| 摘要 |
1,208,548. Control of D.C. motors. WESTINGHOUSE ELECTRIC CORP. 10 June, 1969 [26 June, 1968], No. 29254/69. Heading H2J. [Also in Division H3] In a chopper circuit 15 supplying a traction motor 4, a turn-off charge is maintained on a commutating capacitor 6 regardless of the duration of the " on " periods of a main thyristor 3. The capacitor is charged initially by triggering thyristor 7. Thyristors 3, 9, are then triggered to energize the motor, the capacitor being discharged and recharged in the reverse direction, and the thyristor 7 being turned-off. When the capacitor is fully charged, thyristor 9 turns off. The charge on the capacitor remains substantially constant during the " on " periods of the thyristor 3 since current leakage through the thyristors 7, 9 is earthed through resistor 17. The charge potential on the capacitor 6 is applied to the thyristor 3, together with the potential of the D.C. source, when the turn-off thyristro 7 is triggered.
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