Brushless DC motor with airgap windings-influence of back iron material on motor efficiency

In applications using batteries as a power source, the focus is on high efficiency for the electromechanical energy converters. A disc-type motor is developed using permanent magnets for the rotor and an airgap winding for the stator. According to the type of control, this device will operate as a synchronous motor or a brushless DC motor. The backiron design also contributes to the envisaged low losses. The field and the losses are analytically calculated and compared with experimental values