Brushless DC multiphase reluctance machines and drives

Abstract

In an yet another effort to produce better PM-less, rotor-winding-less, brushless electric motor drives, this thesis reports on design, optimization, numerical analysis and control of a multiphase, high saliency rotor, dual-flattop alternative current control BLDC reluctance machine drives. The aim is to produce high torque density, low loss / torque in a PM-less, rotor winding-less machine by full usage of machine windings and core and of inverter kVA. A new derivation of the principle of operation, essential rotary and linear machine topologies and a 2D FEM analysis for torque density and torque pulsations on the designed prototypes are made available and show promising results. Advanced iron loss computation by FEA indicates moderate core loss, although high air-gap magnetic flux density and current harmonics occurs as a natural behavior of a BLDC machine. Experimental flux-decay and run-out tests results are presented, which, together with standstill torque measurements, validate the FE design. An optimal design code for an automotive application was developed based on particle swarm optimization and magnetic equivalent circuit for performance evaluation. Electrical and mechanical parameter identification is followed by BLDCMRM mathematical model and control strategy development. Running experiments (motoring and generating) with speed reversal and field weakening modes (thus 4-quadrant operation) is also shown on two different test-rigs, one for the 5 phase BLDC-MRM (supplied by a full bridge inverter) and one for the 6 phase BLDC-MRM (working with a reduced number of switches).