Analysis of flux leakage in a brushless permanent-magnet motor with embedded magnets

This paper analyzes the magnetic characteristics of brushless permanent-magnet motors with embedded magnets. It shows that the flux leakage has a substantial effect on the air gap flux density interacting directly with the armature current to produce torque. The flux leakage parameters η and λ are expressed analytically in terms of the magnetic material properties and the motor dimensions. They are essential quantities for the accurate prediction of the average flux densities within the air gap and the magnet. The finite element numerical method is adopted to verify the analytical model. For the numerical example in this paper, the average deviation between the finite element result and the analytical one is about 1-2%. This finding confirms the suitability of the analytical model for the design purpose. Although design is not particularly emphasized in this paper, one section gives a simple explanation of flux leakage considerations in magnet design