MAGNETIC CAPACITIVE CURRENT LIMIT CIRCUIT FOR TRANSFORMERS

摘要

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.

主权项

1. An AC to DC power supply comprising:
an n-step or pulsed power transformer rectifier configured to receive a 3-phase current from a connected 3-phase unregulated AC power source, said n-step or pulsed power transformer rectifier power supply having respective inputs associated with a respective phase, and said power supply including at least a primary transformer winding, and a Delta connected secondary transformer and a Wye connected secondary transformer, each Delta and Wye connected secondary transformer operatively coupled to said n-step or pulsed power transformer rectifier and having windings in parallel to provide a DC voltage; a passive circuit at each respective input of a respective phase, the passive circuit comprising a nonlinear resonant series connected LC circuit wherein L is inductor having an inductance and C is a capacitor having a capacitance, said inductance in combination with said capacitance of values reducing odd harmonic frequency current components from the line current drawn by said power supply in response to a load being placed on said AC to DC power supply, said inductance in combination with said capacitance having values that set said LC circuit near resonance and below the fundamental frequency of said 3-phase current; and wherein said power supply odd harmonic current components from the line current are reduced to less than approximately 2% cent of an uncorrected value to thereby reduce electromagnetic interference while achieving a power factor value of greater than about 0.98 at less than about 1% loss in line operating input voltage.