Effect of rotor eccentricity on electric parameters in a PM brushless motor with parallel winding connections

In this paper, the parallel winding of a 20-pole, 18-slot permanent magnet (PM) brushless motor with common and uncommon neutral points is used to investigate static rotor eccentricity effects. Static rotor eccentricity will cause an imbalance of the back-EMF in each parallel winding and may result in high torque ripple. However, as the common neutral point is applied, it can be observed that the back-EMF becomes balanced and may reduce torque ripple. Moreover, the winding current and inductance in the eccentric motor with a common neutral point are also discussed. This paper provides motor designers with analyses of the relationship between static rotor eccentricity and electric motor parameters, such as back-EMF, winding current, and incremental inductances. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3076420]