GB1060743A - Electric motor - Google Patents

Abstract

1,060,743. Control of A.C. motors. FRANKLIN ELECTRIC CO. Inc. March 16, 1964, No. 11067/64. Heading H2J. When switch (17) is in the position shown, an induction motor is operated by three-phase windings (10), (11), (12). To run the motor at a different speed, the switch (17) selects one of the auxiliary single-phase windings (13), (14) or (15). The motor again starts as a polyphase machine, but operation of centrifugal switch (16) disconnects the polyphase windings and energizes the selected single-phase winding, Fig. 1 (not shown). In another arrangement, the centrifugal switch controls a relay which shifts the motor from the main windings to the auxiliary windings. As shown, the motor is started as a three-phase machine when switch 104 engages its left-hand contact, reversal being obtained by manual operation of switch 85. Reverse torque is applied to the motor causing it to slow down, stop, and begin operation in the opposite direction.- When switch 104 engages auxiliary winding 96, the motor is started as a three-phase machine until centrifugal switch 106 opens to energise relay 89. The motor then operates as a single phase machine at a speed determined by the number of poles of winding 96. To reverse the motor when it is running as a single-phase machine, switch 85 is actuated to shunt the coil of relay 89 through direction-responsive switch 107. The de-energization of relay 89 breaks the circuit for winding 96 and establishes the circuits for windings 101, 100, 94 to apply a reversing torque. After the motor has reversed, the switch 107 changes over so that opening of switch 106 restores the single-phase connection. In a modification, the relay 89 is energized from a coil coupled to the motor windings 100, 96, 97, 98 and switch 85 is replaced by a multiple relay arrangement.