Life Characterisation of PEEK and Nanofilled Enamel Insulated Wires under Thermal Ageing

This paper characterizes and develops life models for two different wire insulating materials: Poly-ether-ketone and nanofilled enamel (Allotherm wire). The article focuses on predicting the lifespan of PEEK and Allotherm wire insulation materials, targeting low voltage electrical machines. The study investigates the effects of thermal ageing on factors such as dissipation factor, insulation capacitance, and partial discharge inception voltage (PDIV). Delamination of the insulation coating is observed in both wires during the ageing process, resulting in an increase in the differential dissipation factor and insulation capacitance. With respect to its unaged condition, Allotherm wire exhibits faster degradation, showing 2.4- and 4.5-times higher changes in the differential dissipation factor and insulation capacitance respectively compared to PEEK wire after the 16th ageing cycle. In addition, Allotherm wire experiences faster deterioration of the PDIV, with a 42% reduction compared to 32% in PEEK after the same ageing cycle. Using a single-stress Arrhenius life model, the study estimates the relative thermal index (RTI) for both materials as 245°C for PEEK and 226.25°C for Allotherm wire. These results indicate a 72.1% decrease in the lifetime of PEEK and a 25.5% decrease in the lifetime of Allotherm wire when compared to the manufacturer’s RTI specification.