Computer simulation of three-phase prestriking transients in cable-connected motor systems

Steep-fronted voltage transients, generated by prestriking conditions in circuit breakers and contactors when closing, produce severe interturn insulation stresses in machine windings. A computer program simulating the production of prestriking transients is described. The simulation is based on a full three-phase system representation, including busbars, switching device, cable and motor winding. The complex interaction between the system and the switching device, and also the interaction between the three poles of the switching device, are fully taken into account. A solution method based on the Fourier transform and using a combination of voltage and current generators to simulate switching actions is used in the calculations. Validation of the accuracy of the simulation is made by a comparison of on-site test results with the computer simulation