START CONTROL CIRCUIT FOR HYBRID MOTOR STARTER IN SYSTEM WHICH ELECTROMAGNETIC CONTACTOR AND ELECTRONIC MOTOR PROTECTION RELAY ARE CONNECTED IN SERIAL

摘要

PURPOSE: A start control circuit is provided to start a motor in a smooth manner in the system in which an electromagnetic contactor and an electronic motor protection relay are connected in serial so as to directly start the motor. CONSTITUTION: A start control circuit comprises a circuit breaker(61) and a mechanical contact unit(69) an electromagnetic contactor which are connected in serial so as to control the three phase power supplied to a motor(70); a current detection unit(64A) for detecting current of each phase; a line voltage detection unit(64B); a control unit(65) for converting a line voltage into a phase voltage, detecting a zero voltage point based on the converted phase voltage, generating a starting current reference level corresponding to load characteristics of motor, and generating a phase angle control signal base on the starting current reference level; and a semiconductor switch driving unit(66) for controlling operations of a semiconductor switch unit(67) which is connected in parallel to the mechanical contact unit by using the phase angle control signal, in such a manner that the motor starts in a smooth manner.