Suppression of an Electric Field and a Local Heat Generation With the Equivalent Circuit of Stator Coil End of an Inverter-Fed High-Voltage Electrical Machine

We have been developing the insulation design techniques based on an equivalent circuit to predict the voltage distribution of the stator coil end of high-voltage inverter-fed electrical machines. A new equivalent circuit was proposed by an additional modeling of cover insulation, the corona protection shield, and the measurement circuits to the conventional equivalent circuit for mains-fed electrical machines. The applicability of our proposed equivalent circuit was verified experimentally and it was confirmed that simulation results of voltage distribution agreed with experiment results with uncertainty of less than 10%. Furthermore, in order to suppress the insulation degradation caused by inverter surge, sensitive parameters to reduce electric field concentration and local heat generation were explored. The capacitance of insulation layer affects both electric field and local heat generation, and those effects are reduced by 17% and 9% by halving the capacitance.