| 摘要 |
1,041,578. Control of D.C. motors. SQUARE D. CO. Dec. 4, 1963 [Feb. 12, 1963], No. 47880/63. Heading H2J. A circuit to shunt one of a series of motorstarting resistors on reduction of armature current or effluxion of time comprises a shunt 23 carrying the armature current connected to a saturable transformer primary winding 20. When the motor is first switched on, the voltage induced in the secondary winding 205 causes a transistor 22 to conduct, energizing a relay 31, 31w controlling a contactor shunting one of the motor-starting resistors, the contacts 31 opening before the contactor closes. When the armature current falls, the transistor blocks and the relay releases closing contacts 31. If the current does not fall, after a time delay, the transformer saturates and the transistor again blocks. A resistor 21 provides a reverse current through the transformer to reset the flux. As the circuit is polarity sensitive, two such circuits connected in reverse series must be provided to operate on bi-directional current. A circuit is described in the Specification for successively shunting two series motor resistors.
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