Design and Modeling of a Two-Winding Rogowski Coil Sensor for Measuring Three-Phase Currents of a Motor Fed Through a Three-Core Cable

Abstract

In this article, three-phase motor currents pass through a three-core cable are measured using a two-winding Rogowski coil. The two-winding Rogowski coil is externally fitted around the three-core cable without the need for removing its insulation layers. This results in reducing the measurement complexity. Two windings are fitted around a circular non-magnetic core considering 120 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> between their center points. The EMFs induced in each winding due to magnetic flux linkage between windings and cable cores are used to reconstruct the three-phase motor currents through the cable cores. In order to reconstruct cable currents, a current reconstruction algorithm is developed. Sensor design and the developed current reconstruction algorithm are theoretically and experimentally validated. Theoretical validation is carried out through Power Simulation Program (PSIM). Regarding the theoretical validation, a three-phase motor fed from a three-phase source is simulated. Motor feeding is carried out using a cable having three cores. The proposed Rogowski coil is simulated and the currents through the cable are theoretically reconstructed considering different operating conditions. Also, experimental validation is carried out considering the measurements of three-phase currents through the cable feeding a 15 HP, three-phase induction motor from a three-phase source. A designed two- winding Rogowski coil is used for sensing the measured currents and a Digital Signal Processor (DSP) is used for implementing the adopted current reconstruction algorithm. Finally, efficacy of the proposed two-winding Rogowski sensor as well as the developed current reconstruction algorithm is proved through the obtained results.