INVERTER

摘要

PROBLEM TO BE SOLVED: To provide a tough inverter not tripped easily in which stabilized vector control of motor torque can be carried out even when a motor is in regenerative state and the regenerative energy being returned back to the inverter can be lessened while taking account of the heating of motor and thereby advantageous with regard to heating at the inverter section. SOLUTION: A positive/negative discriminating circuit 9-6 discriminates between powering state and regenerative state based on the polarity of torque current iq. At the time of regeneration, a switch circuit 9-5b is closed to make a switching from a voltage setter 7 providing an AVR level setting for powering to a voltage setter 7-1 providing an AVR level setting for regeneration in order to increase the V/f ratio. Consequently, an induction motor 5 is brought into over exciting state and a part of regenerative energy is absorbed by the induction motor 5 itself.