Design and Test of a 35-kJ/s high-voltage capacitor charger based on a delta-connected three-phase resonant converter

This paper describes the design, implementation, and analysis of a 35 kJ/s high-voltage capacitor charger based on a delta-connected three-phase series resonant converter that provides a constant charging current with high efficiency and high-power density. In order to obtain the maximum output power for various charging voltages, each high-voltage transformer supplied by a delta-connected resonant inverter is designed with two secondary windings and voltage-doubled rectifiers. This configuration allows not only a flexible output current and voltage with fixed output power but also a high power factor on the input side. On the basis of the analysis of the series-loaded resonant converter operating at a discontinuous conduction mode, the details of the design procedure for the resonant inverter are provided. Furthermore, the implementation of the high-voltage transformers and rectifiers is also explained while considering insulation and compactness. Experiments were carried out on the developed charger with different types of capacitors, depending on their applications, and the results are discussed. In addition, malfunctioning tests were conducted for the open, short, and misfiring during charging conditions. Finally, the developed high-voltage capacitor charger was shown to be very reliable, even under faulty operating conditions in the system.