| 摘要 |
PURPOSE:To enable an AC power phase to be easily synchronized with a gate input signal phase by controlling the gate input of an AC switching element on the basis of a interlinear voltage waveform after the lapse of a given period of time from inputting of power. CONSTITUTION:When a three-phase AC power is inputted, a pulse voltage corresponding to the phase of each interlinear voltage wave-form is outputted from phototransistors 13a-13c of photocouplers 11a-11c. On the other band, a flip-flop 26 is set when the charging voltage of a capacitor 24 has reached a given value after inputting of power. Thus, binary counters 17a-17c start counting said pulse voltage and give output signals to NAND gates 18a-18b. NOR gates 19a-19c output the gate signal of an AC switching element connected with each phase on the basis of output signals of the NAND gates 18a-18c. |
