| 摘要 |
PURPOSE:To simplify the controlling circuit by always driving a plurality of chopper main circuits and separating a defective main circuit at the defective time. CONSTITUTION:First and second chopper main circuits 14, 15 always operate, when the first chopper main circuit 14 becomes defective due to a certain reason, a chopping malfunction detector 18a operates, and the gate of a switching circuit 23 is closed by the output of the detector 18a, the gate of a low-level adder+switching circuit 30 is opened and the signal is simultaneously fed to the gate signal generator 19a of a shortcircuit thyristor 7a. Thus, the thyris fot 7a is conducted, and an NFB 11a is tripped. On the other hand, a comparator 24 compares the output of the circuit 30 with the output of a current detector 16 to produce first and second chopper main circuit firing pulses and to produce the first and second chopper main circuit deenergizing pulses via a differentiating circuit 26. |
