CONTROL APPARATUS FOR AN INDUCTION MOTOR

摘要

A control apparatus for an induction motor comprising a three phase induction motor, a three phase alternating current source for supplying a three phase alternating current voltage for the induction motor, parallel thyristors connected in the reverse direction to each other and inserted in an arbitrary phase of the three phase alternating current source for controlling the current flowing therethrough, contactors for changing the main circuit of the induction motor so as to reverse the direction of the phase rotation of the alternating current voltage when the induction motor is in a single phase operation by control of the thyristors, and a control device for operating the thyristors to substantially eliminate the current flowing therethrough in response to a reduction command and to increase the current again when the contactors complete changing the main circuit.