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Device for measuring an electrical current in a conductor using a Rogowski coil

  • US 5,442,280 A
  • Filed: 09/01/1993
  • Issued: 08/15/1995
  • Est. Priority Date: 09/10/1992
  • Status: Expired due to Term
First Claim
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1. Device for measuring an electrical current in a conductor, comprising:

  • a Rogowski coil through which said conductor passes, said Rogowski coil being of the type comprising at least one printed circuit plate provided with a circular cutout, the coil being implemented by metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof pass through the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated-through holes that pass through the thickness of the plate, wherein the radially-extending metal deposits and the plated-through holes form a coil winding which is constituted by a first clockwise winding and a second counter-clockwise winding which are connected in series and disposed around the circuit cutout, said winding having an input and an output on the same face of the plate, separated by a distance of a few tenths of a millimeter;

    a resistor R connected in series with said Rogowski coil; and

    said resistor R having a value equal to
    
    
    space="preserve" listing-type="equation">R.sub.0 =r.sub.0 (α

    .sub.r -α

    .sub.s -α

    .sub.R)/α

    .sub.swhere;

    R0 is the ohmic resistance of the resistor R at a reference temperature,r0 is the ohmic resistance of the Rogowski coil at said reference temperature,α

    r is the temperature coefficient of the conductive material of said Rogowski coil,α

    s is the temperature coefficient of the sensitivity of the Rogowski coil,α

    R is the temperature coefficient of the resistor R, the current I to be measured being related to the voltage U by the equation;

    
    
    space="preserve" listing-type="equation">U=j S.sub.0 ω

    I R.sub.0 /(R.sub.0 +r.sub.0)where;

    S0 is the sensitivity of said Rogowski coil at said reference temperature,j is the complex operator such that j2 =-1, andω

    is the angular frequency of the current to be measured.

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