Control mechanism for reversible electric motors

摘要

708,414. Control of A.C. motors; controllers; thermal switches; centrifugal switches. GENERAL MOTORS CORPORATION. Aug. 6, 1952 [Aug. 27, 1951], No. 19748/52 Classes 38(3) and 38(5) Relates to means for etfecting continuous automatic reversals of a split phase induction motor 20 involving the use of a cam shaft controller 70 which is driven by a pilot motor and is adapted to be manually operated in the same direction that it is driven. The operating lever 71 of the controller is moved in a clockwise direction to close contacts 81, 82, and energize the pilot motor winding 72 so that the controller is rotated clockwise at a given rate. The running winding 22 of the motor 20 is energized through contacts 81, 82, and 91, 92, the circuit to the starting winding 21 being completed through capacitor 110 as well as centrifugallycontrolled contacts 27. 28, and cam-operated reversing switches 102, 103. When the motor 20 reaches a predetermined speed, a centrifugal switch opens contacts 27, 28, and closes contacts 29, 30, whereby the starting winding is disconnected but the running winding is maintained energized independently of the contacts 91, 92. After the controller has operated for a predetermined period, cam 100 shifts the reversing switches 102, 103, and, when contacts 91, 92, and 96, 97, are next closed, the starting winding 21 is reversely energized through a thermally-operated switch 60 so that the motor 20 is braked to a standstill and then reversed. When the motor speed drops to a given value during braking the contacts 27, 28, of the centrifugal switch are engaged and the circuit of the starting winding is completed therethrough, the switch 60 being opened at a predetermined interval after reversal. At the end of a cycle of operations, involving a number of reversals, the cam 80 opens contacts 81. 82. The motor 20 may drive a laundering machine. The movable contact 63 of the switch 60 is fixed to a blade 62 having a biasing finger 67 which may be moved to either side of the blade by means of a thermo-electric wire 68. The contacts 63, 64, are opened when a current of predetermined value and duration passes through element 68 so causing the wire to expand and allowing a spring-supported actuator 66 to reverse the biasing effect of the finger 67 upon the blade 62. The centrifugal switch, Fig. 2, comprises weights 52 adapted to move outwardly from the motor shaft 42 against the effect of spring 51. The washer 53 then traverses the declining surface 55 of member 33 so that spring 45 causes the member 33 to pivot about contacts 27, 37, until, at a predetermined speed, contacts 27, 37, are opened and contacts 29, 39, are closed.