Time domain simulation of transients will generate waveforms for voltages and currents, from which the circuits can be characterised. Aspects of these include load cycle, harmonic spectrum, short circuit currents, etc.
These characteristics are then used to specify the equipment size (rating of componets, level of insulation, etc), to predict whether the equipment is compabible with the overall system that it is going to be connected into. AC side harmonic spectrum will help assess the harmonic distortion on the utility power grid, and DC side harmonic spectrum will help assess levels of interferences with signalling circuits.
Similarly, simulation of modern traction drives will also help design a better package for the train equipment.
For a technical paper on PSpice simulation of rectifier harmonic emissions and compatibility with signaling circuit, click here.
