Parameter Determination of PMSM Using Coupled Electromagnetic and Thermal Model Incorporating Current Harmonics

With advent in permanent magnet synchronous machine (PMSM) structure and inverter topologies, accurate parameter determination is of significance for high-performance control, analysis, and making critical decisions on inter-dependent design parameter variations for machine optimization. However, the machine parameters, including permanent magnet (PM) flux linkage and dq-axis inductances, vary during operation with machine nonlinearities such as magnetic saturation, temperature rise, and the introduction of spatial- and time-harmonic contents contributing toward inaccuracies during machine parameter determination. While classical dq-axis modeling fails to accommodate non-sinusoidal winding distributions and the effects of temperature rise, finite-element analysis (FEA) is computationally expensive and coupling of electromagnetic and thermal analysis including current harmonics becomes complex. Therefore, in this paper, a novel magnetic equivalent circuit model incorporating the effects of temperature rise and current harmonics has been developed for parameter determination of PMSMs. A lumped thermal model is implemented to determine the temperatures at each point of the machine. The proposed coupled electromagnetic and thermal model has been validated for various operating conditions of a fractional-slot distributed wound laboratory PMSM with FEA and experimental investigations.