| 摘要 |
PURPOSE:To protect an entire control system safely, by blocking the gate of a thyristor upon occurrence of synchronization shift of an output signal from a synchronous signal output means and separating a motor from the output side of a thyristor converter. CONSTITUTION:A speed control circuit 2 outputs a current reference signal corresponding to a speed difference while a current control circuit 4 outputs a phase control reference signal 4a corresponding to a current difference. A power source synchronizing circuit 6 outputs a power source synchronization signal 6a from a voltage signal 5a. A phase control circuit 7 outputs a firing signal 7a for a thyristor inverter 8 based on the phase control reference signal 4a and the power source synchronization signal 6a. A power source synchronization detecting circuit 17 detects shift of synchronization from the phase of phase voltage of an AC power source bus 12 based on the voltage signal 5a, and turns a DC electromagnetic contractor 18 OFF upon detection of synchronization shift and provides a gate block signal 17a to the phase control circuit 7. |
