to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a bell crank lever interconnecting said core with said handle, a thermostatic bimetal connected in series with said contacts and arranged to short-circuit said solenoid while at room temperature but to energize said solenoid when its temperature is raised by a predetermined amount, and heat storage means connected in series with said contacts and arranged when deenergized to maintain said latch in engagement with said trip-free arm and when raised to a predetermined temperature to disengage said latch from said trip-free arm.

9. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary contact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted arm and said dle to maintain said contacts in closed circuit position, a magnetic core, a solenoid positioned to attract said core and connected in series with said movable contacts, a bell crank lever interconnecting said core with said handle, a thermostatic bimetal connected in series with said contacts and arranged to short-circuit said solenoid while at room temperature but to energize said solenoid whenits temperature is raised by a predetermined amount, and a second thermostatic bimetal connected in series with said contacts and arranged when at room temperature to maintain said latch engaged with saidtrip free arm and when raised to a predetermined temperature to disengage said latch from said trip-free arm.

10. In a circuit interrupter, a stationary contact, a movable contact supported on a pivoted arm for engagement with said stationary contact, a pivoted trip-free arm, a pair of toggle links pivoted together and having their free ends respectively pivoted to said pivoted arm and said trip-free arm, a latch for said trip-free arm, a 'pivoted handle connected by a spring to the knee of said toggle links, a spring biasing said handle to close said movable contacts, a magnetic core, a solenoid positioned to attract said core and connected inseries with said movable contacts, a linkage connecting said core to said handle, heat storage means connected in series with said contacts and arranged to short-circuit said solenoid while in its unenergized condition, and a second heat storage means adapted to maintain said latch in engagement with said trip-free arm in its deenergized condition and to disengage said latch from said trip-free arm when its temperature is raised by a predetermined amount.

JOHN W. MAY.

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