| 摘要 |
PURPOSE:To eliminate the roughing of a contact of a contactor in a compound motor due to opening and closing thereof with a current frequently and eliminate the breakdown of a thyristor due to erroneous firing thereby by charing the commutation capacitor of the thyristor through a transistor. CONSTITUTION:A semiconductor switching circuit 60 is provided instead of the conventional contactor for opening and closing it with a current for a compound motor, and a transistor is used in a circuit for charging the commutation capacitor in the circuit. For example, in the circuit shown, switches 7, 3 are sequentially closed to conduct a thyristor TH1 so as to flow a current through the motor 4, and a transistor TR1 is conducted to charge a commutation capacitor C0. In this case, the thyristor TH1 is conducted during the time while rush current of the motor flows to become steady current to avoid the large size of the commutation capacitor. Then, an auxiliary thyristor TH2 is conducted to cancel the current of the main thyristor TH1 by the charge of the commutation capacitor C0 so as to break the motor current. |
