Current sensing apparatus

• US 4,754,218 A
• Filed: 02/21/1985
• Issued: 06/28/1988
• Est. Priority Date: 02/21/1985
• Status: Expired due to Term

• Current Assignee: Soft Wire Limited
• Original Assignee: Soft Wire Limited
• Inventors: Tsals, Izrail, Wagner, Charles G.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): BURNS, WILLIAM
• Application Number:
  US06/703,755
• Time in Patent Office: 1,223 Days
• Field of Search: 324/117 R, 324/127, 324/126, 324/149
• US Class Current: 324/127
• CPC Class Codes: G01R 15/18 using inductive devices, e.g. transformers

Abstract

A current sensing apparatus suitable for sensing the amount of current flowing in a power feeder cable without the necessity for any ohmic connection between the meter and the circuit being measured that does not require separation of the wires in a cable and in fact utilizes both current carrying wires simultaneously includes a magnetically permeable core suitable for concentrating the magnetic fields generated by the current flowing in the pair of wires and includes a single coil disposed upon the core. The core includes a pair of poles which are placed proximate to the feeder cable and the coil yields an induced output voltage proportionate to the current flowing in the feeder cable and may be held in position on the feeder cable with the aid of a resilient member which permits ready removal of the sensing apparatus.

Claims

1. A current sensing apparatus suitable for sensing the amount of A.C. current flowing in one pair of wires of a power feeder cable, comprising:

(a) a magnetically permeable core means concentrating the magnetic field lines of flux occurring between said pair of wires generated by a current flowing in said pair of wires of said power feeder cable by centrally disposing said core means between said pair of wires, said core means including;

(i) at least two pole means, and

(ii) air gap means, said air gap means being disposed between said pole means and sufficiently large to receive said pair of feeder cable wires therebetween; and

(b) a single coil means disposed upon said core means for generating an induced voltage in response to said current flow in said pair of wires.

2. A current sensing apparatus according to claim 1 wherein said pole means are disposed transverse to other portions of said core means and are in one plane.

3. A current sensing apparatus according to claim 1 wherein said core means is laminated.

4. A current sensing apparatus according to claim 1 wherein said core means is a single unitary member.

5. A current sensing apparatus according to claim 1 wherein said core means includes two generally L-shaped members.

6. A current sensing apparatus according to claim 5 wherein each said pole means are disposed transverse to said core means.

7. A current sensing apparatus according to claim 5 wherein said coil means includes means for maintaining said two L-shaped core means in sliding relationship.

8. A current sensing apparatus according to claim 7 wherein said coil means includes a bobbin.

9. A current sensing apparatus according to claim 5 further including clamp means for maintaining said two L-shaped cores in sliding relationship.

10. A current sensing apparatus according to claim 1 wherein said coil means includes a bobbin.

11. A current sensing apparatus according to claim 1 wherein said coil means includes a half bobbin.

12. A current sensing apparatus according to claim 1 further including resilient means disposed between said pole means for holding said current sensing apparatus in position on said power feeder cable.

13. A current sensing apparatus according to claim 5 further including resilient means disposed between said pole means for holding said current sensing apparatus in position on said power feeder cable.

14. A current sensing apparatus according to claim 1 wherein said core means is generally U-shaped when viewed on end with said pole means extending perpendicular to the plane of said U-shaped core means.

15. A current sensing apparatus according to claim 1 wherein said core means is generally E-shaped when viewed in cross-section.

16. A current sensing apparatus according to claim 15 wherein said core means includes a plurality of laminated E-shaped sections.

17. A current sensing apparatus according to claim 15 wherein said core means is generally C-shaped and a separate core member means is affixed centrally to said C-shaped member to form said generally E-shaped configuration in cross-section.

18. A current sensing apparatus according to claim 15 wherein the central portion of said E-shaped core member is provided with sloped sides to reduce the reluctance of said magnetic field path.

19. The method of claim 18 further including the step of:

(e) providing a resilient member disposed between a pair of wires of said feeder cable and said two pole piece means for holding said sensing apparatus in position on said feeder cable.

20. The method of claim 19 further including the step of:

(f) providing gauge means for determining feeder cable size and a proportionality constant between induced coil voltage and cable current.

21. A method of determining the amount of A.C. current flowing in a pair of wires of a feeder cable, comprising the steps of:

(a) providing a current sensing apparatus having a magnetically permeable core means including a single coil means disposed on said core means, said core means having at least two pole piece means, said pole piece means,

(i) extending in one plane,

(ii) being transversely to other portions of said said core means,

(iii) being sufficiently spaced apart to receive said feeder cable;

(b) palcing one of said pole piece means of said current sensing apparatus above and one pole piece means below said feeder cable with said pole piece means extending longitudinally along said feeder cable and centrally disposed between said pair of wires for concentrating magnetic lines of flux generated by said current flowing in said pair of wires; and

(c) connecting said coil means to a device capable of measuring a voltage induced in said coil means; and

(d) converting said voltage to a current reading.