Transient Overvoltage Prediction of an Inverter-Fed Electric Machine

In contrast to supply from an AC source, supplying an electric machine through an inverter has the disadvantage that with each switching of the power semiconductors, the terminal voltage of the machine enters a transient state, surpassing the steady-state value. In addition, knowledge of the terminal voltage is crucial for calculating the electric stress on the insulation in an electric machine. Concerning these two aspects, precalculation of the terminal voltage of a machine fed by an inverter becomes important. In this paper, a method to calculate the terminal voltage based on geometric and material parameters is presented. The method requires electrical models of the inverter, the stator winding and the voltage source. The terminal voltage was calculated for the case of zero vector modulation. The results have shown that the inverter has an effect on the maximum value of the terminal voltage in the transient state, while the voltage source impedance and the cables influence the frequency of the voltage oscillation in the transient state and its damping.