Corona free winding in electrical machines

Corona or partial discharge is one of the parameters that dictate the reliability of the rotating machines. The corona formation is directly associated with the fill factor and hence winding cross section. In the present work, a systematic study is been made to reveal the location of corona formation in different winding cross sections (tetragonal and triangular packing). Acute angle formation at the wire interface is found to be the cause for corona inception. Compaction of winding is found to eliminate the corona location through hexagonal packing. An electrostatic FEM analysis revealed that the electric stress in hexagonal packing is very low compared to the conventional cross-sections, indicating that the former is a corona free winding configuration.