Analytical methods for the radial electromagnetic vibration of stator in permanent magnet motors with an amorphous alloy core

Abstract

The urgent demand for high efficiency of electrical machines leads to the preliminary application of amorphous alloy, however the accompanying vibration problem becomes more complex. The radial electromagnetic vibration of the amorphous stator core in a permanent magnet motor is analytically investigated in this paper. The magnetic field distribution approach considering the slotted effects and eccentricity is proposed and the air-gap magnetic flux density is validated by the finite element method. The magnetization and magnetostriction characteristics of the amorphous alloy are obtained. The dynamic models for the stator core including yoke sections and the tooth-yoke sections are respectively established. The Maxwell stress and magnetostriction stress are integrated in the magneto-mechanical coupling model. Dynamic responses in the stator core for different radii, position angles and times are analyzed. Vibrations of conventional core with silicon steel and amorphous core are compared. The spatial and temporal characteristics of the dynamic responses in the stator core are explored. The origins and corresponding weights in the electromagnetic vibration at different rotating speeds are revealed. Experiments of a modified permanent magnet motor equipped with the amorphous core are conducted. The theoretical results are validated well by experiments. Results demonstrate that the vibration level of the amorphous core is larger than the silicon steel core when other conditions are the same. Radial vibrations of the stator core are caused by the Maxwell stress, magnetostriction stress and their interaction effects. The weight of magnetostriction effects is improved with the increasing rotating speed. These findings provide an insight into the mechanism of electromagnetic vibration in amorphous stator core and can be helpful for the design of high-efficiency electrical machines.