Equivalent Circuit Simulation of Stator Coil End of High-Voltage Electrical Machine at High dV/dt

We have been developing 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 applying additional modeling of cover insulation, the corona protection shield, and measurement circuits to the conventional equivalent circuit for mains-fed electrical machines. The proposed equivalent circuit was used to simulate voltage distribution at dV/dt of inverter surge equal to 5 and 11.5 kV/mu s, and its applicability was confirmed by experiment results. From the comparison of these simulation results, less voltage drop at the end of the corona protection shield was observed when the dV/dt was 11.5 kV/mu s. This voltage drop at the end of the corona protection shield causes voltage drop at the end of stator core.