Numerical Investigation of the Effects of Loading and Slot Harmonics on the Core Losses of Induction Machines

This paper aims to investigate core losses in induction motors running under different loading conditions. The investigation is conducted using 2-D finite-element methods incorporating two different core-loss models. The simplified model disregards the minor loops and skin effect in the lamination. The second approach solves the magneto-dynamic problem in the lamination taking hysteresis and viscosity effects into account. The simulation results show that the core losses increase significantly with loading and the effect of slot harmonics on the eddy-current loss and minor loops can be remarkable. The distribution of the fluxes change dramatically with loading, leading to an overall increase in the harmonic content and a general decrease in the amplitude of the fundamental flux components. Therefore, even though the fundamental flux components decrease by increasing the load, the core losses rise as a result of the increase in the flux distortions and higher harmonics.