| 摘要 |
PURPOSE:To reduce a shock by di/dt of bidirectional thyristor by using zero-volt switch control system in a phase control system, thereby eliminating a noise in principle. CONSTITUTION:Not only a phase controller 16 for varying a switching phase but also a zero-volt switch controller 17 for varying a switching phase at the zero-volt point of the AC power source are selectively connected in the half cycle of the AC power source 11 having a variable charging circuit in a gate trigger circuit 15. When the controller 16 is connected with the circuit 15, a bidirectional thyristor 14 is controlled in the phase. Accordingly, the input of a motor driven blower 13 is variably controlled. If an input variation is unnecessary and ON and OFF are desirably controlled at the maximum input, the zero-volt switch controller 17 becomes connected state with the circuit 15. Thus, the noise due to di/dt at ON/OFF time of the thyristor 14 can be suppressed. |
