FEM based design of third harmonic excitation system for Low voltage salient pole synchronous generators

The synchronous generators for standalone industrial applications with full pitched windings have high harmonic content across line and neutral due to triplen harmonics and single phase loads connected across such machines are adversely affected. To circumvent this problem, conventionally the main winding is wound for 2/3^rd pitch which introduces complexity in winding, reduced KVA and hence results in increased cost. These disadvantages are overcome by inserting a third harmonic excitation winding into the stator slots along with full pitched main winding to generate excitation power for the alternator by utilizing third harmonic flux in the air gap under loaded conditions. The design of the third harmonic excitation winding is done by finite element method and simulation results show that by adopting third harmonic excitation system, triplen harmonics in the output voltage are significantly reduced. Experiments conducted on a prototype machine validate the simulation results.