| 摘要 |
PURPOSE:To allow the normal operation of an electromagnet device, even when it is controlled by means of TRIAC and an antiparallel thyristor, by connecting an impedance for discharge between two input terminals of the electromagnet. CONSTITUTION:An impedance 8 for discharge, for example, a resistor or an inductance, is connected parallelly to the input terminals of an electromagnet to retain a voltage equal to a peak voltage of the alternating source voltage across a condenser 3 when a semiconductor switch 5 for controlling the electromagnet is turned off. However this remaining charge is discharged through a full wave rectifier 1, a coil 2, an impedance 8 and a resistor 4 for discharge so that the semiconductor switch 5 is not broken over, and the electromagnet is not excited by the coil 2 to allow separation of a movable iron core 7 from a fixed iron core 6, resultantly the normal operation of the electromagnet. |
