| 摘要 |
PURPOSE:To compensate a stabilized ignition as well as to reduce a gate power loss by a method wherein a wide pulse voltage is applied to a thyristor gate when a light load operation is performed and a narrow pulse voltage is applied when a heavy load operation is performed. CONSTITUTION:A thyristor current detecting device 5 outputs thyristor current detecting signals 5U-5Z by discriminating between the positive and the negative of the AC side detecting current from current transformers 4U-4W to be used for current detection. For pulse width control device 7, the trigger pulse signals 6U-6Z outputted from a phase control device 6 are converted to a wide pulse voltage when thyristor current detecting signals 5U-5Z are below a safety commutation current, and when said trigger pulse signals are above the safety commutation current, the trigger pulse signals are converted to the narrow pulse voltage and then the trigger pulses 7U-7Z are applied to the gate of thyristors 2U-2Z. |
