Effect of Stress Grading Tape Conductivity on the Electric Field Distribution in Stress Grading System of an Inverter-Fed Rotating Machine

Evaluating the performance of the stress grading system by simulating the electric field and potential distributions in the overhang region shows that high conductive stress grading tape (SGT) reduces the maximum electric field at this region. For simulation studies, an accurate conductivity that takes into account the effects of vacuum pressure impregnation (VPI) process, temperature, and tape builds is measured. As the electric field on the SGT is enhanced under operating conditions, the conductivity of the SGT has been measured in a high electrical field condition under pulse conditions to minimize the effects of temperature rise on the SGT. The conductivity of a one half-lap layer and a double half-lap layer of SGT at different temperatures is measured. The results show that for both designs, the higher the tape conductivity the lower the maximum electric field in the SGT region. For evaluating the simulation model, the temperature profile along the stress grading system is measured and simulated under high frequency sinusoidal voltage.