Optimized dielectric design of stator windings from medium voltage induction machines fed by fast front pulses

AC induction machines are exposed to fast-front pulses when fed from frequency converters. This type of excitation produces additional dielectric stress in the machine's insulation system which can result in premature deterioration or even failure. In this work, a non-uniform transmission line modeling approach is used in combination with FEM-based parameter computation to predict the transient voltage distribution in a machine winding under fast-front pulse excitation. Using this voltage distribution as input, different optimization algorithms are applied to identify and evaluate modifications to the winding design aimed at minimizing the dielectric stress. Test cases considering two different geometrical configurations show that the optimized designs considerably reduce the dielectric stress in the machine coils.