Critical Criteria for Successful Synchronization of Line-Start IPM Motors

In this paper, the critical criteria for successful synchronization of line-start interior permanent magnet (IPM) motors are studied for different loading conditions. An approximate solution technique based on average torque analysis is developed for determining the critical slip and the critical inertia of a line-start IPM motor for steady state and dynamic high inertial loads. Transient analysis of a 1-hp three-phase four-pole line-start IPM motor is conducted to determine the accuracy of the proposed criteria. Experimental investigations are carried out for the same 1-hp laboratory IPM motor. Analytical, simulation, and test results are presented. There is close agreement between analytical, simulation, and experimental results, which validates the accuracy of the proposed criteria.