Influence of Thermal Aging on the Winding Thermal Conductivity in Low Voltage Electrical Machines

It is widely acknowledged that thermal aging can have a detrimental effect on the reliability and lifetime expectancy of electrical machines. Long exposure times to high temperature can deteriorate the dielectric properties of the electrical insulation system. At the same time, high temperature can strongly affect thermo-physical properties of polymeric materials, which are commonly employed for the insulation system of low voltage motors. This work experimentally investigates what is the effect of thermal aging on the winding equivalent thermal conductivity in low voltage electrical machines. The life results of accelerated thermal aging tests, carried out on suitable specimens, are processed through a Weibull-Bayesian approach. The variation of the equivalent winding thermal conductivity with thermal aging is ultimately correlated to the cumulative thermal aging of the insulation system.