Effect of the Main-to-Auxiliary Winding Turn Ratio in Single-Phase Dual-Pole Line Start Permanent Magnet Synchronous Motor

This paper investigates the impact of the main-to-auxiliary winding turn ratio on the transient starting and steady state operation of single-phase pole-changing line-start permanent magnet motor. For this purpose, the turn ratio of the auxiliary winding to the main winding is selected as the main design parameter and properly adjusted to eliminate the negative sequence induction torque component. It is revealed that the turn ratio highly affects the startup process of the motor, and that the best startup characteristics are obtained at the turn ratio corresponding to balanced operation point, (equivalent to the condition that negative sequence excitation current is brought to zero). Additionally, it is revealed that the balanced operation may not necessarily result in the most optimal steady state operation, meaning that the turn ratio corresponding to optimal transient operation maybe different than that to the steady state operation.