Investigation of Adhesion Properties Between Secondary Insulation and Taped Profiled High Frequency Litz Wires

Flat enameled or extruded copper wire windinggenerally known as hairpin windings - for electric motors have become widely established as a standard conductor topology for automotive applications. Previous research has revealed that, particularly in high frequency (HF) applications, flat copper wires can be at a disadvantage compared to profiled HF litz wires due to alternating current <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{AC})$</tex> losses exceeding the direct current (DC) losses. Studies on the electro-mechanical properties of various litz wire topologies have shown, that profiled litz wire taped with polyimide (PI) tape achieves a similar partial discharge and breakdown voltage level under corresponding mechanical load as insulated flat copper wires. Therefore, taped profiled litz wire are the most suitable litz wire topologies especially for high voltage (HV) applications. In order to enable a substitution of flat insulated copper wires by taped profiled litz wires, e.g., in HF applications, this paper investigates the adhesion of secondary insulations to the foil taping of the profiled litz wire which ensures a mechanical fixation against e.g., vibration during motor operation and compares them to those of state-of-the-art flat copper wire.