GB764399A - Improved control arrangement for reversing electric motors - Google Patents

Abstract

764,399. Control of A.C. motors. GENERAL ELECTRIC CO. Jan. 4, 1955 [Jan. 4, 1954], No. 245/55. Class 38(3) Relates to a reversing system for a splitphase induction motor having a squirrel cage rotor with a pair of field windings 3, 4, each of which may be used alternatively as a starting and running winding. The motor is started from rest in one direction by engaging switch 8 with terminal 10 so that winding 4 becomes the main winding. A second circuit is completed through arm 21 and contacts 29, 31, of a speed and direction-responsive switch to capacitor 39 and winding 3. When the motor reaches full speed the contacts 29, 31 are opened to interrupt the starting winding circuit. To reverse the motor, switch 8 is moved to engage terminal 9 thereby completing the main winding circuit through winding 3 and actuating a relay 14 so that arm 21 engages contact 26. The starting winding circuit is now made through capacitor 39, contacts 28, 30, and winding 4 so that reverse-current braking takes place until the motor is brought to a standstill and starts rotating in the opposite direction. Upon the motor reaching full speed in the reverse direction, contacts 28, 30, are separated to open the circuit of the winding 4. Movement of the switch 8 from engagement with terminal 9 to a neutral position causes a closed braking circuit to be established, this circuit comprising winding 3, capacitor 39, contacts 29, 31, and winding 4 connected in a loop. In another arrangement, the reversing switch is of the doublepole, double-throw, type'and the relay 14 is dispensed with Fig. 2 (not shown). In further embodiments employing single-pole reversing switch, the speed and directionresponsive switch comprises two sets each having a member for actuating the movable contacts of two pairs of co-operating contacts. These two members, which are similar to the pivoted actuating member 17, are adapted to move in opposite directions upon a given direction of rotation of the motor, Figs. 3, 4, (not shown). In one of the last embodiments, a relay having a coil carrying the motor current is adapted, when de-energized, to close a series braking circuit including the two windings of the motor.