PWM-Induced Harmonic Power in 75 kW IM Drive System

More and more commonly, the rotating field machine drives are equipped with a frequency converter. The frequency converters enable the control of the magnetization state, torque and speed of the machine according to the needs of applications and, in principle, save energy. In turn, the pulse-width-modulation (PWM) creates additional harmonic losses over the fundamental losses in the machine. The harmonic power induced by the PWM is examined here in a case of 75 kW high efficiency squirrel-cage induction motor. The examination is carried out using an experimental setup with three commercial frequency converters at 30 different operation points of the motor. In each of the measurement points, the three-phase voltage and current waveforms are recorded as well as the corresponding electric power, current and voltage values. In the analysis, the harmonic power is segregated from the total electric power and examined as a function of the frequency, load and switching frequency.