Air-gap force and vibration of an advanced PM vernier machine

The vernier permanent magnet (VPM) machines have been widely studied in recent years due to their high torque density. In this paper, the air-gap force density and vibration of an advanced VPM machine is analyzed and compared to a conventional 12-slot 10-pole PM machine using FEA and experimental test. Due to the flux modulation principle of the VPM machine, it has more harmonics in the air-gap magnetic and force density field than the CPM machine. As a consequence, the acceleration spectrum of the VPM machine is more abundant than that of the CPM machine, in spite that their peak amplitudes are close. On the other hand, the maximum deformation of the VPM machine is much smaller than that of the CPM machine, which is a potential advantage for the VPM machine.