Voltage Distortion in Fractional Slot Concentrated Winding IPM Machines during Field Weakening

Interior Permanent Magnet machines are widely used in electric traction applications due to advantages such as high torque density, wide constant power, and field weakening region. Fractional slot concentrated winding is preferred for its short end winding and compact construction. Voltage distortion is observed during field weakening which qualitatively affects the generated output power. It is desirable to achieve low voltage distortion for better performance. In this work, the impact of rotor topology on voltage distortion is studied. Three outer rotor topologies, V-shape, Spoke and Flat type are considered to analyze the impact of rotor design on voltage distortion. All the key terminal parameters and excitation are maintained same in all machines. It is observed that V-shape rotor topology showed the least distortion. Design guidelines derived from the results are presented for rotor design.