VIBRATION REDUCTION IN ELECTRIC MACHINE BY INTERLOCKING OF THE MAGNETS

A principal source of vibration in permanent magnet motors and generators is the traveling attractive forces from the rotating permanent magnets acting on the stator. This magnetic force can be calculated from the flux density by finite element methods and the Maxwell stress tensor, and the characteristics of the frequency components can be investigated by means of a Fourier decomposition of the traveling magnetic force. To reduce the vibration level, it is desirable to reduce both the number of frequency components of the magnetic force and their amplitudes. In this current research, it is demonstrated that vibration levels may be significantly attenuated, without changing the performance of the motor, by a change of the magnet geometry and an increase of the magnetic energy product near pole transitions.