Design Analysis of Line Start Synchronous Motor with Salient Poles for Efficiency Improvement

Line-start synchronous motors (LSSMs) have emerged as a promising alternative to induction motors in response to increasingly stringent energy-efficiency requirements. However, the salient-pole permanent-magnet rotor topology has been comparatively less studied than other LSSM rotor configurations, particularly with respect to the influence of its design parameters on motor efficiency and dynamic performance. Initially, the effects of the number of rotor bars and the dimensions of the squirrel-cage winding on motor performance are investigated, and the optimal configuration with respect to starting torque and synchronization capability is selected. The chosen design is then subjected to efficiency optimization by varying four design parameters. An optimetric analysis is employed to evaluate numerous parameter combinations under predefined operating conditions, generating a wide range of motor models. The configuration achieving the highest efficiency is subsequently identified and selected. In addition, the optimization with same design parameters is carried out using Genetic Algorithms (GA), confirming the results obtained through the optimetric analysis. The transient responses of speed, torque, and current are subsequently investigated for both the initial and optimized motor model. The analysis provides insight into the effects of the optimization process on motor starting performance, synchronization capability and steady-state operation enabling appropriate conclusions to be drawn.