US2700081A - Automatic reclosing circuit breaker - Google Patents

Description

Jan. 18, 1955 J. M. WALLACE ET AL 2,700,081

AUTOMATIC RECLOSING CIRCUIT BREAKER Filed Dec. 20, 1950 Fig.1.

f INVENTORS Curran James M.Wolvloce and Andrew W.Edwords.

United States Patent 2,700,081 AUTOMATIC RECLOSING CIRCUIT BREAKER James M. Wallace, Pittsburgh, and Andrew W. Edwards,

East McKeesport, Pa., assignors to Westinghouse Electrie Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 20, 1950, Serial No. 201,836 12 Claims. (Cl. 200-89) This invention relates particularly to automatic reclosing circuit breakers of the type where closely successive circuit interrupting operations have different characteristics.

In distribution systems it is generally the practice to provide automatic reclosing circuit breakers with variable tripping characteristics so as to obtain one or more instantaneous trips followed by operations having different tripping characteristics. Heretofore one way this has been done is to employ a time delay device on later operations. For good coordination it is desirable to have the ratio between the fast and slow trips as great as possible. Another method of obtaining such operation has been to change the effective rating of a breaker by using a switching arrangement associated with the integrator which counts the breaker operations to reduce the effective number of ampere turns of the operating coil of the circuit breaker for the later operations. These methods have limitations, in that the ratio between fast and slow trips cannot be conveniently made as large as is desirable in the first case, and proper coordination between series arrangements of reclosing circuit breakers of different ratings may not be obtained in the other case because a change in the effective rating of a breaker may result in a breaker nearer the source being tripped at the same time.

Accordingly, it is one object of our invention to provide in an automatic reclosing circuit breaker, for obtaining a wide range of operating characteristics with currents of different values.

Another object of our invention is to provide in an automatic reclosing circuit breaker, for modifying the normal operation of the breaker in accordance with a present value of current through the breaker.

Yet another object of our invention is to provide in an automatic reclosing circuit breaker for decreasing the effective operating force of a fault current on the breaker armature, in accordance with the initial rate of movement of the armature.

It is also an object of our invention to provide in an automatic reclosing circuit breaker having dashpot delay means, for reducing the effectiveness of the breaker operating coil whenever the dashpot functions to interpose time delay.

We also propose to provide in automatic reclosing circuit breakers, for so coordinating the operation of switch means with the dashpot delay means of the breaker that proper operation of series connected breakers of different ratings may be successfully obtained.

Another imporant object of our invention is to provide in an automatic reclosing circuit breaker having dashpot time delay means controlling the operating time, for using a pressure switch responsive to fluid pressure in the dashpot for reducing the efiective number of ampere turns in the operating coil of the breaker.

Another object of our invention is to provide in a circuit breaker having a series connected solenoid coil which is responsive to overloads on the circuit to cause a circuit opening operation, novel means responsive to operation of the dashpot delay means of the breaker for decreasing the pull exerted by said solenoid on any delayed circuit opening operation.

These and other objects of this invention will become apparent upon consideration of the following detailed description of preferred embodiments thereof, when taken in connection with the attached drawing, in which:

Figure l is a longitudinal section view through a circuit breaker embodying this invention;

Fig. 2 is a schematic showing of the circuit through the breaker shown in Fig. 1;

Fig. 3 is a view similar to Fig. 2 but showing a modified circuit arrangement;

Fig. 4 is likewise a schematic circuit diagram illustrating still another form of the invention; and

Fig. 5 is a chart showing typical time-current curves for circuit breakers under dilferent conditions.

The circuit breaker illustrated in Fig. 1 is contained in a metal tank 2 having an open top adaptedto be covered by a hollow cover structure 4 which may be secured to tank 2 in any desired manner. Preferably, the major part of the interior of tank 2 is covered by a suitable insulating liner 3, of any desired insulating material, such as fiber or the like. The circuit breaker operating mechanism is adapted to be mounted in cover 4, which may have supports 6 (only one of which is shown), at least partly of insulating material, for supporting a supporting casting 8 and a supporting plate 10 between which a solenoid coil 12 may be mounted. Stationary contacts 14 for the breaker may in turn be suspended from supporting plate 10 by means of a tube 16 of insulating material, such as fiber or the like.

bridging contact bar 18 is adapted to bridge stationary contacts 14, and is mounted on the lower end of a contact rod 22, as by a pivot 20, about which the bridging contact may have limited pivotal movement. The upper end of contact rod 22 is connected by a pair of pivoted connecting links 24 of insulating material, such as fiber or the like, to the common pivot 26 of a pair of toggle levers 28 and 30. Toggle lever 28 is adapted to be held in engagement with a pivot bracket 32' supported from cover 4 by a coil tension spring 34 secured at one end to cover 4, and at the other end engaging an opening in toggle lever 30.

Spring 34 acts, at the position of the parts shown in Fig. 1, to bias bridging contact 18 into engagement with stationary contacts 14 of the breaker with a predetermined pressure. However, if contact rod 22 is moved upwardly, the pivot point 26 of toggle levers 28 and 30 moves upwardly with the contact rod and this movement is opposed by contact pressure spring 34. However, the line of action of contact pressure spring 34 approaches the on-center position of toggle levers 28 and 30 during the first part of contact opening movement, so that the opposition of this spring to such opening movement rapidly decreases to substantially zero when the toggle levers are at their on-center position. The contact separating movement required to move toggle levers 28 and 30 from their positions shown in Fig. 1 to their on-center position is kept small because separation of these levers is limited by a hook portion 29 on toggle lever 30 which extends through an opening in toggle lever 28 to limit separation of the levers to a relatively small amount. Furthermore, during the first part of contact separating movement, the levers 28 and 30 are moved to their oncenter position as described above, and at this position, lever 30 engages lever 28 so that further relative movement in the same direction is prevented, and accordingly, contact pressure spring 34 offers substantially no opposition to further contact separation.

After a circuit opening operation by contact rod 22, the force of gravity acts on bridging contact 20 and contact rod 22 to cause these parts to move downwardly toward stationary contacts 14. As is the case during the latter part of contact separating movement, contact pressure spring 34 will have substantially no effect on the circuit closing operation, until the line of action of contact pressure spring 34 moves below the pivot point of toggle lever 28 on bracket 32, whereupon this spring becomes effective suddenly to rapidly move the bridging contact into engagement with stationary contact 14 and to exert the aforementioned contact pressure thereon.

In order to manually operate the circuit breaker contacts, and also to provide for a locked-open condition of the breaker, there is provided a pair of toggle levers 36 and 38 connected by a knee pivot pin 40, with lever 36 being pivotally mounted in cover 4, as by a pivot pin 42, and being extended beyond this pivot pin to the exterior A coil compression lock-out spring 56 is mounted on toggle lever 38 so as to react between supporting lugs 54 and a shoulder provided at the inner end of toggle lever 38. Preferably, toggle lever 38 has an inwardly and downwardly extending operating extension 53 adapted to be engaged by automatic counting means, as will be described.

It will be observed that toggle levers 36 and 38 are shown in Fig. l of the drawing as being held at a position slightly below center by spring 36, with knee pivot 40 below a line drawn between pivot 42 of lever 36 and supporting pin 52 for lever 38, and that a stop bolt 49 mounted in hood 46 of the cover defines this over-center position of the toggle levers. When it is desired to manually open the breaker contacts, handle 44 may be pulled downwardly to move the knee pivot 40 of toggle levers 36 and 38 upwardly overcenter, whereupon spring 56 assists in further upward movement of toggle knee pivot 40. Inasmuch as the toggle knee pivot pin 40 is extended to lie beneath a flange on toggle lever 28, upward movement of this pivot pin likewise causes upward movement of toggle lever 28, contact rod 22 and bridging contact 18 to an open circuit position. Following such 'a manual circuit opening operation, handle 44 may be manually moved upwardly, back to the position shown in Fig. 1, where toggle levers 36 and 38 will be maintained by spring 56, to thereby permit reclosing of the breaker contacts in the same manner described above. With toggle levers 36 and 38 in the positions thereof shown in Fig. 1, it is obvious that operating extension 58 of lever 38, if moved upwardly, will have the same effect as downward movement of handle 44, that is, to cause opening of the breaker contacts, to a locked-open position at which they are held by spring 56.

For the purpose of automatically separating bridging contact 18 from stationary contacts 14 of the breaker in response to overloads, there is provided an actuating sleeve 60 which receives an intermediate portion of contact rod 22, with the lower end of this sleeve being threaded into a solenoid core 62 having a central opening for receiving contact rod 22, and being slidably mounted in a central opening provided in coil supporting plate 10. A light coil compression spring 64 reacts between a pin 66 on contact rod 22 and solenoid core 62 to normally bias the latter to the position shown in Fig. 1. Preferably, solenoid coil 12 is provided with suitable insulation 68 covering the coil, and the interior of the coil additionally has a cylindrical dashpot sleeve 70 of insulating material, such as fiber or a molded insulating material received therein. For the purpose of limiting upward movement of actuating sleeve 60 on contact rod 22, the latter is provided with a flange 72 adjacent the upper end thereof. The upper end of dashpot sleeve 70 is provided with an annular outlet passage 74 formed in supporting casting 8, and communicating with a laterally extending vent passage 76 also formed in the supporting casting which opens to the interior of easing 2. The passage 76 may be blocked by screwing a plug in the threaded opening 77 where time lag operation is desired on all operations.

It will now be apparent that upon the passage of currents through solenoid coil 12, of a value sufiiciently high to attract core 62, that the latter will be moved upwardly while stressing spring 64. Depending upon whether or not vent passage 76 is opened or closed by means to be hereinafter described, upward movement of core 62 and actuating sleeve 60 will be relatively fast (if vent passage 76 is open) or relatively slow (if vent passage 76 is closed), due to the necessity of liquid trapped within the dashpot sleeve 70 escaping through the relatively small clearances between core 62 and the opening in supporting plate when the vent passage is closed. In either case, however, spring 64 eventually becomes compressed to an extent that contact pressure spring 34 is overcome and contact rod 22 then begins to move upwardly to separate bridging contact 18 from stationary contacts 14 in the manner previously described. In the event of any difiiculty with spring 64, upward movement of core 62 and actuating sleeve 60 will eventually cause the latter to engage the flange 72 on contact rod 22 to positively separate" bridging "contact 18 from stationary contacts 14. When solenoid coil 12 becomes deenergized, the contacts may close in the manner previously described, except that the speed of reclosing movement will be dependent, as is the speed of contact opening movement, upon whether or not vent passage 76 is open or closed.

For the purpose of counting closely succeeding circuit interrupting operations of the circuit breaker, there is provided a cylindrical sleeve '78 mounted in an opening provided in supporting casting 8 intersecting vent passage 76, and a counting piston 80 is adapted to be mounted in sleeve 78. The lower end of sleeve 78 is closed by a plug having a small opening controlled by a ball check valve 82 so that while fluid may be freely drawn into the lower end of sleeve 78, it cannot escape outwardly from the lower end of the sleeve. Counting piston 80 has a reduced upwardly extending rod portion provided with a plurality of spaced flanges 84 thereon, and above this it has secured thereto an extension 90, for a purpose to be described.

A pawl lever 92 is pivoted at one end as at 94 on supporting casting S and has its other end engaging the top of a collar 96 secured to actuating sleeve so so that the lever will be moved upwardly each time the breaker contacts separate. Pawl lever 92 has a pawl member 98 mounted thereon which is adapted to engage beneath a flange 84 of the counting piston to move the piston upwardly each time the breaker contacts separate.

It is believed clear that upon the occurrence of a circuit opening operation, counting piston 86 will be moved upwardly a predetermined distance by pawl member 98 and when the breaker contacts are rcclosed, counting piston 80 will remain at the position it was advanced on the preceding circuit opening operation. Counting piston 80 will return very slowly to its normal lowermost position illustrated in Fig. 1 under the force of gravity, it being retarded in such return movement by the necessity of displacing liquid drawn into the lower end of sleeve 78 when the piston was advanced, through the relatively small clearance between the piston and sleeve '78. However, if a number of circuit opening operations occur in close succession, counting piston 89 will not have time to return to its normal lowermost position shown in Fig. 1, because when the contacts reclose, they will immediately reopen, and this time pawl member 98 will engage the 'next 'lowermost flange 84 of the counting piston to advance the latter a further amount upwardly, and this will continue until 'the uppermost extension of the counting piston engages operating extension 58 of toggle lever 38 to move the knee pivot 4-3 of toggle levers 36 and 38 upwardly overcenter, whereupon the breaker contacts will be locked out in the manner previously described.

Another function of counting piston 80 is to control vent passage 76 leading from the upper end of dashpot sleeve 70. Normally the small cross section area extension of counting piston 80 is positioned in the region of the transverse openings through cylindrical sleeve 78 in alignment with vent passage 76, so that relatively free venting of fluid from the upper end of dashpot sleeve 70 is possible, and accordingly, upward movement of solenoid core 62 is relativelyunimpeded, so that the first circuit opening operation will occur substantially instantaneously after the current through coil 12 reaches a value sutficient to attract core 62. Assuming that the contacts then reclose and are again immediately reopened due to excess current still being present in the circuit, counting piston 8t) itself may be advanced to a position blocking vent passage 76, or this may not occur until the third closely succeeding circuit interrupting operation, depending upon the length of sleeve 78 in which the piston is located, and on the length of the piston and its reduced upward extension. In either case, piston 80 will eventually be advanced to a position .where it does block vent passage 76, so that the next closely succeeding circuit interrupting operation will be delayed due to the dashpot action of core 6?. in dashpot sleeve 70 located within solenoid coil 12.

Of course, if the excess current condition through solenoid coil 12 causing a circuit opening operation of the breaker does not persist, counting piston 80 will lowly react as PY D 1Yd so that if a p manent condition comes on the chem at a later time, the

breaker will again go through the same sequence of one or two fast circuit opening operations followed by time delay operations to lock-out the breaker, after the predetermined number of closely successive operations has occurred to cause extension 90 of the counting piston to engage and move operating extension 58 of toggle lever 38 upwardly.

The structure thus far described is substantially identical with the breaker construction disclosed and claimed in the copending applications of J. M. Wallace et al., Serial Nos. 719,524 and 8,044, filed December 31, 1946, and February 13, 1948, respectively, on Circuit lnterrupters, and assigned to the assignee of this invention. Accordingly, for a more complete description of the structure and operation of the breaker parts thus far described, reference is hereby made to the aforesaid copending application of Wallace et al.

Referring to Fig. 5 of the drawing, a breaker such as that described up to this point will have time-current characteristics on the first one or two instantaneous circuit interrupting operations generally like the curve I, and when vent passage 76 is closed, the curve will then shift to the right at its lower end as shown by the dotted curve T in Fig. 5.

According to this invention, it is proposed to cause the breaker to have possibly one or two first instantaneous circuit opening operations on continuing overloads having a characteristic like that shown at I in Fig. 5, but thereafter to have a time-current characteristic which will shift to the right of the normal delayed characteristic T for currents above a predetermined value only, so that a selective action over a wide current range is possible for coordination purposes.

In order to achieve later circuit opening operations of the breaker with a time-current characteristic approaching that of a delayed higher rating of breaker, like that illustrated by the curve B in Fig. 5, it will be observed that switching means 81 is provided, which is disposed to be operated in accordance with the pressure in the dashpot passage 76. Thus, there is provided at one side of the breaker rod 22, stationary contacts 83 and 85 mounted on a supporting plate 86 of insulating material, which is mounted on the supporting casting 8. In alignment therewith is provided a movable bridge contact member 87 which may be resiliently supported by means of a stud 88 and spring 89 on a flexible bellows 99, secured to a plug 91 threaded into the supporting cast ing 8, and having a vent 93 connecting with the passage 76. A ball check valve 95 blocks the return of fluid from the bellows 99, and a leak passage 97 provides for the slow return of fluid to the passage 76.

Referring to Figs. 1 and 2, it will be seen that the circuit through the breaker may now be traced from one breaker terminal mounted on a bushing 108 on the cover 4, by way of conductor 110 to a stationary contact 14 of the breaker. At the closed circuit position of the breaker, the circuit therethrough continues by way of bridging contact 18 to the other stationary contact 14, by a conductor 111 to one end of the solenoid coil 12, and by a conductor 112 to stationary contact 83 of the switch means 81. Stationary contact 85 is connected by a conductor 114 to an intermediate turn of solenoid coil 12, the other end of the coil being connected by a conductor 118 to another terminal bushing (not shown) which may also be mounted on cover 4.

It will be observed that with the pressure switch 81 in its normally open position, stationary contacts 83 and 85 are not bridged by contact member 87, so that (Fig. 2) the entire current flowing in the circuit goes through the entire solenoid coil 12. This gives the maximum possible number of ampere turns for instantaneously opening the breaker contacts. However, as pressure is built up in the bellows 99 due to the passage 76 being closed off by a plug in the opening 77, or by upward movement ofthe integrator piston 80 after the first or second circuit interrupting operation in any sequence of closely succeeding circuit interrupting operations, the contact member 87 engages the contact members 83 and 85, and the circuit to the lower part of solenoid coil 12 is shunted, because contact member 87, as illustrated, now shunts the lower portion of the coil 12, so that current flows through only part, which may be about one-half, of solenoid coil. This results in a substantial reduction in the number of ampere turns, and a corresponding reduction in the force available to attract solenoid core 62 at the same value of overload current. This results in a portion of the time-current curve T shown in Fig. 5, being shifted to the right to coincide with the curve B, which represents the time-current curve of a breaker of twice the rating, thus giving a relatively wide range of selectivity between the first instantaneous operation of the breaker and later delayed operations for coordination with other equipment. While the reduction in the number of ampere turns of solenoid coil 12 in later operations in any sequence of a plurality of close successive circuit interrupting operations results in an increased current rating for such operations, the important factor in achieving a time-current characteristic such as R (Fig. 5) is that for the same value of overload current, the force acting on solenoid core 62 is reduced; or stated in another way, the current at which core 62 will be picked up by solenoid coil 12 is raised. The operation of reducing the number of ampere turns of solenoid coil 12 will be coordinated so as to occur at a time which has a definite relation to the closing of vent passage 76, depending on the fault current, so that a curve such as R is achieved, which not only is shifted to higher currents in the lower portion of its range, but retains an inverse time-current characteristic. This requires the introduction of a time delay means which may be of the dashpot type illustrated, prior to the time the reduced operating force is made effective.

The particular arrangement shown in Fig. 3 involves the use of an auxiliary coil 120 which should be mounted in magnetically coupled relation with respect to solenoid coil 12, with one end of this coil connected to one stationary contact 83, and the other end of the auxiliary coil connected to stationary contact 85.

It is believed apparent that when contact member 87 bridges stationary contacts 83 and 85, the circuit of auxiliary coil 120 will be closed to divert some of the flux of solenoid coil 12, because of the magnetic coupling of the two coils, to thereby reduce the force exerted by solenoid coil 12 to attract its core 62. An advantage of auxiliary coil 120, of course, is that the same coil may be used on existing circuit breakers regardless of the size or rating of solenoid coil 12 which may be employed.

The arrangement shown in Fig. 4 is similar, except that here a resistor 132 is connected between one end of solenoid coil 12 and stationary contact 83, with the opposite stationary contact 85 being connected by a conductor 134 to the opposite end of solenoid coil 12. It is apparent that in this arrangement that resistor 132 will be connected in shunt with the entire solenoid coil 12 when contact member 87 bridges the stationary contacts 83 and 85, to thus reduce the current through the coil, and result in shifting the time-current characteristic as before.

It is believed apparent that in each of the embodiments of the invention described above, an automatic reclosing circuit breaker is provided having means for effecting a first one or two instantaneous circuit opening operations,

fter which a time delay is imposed on the instantaneous acting contact operating means, and the force operating such actuating means may be subsequently de creased so that in all cases the tirne-current characteristic of these two different operations of the breaker will generally correspond to the characteristics I and R shown in Fig. 5. This results in providing a relatively wide current range, particularly at higher values of current, as represented by the range of currents separating curves 1 and R, over which selective operation to obtain proper coordination with other circuit interrupting devices is possible throughout the current range of such devices and the circuit breakers.

Our invention is especially useful where it is desired to obtain proper coordination between automatic reclosing circuit breakers which are connected in series circuit operation. For example, suppose a five ampere and a ten ampere breaker are connected in series circuit relation, the ten ampere breaker being, for example, in a main supply feeder, and the five ampere breaker being in a branch feeder supplied from the main feeder. The ten ampere breaker will usually be set for all time lag operation by closing the opening 77 with a plug, while the five ampere breaker will usually be set for one or two instantaneous trips followed by one or more delayed openings.

If the only time delay provided for the five ampere breaker is that obtained by the integrator piston 80 closing the vent passage 76, the ratio between the fast and slow operations cannot usually be made sufficiently great. If switch means, operated, for example, by th integrator, as described in the copending application Serial No. 787,206 of James M. Wallace et al., entitled Automatic Reclosing Circuit Breakers, and filed November 20, 1947, are used to reduce the effective ampere turns of the solenoid coil 12 after a predetermined number of breaker operations, then the five ampere breaker will be recalibrated after its instantaneous trips to function as a ten ampere breaker, and then there will be in effect, two ten ampere breakers in series, whereupon they will both trip with delayed time on the succeeding operation.

By using automatic reclosing circuit breakers embodying the features of our invention, this undesirable result can be obviated. With two reclosing breakers of ten and five ampere ratings embodying our invention, and the ten ampere breaker being set for all time lag operation by plugging the opening 77, proper coordination of the breaker is obtained under all conditions.

For example, the five ampere breaker trips with one or two instantaneous trips, then the integrator piston blocks the vent passage 76 to give delayed operation. Pressure in the passage '76 is thereupon transmitted to the bellows 99 so that the contact member 87 engages stationary contact members 83 and 85. The elfective ampere turns of the coil 12 are reduced, and the five ampere breaker at tains in eifect a ten ampere rating. At the same time, however, pressure is applied to the bellows of the ten ampere breaker whenever its armature commences to move, and since its opening 77 is plugged, the switch means 8-1 is effective as soon as the armature of the ten ampere breaker moves. The ten ampere breaker is therefore recalibrated into a twenty ampere breaker, so that it does not trip, but instead, permits the recalibrated five ampere breaker to operate, and lock out if the fault is not cleared.

It will be noted, that by using a pressure operated switch for recalibrating the recloser, materially difierent timecurrent characteristics are obtained than when an integrator operated switch is used. The recalibration is made more gradually, instead of abruptly, and the recloser can still retain almost its original rating for relatively low fault currents, where the rate of movement of the breaker armature is slow, and suf'ficient pressure to operate the switch means 81 is not built up for an appreciable time. High fault currents, on the other hand, effect operation of the switch means almost instantaneously, with a resultant rapid transfer to the higher breaker rating. Thus a wide range of breaker ratings is obtainable, including the intermediate ones, depending on the value of the fault current.

Having described preferred embodiments of the invention in accordance with the patent statutes, it is desired that the invention be not limited to these particular structures, inasmuch as it will be apparent to persons skilled in the art that many changes and modifications may be made in these structures without departing from the broad spirit and scope of this invention.

We claim as our invention:

1. An automatic reclosing circuit breaker comprising, separable contacts, means having a movable part operable in response to overloads on the circuit for causing separation of said contacts, means for automatically closing said contacts following a circuit opening operation, time delay means having a chamber filled with fluid subjected to pressure by movement of said movable part operable to delay the separation of said contacts with an inverse time-current characteristic, and means including a switch activated by fluid pressure from the chamber H of the time delay means in each of said delayed circuit opening operations for shifting portions of said inverse time-current cl -racteristic of the breaker to substantiallv higher currer than those of its instantaneous timecurrent characteristic in accordance with the current value of the overload, to thereby obtain a relatively wide current range of operation for purposes of coordination with other circuit interrupting devices.

2. An automatic reclosing circuit breaker, comprising, separable contacts, quick-acting means having a part which is moved in response to overloads on the circuit a predetermined amount before causing a quick separation of said c ntacts, means for automatically closing said contacts following a circuit opening operation, means including a fluid dashpot operable to delay the circuit opentill Qal

ing movement of said part with an inverse time-current characteristic, and fluid-pressure switch means actuated by the fluid in the dashpot operative in response to delayed circuit opening operation so as to 'be selectively operable in response to the rate of movement of said movable part for decreasing the force exerted by said overloadresponsive means to effect movement of said part, whereby a relatively wide current range of operation of the breaker is achieved for purposes of coordination with other circuit interrupting devices.

3. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core for causing separation of said contacts, dashpot means operable to delay circuit opening movement of said core, and means including a switch responsive to fluid pressure in said dashpot means for decreasing the effective number of ampere turns of said coil.

4. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core for causing separation of said contacts, time delay means comprising a chamber containing a fluid subjected to pressure in response to movement of said core operable to delay separation of said contacts for a plurality of successive operations, and means including a fluid-pressure operated switch responsive to fluid pressure in said chamber operative in response to each of said delayed separations to decrease the eiiective ampere turns of said coil to a predetermined value in response to overload currents above a predetermined value.

5. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core after traveling said predetermined distance for causing separation of said contacts, normally ineffective dashpot means responsive to. a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, means actuated during a cycle of operation of said breaker comprising a circuit opening and succeeding closing operation for counting the number of closely successive cycles of operation and rendering said dashpot means effective, switch means electrically connected with said coil, and pressure responsive means actuated by fluid pressure from said dashpot means for operating said switch means in response to the cycle of operation including said predetermined circuit opening operation to cut out of said circuit a predetermined number of turns of said solenoid coil.

6. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core after traveling said predetermined distance for causing separation of said contacts, fluid pressure means responsive to a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, switch means electrically connected in a shunt circuit with at least a part of said coil, and means responsive to the fluid pressure of said delay means for operating said switch means in response to the cycle of operation including said predetermined circuit opening operation for closing said shunt circuit.

7. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a c re at least a predetermined distance, means actuated by said core after traveling said predetermined distance for causing separation of said contacts, means including a dashpot chamber containing a fluid responsive to a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, and switch means electrically connected in shunt circuit relation with at least a part of said coil, fluid-pressure means responsive to fluid pressure in said chamber operative in response to delayed circuit opening operation for operating said switch means in response to the cycle of operation including said predetermined circuit opening operation for closing said shunt circuit.

8. An automatic reclosing circuit breaker comprising,

separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuafed by said core after traveling said predetermined distance for causing separation of said contacts, fluid pressure dashpot means responsive to a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, an auxiliary coil magnetically coupled with said solenoid coil, switch means electrically connected in circuit with said auxiliary coil, and pressure means actuated in accordance with fluid pressure in said dashpot means for operat ing said switch means in response to the cycle of operation including said predetermined circuit opening operation to close said auxiliary coil circuit.

9. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core after traveling said predetermined distance for causing separation of said contacts, means including a fluid pressure dashpot responsive to a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, an auxiliary coil magnetically coupled with said solenoid coil, switch means electrically connected in circuit with said auxiliary coil, and pressure means responsive to fluid pressure in said dashpot for operating said switch means in response to the cycle of operation including said predetermined circuit opening operation to close said auxiliary coil circuit.

10. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents to attract and move a core at least a predetermined distance, means actuated by said core after traveling said predetermined distance for causing separation of said contacts, means including a fluid dashpot responsive to a predetermined circuit opening operation in any series of closely successive circuit opening operations to delay the next circuit opening movement of said core, switch means electrically connected in circuit with said coil so as to decrease the ampere turns of said coil when said switch means is actuated, and pressure means responsive to the pressure in the dashpot for actuating said switch means.

11. In a circuit interrupter, separable contacts, electroresponsive means having a movable part operable in response to a predetermined value of current to effect separation of said contacts, a chamber having fluid therein subjected to pressure by movement of said movable part, and fluid-pressure actuated switch means actuated by fluid from said chamber operable only in response to greater than a predetermined fluid pressure produced by the electroresponsive means, to change the ampere turns of the electroresponsive means.

12. A circuit interrupter comprising, separable contacts, solenoid means operable in response to overloads on the circuit for causing separation of said contacts, said contacts being biased to reclose following a circuit opening operation, time-delay means having a fluid pressure dashpot operable to delay separation of said contacts in each of a plurality of successive opening operations, and means including a fluid-pressure operated switch operable in response to a predetermined pressure in said dashpot in any of said plurality of opening operations to decrease the effective ampere turns of the solenoid means to a predetermined value for a given value of overload.

References Cited in the file of this patent UNITED STATES PATENTS 1,648,508 Schweitzer Nov. 8, 1927 2,134,902 White Nov. 1, 1938 2,172,412 Robinson Sept. 12, 1939 2,468,498 Kyle, Jr., et al Apr. 26, 1949 2,468,851 Wallace May 3, 1949 OTHER REFERENCES An Improved Automatic Circuit Recloser; AIEE Technical Paper 47-50, Nov. 1946 by J. M. Wallace.

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