Finite element based phase-variable model in the analysis of double-star permanent magnet synchronous machines

This paper describes a finite element (FE) based phase-variable model for double-star permanent magnet synchronous machines. In a double-star configuration where two three-phase windings are spatially shifted by 30 electrical degrees, a high amount of the 5th and 7th current harmonics may be excited because of the winding layout. However, a conventional d-q axis model considers only fundamental components, and thus, the machine model may be oversimplified. Improvement in the accuracy can be obtained by introducing an FE-based phase-variable model that includes the higher-order harmonics occurring in the no-load flux linkages and in the self- and mutual inductances. Moreover, when compared with an FE analysis with controlled power electronics, significant reduction in the computation time can be achieved. The effects of the harmonics on the machine behavior are evaluated by simulations, and the accuracy of the proposed model is verified by measurements.