Insulation Technologies for State-of-the-Art Electrical Machines Used in Transport Electrification

This paper aims at presenting the technologies used in the electrical insulation of rotating machines dedicated to transport electrification. An analysis of the materials used in various insulation subsystems, the evaluations required for achieving a partial discharge-free design of hairpin machines, and the impact of cooling fluids will be discussed. The result presented here show that the most critical part is the phase-tophase insulation in the end-winding. The insulation thickness depends on the tolerances in conductor spacing. Cooling oil spayed on the end-windings can decrease the partial discharge inception voltage by about <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10-15 \%$</tex>. This factor should be considered in the design phase.