Low cogging torque PMSM drives with rectangular current control

Abstract

The present thesis investigates an interior permanent magnet synchronous motor with 8 rotor poles and nonuniform (6+6) stator slots and concentrated windings fed with trapezoidal currents. The electromagnetic design of the proposed solution was done algorithmically and it was validated using Finite Element Method (FEM). FEM-analysis offers direct results for torque, back-EMF and inductances. Whenever possible, FEM-calculated characteristics are compared with experimentally obtained ones, in order to validate the FEM-computations for this type of machine. The BLDC model developed in this thesis takes into account the phase commutation phenomenon, the real waveforms of back-EMF and inductances, based on FEM calculations. For the sensorless control of brushless DC PM motor drive, this thesis introduces and investigates a FEM assisted position and speed observer, based on the line-to-line PM flux linkage estimation. Even if the proposed observer relies on the fundamental model of the machine, a safe starting strategy under heavy load torque, called I-f control, is used, with seamless transition to the proposed sensorless control.