Brushless and self-excited 3-phase synchronous machine

The paper describes a brushless and self-excited synchronous machine, which uses current compounding in auxiliary stator and rotor windings to produce an excitation current which increases as the load current is increased. With the machine used as an isolated alternator, the effect is sensitive to the power factor of the load, and the increase in excitation current is greater as the load becomes more inductive. The constancy with which the terminal voltage of an experimental machine is controlled as the load varies is comparable with that obtained with typical static current-compounded excitation schemes, and a feature of the new scheme is the very rapid recovery of the terminal voltage following a sudden increase in load. As with static schemes, the new system is readily adapted to control either the power factor or the reactive power of the input to the machine, operated as a synchronous motor on an infinite busbar. Results obtained from the experimental machine again indicate an accurate control, from no load to well beyond full load.