A self-starting, axial-gap permanent magnet motor and adjustable-speed drive

A 30-hp, 15,000-4/min, axial-gap permanent magnet motor and adjustable-speed drive have been designed, constructed, and tested. The direct-drive motor has 72 slots and uses a full-pitch winding. The rotor consists of eight 2.8 inch diameter NdFeB magnets which provide for high air-gap flux densities over a large range. The drive system provides for optimum motor efficiency at all speeds and loads by locking the Hall probe signal to the bridge inverter by a phase-locked loop. Dynamometer measurements have confirmed the equivalent circuit development using a cylindrical rotor model when saliency effects may be neglected