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Description
Design, implementation and experimental results of a 3-phase series-parallel resonant type high voltage capacitor charger which is operating as a constant current source at a specific switching frequency are described. The operating principle of the capacitor charger as the variation of an input-to-output voltage gain is explained. Several current gain curves as the variation of series-parallel capacitiance (k) and normalized switching frequency using an AC analysis method are derived and are used to decide an optimal resonant tank parameter to minimize the power density of the capacitor charger. A 12 kV, 24 kJ/s prototype charger of which three single-phase high-frequency transformers are wye-connected in primary side and three voltage doubler rectifiers are connected in series in secondary side is implemented. The measurement results about the efficiency and power factor of the implemented capacitor charger as the variation of the charging power by the resistive load are described. The basic charging performance of implemented capacitor charger is verified by the capacitor charging experiment using 600 kJ, 10 kV, and 12 mF capacitor bank. The reliability of the capacitor charger in the malfuction of the load side is verified by the experiments concerning misfiring of the discharge switch and shorting of the output terminal during the charging operation. The implemented 3-phase capacitor charger's electrical characteristics are additionally compared with those of a single-phase capacitor charger of the same size.
