Thermal Life Prediction of High Temperature Polyimide and PEEK Insulated Wires for Use in Low Voltage Electric Motors

This paper evaluates the life of two high temperature wires i.e., Polyimide/Polyamide-imide (Enduro Temp 260+) and Polyether-ether-ketone (PEEK), targeted for low voltage electrical machines where thermal stress is mostly dominant. Insulation life is predicted by using accelerated aging tests where thermal stress is applied above the thermal index of the wire defined by the manufacturer, for at least three thermal exposures. Time-to-Failure is determined for all the specimens under test via "AC Hipot Test". The failure data is collected and post-processed with the help of "Weibull Probability Distribution" to determine the mean lifetime which is compared against the life defined by the wire supplier in the technical datasheet. Moreover, the influence of thermal aging is also investigated by measuring the dissipation factor and insulation capacitance of the aged and unaged specimens. It has been investigated that, with help of diagnostic properties, the influence of thermal aging on PEEK insulated wire is comparatively more than Enduro Temp wire thus the rate at which PEEK wire delaminates is faster than Enduro Temp. In addition, the relative thermal index (RTI) for both Enduro Temp and PEEK wires is determined as 245°C and 250°C which when compared against the manufacturer RTI, results in a life reduction of 72.1% and 49.2% respectively.