抄録
The waveforms of the magnetic flux and induced voltage in the stator core, stator teeth, and rotor core of a 3-phase squirrel cage induction motor driven by a V/f = const PWM inverter power supply were measured and compared with those of the motor driven by a sinusoidal power supply, to estimate the magnetic losses. The waveforms of the induced voltage in each driving condition were similar to those of the primary winding voltage, while those of the magnetic flux in both conditions were approximately sinusoidal. The induced voltage waveform of the stator teeth contained higher harmonics, owing to the rotor slots and the power supply waveform, and differed depending on the positions of the teeth only in the case of the inverter supply. It was found that the voltage waveform for some teeth spaced at constant intervals was sinusoidal owing to self-cancellation of the harmonics. The flux in the rotor core was a sinusoidal waveform of the slip frequency multiplied by the pole pair number, which contained higher harmonics due to the stator slots, the power supply waveform, the primary voltage imbalance, and the air-gap nonuniformity between the stator teeth and the rotor.
