Influences of Magnetizing Modes on Exciting Force Waves of Permanent Magnet Brushless DC Motor

In order to reduce the vibration and noise of the permanent magnet brushless DC motor(PM BLDCM) for underwater vehicle, a finite element analysis model is established for PM BLDCM to investigate the difference between an electromagnetic exciting force waves of PM BLDCM with two different magnetizing modes. And the distribution characteristics of flux density of air gap for parallel and radially magnetizing modes in both no-load and load conditions are obtained and compared. Then, the electromagnetic forces are derived via the Maxwell stress tensor, and the electromagnetic force waves of PM BLDCM in both no-load and load conditions are simulated. The influences of two magnetizing modes on electromagnetic force waves are analyzed, and the distribution characteristics of the waves are achieved. The results show that in no-load and load conditions the electromagnetic exciting force waves are quite different, so the influence of load on exciting force waves must be considered in analyzing the influence of magnetizing mode on the exciting force waves; and compared with in parallel magnetizing mode, the amplitude of the main frequency increases in radially magnetizing mode but the amplitudes of other frequencies reduce.