Improved determination of Floquet´s reference frame for the phase-to-ground short circuit of a nonsalient-pole damped alternator

The unsymmetrical short-circuit operation of a nonsalientpole alternator with dampers is described by four linear periodic coefficient equations. All periodic terms are at fundamental frequency. The equations are solved by indirect use of Floquet\´s theorem, allowing the time constants to be determined first. This determination is based on the fact that there exist recurrent relations for the current\´s harmonics, and it is shown in the paper that convergence of these recurrent relations for can be ensured only if the time constants fulfill a relationship which is one of the findings of the paper. Then, it is shown that a knowledge of the time constants and of the above-mentioned recurrent relations yields a convenient Floquet reference frame. Eventually there is no more difficulty to completely determine the currents from the initial conditions. A complete numerical example has been treated and the results of the present method tally with those yielded by a classical Runge-Kutta method.