Vibration Characteristics of Slotless Rotating Armature Permanent Magnet Motors

In the rotating armature permanent magnet motor (RAPMM), the movement of the rotor slot in relation to the stator results in variations in the electromagnetic excitation force and slot-frequency vibration. To diminish the slot-frequency vibration of RAPMM, a novel slotless rotating armature permanent magnet motor (SRAPMM) is proposed and prototype-tested. The finite element method is used to simulate the magnetic field, torque, and torque ripple, revealing that the air gap flux density and radial force remain relatively constant. Vibration experiments were conducted on two SRAPMMs having different magnetic pole widths. The results indicate that the main vibration frequency is an even multiple of the current frequency when the motor is unloaded. After loading the motor, the amplitude of the electromagnetic vibration is significantly smaller than that caused by mechanical factors, suggesting that the SRAPMM is a reliable option when strict vibration requirements are applied.