US1832201A - Circuit interrupter - Google Patents

Description

Nov. 17, 1931. 'r. T. GREENWOOD 1,832,201

CIRCUIT INTERRUP-TER Filed June 29, 1929 filverftor'.

Patented Nov. 17, 1931 UNITED STATES PATENT? OFFICE TALMA T. GREENWOOD, OF EAST TEMPLETON, MASSACHUSETTS, .ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS CIRCUIT INTERBUPT'ER Application filed June 29, 1929. Serial No. 374,838.

This invention relates to alternating current electric switches and circuit interrupters andparticularly to a method and means for interrupting the alternating current circuitinterrupting are that is drawn between the separable contact members of the switch. The alternating current are goes out periodically at the end of each half cycle, when the current passes through zero, and usually is re-established at the beginning of the succeeding half cycle when the potential across the arc terminals becomes sufliciently great to overcome the resistance of the arc zone.

One of the objects of the present invention is a method and a paratus for removing the conductin ions rom the arc zone during the time t at the arc is out while the current is passing through the zero point of the wave and for delaying for a determined time the re-establishment of voltage across the arc terminals or for increasing the period of time that the potential acrossthe arc terminals is substantially zero, or is insuflicient to pass an arc currentthrough the arc zone, so that the ion-removin means can have an increased eriod 0 time during which to act, thus to e more effective in building up the dielectric strength of the arc zone and thereby 1preventing the re-establishment of the are.

11 carrying out this object of the invention, it is a specific object to impress a potential on the circuit to be interrupted, which impressed potential preferably is less than the maximum potential of the circuit and has a greater frequency as, for instance, triple the frequency, so that it modifies the potential of the circuit to be interrupted and reduces said potential a determined time on 0th sides of the normal zero point of the potential wave. The method thus increases the time at which the arc terminals are substantially free from potential and thus gives the ion-removing device an increased period of time during which to act with greatest effectiveness.

A further object is generally to improve upon circuit interrupting apparatus and methods.

Fi 1 is a diagram illustrating the separab e contact members of an electric switch practically to zero for terrupt the circuit. Upon separation of the contact members, an arc is drawn between them, which are of necessity goes out and, in the ordinary switch, is re-established at successive half cycles of the current. Means are provided herein to remove the conducting ions from the arc zone between the separated contact members whereby to increase the dielectric strength of the medium in the are zone to such a point that the dielectric strength is greater than the potential that is impressed on the arcing members, whereby the arc cannot be re-established.

Said means is most effective at the time that the arc is momentarily extinguished when the arc current passes throughthe zero point of the wave. Said means, as here shown, includes an electrostatic field producing means as a ring 16 which ring surrounds the-arc and the field of the ring is effective throughout the arc zone and the space occupied by the arcing surfaces of the contact members. Said rin is energized by a suitable source, herein iagrammatically illustrated as the battery 18, which source means to act upon the arc zone before t e re-establishment of the arc is relatively small. In accordance with this invention, means are provided to dela the buildin up of potential at the normal zero point 0 t e potential wave whereby to increase the time that the ion-removing means is free'to act unimpeded on the arc zone. Said means includes an alternating current generator 20 which energizes the primary winding 22 of a transformer, the secondary winding of which is connected and, as here shown, is in series with the power circuit 14. The generator 20 thus impresses upon the power circuit an alternating potential which is a function of the potentlal and frequency of the generator. Preferably, the frequency of the generator 20 is higher than the frequency of the potential in the power circuit 14, preferably by some multiple such that both potentials pass through their zero points at the same time. The generator 20 may, for instance, set up a potential in the power circuit 14 that is tri le the frequency of the normal potential 0 said power circuit. The impressed otential acts upon the circuit potential to atten the wave at the zero point as is indicated in Fig. 2. In this figure, 26 represents the potential wave of the power circuit 14 while 28 represents the high frequency impressed potential. The resultant of the two potential waves gives the potential wave 30 which is the one impressed across the arc terminals.

It will be noted that this resultant wave is substantially zero for a number of degrees on both sides of the zero point of the normal potential wave 26 as indicated at 32. If both the potential waves 26 and 28 are sine waves, the resultant potential wave 30 may not be reduced comp etely to zero in the region of the normal zero point but at least the resultant potential will be so low that it is insuflic'ient to re-establish and support a persistent arc.

The resultant potential in the region of the zero point may be reduced more completely to zero if the potential waves 26. and 28 are made complements of each other at this point as by. having the potential wave 28, in an obvious manner, follow a suitable curve that is something other than a sine curve. Thus, by accelerating the decay of the tential wave on one side and delayin the uilding u of potential on the other side of the norma potential zero, a greatly increased time period is provided during which the are potential is zero and the ionremoving means 16 is free to act unimpedi-' ently upon the arc zone, thus to enhance its efiectiveness.

The method and apparatus herein disclosed for removing ions from the zone of the arc is described and claimed in my copending application Serial No. 152,048, filed December 1,1926.

Iolaim:

1. An alternating current circuit interrupter having separable cortact members between which acircuit interrupting arc is established upon separation of said contact members, means to remove ions from the arc zone between said separated contact members, and means to delay the re-establishment of the arc potential between said separated contact members during the reversal of arc polarity including means to modify the character of the wave of the are potential and to maintain it substantially at zero for a definite period of time on both sides of the normal zero point of its wave.

2. An alternating current circuit interrupter having separable contact members between which a circuit interrupting arc is established upon separation of said contact members, means to remove ions from the arc zone between said separated contact members, and means to maintain the arc potential substantially at zero for a definite period of time on both sides of the normal zero point of its wave.

3. An alternating current circuit interrupter having separable contact member's between which a circuit interrupting arc is established upon separation of said contact members, means to remove ions from the arc zone. between said separated contact members, and means to supply the arc with current at an alternating potential which has substantially zero value for definite periods of time.

4. An alternating current circuit interrupter having separable contact members between which a circuit interrupting arc is established upon separation of said contact members, means acting when the arc current is zero to remove ions from the arc zone between said separated contact members, and means to delay the re-establishment of the are potential between said separated contact members during the reversal of arc polarity including means to impress an alternating potential upon the are potential, said alternating potential having a value and being at a frequency which differs from that of the frequency of the are potential by such values as to maintain the are potential substantially atzero for definite periods of g time.

5. An alternating current circuit interrupting apparatus having separated arc terminals between which an alternating current are is supported,.means acting when the arc current is zero to remove conducting ions from the arc zone between said terminals, and means to supply said terminals with an alternatin potential which is maintained substantially at zero for definite periods of time.

6. An alternating current circuit interrupting apparatus having separated arc terminals between which an alternating current arc is su ported, means to remove conducting ions rom the arc zone between said terminals, and means to supply said terminals withan alternatin potential which is at a value that is insu cient to pass an arc current between said terminals for predetermined periods of time.

7. The method of interrupting an alternating current electric arc which consists in supplying the arc with an alternating potential which is substantially at zero for predetermined periods of time, and removing ions from the arc zone during such periods.

8. The method of extinguishing an alternating current are which consists in supplying the arc with a potential that for definite periods of time has a value lower than that necessary to initiate the arc, and removing ions from the arc zone during such periods.

9. The method of interrupting an alternating current electric are which consists in supplying the arc with an alternating potential, modifying said potential by an impressed alternating potential of different frequency such as to provide a resultant are potential that is substantially at zero for predetermined periods of time, and removing ions from the arc zone during such periods.

In testimony whereof, I have signed my name to this specification.

TALMA T. GREENWOOD.

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