Introduction to a novel axial flux PM synchronous machine with excitation control

The ´HB machine´ combines permanent magnet and wound coil excitation to provide a single-stage synchronous machine with excitation control. For small-scale engine-driven generator applications it offers an efficient and compact solution. The simple construction conceals a rather unusual magnetic circuit that displays complex interactions between excitation sources in the presence of saturation and leakage fields. This paper describes the machines configuration and operation. A design procedure based on a lumped-parameter magnetic equivalent circuit model is introduced and a full-scale prototype with a nominal rating of 6 kVA demonstrated.