INVERTER OPERATION CONTROL METHOD FOR INDUCTION MOTOR

PURPOSE:To perform control such that an idling induction motor does not operate as an induction generator, by detecting the number of revolutions of the induction motor and by placing an inverter apparatus in operation only when the command signal has the number of revolutions higher than the number of revolutions of the idling motor. CONSTITUTION:A speed detection signal 4 detected by a speed detector 3 is corrected by a compensation value set by a torque compensator 13 and inputted to a signal priority comparator 7. A speed reference signal 6 set by a speed reference setter 5 and the speed detection signal 4 are compared by a comparator 9. When the speed detection signal 4 is smaller than the speed reference signal 6, a relay 9 does not operate, but when the speed detection signal 4 is larger than the speed reference signal 6, a relay 10 operates to close a relay contact 12 to stop an inverter 1. Thus, an induction motor 2 is placed in a free-running state. The signal priority comparator 7 outputs a signal having a lower signal level, out of the speed reference signal 6 and the speed detection signal 4, as an inverter speed reference value 8 to the inverter 1.