CONTROL CIRCUIT FOR INVERTER DEVICE

摘要

PROBLEM TO BE SOLVED: To apply a constant voltage most suitable for an induction motor regardless of fluctuation in input voltage and prevent the motor from becoming unstable by exercising such control from the estimated primary-side supply voltage of an inverter device that the relation between the output frequency and output voltage of the inverter device will be constant. SOLUTION: The voltage of an alternating-current power supply 5 is estimated by storing in a control computing circuit 16 the relation between a direct- current voltage obtained through a low-pass filter 20 and the state of circuit input/output. The control computing circuit 16 adjusts a signal to an output transformer module drive circuit 17 from the estimated voltage of the alternating-current power supply 5, and exercises control so that the relation between the frequency and voltage output from an inverter main circuit transistor module 4 will be constant independently of the voltage of the alternating- current power supply 5. This makes it possible to always apply the most suitable voltage to an induction motor over a wide range of supply voltage, and to prevent motor current from becoming unstable.