Performance analysis of a diesel engine driven brushless alternator with combined AC and thyristor fed DC loads through PSPICE

A brushless alternator with damper windings in the main alternator and with combined AC and thyristor fed DC loads has been handled ab initio as a total modelling and simulation problem for which a complete steady state performance prediction algorithm has been developed through proper application of Park´s equivalent circuit approach individually to the main and exciter alternator units of the brushless alternator. Details of the problems faced during implementation of this algorithm through PSPICE for the case of a specific 125 kVA brushless alternator as well as methods adopted for successfully overcoming the same have then been presented. Finally a comparison of the predicted performance with those obtained experimentally for this 125 kVA unit has also been provided for the cases of both thyristor fed DC load alone as well as combined AC and thyristor fed DC loads. To enable proper calculation of derating factors to be used in the design of such brushless alternators, the simulation results then include harmonic analysis of the alternator output voltage and current waveforms at the point of common connection of the AC and thyristor fed DC load, damper winding currents, main alternator field winding current, exciter alternator armature voltage and the alternator developed torque and torque angle pulsations