An electric charging system for a vessel, vehicle, or aircraft includes one or more energy storage modules on the vessel, vehicle, or aircraft; a pulse rectifier; a converter; and a voltage control transformer. The one or more energy storage modules are connected to outputs of the pulse rectifier. The voltage control transformer is connected to inputs of the pulse rectifier. The voltage control transformer includes a serial transformer having a plurality of pairs of transformer windings, connected together in series, one winding of each pair being adapted to be connected between the pulse rectifier and an input from an energy source and the other winding is connected to the converter.