FEA-based method for estimating PM demagnetization in electrical motor design: Development and experimental validation

This paper presents a procedure based on finite element analysis (FEA) to determine the maximum allowed current of permanent magnet (PM) motors from a demagnetization point of view. The procedure has several FEA stages, including the identification of PM demagnetized regions under load conditions and the calculation of the back electromotive force (BEMF) voltage waveform after the motor has been subjected to potential demagnetizing currents. Ferrite PM's have been characterized using a hysteresisgraph for higher accuracy and used as input for simulation. The model is validated at worst case conditions, comparing the simulation and experimental results at controlled-negative temperature. The results show a very good agreement among calculated and practical BEMF waveforms, providing a reliable and inexpensive method for estimating the maximum allowed current at early motor design stages.