Faulted current indicators with improved signal to noise ratios
First Claim
1. A sensor for sensing current in a conductor, comprising:
- sensing means for producing an output corresponding to current flowing through the conductor, said sensing means including a coil;
magnetic means passing through said coil for coupling said coil to said conductor said magnetic means forming a substantially closed loop surrounding the conductor so that the conductor passes through the loop of said magnetic means;
said magnetic means including noise reduction means for reducing the sensitivity of said magnetic means to flux fields emanating from outside the loop of said magnetic means and for diverting flux fields emanating from outside the loop of the magnetic means in opposite directions along the loop;
said magnetic means having given magnetic reluctance and said noise reduction means forming a section within said coil with a higher reluctance than the given reluctance;
said section of said noise reduction means being substantially uniform and free of magnetically distorting materials, and said sensing means being substantially responsive to fields in said magnetic means and free of current inputs from other sources.
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Accused Products
Abstract
A sensor in a faulted current indicator includes a coil and a magnetic arrangement passing through the coil and around a current-carrying conductor for coupling the coil to the conductor. The magnetic arrangement has given magnetic reluctance and forms a higher reluctance section, such as a gap, within the coil. Preferably the magnetic arrangement includes a U-shaped laminate and two core laminations joined to the U-shaped laminate by two gaps to allow for installation around the conductor. The ferromagnetic plate outside the coil shields the coil. The sensitivity of the sensor is increased by coating the inner surface of the U-shaped laminate and the core lamination surfaces contacting the U-shaped laminate with a high Ni content ferromagnetic material.
19 Citations
16 Claims
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1. A sensor for sensing current in a conductor, comprising:
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sensing means for producing an output corresponding to current flowing through the conductor, said sensing means including a coil; magnetic means passing through said coil for coupling said coil to said conductor said magnetic means forming a substantially closed loop surrounding the conductor so that the conductor passes through the loop of said magnetic means; said magnetic means including noise reduction means for reducing the sensitivity of said magnetic means to flux fields emanating from outside the loop of said magnetic means and for diverting flux fields emanating from outside the loop of the magnetic means in opposite directions along the loop; said magnetic means having given magnetic reluctance and said noise reduction means forming a section within said coil with a higher reluctance than the given reluctance; said section of said noise reduction means being substantially uniform and free of magnetically distorting materials, and said sensing means being substantially responsive to fields in said magnetic means and free of current inputs from other sources. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A sensor for sensing current in a conductor, comprising:
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a coil; magnetic means passing through said coil for coupling said coil to said conductor; said magnetic means including lamination means having a first laminar portion of a first ferromagnetic material and a second laminar portion of a second ferromagnetic material on the surface of the first portion and having a nickel content higher than the first ferromagnetic material; said magnetic means being divided into two laminar sections; said laminar sections of said magnetic means extending toward each other within said coil to form a gap having a reluctance higher than the remaining portion of said magnetic means, said laminar sections terminating at the gap in two oppositely facing projections projecting transverse to the laminar sections.
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16. A fault indicator comprising:
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sensing means for producing an output corresponding to current flowing through the conductor, said sensing means including a coil; magnetic means passing through said coil for coupling said coil to said conductor said magnetic means forming a substantially closed loop surrounding the conductor so that the conductor passes through the loop of said magnetic means; said magnetic means including noise reduction means for reducing the sensitivity of said magnetic means to flux fields emanating from outside the loop of said magnetic means and for diverting flux fields emanating from outside the loop of the magnetic means in opposite directions along the loop; said magnetic means having given magnetic reluctance and said noise reduction means forming a section within said coil with a higher reluctance than the given reluctance; said section of said noise reduction means being substantially uniform and free of magnetically distorting materials, and said sensing means being substantially responsive to fields in said magnetic means and free of current inputs from other sources; and a display responsive to said sensing means.
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Specification