Optimal Pole-Shaping in Surface-Mounted PM Machines using Analytical Modeling: Cogging Torque and Flux Density Harmonics

Document Type : Original Article

Abstract

An analytical model for prediction of air gap flux density and cogging torque in slotted Surface PM (SPM) ma-
chines have been presented. Cogging torque has been calculated by integrating the Maxwell stress tensor inside the
air gap. Two different magnetization patterns (radial and para llel) have been considered and their results have been
compared with each other.  The obtained model has been verified with Finite Element Analysis (FEA). Using the pro-
posed model, the cogging torque and low-order harmonics of the magnetic flux density have been optimized. The cog-
ging torque and air-gap flux density THD are very sensitive to the pole-shaping, thus changing the pole-shaping opti-
mization can be obtained. Three methods (optimal pole-arc , magnet pole-shifting and mixed materials) have been used
to design pole-shaping in SPM machines. A weighted normalizing method has been applied with direct search method
to find the optimum solution. Finally, the validity of the proposed model and the obtained results has been verified
with FEA .

Keywords


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