| 摘要 |
PURPOSE:To enable the stable making operation even near a minimum operating voltage, by providing a switching element which impresses no voltage on the coil of an electromagnet when an operation voltage is the minimum operating voltage of an electromagnet device or below whereat an operation is unstable, while impressing a voltage on the coil of the electromagnet only when the operation voltage is a voltage enabling a stable operation. CONSTITUTION:An operation coil 4 of an electromagnet is connected in series to a switching element 3, e.g. a Triac, and connected between alternating-current operation source terminals R and S. The switching element 3 is driven by a trigger signal received from an output of a voltage detecting circuit 1 which is connected between the operation source terminals R and S and delivers an output when impressed with a voltage of a certail value or above. The output of the voltage detecting circuit 1 is impressed as a trigger signal on a gate of the switching element 3 through an overcurrent preventing resistor (current restricting resistor) 5. Moreover, a capacitor 2 is connected between the output terminal of the voltage detecting circuit 1 and the connection-side operation source terminal S of the operation coil 4. |
