Comparison of Models for Estimating Magnetic Core Losses in Electrical Machines Using the Finite-Element Method

This paper focuses on the modeling and prediction of core losses in nonoriented magnetic materials of electrical machines. The aim is to investigate the accuracy, efficiency, and stability of certain models, including the commonly used and the advanced ones, and to discuss their advantages and disadvantages when,they are implemented in the finite-element method (FEM). It is shown in the paper that the traditional technique based on the loss separation theory can efficiently produce reasonable results in specific operation conditions but can, on the other hand, over- or underestimate the core losses in other circumstances. The advanced model based on solving the one-dimensional (I-D) Maxwell equations can give accurate results for the prediction of core losses in a lamination strip, but its accuracy, stability, and computational burden are put under scrutiny when it is applied to the prediction of core losses in an electrical machine. A third technique, referred to as the hybrid model, which captures the advantages of the traditional and advanced techniques and merges them into one, has been found to be the best compromise. The principal aim of the hybrid model is to avoid the numerical procedure of the I-D Maxwell equations while maintaining relatively accurate predictions with a reasonable computational burden. A comparative investigation has been conducted for the three core-loss models that have been incorporated into the 2-D FEM analysis of a 37-kW induction motor on which experiments were carried out for comparisons.