Investigation into a class of brushless DC motor with quasisquare voltages and currents

The results of an investigation into brushless DC drives with quasi-square wave voltage and current waveforms are presented. Practical results are used to check the validity of a time stepping analysis for the prediction of instantaneous currents and torque. The analysis is then used as a design aid in drawing up designs of brushless DC motor incorporating ‘square-wave’ features. The influences of phase number and inverter switching instants on performance are examined. Optimised designs for motors incorporating two types of permanent-magnet materials, ferrite and iron/rare-earth, are included.