CONTROL CIRCUIT FOR FLUX CONTROL TYPE INVERTER

摘要

PURPOSE:To stably operate an induction motor without saturating a flux regulating means even if power supply voltage fluctuates by arranging a high capacity smoothing capacitor in a DC intermediate circuit and constituting the circuit so that the flux command value varies in proportion to the voltage of the DC intermediate circuit. CONSTITUTION:A smoothing capacitor 5 is connected with a DC intermediate circuit 4 in order to lower the voltage of an AC power supply 2 slowly at a predetermined time constant thus lowering the torque of an induction motor 7 slowly. Voltage drop of the DC intermediate circuit causes output voltage drop of an inverter and thereby causes deficiency of flux of the induction motor 7. Consequently, a flux regulator 16 is saturated in the direction of a flux increment command thus causing overexcitation when the power supply voltage is recovered, but since the flux command value varies in proportion to the voltage of the DC intermediate circuit output from the flux regulator 16 can be maintained at a constant level and thereby the flux regulator 16 is prevented from saturation.