| 摘要 |
PURPOSE:To control the SCR valve in which adjusting work is not needed by a method wherein the zero points of each phase output wave-form of an AC power supply are detected, oscillating pulses forwarded by the detecting signals are counted, counting value and set value are compared with each other and the gate pulses are forwarded when both value agree. CONSTITUTION:The output pulses of a voltage controlling oscillator 13 are counted by means of a counter 15, and the zero points at every each phase synchronous signal of three-phase AC VR-VT wave-forms functioning as the synchronous power supply are detected by means of a zero point detector 16. The counter 15 is reset by the detecting signals, and starts counting again, the counting value is inputted to a comparator 17 given the digital set value of ignition phase control signals EC and compared with the set value, a distributing circuit 18 is operated by pulses forwarded when both values agree with each other, and gate pulse signals to the SCR valves of each phase are outputted. |
