Circuit and apparatus for improving operating features characteristics of DC power supplies implementing three Phase transformer devices of the type such as 12-step and 24-step transformers. The circuit and apparatus reduces harmonic AC input current while providing almost unity power factor for DC power supply outputs intended for aircraft or marine applications where size and weight are concerns. The circuit includes a passive series connected nonlinear resonant LC circuit connected at each phase of the input to the three phase transformer With the three phase transformer having the added series nonlinear resonant LC circuit, the power supply is enhanced with current limiting for the entire transformer, rectifier and load, due to load shorting, input voltage transients, transformer winding short circuit or rectifier failure. Further, such apparatus provides limiting of power inrush currents during voltage application or turn on, while also providing EMI filtering.
