Analog and digital methods for power measurement in adjustable speed drives

Two widely used different techniques for power measurement in adjustable speed drives (ASD) are compared in this paper. The first one is a digital system that includes sampling and A/D conversion devices along with DSP algorithms, the second technique refers to a set-up based upon analog electronic devices. The hardware requirements and the main features of both methods are discussed to highlight their advantages and limits. Experimental results, related to an induction motor supplied by a pulse width modulation (PWM) inverter, will provide the basis for a comparison between the two approaches, from both a metrological and an economical point of view.