JPS57153596A - Normal and reverse operating method for induction motor by voltage type inverter - Google Patents

Abstract

PURPOSE:To normally and reversely operate an induction motor without contact by eliminating the switching of a phase sequence even if normal or reverse switching command is applied during high speed operation and switching the phase sequence only in the low speed range, thereby reducing the size of the motor. CONSTITUTION:A low speed detector 7 which detects the fact the acceleration of deceleration speed limiting instruction value of an acceleration or deceleration speed limiter 6 is lower than the low speed level, an oscillator 8 which oscillates a clock pulse upon throwing of a controlling power source, and a memory circuit 10 which calculates the logical product of the clock pulse signal of the oscillator 8 and the detection signal of the detector 7 and storing the normal or reverse instruction signal by the output pulse signal of the logic product are provided. The phase sequence of the drive signals of a driving circuit 16 of an inverter is switched in accordance with the normal or reverse instruction signal set by the memory circuit 10. That is, when the accleration or deceleration control instruction value is lower than the low speed level, the output of the drive signal to the driving circuit 16 of the inverter is stopped, and when it is higher than the low speed level, the drive signal is produced.