Current transducers for power-electronic applications

Nowadays, electric current measurements play an utmost important role in processing control. The choice of an appropriate current transducer depends on the requirements of individual applications and a thorough knowledge of various current-sensing technologies. In this paper, a general overview of the existing and well-established measurement principles is presented. Based on the physical foundation (Ohm's law, Faraday's law, Ampere's law and Faraday's effect), the entire area of the current transducers is divided into four categories. For each category, the paper presents typical current-sensing solutions, analyses their operation and critically estimates its performance. Solutions enabling their constructive integration in to the power electronic circuits are offered and experimental measurements are made to determine the commercially available representatives of each category. A dedicated circuit is proposed to generate an adjustable and reproducible current step for the transducers step-response measurements. Their dynamics is evaluated based on the transducers frequency response. The frequency spectrum reveals transducers performance with regard to their distorting the measured signal and detecting specific high-frequency harmonics.