Analytical Modeling and Optimization of a Permanent Magnet Machine With Two-Segment Bread-Loaf Magnets

An analytical technique has been presented for predicting and optimizing the air-gap magnetic field in brushless surface-mounted permanent magnet (PM) machines with proposed two-segment bread-loaf magnets. The equivalently arc-shaped pieced magnets have been modeled and the subdomain model equations have been analytically solved. According to superposition principle, the air-gap magnetic field can be obtained. In addition, the presented analytical technique can also predict the induced back-electromotive force (EMF) and the electromagnetic torque. For the maximal air-gap flux density and electromagnetic torque, the optimum magnetization angle has been analytically derived. The analytical results show that the torque ripple can be significantly reduced for the proposed optimized two-segment bread-loaf magnets compared with the conventional parallel magnetized magnets with equal magnet usage. Predicted results have been validated by finite-element analysis (FEA) for a 6-slot/4-pole PM machine.