Direct Simulation of AC Machinery Including Third-Harmonic Effcts

A method is described for simulating noncommutating electrical rotating machinery. The method is based on the expression of actual coil voltages and currents directly as contrasted with methods in which these coordinates are transformed along special axes. The voltage equations are integrated before computer simulation. This means that voltage inputs to the computer become integrated voltage inputs. Effectiveness of the method is demonstrated by simulating an electromagnetically balanced two-phase induction machine with input voltages of different frequencies. The simple addition of dc input to a rotor coil makes a synchronous machine simulation, which is illustrated for transient starting and short-circuit conditions. The straightforward representation of space MMF harmonics is demonstrated by the addition of a third harmonic of space distribution to the basic simulation. The method should be desirable for analysis of inverter or cycloconverter systems. It can be easily extended to unsymmetrical machines, and there are no restrictions against unsymmetrical inputs, as is amply illustrated by the results obtained with such extreme dissymmetry as inputs of different frequencies.