| 摘要 |
PURPOSE:To protect a self-extinguishing element against an overvoltage by applying a shortcircuiting pulse only near the inversion of positive or negative in the direction of the output AC current of an inverter, thereby suppressing a spike voltage. CONSTITUTION:A frequency command value is input to a voltage/frequency converter 6, and the output is input to a PWM pattern generator 8, a shortcircuiting pulse generator 9 and a ring counter 10. The generator 9 generates a shortcircuiting pulse near the inversion of positive or negative in the direction of the output AC current of each inverter, and the pulse is applied together with the outputs of the generator 9 and the counter 10 a PWM pulse pattern composite circuit 11. The output of the circuit 11 is applied to a gate amplifier 12, and a gate signal for driving a self-extinguishing element is led out. |
