Comparative Experimental Evaluation of a Current Transformer and a Hall‑Effect Current Probe Used for Monitoring Active Electrical Power Absorbed by AC Drive Motors

Abstract

This paper presents a comparative experimental study on the use of a toroidal AC current transformer and a Hall‑effect‑based current probe for measuring the instantaneous AC current absorbed by an electric motor driving a mechanical system (e. g. a car gear box, a lathe gear box). The measured AC current waveforms are then used to determine the active electrical power absorbed by the motor, which directly reflects the mechanical power delivered to the driven system. Experiments confirm a well‑known effect: compared to a Hall‑effect current probe (assumed to operate ideally), the AC current transformers introduce a positive phase shift, causing the measured waveform to lead the real current. Because of this positive phase shift, the measured instantaneous voltage and current exhibit an artificially increased phase difference, which leads to an inaccurate estimation of the active electrical power.

A method for compensating this drawback is proposed. In addition, several limitations of current transformers in capturing severe transient regimes are illustrated.