Is thermo-bonded coils a good solution for electric machines fed by fast PWM inverters?

This paper discuss about the advantages of thermo-bonded coils in rotating machines fed by PWM inverters, relatively to the classical impregnation methods, for aircraft applications. Measurements made on three stators built with different technologies show that thermo-bonding methods give higher Partial Discharge Inception Voltages (PDIV) for the turn-to-turn insulation. A simple Finite Element model of the insulation of two adjacent enameled wires associated with the Paschen law explains the physical causes to these advantages. The model proposes also a method for evaluating the effect of the bonding layer thickness.