US2752534A - Automatic reclosing circuit breakers - Google Patents

Description

June 6, 956 A. w. EDWARDS AUTOMATIC RECLOSING CIRCUIT BREAKERS Filed April 21, 1951 Fig.1.

Fig.3.

Insulation INVENTOR Andrew W.Edwords. BY

5 2/ ATTORNZ WITNESSES: ia 92).

United States Patent 2,754,534 AUTOMATIC RECLOSING CIRCUIT BREAKERS Andrew W. Edwards, East McKeesport, Pa., assignor t0 Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 21, 1951, Serial No. 222,283

8 Claims. (Cl. 317-22) This inventionrelates generally to automatic reclosing circuit breakers, and it has: reference in particular to the protection of such devices from overloads which may be of suflicient value to cause excessive heating, without being sufficient to normally cause tripping of the breaker.

In practice, it is common to design automatic reclosing circuit breakers so that the minimum value of current required to trip the breaker is. just about twice the normal current rating of the breaker. This is usually done with the best interests of service continuity in mind, but it also poses a problem of coil overheating on currents which are above the normal rating, but below the minimum trip value.

One method of surmounting the problem is to design the coil with a suificiently low temperature rise on rated current, that it will not be damaged by sustained currents of values just. below the minimum trip value. This re sults in a large coil, which is expensive. Another method utilizes bimetallic means to mechanically actuate the tripping mechanism and open the breaker. Such means require a relatively large amount of force, and must of necessity be relatively large and expensive.

One object of this invention is to provide in a novel manner, for protecting the operating coil of an automatic reclosing circuit breaker against dangerous temperature conditions.

Another object of my invention is to provide in a circuit breaker of the automatic reclosing type, for increasing the effective ampere turns of the operating coil so as to trip the breaker when temperature conditions reach a dangerous value on sustained, currents above the normal rating but below the minimum trip value.

Another object of this invention is to provide for utilizing a thermoresponsive switch device in an oil-immersed automatic reclosing circuit breaker to increase the effective ampere turns of the breaker operating coil and trip the breaker in response to predetermined. temperature conditions of the oil surrounding the coil.

Yet another object of my invention is to provide in an automatic reclosing circuit breaker having switch means operable to increase the effective rating, after one or more operations, for reducing the efiective rating of the breaker to cause lockout when temperature conditions reach a predetermined maximum safe value.

Another object of this 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 a predetermined rise in operating temperature of the coil for increasing the pull exerted by said solenoid so as to effect a circuit opening operation even though the overload is less than the normal trip value for the breaker.

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;

Fig. 5 illustrates still another circuit which may be employed in a circuit breaker of the type shown in Fig. 1; and

Fig. 6 illustrates yet another circuit arrangement which may be employed in a circuit breaker of the type shown in Fig. l.

The circuit breaker illustrated in Fig. l is contained in a metal tank 2 having an open top adapted to 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, and the tank may be substantiaily filled with an arc extinguishing liquid such as insulating oil. The circuit breaker operating mechanism is all adapted to be mounted on the cover 4, which may have supports 61 (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 sup porting plate 10 by are chutes 16 of insulating material, such asv fiber or the like.

A bridging contact bar 18' is adapted to bridge stationary contact 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. l, to bias bridging contact 18 into engagement with stationary contacts 14 of the breaker with a predetermined pressure. 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 initially 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 oil-center position. The contact separating movement required to move toggle levers 28 and 30 from their positions shown in Fig. l to their oncenter 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 3t) are moved to their on-center 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 otters substantially no opposition to further contact separation.

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 of cover 4 where it normally is positioned beneath a hood portion 46 integral with the cover. The handle extension 44 of lever 36 has an operating eye 48 at the outer end thereof for receiving a hook stick or similar operating member. The other toggle lever 38 is provided with a slot 50 at its outer end for receiving a pin 52 mounted between spaced supporting lugs 54 integral with cover 4. 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 58 adapted to be engaged by automatic counting means, as will be described.

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 covering the coil, and the interior of the coil additionally has a cylindrical dash-pot 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, and 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 sufliciently 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 open 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 such 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 difflculty 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 4- 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 one above the other, a plurality of extensions 86, 88 and 90, for a purpose to be described.

A pawl lever 92 is pivoted at one end, as at 94, on supporting casting 8, and has its other end engaging the top of a collar 96 secured to actuating sleeve 60 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 80 will be moved upwardly a predetermined distance by pawl member 98, and when the breaker contacts are reclosed, 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 space provided by the relatively small clearance between the piston and sleeve 7 8. However, if a number of circuit opening operations occur in close succession, counting piston 80 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 90 of the counting piston engages operating extension 58 of toggle lever 38 to move the knee pivot 40 of toggle levers 36 and 38 upwardly over center, 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 sectional 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 71) is possible, and, accordingly, upward movement of solenoid core 62 is relatively unimpeded, so that the first circuit opening operation will occur substantially instantaneously after the current through coil 12 reaches a value sufricient 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 itself may be advanced to a position for 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 62 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 slowly reset as previously described, so that if a permanent condition comes on the circuit 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.

In order to achieve later circuit. opening operations of the breaker with a delayed inverse time-current characteristic, it will be observed that the upper extensions. 86, 88 and 90 of counting piston 80 form switchingmeans operated in accordance with the position of counting piston 80. Thus, there is provided at one side of the upper extensions of counting piston 80, a stationary contact 102 mounted on a supporting plate 104 of insulating material, supported from supporting casting 8. At the oppositeside of the upper extensions of counting piston 80, a stationary contact 106 is located at a point below opposed contact 102, with contact 106 also being supported from supporting casting 8.

It will be observed that the upper extensions 86, 88 and 90 of the counting piston are of different materials, with the extensions 86 and 90 being of an insulating material, and with extension 88 being of an electrical conducting material. Accordingly, at the normal position of counting piston 80, stationary contacts 102 and 106- are not bridged by counting piston extension 88, so that. (Fig. 2) the entire current flowing in the circuit goes through the solenoid coil 12. This normally gives the maximum possible number of ampere turns for instantaneously opening the breaker contacts. However, as

integrator piston 80 is advanced upwardly on the first or second circuit interrupting operation in any sequence of closely succeeding circuit interrupting operations, a shunt circuit will be provided about solenoid coil 12 because counting piston extension 88 moves up to a position between stationary contacts 102 and 106 to establish a circuit between these contacts so that, as illustrated, a resistor 107 now shunts the coil 12, and only part of the circuit current flows through solenoid coil 12.

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 time valueof overload current. This results in the timecurrent curve of the breaker being shifted on the current scale so as to delay opening of the breaker, because of the reduced operating force available for a given value of current, and give a relatively wide range of selectivity between the first instantaneous operation of the breaker and later delayed operations for coordination with fuses. While the reduction in the number of ampere turns of solenoid coil 12 in later operations in any sequence of a plurality of closely successive circuit interrupting operations results in an increased current rating for such operations, the important factor in achieving a shifted timecurrent characteristic is that for the same value of current, the force actin 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 should be coordinated, so as to occur at the same time as the closing of vent passage 76, so that a timecurrent curve is achieved, which not only is shifted in its entirety to higher currents throughout its range, but retains an inverse time-current characteristic approaching that of the fuses with which it is coordinated. This requires the introduction of a time delay means which may be of the dashpot type illustrated, at substantially the same time the reduced operating force is made effective.

The structure thus far described is substantially identical with that disclosed in detail and claimed in the copending application of J. M. Wallace et al., Serial No. 787,206, filed November 20, 1947, on Automatic Reclosing Circuit Breakers and assigned to the same assignee of this invention. For a more complete description of the structure and operation of the breaker parts thus far described, reference may be made to plication of Wallace et al.

In order to protect the coil overheating due to the flow of currents of a value above the normal rating, but below the minimum tripping value. (usually twice the normal rating), thermoresponsive switch means 108' may be provided. The switch means may be mounted on the support casting 8 where it will be subjected to coil temperature conditions and may, for example, as shown in Fig. 2, comprise a bimetal, element 109 composed of laminations of two metals having different coefiicients of expansion so that the element flexes in response to changes in temperature. The element 109 may be mounted in a frame 1100f insulating material for actuating a moving switch element 111 having contact members 111a, 111k and 1110. The coil 12.may,. as, shown in Fig, 2, comprise sections 12a and 12b which may be normally connected in parallel circuit relation through contact members 111a and 1110, and. may be disposed, for connection in series circuit relation through contact member 1111) when the bimetal element 109 flexes intesponse to a predetermined temperature condition of the coil. 12 to operate the switch means 108.

Under normal operating conditions with the circuit as shown in Fig. 2, a circuit may be traced through the breaker from one breaker terminal mounted on a bushing 113 on the cover 4, by way of conductor 114 to one stationary contact 14 of the breaker. In the closed position. of the breaker, the circuit continues through bridging contact 18 to the other stationary contact 14, and by conductors 115 and 116 to contact 106 and the lower end of coil section 12b, respectively. The circuit from contact 102 is open at insulating extension 90, but the circuit from conductor 116 extends through contact member 111C of switch means 198 to the lower end of coil section 12a by way of conductor 118. The upper end of coil section 12a is connected to the other breaker terminal by way of conductor 119, while the coil section 121) is connected by conductor 120, contact member 111a, and conductor 121, in parallel circuit relation therewith to provide the normal ampere turns for normal operation.

Should the coil 12 be subjected to a current above the normal value, yet below the minimum trip value for an appreciable length of time, the bimetal element 109 will flex upwardly, opening contact members 111a and 1110, and closing contact member 111b. This reconnects the coil sections 12a and 12b. in series circuit relation. Thus for a given line current, the ampere turns will be doubled, and the breaker will now trip, and if the overcurrent condition continues, the breaker will lock out and prevent damage to the coil.

The switch means 86, 88, 90, 102, 106 serves primarily to coordinate the breaker time current characteristics with fuse characteristics While increasing the effective rating of the breaker after one or two instantaneous operations, to give fuses in the circuit time to blow and prevent breaker lockout if the fuses can clear the faulty section. This is accomplished by having the conducting extension 88 connect contacts 102 and 106 after one or two fast operations, whereupon the resistor shunts the sections of coil 12, which are normally connected in parallel circuit relation.

With an overload of sufficient value to trip the breaker, the shunting effect of the resistor will obviously reduce the effective ampere turns, and in effect increase the rating of the breaker. This might appear to be inconsistent with the operation of the switch means 108, but it should be understood that the integrator switch functions after one or more fast operations to maintain continuity of service by coordinating the characteristics of the breaker with those of the fuses in the system, while the thermoresponsive switch is a protective device and functions only when it is necessary to prevent damage to the breaker. Accordingly, the thermoresponsive switch will predominate when it functions, as will be understood when it is said, copending ap- 12 against damage from observed that even when the integrator switch operates t connect the resistor in circuit relation with the coil 12, it can connect it in shunt circuit relation with only the coil section 12b when the thermoresponsive switch 108 has operated to connect the coil sections in series relation. Accordingly, it cannot offset the efiect of switch 108, and lockout will occur.

The particular arrangement shown in Fig. 3 involves the use of a coil 12 having coil sections 12a and 12b which are normally connected in parallel circuit relation with each other as in the circuit shown in Fig. 2, and are connected in series relation by a thermoresponsive switch 108 when the temperature of the coil 12 reaches a dangerous value. Except for the omission of the resistor 107 and the integrator extension switch, it is substantially identical with the system of Figs. 1 and 2.

It is believed apparent that when the thermoresponsive switch 108 operates because of an excessive temperature condition, the eifective ampere turns of the coil 12 will be substantially doubled, as the coil impedance is small compared with the overall circuit impedance. Accordingly, the breaker will now trip in response to current of a value below the normal minimum trip value, and the coil will be protected from damage by overheating.

In the arrangement shown in Fig. 4, the integrator switch 102-88106, is connected between one end of solenoid coil 12 and an intermediate turn thereof, for normally shunting the lower portion of the coil to reduce the effective ampere turns thereof, upon operation of the integrator switch after one or two instantaneous breaker operations. A thermoresponsive switch 108' is connected in series relation with the integrator switch, so that when the thermoresponsive switch operates in response to a dangerously high temperature condition of the breaker, it renders the integrator switch ineffective, and restores the normal ampere turns of the coil 12, so as to insure operation of the breaker to interrupt the circuit.

In Fig. 5, an arrangement is shown wherein the integrator switch normally operates to connect a resistor 132 in shunt with the entire solenoid coil 12 when counting piston extension 88 arrives at the position where it bridges the stationary contacts 102 and 106, to thus reduce the current through the coil, and result in shifting the timecurrent characteristic as before. A thermoresponsive switch 108' is connected in series relation with the integrator switch to render it ineffective and restore the normal ampere turns of the coil 12 to open the breaker, when the coil temperature exceeds a safe value.

A similar shunting resistor arrangement is illustrated in Fig. 6, except that instead of a switch operated by counting piston 30, a resistor 142 is adapted to be connected in shunt relation with solenoid coil 12 by a bimetal switch member 138 adapted to be heated and thereby flexed, by a heating resistance 136 permanently connected in series circuit between solenoid coil 12 and one stationary contact 14 of the breaker. Bimetal member 138 is supported at one end in any desired manner and is constructed in a manner well known in the art of a pair of metallic laminations having different coeflicients of thermal expansions, respectively, .ich as a lamination of steel and a lamination of brass or copper. The laminations are secured together in any desired manner, as by welding or the like, with the lamination having the higher coefiicient of thermal expansion being positioned lowermost so that when birnetal element 138 is heated, it will deflect upwardly to engage a contact 140 and thus establish the shunt circuit for solenoid coil 12 including resistor 142. Inasmuch as heating resistance 136 is in series circuit with solenoid coil 12, it will be heated by the fault current of the first and second circuit interrupting operations, so that if these operations occur relatively close together, sufficient heat will thus be developed to cause birnetal element 138 to deflect and engage shunt contact 140.

A thernioresponsive switch 108 is connected in series safe value, and thus effect operation of the breaker to lock out and protect the coil from damage. This construction permits omission of the integrator switch 88102 106 of Figs. 1, 2, 4 and 5, while still retaining the benefits of protecting the coil from overheating.

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 increasing the effective ampere turns to trip the breaker and prevent coil damage from overheating as a result of over-currents below the trip value. This is accomplished whether elfecting a first one or two instantaneous circuit opening operations, afterwhich a time delay is imposed on the instantaneous acting contact operating means, and the force operating such actuating means is simultaneously decreased, or whether the operating force is not reduced by means of an integrator switch or the like. In all cases the breaker will be protected against coil damage resulting from over-currents of a marginal value, which lie between the normal rated current of the breaker, and the minimum trip value which is usually twice the normal rating. As soon as the coil temperature subsides, the coil will be reconnected for normal operation, thus providing the maximum continuity of service consistent with safe operation of the equipment.

'Having described performed embodiments of the inven tion in accordance with the Patent Statutes, it is desired that the invention be not limited to these particular struc tures, 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. Accordingly, it is desired that the invention be interpreted as broadly as possible, and that it be limited only as required by the prior art.

I claim as my invention:

1. An automatic reclosing circuit breaker comprising, separable contacts, solenoid means responsive to overloads on the circuit above a predetermined value for causing separation of said contacts, means for automatically closing said contacts following a circuit opening operation, means operable to provide the contacts with an inverse time-current operating characteristic, and thermoresponsive means arranged in non-current-conducting relation with the solenoid but in heat transfer relation thereto so as to be actuated by heat produced by the solenoid and thus be responsive to a predetermined temperature condition of said solenoid caused by an overload below said predetermined value but of sustained duration for shifting said inverse time-current characteristic of the breaker to a substantially lower current rating to thereby obtain operation of said breaker at said lower value of overload to disconnect said solenoid from said circuit.

2. An automatic reclosing circuit breaker comprising,

, a casing having an insulating fluid therein, separable contacts, a solenoid coil in' said fluid responsive to overload currents of a predetermined value to attract and move a core at least a predetermined distance, means actuated by said core for causing separation of said contacts, means for reclosing said contacts following a separation, 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 a succeeding closing operation for counting the number of closely successive cycles of operation, switch means electrically connected in circuit relation with said coil, means actuated by said counting 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 thereby rendering the solenoid coil responsive only to overload currents above said predetermined value, and additional switch means having thermoresponsive means arranged in non-current-conducting but in heat transfer relation with the coil and actuated by heat mainly produced by the coil during overloads of said predetermined value but of long duration so as to be responsive to the temperatures of the fluid operable to render the aforesaid switch means ineifective to out said turns out of said circuit.

3. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil having two sections responsive to overload currents to attract and move a core, means actuated by said core for causing separation of said contacts, means for causing reclosing of said contacts, 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 a succeeding closing operation for counting the number of closely successive cycles of operation, switch means electrically connected in circuit with one of said coil sections, means actuated by said counting means for operating said switch means in response to the cycle of operation including said predetermined circuit opening operation to provide a shunt around at least said one coil section and thermoresponsive switch means normally connecting said coil sections in parallel, said switch means having a thermoresponsive element in heat transfer relation with the coil so as to be actuated by heat from the coil and thus operable in response to a predetermined temperature condition of the coil to connect said coil sections in series relation.

4. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil having two sections and being responsive to overload currents above a predetermined value to attract and move a core, means actuated by said core for causing separation of said contacts, means for causing reclosing of said contacts, switch means normally electrically connecting said coil sections in parallel at least for the first opening of said separable contacts and operable to connect said sections in series, and means in heat transfer relationship with the coil for operating said switch means to connect the coil sections in series in response to a temperature condition of the coil caused by a sustained overload below said predetermined value to increase the eifective ampere turns of the coil and trip the breaker.

5. An automatic reclosing circuit breaker comprising, separable contacts, a solenoid coil responsive to overload currents of a predetermined value to attract and move a core a predetermined distance, means actuated by said core for causing separation of said contacts, means for reclosing said contacts, 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 circuit relation with said coil so as to decrease the ampere turns of said coil and make the solenoid coil responsive only to overload current in excess of said predetermined value when said switch means is actuated, means responsive to the magnitude and duration of overload currents in the circuit for actuating said switch means, and thermoresponsive switch means having a bimetallic element in heat transfer relation with the coil responsive to a predetermined temperature condition of the coil caused by an overload of no more than the predetermined value but of sustained duration connected in circuit relation with said switch means to render it ineffective.

6. An automatic reclosing circuit breaker comprising, a casing having an insulating fluid therein, separable contact means disposed in said fluid, a solenoid coil disposed in the fluid responsive to overload currents above a predetermined value to move a core, means actuated by the core for causing separation of said contacts, means for reclosing said contacts, time delay means delaying at least one separation of the contacts in any closely successive series of separations, switch means in addition to said time delay means operable to reduce the effective ampere turns of the solenoid coil after a predetermined number of contacts separating operations, and thermoresponsive means arranged in non-current-conducting but heat transferring relation with the coil heated by heat applied to the fluid by the coil and operable in response to a predetermined temperature condition of the fluid produced by overloads of said predetermined value but of long duration to oppose the effects of said switch means.

7. A circuit interrupter comprising, separable contacts, a solenoid coil responsive to an overload current above a predetermined value to move a magnetic core, means operated in response to movement of said core to cause separation of said contacts, delay means for delaying one or more of such separations, and means including a switch having a thermal actuating element in non-current-conducting but in heat transfer relation with the coil so as to be heated mainly by heat produced by current flow in said coil below said predetermined value but of sustained duration responsive to a predetermined temperature condition of the coil for increasing the ampere turns of the coil.

8. In a circuit interrupter, separable contacts, a solenoid coil having an initial number of ampere turns responsive to overload currents above a predetermined value for effecting separation of said contacts, means automatically reclosing said contacts following a separation, and means including a thermal responsive switch having a thermoresponsive element in heat transfer relation with the coil operable in response to a temperature condition produced by heat from the solenoid coil resulting from overloads below said predetermined value but of sustained duration prior to the first separation of said contacts in any series and connected to increase the effective ampere turns of the coil from said initial value.

References Cited in the file of this patent UNITED STATES PATENTS 1,030,030 Steen June 18, 1912 1,517,280 Crichton Dec. 2, 1924 1,798,687 Landsmann Mar. 31, 1931 2,056,040 Dozler Sept. 29, 1936 2,468,634 Laxa Apr. 26, 1949 2,468,851 Wallace May 3, 1949 FOREIGN PATENTS 611,871 Great Britain Nov. 4, 1948

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