Coupled Field and Circuit Permanent Magnet Model for High-Speed Motor Analysis

In this article, a particular methodology is introduced based on a coupled 2-D FEA and circuit approach for the representation of permanent magnets in electrical machines, including eddy current losses due to slot harmonics and switching frequency of pulse width modulation (PWM) inverter supplies. The governing equation is diffusion equation expressed in the Cartesian 2-D configuration in terms of magnetic vector potential, while the gradient of the electric scalar potential term enables end effects consideration of eddy currents developed in the permanent magnets. Accurate representation of eddy currents flowing in well-defined paths in the permanent magnets has been achieved under dissymmetrical field conditions by introducing a particular segmentation of the magnet end regions through appropriate equivalent circuit coupling. The comparison of the results obtained by the 3-D FEA and the introduced coupled 2-D model in a C-core magnetic circuit has illustrated the accuracy and the feasibility of the proposed methodology.