PDIV Modeling for Rectangular Wire Turn-to-Turn Insulation of Inverter Fed Motors Through Thermal Aging

This contribution develops the partial discharge inception voltage (PDIV)-finite-element method (FEM)-based model based on Schumann’s streamer inception criterion (SCSIC) with respect to thermal aging time (TAGT) or the insulation lifetime for the turn-to-turn insulation of coil winding made by rectangular insulated wires. The accelerated thermal aging is performed at 250 °C, which is 50 °C higher than the thermal class, with aging intervals of 156 and 312 h. PDIV measurements are conducted at a constant temperature of 25 °C, 40% relative humidity, and atmospheric pressure (1013 mbar). The measurements are done under ac 50-Hz excitations, following IEC 60034-18-41 guidelines for inverter fed motor insulation system qualification. Furthermore, this study analyzes streamer inception parameters such as critical field line length (CFLL), effective ionization coefficient ( $\alpha _{\text {eff}}{)}$ , partial discharge (PD) inception field ( ${E}_{\text {discharge}}{)}$ , firing voltage ( ${V}_{\text {firing}}{)}$ , and its correlation with PD charge amplitude as a function of TAGT or the insulation lifetime.