Vibration Characteristics of Slotless Rotating Armature Permanent Magnet Motors

For the rotating armature permanent magnet motor (RAPMM), the rotor slot move relating to the stator, which causes the variation of electromagnetic excitation force and the slot-frequency vibration. In order to reduce the slot-frequency vibration of RAPMM, a slotless rotating armature permanent magnet motor (SRAPMM) is proposed and prototyped. The magnetic field, torque, and torque ripple are simulated by finite element method, which shows that the air gap flux density and the radial force keep nearly constant. Vibration experiments were carried out on two SRAPMMs with different magnetic pole widths. The results show that when the motor is no-loaded, the frequency of the main vibration is even times of the current frequency. After the motor is loaded, the amplitude of the electromagnetic vibration is significantly smaller than that caused by mechanical reasons, indicating that the SRAPMM is a good alternative in the application of strict requirements for vibration.