Simulation of fault performance of a diesel engine driven brushless alternator through PSPICE

Analysis of the fault performance of a brushless alternator with damper windings in the main alternator has been handled ab initio as a total modelling and simulation problem through proper application of Park's equivalent circuit approach individually to the main and exciter alternator units of the brushless alternator and the same has been implemented through PSPICE. The accuracy of the parameters used in the modelling and results obtained through PSPICE implementation are then evaluated for a specific 125 kVA brushless alternator in two stages as follows : First, by comparison of the predicted fault performance obtained from simulation of the 125 kVA main alternator alone treated as a conventional alternator with the results obtained through the use of closed form analytical expressions available in the literature for fault currents and torques in such conventional alternators. Secondly, by comparison of some of the simulation results with those obtained experimentally on the brushless alternator itself. To enable proper calculation of derating factors to be used in the design of such brushless alternators, simulation results then include harmonic analysis of the steady state fault currents and torques. Throughout these studies, the brushless alternator is treated to be on no load at the instant of occurrence of fault.