Equivalent Circuit of Stator Coil End of Inverter-Fed High-Voltage Electrical Machine

We have been developing insulation design techniques based on an equivalent circuit for the stator coil end of inverter-fed electrical machines. The electric field at high frequencies of inverter voltage was calculated by the finite element method. By the calculation, the increase of electric stress at the end of a corona protection shield and the movement of the area where the electric stress is at its maximum from the end of the corona protection shield to the stator core end was confirmed. To reproduce the above-mentioned phenomena, we have proposed an equivalent circuit by applying additional modeling of cover insulation, the corona protection shield and 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%.