Comparison of Core Loss Prediction Methods for the Interior Permanent Magnet Machine

The Interior Permanent Magnet (IPM) machine has been adopted for many high-performance applications including highly competitive automotive field. One of the many advantages offered by the IPM machine is lower losses due to absence of rotor copper loss. However, in high speed operation, eddy current and hysteresis losses of the core are non-negligible. The precise prediction of core loss at all operating condition is necessary to ensure optimal utilization of the machine. There are a number of ways to predict core loss in IPM machines. The commonly used methods are - empirical formula, finite element prediction, and equivalent circuit modeling. In this paper, above mentioned methods are applied to predict core loss of a laboratory IPM machine. The predicted losses are compared with measured values. Among the three methods investigated here, the finite element method gives fairly close prediction to measured values in all speed ranges provided rotational field loss is included. In other methods, errors tend to increase with rising speed. The relationships between flux distributions and core loss with maximum torque per ampere and flux-weakening control are also investigated in the same machine