OPERATING DEVICE FOR 3-PHASE INDUCTION MOTOR

摘要

PURPOSE:To restrain the fluctuations of a torque and a current upon starting, by a method wherein an output voltage and an output frequency are kept in predetermined values until the phase of the output voltage of an inverter circuit is changed by 60 deg. in electric angle. CONSTITUTION:Upon starting, the output frequency of an inverter circuit 2 is set at F0 (2-4 times of the stationary slip frequency of an induction motor 1) while the output voltage of the same circuit 2 is set at V0 (a value corresponding to the output frequency F0 with a predetermined V/F ratio). When the phase of the voltage, outputted from the inverter circuit 2, has become 60 deg., the phase of the output voltage is advanced by 60 deg. in electric angle while the output voltage is set at V0/2 and the output frequency is set at F0/2. Thereafter, the output voltage and the output frequency are risen up gradually while keeping a given relation between them. According to this method, the fluctuations or the like of the torque and current upon starting may be restrained.