Method and apparatus for the protection of electrical equipment from high voltage transients

Claim 1

A unit for protecting electrical equipment against damage due to high voltage surges or transient components which periodically emanate from the power distribution system supplying the electrical equipment with operating current, said unit comprising: (a) a casing; (b) ground plate means for capping one end of said casing and for providing an electrical ground source; (c) elongated input conductor means mounted on but electrically insulated from said ground plate means for conducting operating current from the power distribution system to the interior of said casing; (d) output conductor means mounted on but electrically insulated from said ground plate means for conducting operating current from the interior of said casing to the electrical equipment; (e) spark gap means connected between said elongated input conductor means and said ground plate means for dissipating the energy in high voltage transient components emanating from the power distribution system with voltages greater than a predetermined firing voltage; (f) variable resistor means connected between said output conductor means and said ground plate means for dissipating the energy in high voltage transient components emanating from the power distribution system with voltages below said predetermined firing voltage and above a predetermined minimum voltage; and (g) filter means for conducting operating current between said elongated input conductor means and said output conductor means while providing a time delay sufficient for enabling said spark gap means to dissipate the energy in high voltage transient components having voltages greater than said predetermined firing voltage before the high voltage transient components having voltages greater than said predetermined firing voltage reach the electrical equipment, said filter means including: (1) an inductor winding connected between said elongated input conductor means and said output conductor means, (2) a capacitor connected between said output conductor means and said ground plate means, and (3) a winding former means mounted in the interior of said casing to support said inductor winding and to provide an air core for said inductor winding, said winding former means having a former structure with a hollow interior through which said elongated input conductor means extends and within which said spark gap means is positioned.