Method and apparatus for measuring current

• US 7,746,068 B2
• Filed: 05/25/2005
• Issued: 06/29/2010
• Est. Priority Date: 05/29/2004
• Status: Active Grant

• Current Assignee: Lem Heme Limited (LEM Holding SA)
• Original Assignee: Lem Heme Limited (LEM Holding SA)
• Inventors: Mahon, James Stephen
• Primary Examiner(s): Tang; Minh N
• Assistant Examiner(s): Nguyen; Trung Q
• Application Number:
  US11/569,550
• Publication Number:
  US 20070290695A1
• Time in Patent Office: 1,861 Days
• Field of Search: 324/158.1, 324754-765, 336223-225, 438/769, 438/782
• US Class Current: 324/225
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils

Abstract

Current testing/measuring apparatus 10 comprises a flexible member 12 having a first end 14 and a second end 16. In use, the flexible member 12 is arranged to locate around a conductor 11 carrying a current to be measured. In particular, the current measuring apparatus 10 comprises a Rogowski coil. The ends of the flexible member 12 are coupled together in use but a gap is created between the ends. This distance can generate errors in the current measurement and the present invention provides compensation means 28 in the form of a compensation windings. The compensation windings comprise a planar spiral conductor provided on a printed circuit board to compensate for the separation distance between the first end and the second end.

Claims

1. Compensation means for current measuring apparatus wherein the compensation means comprises a conductor in which the conductor is arranged to wind around a fixed point wherein the distance from a first point on the conductor to the fixed point is greater than the distance from a second point on the conductor to the fixed point and wherein the current measuring apparatus comprises a flexible member having a first end and a second end, in which, in use, the first end is arranged to locate adjacent to the second end.

2. Compensation means according to claim 1 in which the conductor of the compensation means and the fixed point all lie within the same plane.

3. Compensation means according to claim 1 in which the compensation means is planar.

4. Compensation means according to claim 1 in which the compensation means comprises a planar spiral conductor.

5. Compensation means according to claim 1 in which the distance between the fixed point and the conductor increases along the conductor.

6. Compensation means according to claim 1 in which the distance between the fixed point and the conductor increases in order for the conductor to form a spiral around the fixed point.

7. Compensation means according to claim 1 in which the fixed point is arranged, in use, to locate on or be coincidental with the longitudinal axis of a central conductor of the current measuring apparatus.

8. Compensation means according to claim 1 in which the fixed point is arranged, in use, to locate on or be coincidental with the centre of an outer coil of the current measuring apparatus.

9. Compensation means according to claim 1 in which the conductor comprises at least a first curved section and a second curved section and wherein the radius of curvature of the second curved section is less than the radius of curvature of the first curved section.

10. Compensation means according to claim 1 in which the compensation means comprises a spiral compensation means.

11. Compensation means according to claim 1 in which the conductor comprises a spiral winding formed from a conductor.

12. Compensation means according to claim 1 in which the current measuring apparatus comprise an outer coil located around a central conductor.

13. Compensation means according to claim 1 in which the current measuring apparatus comprises a Rogowski coil.

14. Compensation means according to claim 1 in which the first end is spaced from the second end, in use.

15. Compensation means according to claim 14 in which the compensation means is arranged, in use, to locate between the first end and the second end.

16. Compensation means according to claim 15 when dependent upon claim 15 in which the compensation means is arranged to compensate for the separation distance of the first end and the second end, in use.

17. Compensation means according to claim 1 in which the current measuring apparatus forms a loop around a conductor, in use.

18. Compensation means according to claim 1 in which the current measuring apparatus forms a contiguous loop around a conductor, in use.

19. Compensation means according to claim 1 in which the compensation means locates between a central conductor and an outer coil of the current measuring apparatus.

20. Compensation means according to claim 1 in which the compensation means comprises a spiral section of a conductor which is arranged, in use, to spiral around a longitudinal axis of a central conductor of current measurement apparatus.

21. Compensation means according to claim 1 in which the compensation means is arranged, in use, to located between Rogowski coil and calculation means for calculating the current measured by the current measuring apparatus.