US2327576A - Balanced interrupter circuit - Google Patents

Description

Aug. 24, 1943 H. J. BROWN BAL-NCED INTERRUPTER CIRCUIT Filed Jian. 3l, 1942 /MFEDHNCE @Marr-Quien@ mamme-f INVENTOR. BY HMM @M Patented Aug. 24, 1943 t UNITED STATES PATENT OFFICE BALANCED INTERRUPTER CIRCUIT Harold J. Brown, Indianapolis, Ind.

Application January 31, 1942, Serial No. 429,077' 14 claims. (ci. 175-365) My invention relates in general to interrupter circuits and more particularly to an arrangement to prevent the damaging of the interrupting means. This application relates to the subject matter of my Patent No. 2,286,842 and my pending applications Serial Nos. 429,074, 429,075 and 429,076.

In the design of vibratcry converters, substantially no difliculty is encountered in building a vibrator that is immuned to mechanical wear on the contact points. The impacts on closing and the Wear due to rubbing can be so reduced that the device will operate indefinitely, if at the same time', the stressed parts are properly strainrelieved and loperated well below their endurance limit. With such a vibrator, the problem is primarily oneof reducing the effects of the electric current and voltages on the contacts so that any required perfomance may be achieved. Experience shows that in a, vibrator where the make-and-break operating cycles run into the' billions, the life and performance is strictly determined by the ability of the contact points to withstand the pitting and erosion of the electrical current flowing at the instance` of the make-and-break. Nothwithstanding the fact' that the most resistant materials available to the engineering art are used, the vibrator in many applications fails to meet the standards of reliability and life ,which are normaily required. Also, there is need for increased power output capabilities for vibratory converters, By using larger transformers and larger vibrators, increased power has been obtained, but in general,

a less satisfactory result is noted especially as regards Vibrator life and reliability on the contact interrupting points. Vibrators with several sets of points in parallel have also been used in an effort vto increase the power handling capacities, but here too the life and reliability ci' the contacts do not come up to expectations. The principal reason for the lack of satisfactory results lies in the character of the contacting materials when interrupting the current. Generally speaking, the current in a contact necks down to an extremely high current density prior to separation, even though large shunting capacities be used. For reasonable values ci current relative to the material4 used, the contact is subject to melting and vaporization at the final tip, and if two or more contacts are in parallel, the flnal single trailingcontact is subject to the attack of this high current density. Similar destructive effects take place when the contact engagement is made, as the condensers necessary to operate the equipment are then charged or discharged. One of the more noticeable eiects is material transfer from one contact tothe other, another is pitting and erosion, and in severe cases,y there is ar'cing which is very destructive.

Contact point disintegration due to electrical current falls in two categories; namely, the disintegration resulting from making the contact and the disintegration resulting from breaking the contact. Both may be partially controlled by the proper handling of "the circuit constants but it is unfortunately true that changes in the circuit which improve the performance at the break may harm the performance at the make, and vice versa. Therefore, the design of a good and efiicient converter circuit which will give long life and reliability against breakdowns presents a difiicult problem to solve and a satisfactory circuit cannot be prescribed on the basis of a superficial examination. Furthermore, the absence of sparking is no criterion ofI a satisfactory circuit, as it is often: true that the performance of mildly sparking contacts will be superior to dark ones. A further characteristic of contact points is that Various thresholds of current exist below which material transfer and erosion do not occur at all or in small amounts.

An object of my invention is, therefore, the provision of reducing the electrical disintegration effect below the threshold value where material transfer and erosion do not occur at all or in small amounts.

Another object of my invention is to prevent the current flowing through one contact from diverting into another, as one contact is opened prior to another.

Another object of my invention is to forcibly prevent the current flowing in two or more vibrator contacts from re-establishing itself in a single final trailing contact tip during the short interval of time involved between the successive openings of the parallel contacts and to insure that the burden of interrupting the circuit is divided between the pair of parallel contacts.

Another object'of my invention is the provision, in a circuit interrupter having a plurality of parallel interrupting paths, of preventing the current which is interrupted in an interrupted path incident to slight variations in the interruptions of the plurality of interrupting paths from. suddenly re-establishing itself in a yet uninterrupted path during the short interval ofv parallel contacts will not eiect the total currentV low, andthe total current will then flow through the remaining closed trailing contact. The time required for this diversion will be Very small, perhaps less than 6 seconds, as indi# cated by the residual inductance and resistance of the closed loops through theA two parallel contacts. Irrapy'v practical vibratorfthe dinerences in opening time may be a thousand times this value so the problem may be stated as one of increasing the diversion time perhaps a thousand or more times its ordinary value.

Therefore, another object of my invention is to provide for increasing the diversion time perhaps a thousand or more times its ordinary value.

Another object of my invention is the provision of a balancing inductance taken in combination with a current-diverting impedance for preventing the current flowing in two or more vibratory contacts from re-establishing itself-r in a single final trailing contact tip during the short interval ottime involved between the successive openings of the parallel contacts and to insure that the vburden of interrupting the current is divided between the pair of parallel contacts.

Another object of my` invention is tokprevent the current owing through one Contact frornV diverting into another asone contact is open prior to the other without the liability of inductance in the vibratory load circuit.

Other objects and afuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction wth the accompanying drawing, in

Figure 1 diagrammatically illustrates a vibratory interrupting circuit involving the features of my invention;

Figure 2 is a diagrammatic illustration show- I ing an extension of the circuit in Figure 1 in that the current flows through four sets of parallel contacts for the vibratory converter instead cuits 32 and 33.

parallel through a first circuit connection means comprising a conductor 3i and two branch cir- The right-hand end of the conductor 3i is connected to the end I: of the primary windingv I2 of the transformer and the left-hand end of the conductor 3l is connected to a center-tap @Il on the balancing inductance 39 which divides the winding thereof into two drop that may exist. l

During `the interruption of the parallel con-V4 of two sets of parallel contacts in Figure 1; and

Figures l3, 4, 5 and 6 illustrate, respectively, the different kinds of current-diverting impedances which may be employed in my circuitinterrupting system. l

invention comprises in generala vibratoryvinterrupter, I0, a transformer iI, a secondarybuffer With reference to Figure 1 of thedrawing; my.

condenser 29, two balancing inductances 3Q and the vibratory interrupter comprises two parallel l sets of interrupting contacts in which one set comprises the, oppcsitely disposed contacts .I9 and 2,0 with the vibrating reed I I operating therebetween and in which the other set comprises the -Veppositely, disposed contacts 2| and 22 .withl the vibrating reed I1 operating therebetween. The

vibrating reed I1 is actuated by an electro-mag net 21 which is' energized through an additional contact 2 3 engaging the vibrating reed I1. vThe oppositely disposed contacts I9 andZI onfo'ne `side of the vibrating reedl IIA are V connected in halves i I and l2 which are respectively connected in series with the two branch circuits 32 and 33. The. current-diverting impedance 3l is connected across the two branchcircuits 32 and 33 in parallel with the winding of the balancing inductance 39.

The oppositely disposed contacts 2G and 22 on the other side of the vibrating reed Ii are connected in parallel through a second circuit connection means comprising a conductor 3Q and two branch circuits 35 and 36. The right-hand end of )the conductor 3l?, is connected to the end I5 of the primary winding l2 of the transformer and the left-hand end Vof the conductor 3ft is connected to a center tap t9 of the winding for the balancing inductance 4E and divides-the winding into two halves @l and i8 which are respectively connected in series with the two branch circuits 35 and 36. The capacitor 29 isconnected in the secondary loadcircuit of the transformer and constitutes the buier condenser for the system.

In operation, the'load current divides substantially equally between the two sets of parallel contacts when the contacts are closed. 'Ihe flowing of the current through the two halves of the windings of the balancing inductances cancel out the inductive impedances of the said winding with respect to the vibratory load circuit. Consequently, I am able to achieve parallel operation of two sets of contacts without liability of -feet upon the load circuit will be that of any IR 3S and the current-diverting impedance 37 operates to prevent the current which is interrupted by the contactIS f rom suddenly 1re-establishing itself in the yet uninterruptedr parallel contact 2l during the short interval involved between the successive openings of the parallel sets of contacts. 'I'he description with reference to the operation of the joint action of the balancing winding and the current-diverting impedance during the short interval of time involved between the successive openings of the parallel sets of contacts I9 and 2l may be described with reference to the following assumption: let it be assumedl that the system possesses a resistance of one ohm between the secondary capacitor 29 and the E. M. F. of the directcurrent source 25 and 26, and further that 10 amperes is flowing through the vibratory primary circuit, making 5 amperes through each ofthe setsof parallel contacts.v

With one ohm appearing in the system, then the resistance of the current-diverting impedanceis preferably made 4 ohms, since it is *Vconnected .across both halves of the balancingwindings 4I and 12.v In other words, the impedance ratio of a transformeris equalto the square of the turns and in the instant case the secondary turns-of the balancing inducta'nce 39,rwhich 'comprises-both halves of the windingstl andra .is twice the A number ofturns lupon the winding 4I, which 7.5-

comprises the primary windingof the balancing assigne inductance, acting as a transformer during the short interval of time during the successive openings of the contacts I9 and 2|. With the resistlance of the current-diverting impedance 4 ohms "and with the resistance of the system one ohm,

then the burden upon the interruption of the contacts I9 and 2| is equally divided.

The reverse situation wouldoccur should the contact 2| open slightly prior to the contact I9. Similarly, the description with reference to the contacts I9 and 2| applies the same for the contacts 2n and 22 wherein the balancing inductance 40 and the current-diverting impedance 38 act to keep the current which is interrupted in an interrupted contact from re-establishing itself in a yet uninterrupted contact. 'I'he impedance ofl the current-diverting impedance may be of any value other than the ideal value explained in the above mentioned calculation but it must be remembered that as the impedance of the current-diverting impedance increases beyond its ideal value then the first contact which opens takes a larger share of the'burden upon the interruption of the contacts and should the value of the current-diverting impedance be decreased below the ideal value then the second contact to open takes the increased burden during the interruption of the contacts. In other words, as the impedance of the current-diverting impedance approaches innity,ithen the first contact to open takes all the burden and as the impedance of the current-diverting impedance approaches zero then the second contact to open takes all of the burden. By makingthe impedance of the current-diverting impedance four times the impedance of the vibratory load circuit, an ideal situation exists to keep the current flowing through the contact which is last to open the same throughout the period involved between the successive openings of the contacts. Therefore, in Figure 1 I have illustrated a system which achieves parallel operation of the contacts without the liability of inductance in the load circuit while at the same time I prevent the currentwhich is interrupted in one of the contacts from being re-established in the other contact during the short interval of time between the successive openings of the contacts.

The current-diverting impedances 31 and "38l the vibratory circuit, if an inductance as shown in Figure 4 is employed, the inductance is prefer.- ably made substantially four times the inductance of the inductance. oi the vibratory circuit. If the circuit contains both resistance and inductance in series, then the current-diverting impedances may be made preferably as shown in Figure 5 and here again the resistance is preferably made four times the resistance of the vibratory circuit and the inductance is preferably made four times the inductance of the circuit. If the vibratory circuit containsresista'nce and inductance in parallel, then the arrangement shown in Figure 6 may be preferably employed in which the resistance is made four times the resistance of the circuit and the inductance Ais preferably made substantially four times the inductance of the vibratory circuit.

In Figure 2 I show an extension of the circuit f arrangement'as shown in Figure 1 in that I control the proper division of the current between four sets of parallel contacts 58, 59, 80 and 6| by employing four balancing inductances 5l, 55, 5i and 51 together` with current diverting impedances 52, 63, 64 and 65. The operation of the balancing inductances and the current diverting impedances for the four sets of parallel contacts 58, 59, 60 and 6| is the same as that described with reference to Figure 1. The four balancing inductances 54, 55, 56 and 51 are connected to the primary winding 1| of the transformer 10 through a balancing inductance having two windings 68 and 69. As illustrated, the two ends of the winding 68 for the balancing inductance 61 are connected respectively to the center tap for the windings 54 and 55. Similarly, the two ends for the winding 69 upon the balancing inductance 51 are connected respectively to the center tap for the two windings 56 and 5l.

. The two center taps for the windings 68 and 69 are connected to the two ends of the primary winding 1| of the transformer 10. tap for the primary winding 1| is connectedV to oneV side M of the direct current source and the other side 15 of the direct current source is connected to the Vibrating reed of the vibratory interrupter 16. -The secondary winding 'l2 of the transformer 10 supplies alternating current to the load and the capacitor 13 connected across the secondary winding of the transformer constitutes the buffer. condenser for the vibrating system. The operation of the arrangement in FigureZ is substantially the same as that explained in Figure 1 except that it comprisesan extension thereof and here again I am able to achieve parallel operation of a plurality of sets of parallel contacts without adding impedance in the vibratory load circuit.

summarizing, my invention includes the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking l' of the plurality of sets of contacts from suddenly re-establishing itself in the yet uninterrupted parallel contact path during the short interval of time involved between the successive openings of the contact means to prevent the damaging ofV the contacts.

While I have illustrated and described my invention as having particular utility in connection with interrupting parallel contacts, it is to be understood that my invention is not limited thereto and, therefore, includes any interrupting system comprising interrupting means having a plurality of parallel interrupting paths which are substantially simultaneously interrupted for jointly interruptingthe current in the electrical system.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1.'In an electrical system for converting current from a direct current source into alternat- The center alternati-ng current to the load, andJ a vibratory interrupter having two interrupting sets of parallel contact means substantiallysimultaneously operated during a vibratory interval for jointly supplying an interrupted direct current through Ia, plurality of parallel contact paths to the primary winding means of the transformer, each of the two sets of parallel contact means including oppositely disposed contact means and vibratory connecting respectively an oppositely disposed Contact means on the other side of the vibratory Contact means to the other end of the primary winding means; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contact means from suddenly re-establishing itself in a yet uninterrupted parallel Contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of first current-diverting means connected across the oppositely disposed contact means on one side of the vibratory contact means, second current-diverting means connected across the 0ppositely disposed contact means on the other side of the vibratory Contact means, and balancing inductancc means having a rst balancing winding with two ends and a center-tap dividing the said irst balancing winding into two halves with a half thereof included in each of the branches of the first circuit connection means and having a second balancing winding with two ends and a center-tap dividing the said second balancing winding into two halves with a half thereof included in each of the branches of the second circuit connection means for developing, in series with each of the sets of parallel contact means, an inductive impedance to the flow of the current therein, the'inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of an interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the -yet uninterrupted parallel path, thereby preventing the damaging ofthe contacts, the said center-tap of the first balancing winding being connected to one end of the primary Winding means of the transformer and the two ends of the rst balancing winding being connected respectively to thetwo branches of the first connection means, thus forming a T-connection to balance out the inductive impedance of the said first balancing winding with respect toy the current flowing through the primary winding means of the transformer, the said center-tap of the second balancingpwinding being connected to the other end of the primary winding means of the transformer and thetwo ends of thejsecond balancing winding being connected respectively to the two branches of the second connection means, thus forming a T-connection to balance out-the inductive impedance of the said second balancing winding with respect to the current owing ythrough the primary winding means of the transformer.

2. In an electrical system for convertingcur rent from a direct current source into'alternating current and supplying the latter to'a load, said system comprising a transformer having primary winding means with two ends and a center tap and secondary winding means supplying the alternating current to the load, and a vibratory interrupter having two interrupting sets of parallel contact means substantially simultaneously operated during a vibratory interval for jointly supplying an interrupted direct current through a plurality o1" parallel contact paths to the primary winding means of the transformer, each of the two sets of parallel-contact means including oppositely disposed contact means and vibratory contact means operating therebetween, said center tap being connected to one side of thedirect current source and said vibratory contact means being connected to the other side of the direct current source, first circuit connection means includingtwo branches each connecting respectively an oppositely disposed contact means on one side of the vibratory contact means to one end of the primary winding means and'second circuit connection means including two branches each connecting respectively an oppositely disposed contact means on the other side of the vibratory contact means tc the other end of the primary winding means; the arrangement for preventing the current which issinterrupted in an' `interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contact means from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden onthe set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of first resistance means connected across the oppositely disposed contact means on one side of the vibratory contact means, second resistance means connected across the oppositely disposed contact means on the other side of the vibratory contact means, and balancing inductance means having a rst balancing winding with two ends and a center-tap dividing the said iir'st balancing winding into Ytwo halves with a half thereof included in each of the branches of the nrst circuit connection means and having a second balancing winding with two ends and a center-tap dividing the said second balancing winding into two halves with a half thereof included in each of the branches of the `second circuit connection means for developing,

current therein, the vinductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of an interrupted parallel contact path during the short f interval involved between the successive openings of the parallel sets of contacts in the'yet uninv terrupted parallel path, thereby preventingthe ing winding being connected respectively tp the two branches of the first connection means, thus forming a T-connection to balance out the inductive impedance of the said rst balancing winding the current flowing through the primary winding means of the transformer. s

.3. In an electrical system for converting current from a direct currentsource into alternating current and supplying the latter to a load, said system -comprising a transformer having primary winding means with two ends and a center tap andsecondary winding means supplying the alternating current to the load, and a vibratory interrupter havingtwo interrupting sets of paralrespect to the current flowing through the pri-- mary winding means of the transformer, the said center-tap of the second balancing winding being connected to the other end of the primary winding lel contact means substantially simultaneously operated during a vibratory interval for jointlyv supplying an interrupted direct current through a plurality of parallel contact paths to the primary winding means of the transformer, each of the two sets of parallel contact means including oppositely disposed contact means and vibratory contact means operating therebetween, said center tap being connected to one side of the direct current source and said vibratory contact means being connected to the other side of the direct current source, first circuit connection means including two branches each connecting respectively an oppositely disposed contact means on one side ofthe vibratory contact means to one end of the primary winding means and second circuit connection means including two branches each connecting respectively an oppositely disposed contact means on the other side ofthe vibratory contact means to the other end of the primary winding means; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contact means from suddenly refestab- A lishing itself in a yet uninterrupted parallel con-y tact path and increasing the burden on the set'of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts ,said arrangement comprising the combination of rst current-diverting inductance means connected across the oppositely disposed contact means on one side ofthe vibratory contact means, second current-diverting inductance means connected across the `oppositely disposed contact means on the other side of the vibratory contact means, and balancing'inductance means having a rst balancing winding with two ends and a center-tap dividing the said rst balancing winding into two halves with a half thereof included in each of the branches of the first circuit connection means and having a second balancing winding with two ends and a centertap dividing 'the said second balancing winding into two halves with a half thereof included in each of the branches of the second circuit connection means for developing, in series with' each of the setscf parallel contact means, an inductive impedance to the flow of the current therein, the indiictive impedance in the yet uninterrupted parallel contact path opposing the sudden reestablishment of the current of an interrupted parallel contact path during the short interval involved between the successive openings of the means of the transformer and the two branches of the second connection means, thus forming a T- connection balance out the inductive impedance of the said second balancing winding with respect to the current flowing through the primary winding means of the transformer.

4. An electrical system for converting current from a direct current source into alternating cur-` rent; and supplying the latter to a load, said system comprising a vibratory circuit including a transformer and a vibratory interrupter having two sets of parallel contact means with each set comprising oppositely disposed contact means and a vibratory contact means operating therebetween, first current-diverting means connected across the oppositely disposed contact means on one side of the vibratory contact means, second current-diverting means connected across the oppositely disposed contact means on the other side of the vibratory contact means, and balancing inductance means having a first balancing winding with a center-tap connected to the transformer and dividing the said first winding into two halves with a half thereof connected respectively in series with the oppositely disposed contact means on one side of the vibratory contact means and having a second balancing wind- -ing with a center-tap connectedy to the transformer and dividing the said second winding into two halves with a half thereof connected respectively, in series with the oppositely disposed contact means on the other side of the vibratory contact means.

5. An electrical system for converting current from a. direct current source into alternating current and supplying the latter to a load, said-system comprising a vibratory circuit including a transformer and a vibratory interrupter having four sets of parallel contact means with each set comprising oppositely disposed contact means and a vibratory contact means operating therebetween, flrst current-divertingmeans connected across the oppositely disposed contact means on one side of the vibratory contact means, second current-diverting means connected across the oppositely disposed contact means on the other side of the vibratory contact means, a first balancing inductancemeans having a first balancing winding with a center-tap dividing the said rst winding into two halves with a half thereof connected respectively in series with oppositely disposed contact means on one side of the vibratory convtact means and having a second balancing winding with a center-tap dividing the said second winding into two halves with a' half thereof connected respectively in series with two disposed opposite contact means on the other side of the vibratory contact means, a second balancing-inductance means having a third balancing winding with a center-tap ldividing the said third winding into two halves with a half thereof connected respectively in series with the two remaining oppositely disposed contact means on said one side of the vibratorJ contact means and having a fourth balancing winding with a center-tap dividing the said fourth winding into two halves with a half thereof connected respectively in f respectively in series with the center-taps of the second'and fourth balancing windings.

6.' In a vibratory circuit having two parallel sets of interrupting contacts. with each'set including oppositely disposed contact means with "a vibratory contact means operating therebetween, first current-diverting means connected across the oppositely disposed contact means on one side of the vibratory contact means, second currentdiverting means connected across the oppositely disposed contact means on the other side of the vibratory contact means, rst balancing inductance means having a rst balancing winding with a center-tap included in the load circuit and dividing the said iirst winding into two halves with a half thereof included respectively in series with the two oppositely disposed contacts on one side of the vibratory con'tact means, and a second balancing inductance means having a second bali ancing winding with a center-tap included in the load circuit and dividing the said second winding into two halves with .a half thereofincluded respectively inseries with the two oppositely disposed contacts.

3. in a vibratory circuit having two parallel sets I" interrupting contacts? with each set including oppositely disposed contact means with a vibratory contact means operating therebetween, rst current-diverting means connected across the oppositely disposed contact means on 'one side, of the vibratory contact means, second currentdiverting means connected across the oppositely disposed contact means on the other side of the vibratory contact means, iirst balancing inductance means having a first balancing winding with diverting relation with the interrupting paths or the said plurality of interrupting groups, and balancing inductance means having a plurality of groups of inductance windings, each group of inductance windings being respectively connected With the interrupting groups of the parallel paths y with an inductance' winding in series withl each of the interrupting parallel paths for developing inv series with each of the interrupting parallel pedance to the iiow of the current in the system.

9. In an interrupter system having interrupting means for interrupting a plurality oi groups ,of .parallel interrupting paths, the interrupting paths of each interrupting group comprisingitwo parallel paths and Vbeing substantially simultaneously interruptedbythe interrupting means ior jointly interrupting the current in the system;y

the arrangement for preventing the current which is interrupted in an interrupted parallel Ypath of a group incident to slight variations in the interruption of the parallel paths of the groupfrom suddenly re-establishing itself in a yet uninterrupted parallel path andincreasing the burderi'on the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths of a group, said arrangement comprising current-diverting means connected across the two intera center-tap included in the load circuit and t dividing the said iirst winding into two halves with a half thereof included respectively in series with the two oppositely disposed contacts on one side of the vibratory contact means, and a second balancing inductance means having a second balancing winding with a center-tapincluded in the load circuit and dividingfthe said second winding into two halves with a. half thereof included respectively in series with the two oppositely disposed contacts, leach of said current-diverting 'impedances having a value substantially four times the value of theV impedance ofthe v ibratory load circuit.

8. In an interrupting system having interrupting means for interrupting a plurality of groups of parallel interrupting paths, the par- 'allel paths of each interrupting groups comprising a plurality of paths and being substantially y interrupted by the interruptingmeans 'for jointly interrupting the current in the system, current diverting means connected-in eiective currentrupting parallel paths of eachgroup, and balancing inductance means having a plurality of groups' of inductance windings with each group of inductance windings being respectively ccnnected to the interrupting groups` of parallel paths, each group of inductance windings having a center-tap connection dividing the inductancev winding into two halves with a half thereof connected in series with each of the interrupting parallel paths for developing",VJ in series with each of the interrupting parallel paths, an inductance impedance to the ilow of the current therein7 the inductance impedance in the yet uninterrupted parallel path in combination with the currentdiverting means opposing the sudden reestablishment of the current of aninterrupted parallel path of a group during the short interval involved between'the successive interruptions of the parallel paths of the group in the yet uninterrupted path, thereby preventing the damaging of the interrupting means.

l0. In an interrupter system having interrupting means for interrupting a plurality of groups of parallel interrupting paths, the parallel paths of each interrupting group comprising a pluralityof paths and being substantially simultaneously` interrupted by the interrupting means for jointly interrupting the current in the system; the arrangement for preventing the current which is interrupted in an interrupted parallel path of a group incident to slight variations in the interruption of the parallel paths of the group from suddenly reestablishing itself in a yet uninterrupted parallel path and increasing the `burden on the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths of a group, said arrangement comprising current-diverting means connected across the interrupting parallel paths of each group, and balancing inductance means having a plurality of vgroups of inductance windings, each group of inductance windings being respectively connected with the interrupting groups of parallel paths with an inductance winding in series with each of the interrupting parallel paths for developing, in series with each of the interrupting parallel paths, an inductive impedance to the iiow of the current therein, the

inductive impedance in the yet uninterrupted f parallel path in combination with the currentdiverting means opposing the sudden re-establishment of the current of an interrupted parallel path of a group during the short interval involved between the successive interruptions of the parallel paths of the group in the yet uninterrupted path,-thereby preventing the damaging of the interrupting means, each group of inductance windings having tap connection means to establish opposing fluxes within each group of inductance windings to minimize the inductive impedance to the iiow of the current in the system.

1l. In an interrupter system having a common circuit and interrupting means forinterruptingly connecting a plurality of groups of parallel interrupting paths to the common circuit, the parallel paths of each interrupting group comprising a plurality of paths and being substantially simultaneously interrupted by the interrupting means 'A for jointly interrupting the current in the system; the arrangement for preventing the current which is interrupted in an interrupted parallel path of a group incident to slight variations in the interruption of the parallel paths of the group from suddenly 1re-establishing itself, in a yet uninterrupted parallel path and increasing the burden on the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths of a group, said arrangement comprising currentdiverting means connected across the interrupting parallel'paths of each group, and balancing inductance means having a plurality of groups of inductance windings, each group of inductance windings being respectively connected with the interrupting groups of parallel paths with an inductance winding in series with each of the interrupting parallel paths for developing, in series with each of the interrupting parallel paths, an inductive impedance to the flow of the current therein, the inductive impedance in the yet uninterrupted parallel path in combination with the current-diverting means opposing the sudden reestablishment of the currentv of an interrupted parallel path of a group during the short interval involved between the successive interruptions of h the parallel paths of the group in the yet uninterrupted path, thereby preventing the damaging of the interrupting means, each group of 1inductance windings having tap connection means to establish opposing fluxes within each group of inductance windings to minimize the inductive impedance to the ilow of the current' in the system.

12. In an interrupter system having rst and second electrical circuit connections and interrupting means for interrupting two groups of parallel interrupting paths, the interrupting paths of each interruptinggroup comprising two' parallel paths, each being substantially simultaneously interrupted by the interrupting means `for interrupting the current in the system, nrst current-diverting means connected across the two interrupting parallel paths of the first group, secondlb'urrent-diverting means connected across the two interrupting parallel paths 'of the second group, and balancing inductance means having a first balancing winding with a center tap connected to said rst electrical circuit connection and dividing the said first winding into two i halves with a half thereof connected respectively in series with each of the two interrupting paths of said first group and having a second balancing winding with a center tapconnected to said second electrical circuit connection and dividing the said second winding into two halves with a half thereof connected respectively in series with each of two interrupting paths of said second group.

13. In an interrupter system comprising a transformer having a rst and second circuit connection, and interrupting means for interrupting four groups of parallel interrupting paths, the interrupting paths of each interrupting group comprising two parallel paths and being substantially simultaneously interrupted by the interrupting means for interrupting the current, current-diverting means connected across the two interrupting parallel paths of each group, a first balancing inductance means having a first balancing winding with a center-tap dividing the first winding into two halves with a half thereof connected respectively in series with the two parallel paths of the first group and having a second balancing winding with a center-tap dividing the said second winding into two halves with a half thereof connected in series with the two parallel paths of the'second group, a second balancing inductance means having a third balancing winding with a ycenter-tap dividing the said third winding into two halves with a half thereof connected respectively in series with the two parallel paths of the third group and having a fourth balancing winding with a center-tap dividing the fourth winding into two halves with a half thereof connected respectively in series with the two parallel paths of the fourth group, and a third balancing inductance means having a fifth balancing winding with a center-tap connected to said first circuit connection on the transformer and dividing the said fifth winding into two halves with a half thereof connected respectively in series with the center-taps of the rst and third balancing windings and having a sixth balancing winding with a center-tap connected to the said second circuit connection on the transformer and dividing the said sixth winding into two halves with a half thereof connected respectively with the center-taps of the second and fourth balancing windings.

14. In an interrupter system having interrupting means for interrupting aplurality of groups of parallel interrupting paths, the interrupting paths-of each interrupting group comprising two parallel paths-and being substantially simultaneously interrupted by the interrupting means for jointly interrupting the current* in the system, current-diverting means connected in effective current-diverting relation with the interrupting paths of the said plurality of interrupting groups, and balancing inductance means each having a plurality of groups of inductance windings, each group of inductance windings being respectively connected with the interrupting groups of parallel paths and having a center tap connection dividing the said inductance winding intoltwo halves with a half thereof connected in series with each of the interrupting parallel paths f or developing, in series uwith each of the. said interrupting parallel paths 4an inductive impedance to the now of the current therein.

HAROLD J. BROWN.

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