Radial Force and Vibration Calculation for Modular Permanent Magnet Synchronous Machine With Symmetrical and Asymmetrical Open-Circuit Faults

This paper studies the radial force and vibration performance of the modular three-phase permanent magnet synchronous machine under typical two-phase open-circuit faults: symmetrical and asymmetrical. First of all, the expressions of armature magnetomotive force are formalized in normal and fault conditions; thus, the air-gap magnetic fields and radial force density can be analyzed theoretically. Second, the theoretical analysis is verified by running the finite-element simulation of a four-unit modular machine. The relationship between the fault types and radial force harmonic contents is also discussed with the help of 2-D fast Fourier transform. This is followed by the transient and harmonic structural analysis, with the exciting forces imposed on the stator system in order to get the acceleration response. The simulation results are validated by vibration measurement experiments of a similar small-sized modular motor. This investigation can instruct the designer to lower the modular machine's vibration under different fault conditions.