Fine grain commutation: Integrated design of permanent-magnet synchronous machine drives with highest torque density

Permanent-magnet synchronous machine (PMSM) design is limited by peak magnetic flux due to material saturation or available permanent magnet remanence, RMS current due to losses and speed due to centrifugal forces. This paper describes the theoretical limit of torque density in a surface-mounted PMSM given these constraints and a means to approach it. It also explains an integrated methodology to design the high torque density motor in which each slot pair of the machine has individually controlled currents. Recent advances in device technology making power transistors faster, smaller and lighter will be the key enabler of such fine grained commutation. The integrated motor drives, apart from being compact, will eliminate separate heat sinks for inverter and motor.