Electromagnetic performance of interior permanent magnet machines with eccentricity

This paper comparatively investigates the electromagnetic performance, such as airgap flux density, flux linkage, radial stress, back-EMF and output torque of two rotational symmetrical and asymmetric interior permanent magnet BLDC and BLAC machines having static/rotating eccentricities by FE model and a simple analytical model. It shows that the static/rotating eccentricities hardly affect the back-EMF and output torque of symmetrical machine, although they significantly change its airgap flux density and radial stress. On the contrary, both eccentricities can significantly distort the back-EMF and output torque of asymmetric machines. Asymmetric machines can have larger torque ripple with eccentricity than symmetrical machines, although asymmetric machines produce smoother torque without eccentricity. The static and rotating eccentricities result in many different orders of the back-EMF and torque components.