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The HB (Haydock Brown) machine combines permanent magnet and wound coil excitation to provide a single-stage brushless alternator. It offers efficient and compact solutions for small-scale engine-driven generator requirements. The simple construction conceals a rather unusual magnetic circuit that displays complex interactions between excitation sources in the presence of saturation and leakage fields. The paper describes the machine's 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 is demonstrated.