Permanent magnet volume minimization of spoke type fractional slot synchronous motors

The combination of the spoke type interior permanent magnet synchronous motor together with the NdFeB is an effective solution when high torque density is required. On the other hand, in the last years, the instability and the high price of the rare earth make the magnet minimization and the optimization of the motor design critical and mandatory. This paper deals with the design criteria of a spoke type, fractional slot concentrated winding, interior permanent magnet motor, especially as regards the minimization of the magnet volume, maximization of the airgap flux density and optimization of the split ratio. An analytical procedure is presented and validated by means of finite element analysis. At last, the advantages and the differences among the solutions are highlighted.