Evaluation of brushless permanent magnet motor rotor configurations for square wave current excitation

This paper evaluates different rotor configurations for 120 degree square wave current excited motor, or the trapezoidal back emf type permanent magnet (PM) motor. A two dimensional finite element analysis (FEA) method along with an averaging technique is used to evaluate the motor torque. The rotor structures considered here are rotors with various magnet arc widths (surface mounted magnets) and also rotors with various magnet arc widths with the interpolar region filled with soft magnetic material (inset magnet rotor). Three different rotor structures are fabricated and experimental results from the three motors are provided.