US1425640A - Motor-control system - Google Patents

Description

I A. A'. GAZDA. MOTOR CONTROL SYSTEM. APFLICATION FILED MN. 29,1917.

1,425,640, Patented Aug. 15, 1922.

a L z I E r fil l l l l T g WITNESSES: INVENTOR V i V Adolph AGazda.

' V i ATTORNEY uuirau stares rsrsur orricu.

ADOLPH A. GAZDA. 01* WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 W'ESTING- HOUSE ELECTRIG AND ELANUFACTURING-LQHCPANY, A CQBPORihTION OF IEENN- SYLVANIA.

MOTOR-CONTROL sYsTnM.

To all whom it may concern: Be it known that I, Aoonrrr A. GAZDA, a

citizen of the United States, and a resident that shall be simple and inexpensive in con struction and efficient in operation to effect the acceleration of an induction motor in a smooth and uniform manner and with a minimum degree of unbalancing of the currents traversing the several phase-windings.

Numerous methods have been proposed heretofore for effecting the acceleration of induction motorshavin r phase-wound secondary members and external resistors connected in circuit with the several phasewindings. One of such methods consists in successively shunting like portions of each of the several resistors and repeating this operation. until the resistors are entirely shunted. This method requires a relatively lar 'e number of switches, since a separate switch is required for each resistor section; It has been found, in practice, also, that excessive currents traverse the secondary windmg and sudden increases in torque occur at sult from the fact that the shunted portions. of the two resistors are in parallel relation.

to each other whereas, the corresponding section of the third resistor is in series with its respective phase-winding. The resistv ance of one phase is thus materially higher than that-of the other two phases.

I provide an arrangement in which. the phase-w ndings of an induction motor and Specification of Letters Patent. iPg-tgntgd Aug; 15, 1922 Application filed January 29, 1917.

Serial No. 145,268.

the resistors in circuit therewith are arranged in starconnection. A series of switches or contact members, which may be controlled in any suitable manner, operate to successively shunt a portion of one of the resistors and to simultaneouslyconnect sul stantially equal portions of the other resistors in a loop circuit. This process continues until the resistors are entirely shunted.

This arrangement possesses theadvanta'ge that the 'numberof switches required is smaller than that for either of the systems referred to" above. It has been found. in practice, that the acceleration of themotor maybe accomplished in a manner that more smooth and uniform than is possible by either of the methods of the prior art. The increases in torque are uniform throughout the operation of acceleration and the unbalancing of the secondary currents is of .minimum degree.

These conditions obtain because the resistor, of which the first sect-ion to be shunted is a part, is, upon the shunting of the first section, of lower value than the other two resistors which are in parallel relation to each other. The effective resistances of the several phasecircuits are thus maintained more nearly equal than is the case in either o l the methods previously described.

In the accompanying drawing, Fig. 1 is a diagrammatic view of circuits andapparatus embodying my invention. Fig. 2 is a diagrammatic view of the circuits for controlling the switches embodied in the system of Fig; 1. l

Referring particularly to Fig. 1, lineconductors 1., 2 and 3, which may be connected to any suitable source of three-phase alter ating current, supply energy to an induction motor 4. having a plnise-wmind secondany member. The secondary winding of the motor 18 connected, through the usual slip rings, to external resistors 5, 6 and 7. The

resistor sare controlled by eleotromagnetic switches 8, 9, 10, 11., 12, 13 and 14;.

Reference may now he had to F in which is illustrated an arrangement for controlling the circuits of the actuating coils of the several electromagnetic switches. For convenience, the several coils aredesignated by the same reference numerals as are employed to designate the corresponding switches. A controlling mechanism .15 is provided with a series of contact segments sect on oi resistor r u i- .1. o are cucuis 0. .nc stront my thum is reduced. since each phase-winding is in series with the narallcl oaths of the other )lldSG- \'\'lll(ll]l ;S. The unbalancing produced by the shunting of the section of resistor T is not PI'OHO'UHCQ(l because the corresponding sections of resistors 5 and 6 are in parallel relation to each. other and in series relation to the resistor 7 which has been reduced.

In the second position of the controller 1:, the circuit of the actuating coil of switch 9 is closed and the latter operates to complete a connection for the terminals of sections of resistors 5 and 6 which correspond in arrangement and substantially in i'alue, to the .ection of resistor 7 that is controlled. by switch 8. The resistances of the several circuits of the phase-windings are again re duced by the shunt circuit thus established.

The sections of resisto controlled by the switch 9 are not entirely removed from the circuits of all of the phase-windings, as will be readily understood. The sections of resistors 5 and 6 connected in a loop circuit by the switch. 9 are in parallel relation to each other with respect to circuits comprising the resistor '7 and are shunted with regard to the circuit comprising the resistors 5 and 6 and the corresponding phase-windings. This ar rangement produces the minimum degree ot unbalanced resistance in the secondary cir- CHlLS without actually shunting equal portions of each of the several resistors.

In a similar manner, the switch 10 opcr-' ates to shunt a second section oil? resistor 7 and the switch ll operates to shunt substantially equal portions ol the resistors o and 6. The conditions obtaining at these steps correspond to those caused by the closing of switches (l and 9. respectively. Similar conditions obtain, also, upon the respeclii ve closot switches l2 and 13. The closing of switch .ll (JOIDPlLtLS a shunt circuit tor the entire resistors.

It will be noted that only seven switches are required to etlec the acceleration ol the motor. A. correspondingg number of steps of acceleration are provided. Tn the lust arrangement oi" the prior art to be described, at least nine switches are required to cll'ect the shunting of resistors hating like numbers of sections and in addition, the acceleration is not smooth and gradual as in the applicants arrangement. In the second arrangement, it is necessary to employ eight switches to accomplish similar results and the unbalancmg of currents in the several phase-windings is greater than that obtaining; in the system arranged according to my invention.

lVhile l have shown and described a three phase alternating-c1irrent system. it will he understood that such arrangement is shown by way of example only and that my arrangcl'l'ieut is adapted equally well for use in connection witl systems of any desired numher oi phases.

1 claim as my invention:

1. ln a motor-control system, the combination with an alternatin. current motor having a plural-phase windirr and resistors in circuit therewith, 01'; means for successively shunting a portion of one oi? said resistors and simultaneously connecting portions of other of said resistors in parallel relation to each other and in series relation to said one resistor.

2. In a motor-control system, the combination with an alternatirig-current motor having a secondary winding and resistors in circuit therewith, of means for successively shunting a portion of one of said resistors and connecting portions of other ot said resisters in a loop circuit.

In a motor-control system, the combination with an alternating-current motor having a tl'nree-phase secondary Wll'ltllng and resistors in circuit therewith, of means :tor successively shunting a portion ol? one of said resistors and simultaneously connecting portions of the other resistors in parallel relation to each other.

l. The method of accelerating an alternatinggycurrent motor which consists in sucrcssivcly reducing theresistance in circuit with one phase section oil? one 01' the motor winding? and then simultaneously redi'icing the resistance in, circuit with other phase sections oil the motor winding; and increasing the resistance in circuit with said one phase section.

The method oi accelorating; an alterv nntingycurrent motor which consists in successively shunting; a POl'tlOll ot' a resistor in circuit with one phase section of the motor \i'indings and then coniiecting comicsponifling portions of the other resistors in a loop circuit.

6. The method of accelerating an nltcr nating-current motor which consists in lirst reducing ti 9 resistance in circuit with one phase section ol one of the motor windings and then reducing: the resistance in the other phase sections o'l said not-or winding and. increasing the resistance in said first phase section.

7. The method of accelenting an alter listing-current motor which consists in first short-circuiting a portion of the resistance in circuit with one phase section of one of the motor windings and then short circuitinc; portions of the resistance in circuit with the other phase sections of said motor ducing the resistance in circuit with one of the phase sections, simultaneously reducing the resistance 1n clrcultwlth a plurality of the other phase sections and increasing the resistance of said one-phase circuit and then repeating the operatlons 1n order.

9. The comblnat-lon wlth an alternatingcurrent motor having a secondary Winding and a resistor in each phase circuit of said Winding, of means for successively shunting a port-ion of one of said resistorsrand connecting substantially equal portions of the other resistors in a loop circuit and then repeatingthe operations in the order named.

In testimony whereof, I have hereunto subscribed my name this 20th day of J'anuary, 1917.

ADOLPH A; GA ZDA.

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