Investigation on Parameters Influencing Turn-to-Turn Insulation Stress of Form-Wound Medium-Voltage Induction Machines

In this paper the influence of the voltage step on the turn-to-turn insulation is investigated when using silicon carbide (SiC)-MOSFET. As already known, the steep voltage gradient dv/dt by using of the modern inverter semiconductor devices leads to additional stress on the stator winding insulation system, especially the turn-to-turn insulation. The transient voltage distribution within the stator winding is measured to determine maximum stress on turn-to-turn insulation. Changing the values and distribution of the inter-turn capacitances it is possible to identify the influence of this parameter on the turn-to-turn insulation stress. Using the measurement results it is possible to define a maximum allowable voltage gradient in order to keep the turn-to-turn insulation within its specified safe operating range.