Comparison of analytical models for predicting electromagnetic performance in surface-mounted permanent magnet machines

The paper compares four analytical models, viz. relative permeance (RP), complex permeance (CP), subdomain (SD) based on single slot/pole and exact SD, for predicting electromagnetic performance of surface-mounted permanent magnet brushless machines. The RP model is simple, takes less computational time for predicting electromagnetic torque although modification is often required to account for fringing effect. All analytical models predict the back-EMF and electromagnetic torque with high accuracy. The error in flux density associated with the CP model has less influence on electromagnetic torque but results in large error in cogging torque. As for the torque ripple excluding cogging torque, both SD models have similar waveforms and tend to underestimate, while RP and CP models tend to overestimate. Overall the SD models are most accurate for predicting the electromagnetic performance although much time consuming for computation.