Alternator short-circuit currents under unsymmetrical terminal conditions

IN A PREVIOUS PAPER¹ the solution for the ideal alternator under symmetrical terminal conditions was developed. In this paper the application of the equations developed in this previous paper are used, together with symmetrical components of currents, to obtain the solution of currents in the armature and field circuits of an alternator under unsymmetrical fault conditions. These equations and solutions are applied to a 3-phase alternator having a line-to-ground and a line-to-line fault condition, under various conditions. Oscillograms and calculated graphs are compared to check the method used in this solution, and excellent results are obtained. Due to the inclusion of resistance simultaneously in the armature and field circuits, the frequency of the harmonics in the circuits are seen to be somewhat different than usually given under less approximate assumptions. Also, the effect of resistance is more closely determined by this method of solution.