Simplified Calculation of Eddy Currents in Segmented Rotor Magnets of Inverter-Fed Synchronous Machines

The eddy current losses in segmented rotor magnets of a commercial permanent-magnet synchronous machine of 84 kW rated power are determined by two-dimensional finite element simulations and compared with no-load measurements of a test machine for different pulse-width-modulated inverter switching frequencies. The focus is on the additional losses due to the voltage source inverter feeding. Therefore, the losses due to sinusoidal feeding are not considered. The additional eddy current losses are calculated in two ways: a) with composed harmonic voltage source feeding of the finite element model, which require rather long simulation times, b) with pre-calculated loss maps. Both methods show quite good agreement with the measured values. In addition, the loss map approach is used to give an indication of the loss distribution for different numbers of rotor magnet segments.