Novel rotor pole design of switched reluctance motors to reduce the acoustic noise

Although the switched reluctance motor has many features, the relatively large torque ripple and acoustic noise are major disadvantages. Many reports have been published on the torque ripple reduction but only few papers have been published on the acoustic noise reduction. The acoustic noise of the switched reluctance motor is generated by the stator deformation due to the radial force generated by excitation. The paper deals with a comparative study of switched reluctance motors from the standpoint of the maximum torque/radial force ratio. The comparative studies are based on the FEM analysis and experimental verification. Three types of stator/rotor pole combinations, 12/8, 816 and 6/4, are selected for comparisons and each type is optimally designed to obtain the maximum torque/radial force ratio under the same stator outer diameter, gap length and excitation per pole. The authors also propose a new rotor configuration, which has an air gap window inside the pole, to reduce the acoustic noise. As a result, the 12/8 combination has the best performance among them. If the higher drive frequency is undesirable, a 6/4 motor with a rectangular air gap window inside the pole is recommended.