US2905865A - Flux shifting trip magnet for circuit breaker - Google Patents

Description

Sept. 22, 1959 c. l. cLAuslNG ETAL 2,905,865

FLUX SHIFTING TRIP MAGNET FOR CIRCUIT BREAKER Filed Dec. 19, 1956 l A 2 Sheets-Sheet 1.

Ami/@ff Sept 22, 1959 c. l. CLAUSING ETAL 2,905,865

FLUX sHIFTING TRIP MAGNET RoR CIRCUIT BREAKER Filed Dec. 19, 195e 2 Shets-Sheet 2 Til@ E;

f/gg /32 BY h? WM United States Patent C) FLUX SHIFTING TRIP MAGNET FOR CIRCUIT BREAKER Challiss I. Clausing, Collingswood, NJ., and Frank J. Pokorny, Hatboro, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application December 19, 1956, Serial No. 629,392

11 Claims. (Cl. 317-43) Our invention relates to a flux shifting type of magnet which serves the dual function of a high speed reverse current trip unit and a magnetic latch for high speed D.C. breakers.

The type of magnetic latch to which our novel invention is directed is set forth in U.S. Patent No. 2,412,- 247 to D. I. Bohn land assigned to the assignee of the instant invention. As set forth in the above reference, the movable contact structure of a D.C. circuit breaker is maintained in engagement with its cooperating stationary contacts by means of a magnetic armature which is sealed to a closing magnetic structure. This closing magnetic structure is comprised of a polarizing coil for creating a unidirectional liux in the magnetic core and linking the armature, and a bucking bar which carries at least a portion of the D.C. load current -and serves to create a linx which adds to the armature liux created by the polarizing coil when D.C. current is being carried in the normal forward direction.

In the event of a reversal of the liow of D.C. current, the current through the bucking bar reverses in direction, and its associated magnetic liux reverses and serves to buck down or shift the linx of the polarizing coil through the armature so as to reduce the magnetic linkage between the magnetic armature and the closing magnetic structure. The movable contact may then be moved to a disengaged position to open the circuit by biasing means once the magnetic latch is defeated as noted above.

This type of trip unit 'and magnetic latch has had wide application in D.C. breakers of high current low Voltage rectifying systems. When a plurality of rectifiers are connected in parallel, it is important that a back-firing rectifier or a rectifier which is short circuited so as to allow reverse current to liow therethrough is taken off the line as soon as possible, and that the total load current be redistributed between the remaining unfaulted rectilier units.

It has been found, however, that the above described magnetic trip unit of the breakers associated with the unfaulted rectiliers operate to release their armatures when current in the forward direction increases from a first value to a second higher value in a short time, this condition being obtained when the load current of a faulted unit is redistributed between the remaining units.

It has further been found that the magnetic armature is released when forward current is rapidly decreased from an excessively high value to a lower value, this condition occurring when one or more rectifier units are connected in parallel with other rectifier units which are already carrying a forward load current.

Also, this condition occurs when a backfire current is suddenly cleared in one rectifier unit and the forward current contribution of the units, thus suddenly removed. This condition prevails when the magnetic trip unit has not released on the initial rise of forward fault current contribution described above.

Clearly, it is desirable, and in some cases essential,

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as in certain electrolytic applications, that the remaining units carrying load current are not taken olir the line due to a rapid increase or decrease in their load currents.-

This is highly undesirable since the service of many rectifiers may be lost when only one is faulted, or 'another rectifier is cut into parallel operating service.

One explanation for the above type operation is that extraneous magnetic fields generated by current fiowing in other parts of the circuit breaker and in the external bus work tend to distort or cancel the desired flux linkages between the closing magnet and its cooperating armature.

In the first case Where the breaker trips due to the application of increased forward current of sufficient magnitude and rate of rise, it is possible that external fields are applied in the same general direction as the flux linking the armature and closing structure to distort the total linx linkages and cause release of the armature. When the external field is applied in an opposite direction as the original armature field there is, of course, a reduction in linking liux due to cancellation and once again the armature is released.

In the second case where the breaker is operated due to a sudden removal of a portion of the forward current and an external field is applied in a direction opposite that of the core linx, there will be a cancellation of flux and possible operation of the armature.

When, on the other hand, the external field is in a direction to create magnet-armature linkages of its own which would hold the breaker closed, then upon removal of this excessive external field there will be a time lag before polarizing flux builds up, and during this period the liux linkages may be reduced to a tripping point where the armature is released.

The principal object of our invention is to provide a magnetic structure wherein the magnet and its armature are free of the effects due to external fluxes.

More specifically, we provide a feed-back type of control Which utilizes a transformer means operable responsive to change in forward current, which induces compensating magnet-armature linking linx responsive to a change in the forward current.

In each case, our novel feed-back or transformer compensating means carries at least a portion of the load current of the D.C. breaker in a primary winding, land the secondary winding output is determined by variations in this D.C. load current. This secondary winding output is then connected to the magnetic structure to induce a compensating linx in this magnetic structure so that variations in the liux linking the armature and the magnet due to variations in the bucking bar current are compensated. Thus, when the bucking bar current is rapidly increased, as would be the case when the device is used as the D.C. breaker of a rectifier system of parallel connected rectifiers and one of the rectifiers backlircs, the current increase in the bucking bar and iiux increase associated therewith is compensated for by the novel feed-back transformer means.

if desired, the output of our novel transformer means could be rectified so that compensating linx will be activated within the core only when the change in current in the bucking bar is in a predetermined direction. By way of example, if it is desired to only compensate the magnet so that the armature will remain sealed during the rapid increase in current from a predetermined value, then the transformer secondary output will be rectified so y that a compensating pulse will be passed to the magnet high value to a second and lower value, the compensating device will induce'a blocking ux in the magnet which would tend to cause a release of the armature.

If, however, the device is to operate in an application where this condition is not likely to appear, this creation of-a blocking fiuX responsive to a decrease in bucking bar current may be desirable, since during a reverse current fault it, will aidthe reversal'of bucking bar flux to oppose the ux due to the polarizing coil and thereby allow a more rapid' disengagement of the armature with respect to the magnetic structure.

Our novel compensating means could also be applied where the D;C. breaker current may be decreased from excessively high currents to some lower currents, this compensation being achieved by reversing the rectifying means ofthe secondary transformer winding. Thus, a compensating fiux will now appear only when the buckingbar current decreases, but will not appear during anincrease inV bucking bar current due to the rectifying means-in the transformer output.

Clearly, each ofthe above conditions co-uld be simulT taneously compensated forby providing av first and second feed-back transformer means of the above described type wherein the rst transformer output is so rectified as to produce a` compensating fiuX for an increasing rectitier current, while the second transformer output is so rectified that a compensating pulse appears only during adecrease in bucking bar current.

While the aboveY described transformer means could be of any desired type, we have found it preferable to utilize a pulse type transformer so as to prevent saturation of transformer core-within the predeterminedN limits of current variation. However, normal types of current transformers couldy be used.

We have further found that our novel transformer means could utilizethe magnetic structure of the magnetic latch for its magnetic circuit so as to eliminate a separate and distinct magnetic structure for the transformer primary and secondary windings. T-his is possible when the magnetic latch structure has the usual high reluctance path interposed between the armature leg andthe polarizing coil leg. In this case the-flux through the polarizing coil and the flux due to the bucking bar during current conduction in the forwardvdirection are in seriesV through the` armature leg, but arelinopposingHV relationshipin the high reluctance leg. Thus, when thecurrent'in the bucking bar varies there will be afluX change in the high re' -luctance leg. By utilizing the bucking'bar as the primary windingfor our novel transformer compensating means, and byV placingpa secondary winding on the high reluctance leg, 1t is clear that this. secondary winding will have an output responsive to variations inthe bucking bar current. This output may then be applied to` another portion of the magnetic latch structure inthe manner described heretofore so as to compensate for variations in iiux linkagesbetween the magnet and its armature due to variations-in the current through the buckingtbar.

Accordingly, the primary object of our invention is to provide a compensating fiux through the armature of' a D.-C. breaker trip unit responsive tovariations in the current passing through the breaker.y

Another object of this invention is to provide a novel transformer means having a secondary winding energized-responsive to variations in a bucking bar current angl,` to. connect the secondary winding to the armature magnetic structure for compensating for flux changes due to the bucking bar current.

Another object of this invention is to provide a magnetic structure compensating means wherein the current through a main current conducting member alters the linking flux between an armature and the magnetic structure, and the variation in ux due to the varying current is compensated for by anovel transformer having a primary windingV connected to conductthe current of the current 'carrying means.

Another object of this invention isto provide a novel compensating means for preventing the operation of an armature of a magnetic trip unit responsive to a rapid increase in current through the main conducting member.

A still further object of this invention is to provide a novel transformer compensating means for the magnetic structure of a magnetic trip unitA wherein the main co11- ducting member serves as a primary winding,and'alsec ondarywinding is woundgin ahigh reluctance leg of the magnetic structure and is connected to induce compensating fluxes inthe magnetic structure` to compensate for variations in the currentv throughr the main. conducting member.

A still further object of this invention is to provide a novel transformer compensating meansfor. amagnetio trip unit wherein the secondary windingis energized responsive to variations of the current through the main conducting member and the output of the secondary winding is rectified to produce compensationresponsive to'current changes in a predetermined direction;

These and other. objects of` my invention will now be apparent from the following description when taken inconnection with` the drawings, in. which:

Figure l schematically shows themanner in which a magnetic trip unit of the type towhich our'invention could be applied can. be connected to-a. contact structure of al circuit breaker.

Figure 2 shows a cross'sectional, view ofthe magnetand armature of Figure. 1y whentaken across the'lines 2 2.

Figure 3 is similar to Figure l and:shows\the armature and contact structure in a disengagedposition.

Figure 4 schematically represents a plurality of parallel connected rectifiers. which could have D.C. circuit breakers with magnetic latch type trip unitsandillus- 'rates the current conditions. with one ofv the rectifiers carrying back-feed current;

Figure 5 shows. a plot. o-fvforwardlcurrent versus time for the current through. the Ds-C. breaker contacts of one of the unfaultedrectifiers of.` Figure 4.

Figure 6 illustrates a first. embodimentv ofour novel invention when applied to the. magnetic struc-ture of Figure l.

Figure 7 illustrates asecond embodimentoffour'novei invention wherein the novell transformer compensating means are arrangedttocompensate for bothvincreaseor decrease in forward current. f

Figure 8 illustrates `a further. embodiment ofour' novel invention when the, magnetic latch, magneticA structure servesthe purpose ofthe compensating.transformer magnetic structure.

Figure 9 illustrateshow the. device of 'Figure 8 may-be modified so, as tocompensate for bothincreaseand' decrease of forward current.

Figure l0 showsa top.crossrsectional'viewoff a second type of magnetic structure which could operateas a magnetic trip unit and'could be provided with ournovel compensatingv means.

Figure ll shows. a cross-sectional View of FigureA l0 when taken acrosslthelines 11e-11.

Figure 12 showsa cross-sectional view of the armature of Figure l0 when taken acrossthelnes- 12*12.k

Referringfirst toFigure l which shows a well known typeof magnetic structure inconjunction withits operativeconnection to the circuit breaker; contacts,l it isseen that the. magnetic latch unit is comprised of` ama-gnetic structure Zie-and an armature 22 which.ismovable'` into androutgof engagement withtthe armature fluX-V path- 24 of magnet 20. Magneticstructure/ 2f), which may. be a laminated structure asshownin-.Figure 2'; is furthercomprised of ahigh reluctance path 26 andiapolarizing coil flux p ath 28.

The magnetic structure,- is energized by. a polarizing coil 30 whichisenergized at terminals.32 and eby. a D.C. source lso ask tocreate atunidirectional fiuxwhich will. @QW through. the'armature flux path. 24? and the armature22 to` thereby maintain armature 22 sealed to the magnetic structure 20.

Magnetic structure 20 is further energized by a second winding or bucking bar 36 which passes between the armature flux path 24 and the high reluctance flux path 26. During normal forward current flow indicated by the arrow 38, bucking bar 36, which will hereinafter be interchangeably described as a current conducting means, will pass a flux through the armature flux leg 24 in the same direction as the flux created by the polarizing coil 30.

Thus, while the bucking bar 36 carries current, the armature 22 will see llux linkages which are given by the sum of the fluxes due to bucking bar 36 and polarizing coil 30.

`In the high reluctance leg 26, however, the fluxes of polarizing coil 30 and bucking bar 36 are in opposing or cancelling directions.

The bucking bar 36 is operatively connected to the moving contact structure 40 of a D.C. circuit breaker by means of the flexible conducting member 42.

In Figure l it is seen that movable contact structure 40 is in engagement with the cooperating stationary contact structure 44 so as to complete a current path from a point 46 of bucking bar 36 to the point 48 of the stationary contact structure 44, which points could lead to subsequent terminal members.

The operative connection between armature 22 and movable contact structure 40 is shown schematically in Figures l and 3 as being formed by the flexible member 50 which passes over a fixed guide member 52. Thus, in the contact engaged position, the armature 22 is sealed to the magnetic structure 20 and connecting means Sil will maintain contact 40 closed against the force of a biasing means 54.

In the event of a reversal of current through bucking bar 36, the flux due to bucking bar 36 will reverse and buck down the flux of polarizing coil 3G in armature path 24 so as to decrease the total linkages between magnetic structure 20 and armature 22. Thus, the force of the opening bias means 54 may then move contact structure 40 to a disengaged position and remove armature 22 from its sealed or engaged position with respect to magnetic structure 20, as is shown in Figure 3.

It is to be clearly noted at this point that the connection between magnetic structure 20 and circuit breaker mechanism set forth in Figures l and 3 is meant to be for illustrative purposes only, and is schematic in nature. Obviously, the type magnetic latch set forth in Figure 1 could be applied to any desired type of circuit breaker mechanism wherein the armature 22 would normally control the position of the circuit breaker cooperating contacts. Furthermore, trip free type mechanism and any other type desired mechanism could be interposed or added to the connection between the armature 22 and the circuit breaker Contact structure.

It has been found in the past that when utilizing the type of magnetic structure set forth in Figures l, 2 and 3 that the armature 22 will be released from the magnetic structure 20 responsive to relatively rapid increases in current or decreases in current. Thus, in the case of Figure 4 which shows a first, second and third rectifier 56, 58 and 60 respectively connected in parallel to feed a common load 73 and rectifier 60 is subjected to backtire, then the magnetic latch mechanisms 62 and 64 of circuit breakers 66 and 68 respectively will see a rapid increase in current since they will now feed current into the short circuited unit 60. By way of example, Figure 5 shows this condition for either of units 56 or 58 where at time t1 the unit 60 is faulted and the current rises from magnitude I1 to I2 in the time interval t2 minus t1. This rise in current through the trip units 62 and 64 which are here assumed to be of the type set forth in Figures l, 2 and 3 has in the past caused a tripping of their associated breakers 66 and 68 respectively by a release of their armature members.

Thus, while the faulted unit 60 is removed from the line due to the normal reverse current trip action of circuit breaker 70 as initiated by magnetic trip unit 72, the load 62 is completely taken out of service in View of the disconnection of rectiers 56 and 58.

As will be set forth hereinafter, our novel compensating means will operate on the magnetic trip structure tin such -a manner that la compensating flux will be introduced `into the magnetic structure responsive to an increase in current o-f the Itype set forth in Figure 4 between the time limits t1 and t2.

It has been further found that if rectiflers 56 and 58 of Figure 4 are normally carrying the excessively high current I2 and the rectifier, such as rectifier 60, after having its fault corrected is returned .to the line so as to cause a relatively rapid decrease in current I2 to the current I1 Ain the time t3 minus t4 (Figure 5), once again the ltxrip units 62 and 64 Will operate to open the breakers 66 .and 68 and once again remove the rectiers 56 and 58 respectively from the line. Here again, however, our novel compensating means may be adapted so as prevent this undesired condition.

The general principles of our novel invention may be understood by reference to Figure 6 which shows the magnetic structure of Figures l, 2 `and 3 when adapted with our novel transformer compensating means. Figure 6 shows our novel transformer compensating means, or a feed-back means, as being comprised of the transformer means 74 which includes a magnetic core 76 having the bucking bar 36 as a primary winding and secondary winding 78. The output of the secondary winding 78 is connected to van auxiliary winding 80 wound'on the magnetic structure 20 of the magnetic trip unit. If desired, .a rectifier 82 may be connected in the output of secondary winding 78, or as is indicated by the dotted lines, the connection may be ra direct one as will be described hereinafter.

The connection shown in Figure 6 fis specifically directed to a connection for adding a compensating flux to the magnetic structure 20 responsive to a rapid increase in current through the bucking bar 36 as shown Ibetween time t1 to time t2 of Figure 4. As has been described hereinbefore, a rapid increase in this current for some reason decreases the ux linkages between the magnetic structure 20 and the armature 22 so as to allow the 'armature 22 -to be moved to a disengaged position with respect to structure 20.

In the structure of Figure 6, however, transformer 74 is energized responsive to this rapid increase in current through bucking bar 36 so as to induce a voltage across winding 78, which voltage is subsequently impressed upon winding 80 to induce a compensating flux in core 20. This compensating flux then compensates for ythe decreased flux linkages between magnetic structure 20 and armature 22 and prevents operation of the tnip umt.

It has Abeen found desirable to construct core 76 in such .a manner that it would be maintained unsaturated throughout a predetermined current change interval, although it is possible to utilize normal current transformers for this purpose.

The purpose of rectiier 82 is to prevent energization of coil 80 by secondary Winding 76 when the current through bucking bar or current carrying means 76 decreases from a predetermined value. For with this condition, the flux in coil 80 will be in a direction to buck down :the flux through armature 22 and thereby allowv release of the armature member. This condition would be undesirable when the current in the bucking bar 36 is being reduced from -an excessively high value to a relatively low value as the reduction in current from value I2 and I1 between times t3 and f4 of Figure 5.

However, this conditioncould be extremely desirable during reverse current conditions, since the ux induced in coil 80 will aid the reversed flux due to the buckingbar 36S'to buck down the ilux through-armature 22' due tothe polarizingcoil 30, and' thereby cause faster operation off the trip unit.

Thus, the rectifier 82 could belaincluded in the circuit depending upon particular applicationV of: the magnetic trip-unit. That bis, when. it is not necessary to` prevent operation of the magnetic latch'` during decrease ofcurrenti from` an excessively high value to al'ower value, then the exclusionof' rectifier 82f would' serve to increase the speed of# magnetic latchunit.

Figure 7 shows the manner in which the magnetic latch unit could be adapted toV compensate lfor conditions of both. increase and `decrease of current in` the bucking lbar 36. .andi comprises the components of Figure 6-which operate inthe same manner as described above for rapid increaseof current plus an additional compensating transformer 84 which has a secondary windingl 86.

During a decrease in current from anw excessively high value, secondary winding 86. connected! in series withv rectier. 88; and magnetic core Windingy 90l willinduce a. compensating iiux in the proper direction in the magnetic structure responsive toa decrease in currentin the bucking bar 36.

AsA will; be apparent' to those 'skilled' -in the art coils 7.8-` and 86Ucould be mounted on the same magnetic structure 74; the two independent magnetic structures being shown. in Figure Tfor illustrative purposes only.

While each of'Figures 6.and7 have shown our novel transformer compensating means as having a separateV and independent magnetic core, Figure 8 shows a= manner in! which the magnetic structure of: the magnetic trip unit may be utilized as the magnetic core of" the compensating transformer.

Referring now to Figure 8, -it isseen that a compensating winding or secondary winding 92 is` wound' on Figure 8 then shows the output secondary winding 92.Y as being applied directly across the polarizing Winding 3,0 inV series. with the rectier. 94 so that compensating iluxis induced into vthe magnetic structure responsive :to `a change lin current: in the bucking bar 3,6'r in. theysamemanner `as theembodimentV of Figure 6.

Itis to be noted that. the polarizing coil 301 is now used. to serve both as a polarizing coil aswell as an auxiliary coil to receive the compensating signal pulse. It ishoWever, necessary to provide a diode means 96 in the polarizing circuit. so as to prevent short circuiting of the pulse through the voltage source ofpolarizingv potential. Clearly, the same structure could have been set forth in Figures 6 and 7 Where in Figure 6y the output of secondary winding78could have been applied directly tothe polarizing coil 30, rather than to the auxiliary coil 80.4

While Figure 8 speciiically shows the circuit connection as including rectier 94f for allowing passage of a compensatingipulse only when current through the bucking bar. 36 increasesfrom a predetermined value as seen in Figure 5., Figure 9A shows the manner in which the circuit of Figure 8 could be modifiedl to provide compensation for both an increase in current through the bucking bar. 36 and a decrease in current through the bucking bar 36. In this case, the secondary winding is-comprised of two halves 98 and 100'ofy a center tapped coil wound on the high reluctance leg 26 Where Winding-portion 98 is connected to polarizing coil 301through the rectier 94and serves thefsame purpose asy did secondary winding 92 of1Figure8.

Winding portion 100, however, which is connected through the rectifier 102 will induce a compensating voltage into winding 301'esponsive to al decrease incurrent through bucking bar 36 from a predetermined value which is excessively high to a lower Value as between the times t3 and t4 of Figure 5 While our novel compensating or feed-back means has been set forth in Figures 6, 7, 8 and` 9 in conjunction with the magnetic structure of the type setforth in Figures l, 2 and 3, it is to be clearly understood thatI our novel invention could now be applied to a wide variety of magnetic structures.

By way of example, the magnetic structure'couldl take the form set forth in Figure 10 wherein an armature 106 is scalable to the armature flux path 108; The' armature flux path 108 carries ilux due to the polarizing coil 110 which is wound on the polarizing luxpathl 112 and the bucking bar 114 which circulates its flux to armature liux path 108 through the high reluctance magnetic structure 116.

In the case of the structure of Figure 10 and assuming the bucking bar 114 carries current in a normal forward direction, the ux due to the polarizing coil' 110 and the bucking bar 114 owing through the armature ilux path 108 will flow in the same direction. The ux in the polarizing iluxpath 11'2A will be that due only to the polarizing coil 110, while the ux iiowing in high reluctance structure 116` will be that due to the polarizing flux and bucking bar flux flowing in opposing directions.

It is to be further noted that the armature flux path 108 as seen in Figures 10 and 11 is comprised' of a plurality of horizontally stacked laminations and has air gaps 118, 120 and 122 extending thereacross.

The armature 106, as is best seen in Figure 12, is composed of alternating magnetic and non-magnetic laminations which are fastened together in any desired manner. The magnetic portions 128 and 130 and 132' are then positionedto straddle the air gaps 118, 120 and 122 of the armature flux path 108, as best seen in Figure 10.` By this type of construction the flux linking the armature flux carrying structure 108 and the armature 106 must rst enter magnetic portion 128 of armature 106, and is thereafter turned into the magnetic structure 108 because of the non-magnetic portion 124, and after passing non-magnetic portion 124, re-enters the armature and then leaves the armature 106 after passing slot. 120'andso on.

Hence, for the particular structure set forth in Figures 10, 1l and l2, the ux linking the armature ux path 108 andthe armature 106 enters and leaves the armature 106 six times to thereby effectively increase the number of flux linkages between the magnetic structure and its armature, and thus provide a substantially higher holding force for a predetermined amount of magnetic llux.

Furthermore, once the armature 106 is slightly separated from the armature path 106 the effective air gap will be six times the normal physical air gap, thus increasing the speed at which the armature is released from the magnetic structure.

In the case of the embodiment of Figures 10, l1 and 12, it is clear that an auxiliary winding 136 would be added on the polarizing structure 112, this Winding being energized in a manner set forth in Figure 6 for a case of compensating Winding 80. A still further winding coil be added to the structure of Figure l0 for receiving another winding similar to winding 90 of Figure 7.

If, however, it is desired to utilize the structure set forth in Figures 8v and 9 wherein the latch magnetic structure is utilized as the transformer iron of the compensating transformer, then the secondary winding could be positioned on the high reluctance structure 116, this secondary winding being seen in Figure l() as secondary winding 138. In this case, secondary winding 138 will be connected to a compensating winding such as winding 136 for achieving any desired compensation, as has been set forth hereinbefore.

More specifically, the compensating transformer in this case would include the high reluctance path 116, armature path 108 and armature 106. The primary winding would be the bucking bar or current carrying member 114, and the secondary winding, of course, is the winding 138. f

Although we have described preferred embodiments of our novel invention, many Ivariations and modifications will now be obvious to those skilled in the art, and we prefer therefore to be limited not by the speciiic disclosure herein but only by the appended claims.

We claim:

l. A magnetic latch for D.C. circuit breakers; said magnetic latch comprising a magnetic core and an armature movable into and out of magnetic engagement with respect to said magnetic core; said armature being operatively connected to a movable contact of a pair of cooperating contacts of said D.-C. circuit breaker; Vsaid movable contact being normally maintained in engagement with its cooperating contact by said armature when said armature is in said engagement with said magnetic core, said movable contact being movable to a disengaged position with respect to said magnetic core when said armature is moved out of said engagement with said magnetic core; current carrying means carrying at least a portion of the load current of said D.C. breaker positioned to induce flux linkages between said magnetic core and said armature to maintain said armature engaged to magnetic core when said current flows in a forward direction and polarizing means associated with said magnetic core for inducing polarizing ux linkages in the same direction as said ux linkages due to said current carrying means; reversal of current through said current carrying means causing a decrease in flux linkages between said armature and said magnet core yto'allow said armature to'be moved to said disengaged positionfwith respect to said magnet core; and feed-back means including transformer means connected to be energized responsive to a change in current through said current carrying means, said transformer means being further connected to induce compensating flux linkages between said magnet core and said armature responsive to variation in the current of said current carrying means in an increasing direction; said feed-back means including diode means therein for blocking operation of said transformer means when said current of said current carrying means varies in a decreasing direction.

2. A magnetic latch for D.C. circuit breakers; said magnetic latch comprising a magnetic core and an armature movable into and out of magnetic engagement with respect to said magnetic core; said armature being operatively connected to a movable contact of a pair of cooperating contacts of said D.C. circuit breaker; said movable contact being normally maintained in engagement with its cooperating contact by said armature when said armature is in said engagement with said magnetic core, said movable contact being movable to a disengaged position with respect to said magnetic core when said armature is moved out of said engagement with said magnetic core; current carrying means carrying at least a portion of the load current of said D.C. breaker positioned to induce ilux linkages between said magnetic core and said armature to maintain said armature engaged to magnetic core when said current flows in a forward direction and polarizing means associated with said magnetic core for inducing polarizing flux linkages in the same direction as said flux linkages due to said current carrying means; reversal of current through said current carrying means causing a decrease in flux linkages between said armature and said magnet core to allow said armature to be moved to said disengaged position with respect to said magnet core; and feed-back means including transformer means having said current carrying means as a primary winding, said transformer means having a secondary winding connected to induce compensating flux linkages between said magnet core and said armature responsive to variation in the current of said current carrying means in an increasing direction; said feed-back means including diode means therein for blocking operation ,of said transformer means when said current of said current carrying means varies in a decreasing direction.

3. A magnetic latch for D.C. circuit breakers; said magnetic latch comprising a magnetic core and an armature movable into and out of magnetic engagement with respect to said magnetic core; said armature being operatively connected to a movable contact of a pair of cooperating contacts of said D.C. circuit breaker; said movable contact being normally maintained in engagement with its cooperating contact by said armature when said armature is in said engagement with said magnetic core, said movable contact being movable to a disengaged position with respect to said magnetic core when said armature is moved out of said engagement with said magnetic core; current carrying means carrying at least a portion of the load current of said D.C. breaker positioned to induce iiux linkages between said magnetic core and said armature to maintain said armature engaged to magnetic core when said current flows in a forward direction and polarizing means associated with said magnetic core for inducing polarizing flux linkages in the same direction as said flux linkages due to said current carrying means; reversal of current through said current carrying means causing a decrease in flux linkages between said armature and said magnet core to allow said armature to be moved to said disengaged position with respect to said magnet core; and feed-back means including transformer means having said current carrying means as a primary winding, said transformer means having a secondary winding connected to induce compensating flux linkages between said magnet core and said armature responsive to variation in the forward current of said current carrying means; and rectifier means connected in said secondary winding to prevent induction of compensating iiux in said magnet core when said variation in current is in a predetermined direction; said feed-back means further including diode means to prevent operation of said transformer means when the variation of current is in a direction opposite to said predetermined direction.

4. A magnetic latch for D.C. circuit breakers; said magnetic latch comprising a magnetic core and an armature movable into and out of magnetic engagement with respect to said magnetic core; said armature being operatively connected to a movable contact of a pair of cooperating contacts of said D.C. circuit breaker; said movable contact being normally maintained in engagement with its cooperating contact by said armature when said armature is in said engagement with said magnetic core, said movable contact being movable to a disengaged position with respect to said magnetic core when said armature is moved out of said engagement with said magnetic core; current carrying means carrying at least a portion of the load current of said D.C. breaker positioned to induce flux linkages between said magnetic core and said armature to maintain said armature engaged to magnetic core when said current flows in a forward direction and polarizing means associated with said magnetic core for inducing polarizing liux linkages n the same direction as said flux linkages due to said current carrying means; reversal of current through said current carrying means causing a decrease in flux linkages between said armature and said magnet core to allow said armature to be moved to said disengaged position with respect to said magnet core; and feed-back means comprising a first and second transformer; each of said first and second transformers having said current carrying means as a primary winding; each of said first and second transformer means having secondary windings connected to induce asoman compensating hun linkages between saidi magnet core andi said armature responsive to. an increase: from: a` predetermined value anda decreasefrom an excessively.- high value respectively of. current through said? current carrying means, each of said irst and secondl transformer secondary windings having rectilier means associated therewith for preventing induction of compensating flux' responsive todecrease' of current from saidi excessively-high value and increase of current from` said predetermined value respectively.-

Al magnetic latch for D.C. circuit breakers; said magnetic latchv comprising a magnetic core and an armature movable into and out of magnetic engagement with respect tosaid magnetic core; said armature beingloperatively connectediftd a movable contact of al pair of cooperating contacts ofsaidI D.C. circuit breaker; said movable contact being normally maintainedin engagement with its cooperating contact by said armature when said armature isin said engagement with'- said magnetic core, saidmovable contact being movable tovadisengaged position with respect to said-magnetic core when said armature is moved out of said engagement with said magnetic core; current carrying means carrying at least a portion ofthe load curr-ent of said DL-C.' breaker positioned toinduce fluxl linkages betweenI said? magnetic core andi said armature tomaintain saidl armature engaged to magnetic core when said cur-rent flows in a forward direction and polarizing means associated with said magneticcore for inducingl polarizing ilux linkages in the same directionas said ux. linkages due to said current carrying means; reversal of! current through said currentcarrying means causing a decrease in flux linkagesbetween said armature and; said magnet core to allow said armature to be movedI to said disengaged position-with respect to said magnet core; and feed-backmeans including transformer means having said current carrying means as a primary winding, said transformer means having a secondary` winding. connected to` induce compensating` liux linkages between said magnet core and saidarmature responsive to an increasey in the current of' said current carryingy means in an increasingdirection; said eedeback means including diode means therein for blocking-'Opern tion of said transformer means-whensaid current of said currents carrying means var-ies in a decreasing direction;

6. In' az magneticv structure forsealing an armature; said magneticV structure: havingv magnetic iiuxl induced therein in linking relationship with'- respect` tosaidi armature by a irst and secondlwinding, saidiir-st and! second windings creating flux` in the same directionl for linking said armaturey and: magnetic structure when= current in said first winding is. in a irst direction and' inA opposite directions-whenI current in-saidirst winding-is in asecond direction; a compensating means for compensating for a changein iluxlinkages betweeng said armature: and said magnetic structure whenl saidcurrent in saidfir-stf winding varies,A said' compensating meanscomprising atransformer: having a primaryv winding and' a secondary winding,v saidV primary-winding: being connectedto conduct at leastt a. portionof the current' in said! first winding, said secondaryl winding beingA connected to induce compensating luxin: saidmagnetic structure responsiveto variation of current: in saidprimary windingv in an increasing directionggsaidl secondary winding having a diode connected therein; said: diode preventing operation or said* compensating'meanswhen said variation ofcurrent in said primary winding is in adecreasingdirection.

7.11m; a magnetic structure for sealingI an armature; said: magneticV structure having magneticflux induced therein in linking relationship withrespect tov said armatureby a=` iirstf and: secondiwinding, said lirst` and second windings creating; iiuX in; the same direction for linking said armature and magnetic; structure when. current in said iirst windinglisin-a firsts directionaand:inaopposite diev rections. when: currentzinsaid rst winding isdn: asecond directiong; al compensating; means for compensating for a change: influx linkages between said armature-and said' magnetic: structure when said current in? said iirsr winding varies, said compensating means comprising; a: transformen havingx a primary,y winding and'` ai secondary winding, sai-df primary Winding being. connectedto conduct at leash a portiona of the: current in' said" irst winding, Vsaid secondaryl winding: being connected to induce compensatr ingun in said magnetic structure responsivey toi variation of current in said primary winding in-.an increasing direction;V said secondary winding having a diode connected therein; said diode preventing operation of said compensating. means whensaid variation of currentinsaid` primary winding' is in ai decreasing direction;` said transformer being constructed to' bemaintainedunsaturated over a predetermined range of variationof current in said primary winding. y

8. Ina magnetic structure for sealing anl armature; said magnetic structure` having magnetic uX induced therein inlinkingl relationship with respect tov said armature by a first and second winding, said iirst and second windings creatingv flux in the same direction for linking said armature and magnetic structure whencurrent inV said rst Winding is; ini a rst directionand in opposite directions-,when current` in said rst winding is in asecond direction; a compensating means for compensating for a changein flux linkages betweensaid armature and said magnetic structure when-*said current in said iirstawinding varies, said compensating means comprisingl a transformer having a primary winding and asecondary winding, saidprimary winding being connected to conduct at leastv a portion ofthe current in said irst winding, said secondary'windingbeingr connected to induce compensate ing fluir` insaid magnetic structure responsivetol variation of current inzsaid: primary windinggsaid transformer be'- ing constructed tobe maintained unsaturated over apredetermined range of variation of current! in said primary winding, and rectifier means connected in said secondary winding to prevent induction of said compensating ux when said currentin said primary winding varies ina predetermined direction;

9. `Ina magnetic structure for sealing an armature; said magnetic structure comprising; an armature iiux path,y aA polarizing iiux path and, ahigh'reluctance path; polarizing means wound on: said polarizing path for inducing unidirectionall flux insaid armature path and bucking bar means for inducing flux-insaid armature path-inthe Same. direction. as that due to said polarizing meanswhen current insaid buckingbar is inthe same direction; said high reluctance path being'positionedwithrespect to said polare izing means and said bucking bar means to carry their said uxes in: opposing/directions; a compensating coil wound on said highreluctance ux path; said compensating coil being energized responsive, to Variations in thev current of said.bucking;bar;lsaid compensating coil being connected to-induce. compensating flux; in said' armature path responsive to variations in current' of saidbucking bar in an-increasing direction; saidcompensatingfcoil hav` inga diode connected therein to prevent' operation of said compensating means when said variation of current in said bucking. bar is in: a: decreasing directiona l0. In a magnetic structure for sealing an armature; said. magnetic. structure comprising an t armature: flux path', a polarizing hun path and athigh reluctancepathg; polar*- izingmeansiwound on said polarizingpath for inducing unidirectionallnxin saidarmature path and bucking bar means-for inducing ux insaid armature path in the. same direction asf thatdue tosaid' polarizingmeans when current insaidbucking bar is in the: same directionysaid' high reluctancey path: being positioned with respect tosaid polarizing, means andY said: bucking barl means to carry their said fluxes int opposing direction;- a compensating coil wound oni said: high; reluctance flux path; said conrpensating coil: being energized responsive -to variations in the` currentl off-'saidl bucking' har;l said compensating coil beingconnectedto induce compensating iuxl in' said arrna' 13 ture path responsive to variations in current of said bucking bar; the output of said compensating coil being rectiiied to provide compensation ux only when said current variation in said bucking bar is in a predetermined direction.

11. In a magnetic structure for sealing an armature; said magnetic structure comprising an armature flux path, a polarizing flux path and a high reluctance path; polarizing means Wound on said polarizing path for inducing unidirectional flux in said armature path and bucking bar means for inducing ux in said armature path in the same direction as that due to said polarizing means when current in said bucking bar is in the same direction; said high reluctance path being positioned with respect to said polarizing means and said bucking bar means to carry their said uxes in opposing direction; a rst and second compensating coil Wound on said high reluctance ux path; said rst and second compensating coil being energized responsive to variations in the current of said bucking bar; said rst compensation coil causing induced compensating ftux in said armature path only when said bucking bar current increases, said second compensation coil causing induced compensating ux in said armature path only when said bucking bar current decreases from an excessively high value.

References Cited in the le ot this patent UNITED STATES PATENTS 1,787,931 Besold Jan. 6, 1931 1,920,745 Grunholz Aug. 1, 1933 2,672,584 Rolf Mar. 16, 1954

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