A Fast Calculation Method of Optimal Ratio of Outer Diameter and Axial Length for Torque Improvement in Switched Reluctance Motor

In this paper, a fast calculation method using finite-element method (FEM) analysis-based magnetostatic data with a parameterized geometry is proposed to find the optimal ratio of the outer diameter and the axial length for switched reluctance motors (SRMs). The proposed method shortens the amount of calculation time by a factor of more than one-hundred compared to the transient FEM analysis. The proposed method is verified by two SRMs for automotive traction applications. It is found that the optimal ratios of the outer diameter to the axial length and the stator outer diameter to the rotor outer diameter are around 2.5 and 0.65, respectively. It is also found that the motor volume has little influence on the optimal ratio, whereas the current density increases the optimized ratio of the stator and rotor outer diameters.