A measuring equipment for the measurement of the electric quantities at the terminals of an inverter-fed induction motor

This paper is concerned with the problem of measuring the electric quantities at the terminals of an inverter-fed induction motor. The critical point in performing such measurements lies in the heavy distortion of both voltages and currents, which requires special care in the evaluation of rms values and powers. A measuring device is proposed for the measurement of voltage and current rms values, their frequency, their frequency-domain components and the active power consumed by the motor. The measuring instrument is based on digital signal processing techniques and is organized as a Virtual Instrument. The results of some experimental work done on a 3 kW induction motor supplied by a six-step inverter are reported