Design of slotless TORUS generators with reduced voltage regulation

The slotless toroidal-stator permanent-magnet machine ´TORUS´ can be integrated with an engine to form a compact generating set, but the terminal voltage naturally reduces on load because the armature reaction MMF leads to reduced flux. However, if a stator core of reduced thickness is used, heavy saturation takes place on no-load so that, on load, the armature reaction MMF simply reduces the degree of saturation. The stator coils may then link the same rotating flux whether current is drawn or not, with the terminal voltage without being greatly affected by armature reaction. The design and analysis of the resulting machine with reduced voltage regulation are presented with supporting test results taken from two prototype machines.