Practical Optimum Design Based on Magnetic Balance and Copper Loss Minimization for a Single-Phase Line Start PM Motor

This paper introduces the condition of balanced operation to solve problems caused by an unbalanced magnetic field when a single-phase line start permanent magnet motor operates in steady-state. Using an equivalent circuit on the basis of symmetric field theory, conditions are found for balanced operation at rated conditions and for copper loss minimization in the stator. The initial model is modified applying these two conditions from commercial model. In addition, an optimum design is implemented in order to improve starting characteristic. In an optimum design process, the sampling points are chosen by latin hypercube sampling and from the results, an approximation model is made by the radial basis function. Then the optimization results are obtained by a genetic algorithm. The validity of the proposed design is verified by confirming the efficiency, torque ripple, ohmic loss of the rotor, and starting characteristic through time step FE-analysis and experimental results.