Analysis of Overhang Effect for a Surface-Mounted Permanent Magnet Machine Using a Lumped Magnetic Circuit Model

This paper presents a magnetic field analysis of a surface-mounted permanent magnet machine with an overhang structure wherein the rotor axial length exceeds that of the stator. A 2-D analytic method using a lumped magnetic circuit model (LMCM) is proposed for more rapid computation of the overhang effect compared with a conventional 3-D or quasi-3-D finite element analysis (FEA). In the LMCM, the effective overhang length is calculated, and a leakage flux generated in the overhang region is estimated. The accuracy and usefulness of the proposed analytic method is confirmed through the 3-D FEA and the experimental results according to the diverse overhang length, the number of slot/pole, and stator core length.