Vibration of Permanent Magnet Brushless Machines Having a Fractional Number of Slots per Pole

In this paper, a method for predicting the electromagnetic vibration of PM brushless motors is presented. It calculates the electromagnetic force on individual stator teeth by the Maxwell stress method, based on 2-D finite element analysis of the electromagnetic field. The resulting radial force contour is then used in an analytical shell model to predict the stator vibration. The method has been validated experimentally and used to predict the vibration of various PM brushless motors with different fractional slot/pole number combinations, such as 9/6, 12/8, 15/10, 12/10, 18/6, etc., on both no load and on load.