Analysis by finite element method of a coupled inductor circuit used as current injection interface

Abstract

In the case of three-phase diode bridge rectification, the harmonic content of the input currents can be reduced by injecting a calculated amount of third harmonic current on the AC side. The paper presents an analysis, by the finite element method, of a magnetic device (coupled three-phase inductor) used as current injection interface in a third harmonic modulation circuit. The magnetic device is designed to block fundamental currents and to offer least resistance to third harmonic currents. In order to reduce its zero sequence inductance, which may affect the operation of the diode bridge, a conductive shield is added to cover the coupled inductor. On the other hand, the conductive shield produces excessive power losses due to high eddy currents induced by the third harmonic field. The electrothermal aspect of the coupled inductor is therefore investigated. The analysis is performed using a realistic 3D model of the magnetic device.