A study of rotor pole shape of in-wheel direct drive SR motor

A switched reluctance (SR) motor has an extremely simple and robust structure, and high heat capability because of no magnet. Therefore, these advantages are suitable for an application of the in-wheel direct drive SR motor to electric vehicles. Outer-rotor-type multipolar SR motors, however, have the invalid space where the inside of the stator core. The authors propose that a drive circuit is integrated into this space because of an effective use of interior space in the car. They developed the integrated type in-wheel SR motors and the electric vehicle which equipped with these SR motors underwent a driving trial. And yet it is necessary to accelerate more powerfully and expand the space to integrate the drive circuit. This paper presents an in-wheel SR motor improved torque density. The proposed SR motor, whose integrated space is broader and stator pole is longer than previously, has two features for improvement of torque density; the first one is asymmetrical rotor pole structure that torque is improved in only one rotational direction; the second one is the overlap of the excitation to increase effective voltage. In the proposed SR motor, the maximum torque volume ratio is about 38 N·m/L.