Design Improvement of a Line-Start Ferrite-Assisted Synchronous Reluctance Motor

This paper presents the systematic attempts made to improve the performance of an existing optimized Line-start ferrite magnet-assisted synchronous reluctance motor (called the “base model” henceforth in this paper) designed for water pumping applications. The improvement is achieved by reducing the thickness of the tangential ribs and eliminating the radial ribs altogether from the rotor structure. Structural and electromagnetic study of the machine model is carried out using finite element analysis. The modified motor demonstrates an improved power factor and higher torque capability for the same electric loading. It also has better synchronization capability and can synchronize at its rated load at 74% of rated voltage. Using this improved rotor structure, an additional study is conducted to identify the role of rotor cage bars in preventing demagnetization of permanent magnets of the rotor during starting. It is found that the cage bars adjacent to the magnets are responsible for protecting them from demagnetization during starting.