Effect of air gap eccentricity on rotor eddy current loss in high speed PMSM used in FESS

This paper investigates the effect of eccentric rotor on the eddy losses in high speed external rotor PMSM, which is used in Flywheel Energy Storage System (FESS). Analytical expressions for the no-load magnetic field distribution with static and dynamic rotor eccentricities are presented. The relationship between additional eddy loss and eccentricity ratio is given. Then the finite element simulations are used to analyze the rotor loss and the eddy current distribution respectively due to different types of eccentricity (static and dynamic eccentricity) and eccentric angles. It is showed that static eccentricity makes rotor eddy loss multiply increase and dynamic eccentricity at a specific angle will cause the eddy current loss concentrated in certain magnet.