| 摘要 |
PURPOSE:To protect the thyristor element avoiding the application of the step voltage to the other thyristor while making the circuit smaller employing the gate turn off thyristor in the forced commutation circuit. CONSTITUTION:As soon as the gate turn off thyristor (GTO)SA1 is fired at the time t1, the commutation condenser C starts resonance. As soon as the auxiliary thyristor SA3 is fired at the time t5, the reverse voltage for turning off is applied to the main thyristor S1 as shown by the dotted line of the waveform diagram. In addition, the current transformer CT, for example, detects the current of GOTO SA to be zero and the gate signal for turning off is generated to the thyristor SA1 at the time t2 from the control circuit 6 to lessen the gate signal current for turning off. Thus, as compared with the conventional type, the element can be protected while the commutation circuit is miniaturized. |
