| 摘要 |
PURPOSE:To prevent erroneous operation of the motor by automatically switching full-wave and half-wave conductions in response to the supply voltage value from a gate circuit for controlling the firing and extinguishing of a semiconductor switching element. CONSTITUTION:When voltage 100 volts is applied to an input terminal, the voltage divided by resistors R3, R4 is applied through a diode D4 to a zener diode ZD, and since the voltage does not reach breakdown voltage, it does not charge a capacitor C2 to cause the transistor TR to be in off state. Accordingly, the SCR of a rectifying bridge 1 is fired by the arcing circuit 2, and the voltage of full-wave rectification is applied to a motor M. When 200 volts is applied thereto, the voltage divided by the resistors R3, R4 is applied through the D4 to the ZD, and since the voltage of one direction becomes higher than the breakdown voltage, the capacitor C2 is charged to turn the TR on. Accordingly, the SCR of the bridge 1 is extinguished to become off, and the other voltage is energized to apply the voltage rectified by half-wave to the motor M. Therefore, it can prevent the erroneous operation of the motor. |
