Analytical Expression for Discharge Process of Multiphase Air-Core Pulsed Alternators

Multiphase pulsed alternators use a thyristor converter to generate the direct current to power railguns. The desired current shape can be obtained by adjusting firing angles of thyristor. The discharge process of multiphase pulsed alternators is complicated due to a special air-core topology and the interactions between multiple current pulses, so the appropriate selection of firing angles only is obtained using a cut and try method within a system simulator. To quickly get the appropriate firing angle, this paper analyzes the discharge process of multiphase pulsed alternators. The calculations of the short-circuit current and transient parameters are obtained based on the classical theory of short circuit. Two types of interactions among multiple current pulses are revealed by theoretical deduction. A formula of peak current, relating to firing angles, is obtained. A finite-element method is used to verify the theoretical analysis. The results of those two methods are close and errors are acceptable. Therefore, the analysis of discharge process is valid. The analytical expression of discharge process can provide the theoretical guides for the selection of firing angles and current waveform control in the future.