Methodology for determination of additional losses of permanent-magnet synchronous machines due to inverter feeding

Abstract:
The additional losses due to inverter feeding are determined in three manners: From no-load measurement, with 2D finite-element-method (FEM) simulations from measured harmonic current values, and with 2D FEM simulations from calculated harmonic current values via a MATLAB Simulink model of a sinusoidal PWM with fixed switching frequency. For a commercially available 8-pole permanent-magnet synchronous motor as test machine with surface-mounted rotor mag-nets and a rated power of 84 kW measurements at inverter no-load operation are carried out with a commercially available inverter of a separate supplier. The additional losses due to inverter feeding, measured by a three-phase power analyzer for the two switching frequencies 4 kHz and 8 kHz, show a distinct maximum at about 60 % ... 70 % modulation ratio. With help of a detailed transient 2D FEM motor model, fed by harmonic current spectra, the influence of these harmonics on the active motor parts at no-load operation is analyzed. The additional iron losses Δ