Voltage-controlled starting relay for induction motor

摘要

There is provided a voltage-controlled electronic relay for starting a single-phase induction motor, which includes: a power supply unit (310), configured of a bridge diode (BD), for supplying power to circuit elements of the starting relay when AC power of the induction motor is turned on; a triac (306) for applying the AC power to a starting coil (W3) of the induction motor or cutting off the AC power; a signal input unit (322) for sensing a voltage induced to the starting coil; a hysteresis unit (324) for outputting an ON control signal at the initial starting stage, generating an OFF control signal for turning off the switch when the induced voltage sensed by the sensing element reaches a predetermined OFF reference voltage, and generating the ON control signal for turning on the switch again when the induced voltage becomes lower than a predetermined ON reference voltage during a normal operation period; and a triggering unit (330) for turning on the switch according to the ON control signal of the hysteresis unit and turning off the switch according to the OFF control signal. Accordingly, impulse noise generated across the triac is removed using a spark killer and stabilized voltage is provided to the circuit elements.