Design and Analysis of T-L Stator-Rotor Pole Combination of Outer-Rotor SRM Considering Dynamic Torque Characteristic

In this paper, the design of a T-pole for stator and an L-pole for rotor is proposed to improve the output torque quality of an outer-rotor (OR) type SRM. The design strategies of OR motors are different than the conventional ones, especially due to the limited space of the windings. The geometry of the stator and rotor pole tips determine the torque shape. Firstly, T-pole stator is implemented to help widen the arc to increase the average torque without affecting the winding area. Then, the L-pole rotor is adopted by adding a ‘protruding nose’, which results in the shifting forward of the torque waveform. Dynamic torque is observed in this study instead of the static one since switching actions must be taken into consideration as SRM performance is heavily affected by excitation. Both simulations and experiments show the effectiveness of the proposed design.