Three-dimensional simulations of an induction motor including eddy current effects in core laminations

This work is motivated by the investigation of the common mode ground current which occurs in induction machines controlled by pulse-width modulation (PWM) at higher frequencies. In order to quantify this current, the common mode impedance of the motor has to be determined. Using the transmission line approach the model parameters are extracted from both two-dimensional (2D) and three-dimensional (3D) field simulations. 2D finite-element (FE) analysis is an efficient tool for simulating the entire motor cross-section. However, eddy currents in the laminations cannot be modelled explicitly and have to be approximated by a semi-analytical formulation. The study investigates the accuracy of this model for a wide frequency range (10 Hz, , 1 MHz). For this purpose, a specialised 3D simulation tool for induction motors was developed, taking into account the actual distribution of eddy currents in the laminations. Simulation results are presented for a simple one conductor test case as well as for an entire motor cross-section of an existing 240 kW motor.