Magnetic core non-contact clamp-on current sensor

• US 5,767,667 A
• Filed: 03/03/1995
• Issued: 06/16/1998
• Est. Priority Date: 03/03/1995
• Status: Expired due to Term

• Current Assignee: OECO, LLC (Meggitt PLC)
• Original Assignee: Beloit Technologies, Inc. (Komatsu Ltd.)
• Inventors: Shafie, Matt H.
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US08/399,710
• Time in Patent Office: 1,201 Days
• Field of Search: 324/117 R, 324/127, 336/175, 336/212
• US Class Current: 324/117.00R
• CPC Class Codes: G01R 15/185 with compensation or feedback windings or interacting coils, e.g. 0-flux sensors using galvano-magnetic field sensors G01R15/20; conversion of DC into AC using transductors G01R19/20
• CPC Class Codes: G01R 15/186 using current transformers with a core consisting of two or more parts, e.g. clamp-on type G01R15/142 - G01R15/16 take precedence; tong testers G01R1/22
• CPC Class Codes: G01R 19/20 using transductors , i.e. a magnetic core transducer the saturation of which is cyclically reversed by an AC source on the secondary side

Abstract

A magnetic core for a non-contact clamp-on current sensor having a magnetic core that is adapted for encircling a current-carrying conductor wherein the magnetic core includes a first portion having a first integral toroidal section and a first pair of opposing side walls extending therefrom, a second portion having a second integral toroidal section and a second pair of opposing side walls extending therefrom such that the first portion and second portion are coupled together at the first and second pairs of opposing side walls so to define an aperture therebetween for receiving a current carrying conductor and measuring the line current therein. The first and second integral toroidal sections of the magnetic core are designed so to be void of any discontinuities within the flow path of the magnetic flux and so to have a circular shape which promotes a more thorough flux saturation. The lack of discontinuities in, and the circular shape of, the flow path of the magnetic flux in the toroidal sections promotes a more thorough saturation of the magnetic core which results in the reduction of zero errors and the obtaining of more accurate line current measurements.

Claims

1. A current sensor for measuring the flow of line current through a current carrying conductor having a magnetic core adapted for encircling said conductor, said magnetic core comprising in combination:

a first portion, said first portion including a first integral toroidal section having a first internal side, a first pair of opposing side walls extending from said first internal side, a first cut portion positioned between said first pair of opposing side walls, and a second cut portion positioned between said first pair of opposing side walls opposite said first cut portion;

a second portion, said second portion including a second integral toroidal section having a second internal side, a second pair of opposing side walls extending from said second internal side, a third cut portion positioned between said second pair of opposing side walls, and a fourth cut portion positioned between said first pair of opposing side walls opposite said third cut portion, said second pair of opposing side walls being in alignment with and coupled to said first pair of opposing side walls thereby forming an aperture therethrough, said aperture facilitating the placement of said current carrying conductor therein;

a first set of windings positioned on said first integral toroidal section thereby producing flux in said first integral toroidal section due to an excitation current flowing through said first set of windings;

a second set of windings positioned on said second integral toroidal section thereby producing flux in said second integral toroidal section due to said excitation current flowing through said second set of windings; and

a means for connecting said first and second sets of windings to form a circuit.

2. A current sensor for measuring the flow of line current through a current carrying conductor having a magnetic core adapted for encircling said current carrying conductor, said magnetic core comprising in combination:

a first portion including a first integral toroidal section having a first internal side, a first pair of opposing side walls extending from said first internal side, and a first set of windings on said first integral toroidal section;

a second portion including a second integral toroidal section having a second internal side, a second pair of opposing side walls extending from said second internal side, and a second set of windings; and

a means for connecting said first and second sets of windings to form a circuit, whereby said first portion and said second portion are coupled to each other at said first and second pairs of side walls to thereby encircle said current carrying conductor with said magnetic core, said first set of windings thereby producing a flux in said first integral toroidal section due to an excitation current flowing through said first set of windings, said second set of windings thereby producing flux in said second integral toroidal section flowing in an opposite direction as in said first integral toroidal section due to said excitation current flowing through said second set of windings, said magnetic core being in a toroid shape so as to facilitate having a more thorough flux saturation therein thereby reducing the occurrence of zero errors in measurements.

3. A method for measuring a line current in a current carrying conductor comprising the steps of:

providing a magnetic core having a first portion and a second portion, said first portion including a first integral toroidal section having a first internal side, and a first pair of opposing side walls extending from said first internal side, said second portion including a second integral toroidal section having a second internal side, and a second pair of opposing side walls extending from said second internal side, said first and second portions forming an aperture therethrough being coupled together at said first and second pairs of opposing side walls thereby providing a first set of windings coupled to said first integral toroidal section whereby said first set of windings produces a flux in said first integral toroidal section;

providing a second set of windings coupled to said second integral toroidal section whereby said second set of windings produces a flux in said second integral toroidal section of which flows in an opposite direction than in the first integral toroidal section;

placing a current carrying conductor through said aperture in said magnetic core;

providing an excitation current source electrically coupled to said first and second sets of windings whereby an excitation current flows through said first and second set of windings;

providing output terminals positioned intermediate to said first and second sets of windings; and

providing a means for detecting an output voltage on said output terminals that is proportional in amplitude and polarity to the line current being measured.