Finite-element surrogate model for electric machines with revolving field-application to IPM motors

The model allows the ultrafast nonlinear simulation of the steady-state performance of synchronous machines and is particularly suitable for brushless motors with nonoverlapping windings having coils concentrated around the teeth. Finite-element analysis (FEA) is employed only for calculating the magnetic vector potential in the coils, and the motor performance is then estimated through analytical formulas. For the example interior-permanent-magnet motors presented, as little as one magnetostatic finite-element (FE) solution was used for the fundamental flux linkage and average torque computation. Two FE solutions were employed for the core flux density waveforms and power loss estimation. A minimum of three solutions is recommended for the torque ripple, back electromotive force, and induced voltage. A substantial reduction of one to two orders of magnitude was achieved for the solving time as compared with the detailed time-stepping FEA. The surrogate FE model can also be tuned for increased speed, comparable with that of magnetic equivalent circuit solvers. The general applicability of the model is discussed, and recommendations are provided. Successful validation was performed against the detailed FEA and experiments.