Abstract: A control circuit for controlling a power converting apparatus, maintaining a stable operation of an induction motor. The control circuit includes an exciting current obtaining circuit which obtains the exciting current component from a detected signal of primary currents of the induction motor, a circuit which obtains an exciting current oscillation component from the exciting current correlate, a circuit which obtains correcting quantity from the exciting current oscillation component, and circuits which correct the voltage command or the flux command by the correcting quantity, and provide it to the power converting apparatus as stator axis voltage command values.

Abstract: A current transformer (4) detects the output currents of a voltage-type inverter (INV), and comparators (6) check whether the outputs from the current transformer exceed a predetermined limit value. The detected output currents are fed to a vector analyzer (8) to determine the location of the output current vector. A zone determining circuit (9) determines the location of the current vector in the zones. An output pattern generating circuit (10) responds to the output from the zone determining circuit (9) and provides a switching pattern corresponding to the voltage vector nearest to a vector having the direction opposite to that of the output current vector. A selector (2), being controlled by the comparator (6), selects a switching pattern from the output pattern generating circuit and provides it to the inverter (INV), when the comparator (6) detects that the magnitude of the current vector exceeds the predetermined limit value.