Hybrid Excitation Method for Higher Pole Number Grid-Tie Synchronous Generators

In this paper, a hybrid excitation method is proposed and evaluated for classical rotor-excited higher pole number synchronous machines. The hybrid excitation is obtained by means of an integrated parallel hybrid-excited rotor using permanent magnets and field windings. Synchronous machines with both overlap and non-overlap stator windings are considered. The investigation is done by means of frozen permeability finite element analysis. It is explained that the method is applicable for synchronous machines with pole numbers of eight and higher. Detailed information is given of the variable-flux and number- of-parallel-circuit possibilities for a series of higher pole number synchronous machines. The results presented of a 15 kW, 48-pole synchronous machine prove that the method is excellently suited for grid-tie synchronous generators.