Broad-band low-inductance cables for making kelvin connections to electrochemical cells and batteries

• US 20060017447A1
• Filed: 07/22/2004
• Published: 01/26/2006
• Est. Priority Date: 07/22/2004
• Status: Active Grant

• Current Assignee: Midtronics Incorporated
• Original Assignee: Midtronics Incorporated
• Inventors: Bertness, Kevin I., Champlin, Keith S.
• Granted Patent: US 7,106,070 B2
• Time in Patent Office: Days
• US Class Current: 324/538
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382

Abstract

A broad-band technique for reducing the distributed inductance of a four-conductor Kelvin cable is disclosed. A special inductance-canceling cable section is connected in tandem with the cable section contacting the cell/battery. Connections between the two cable sections are transposed such that conductors in each conductor pair of the canceling section connect to current-carrying and voltage-sensing conductors from different conductor pairs in the contacting section. The canceling section thereby exhibits a distributed negative mutual inductance between its current-carrying and voltage-sensing conductors that can effectively cancel the distributed positive mutual inductance introduced by the contacting section. In one embodiment, conductor pairs comprise pairs of insulated wires which may be twisted together. In other disclosed embodiments, conductor pairs comprise shielded coaxial cables.

Claims

1. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a contacting cable section comprising first and second conductor pairs, said first conductor pair contacting a first terminal of said cell or battery with a first current-carrying conductor and a first voltage-sensing conductor, said second conductor pair contacting a second terminal of said cell or battery with a second current-carrying conductor and a second voltage-sensing conductor, said contacting cable section characterized by positive mutual inductance coupling between its current-carrying and voltage-sensing conductors; and

,

a canceling cable section comprising third and fourth conductor pairs interposed between said contacting cable section and said measuring circuitry, said third conductor pair comprising a third current-carrying conductor and a third voltage-sensing conductor and said fourth conductor pair comprising a fourth current-carrying conductor and a fourth voltage-sensing conductor, said third and fourth current-carrying conductors adapted to couple current-carrying conductors of said contacting cable section to current carrying conductors of said measuring circuitry and said third and fourth voltage-sensing conductors adapted to couple voltage sensing conductors of said contacting cable section to voltage-sensing conductors of said measuring circuitry, said canceling cable section characterized by distributed negative mutual inductance coupling between its current-carrying and voltage-sensing conductors.

2. The apparatus of claim 1 wherein said first conductor pair comprises conductors of a first shielded coaxial cable, and said second conductor pair comprises conductors of a second shielded coaxial cable.

3. The apparatus of claim 1 wherein said first conductor pair comprises conductors of a first insulated wire pair, and said second conductor pair comprises conductors of a second insulated wire pair.

4. The apparatus of claim 3 wherein said conductors of said first insulated wire pair are twisted together and said conductors of said second insulated wire pair are twisted together.

5. The apparatus of claim 1 wherein said third conductor pair comprises conductors of a third shielded coaxial cable, and said fourth conductor pair comprises conductors of a forth shielded coaxial cable.

6. The apparatus of claim 1 wherein said third conductor pair comprises conductors of a third insulated wire pair, and said fourth conductor pair comprises conductors of a fourth insulated wire pair.

7. The apparatus of claim 6 wherein said conductors of said third insulated wire pair are twisted together and said conductors of said fourth insulated wire pair are twisted together.

8. The apparatus of claim 1 including a Y-junction interconnecting conductors of said contacting cable section and said canceling cable section, said Y-junction directly connecting first and second current-carrying conductors to third and fourth current-carrying conductors, said Y-junction transposing connections between first and second voltage-sensing conductors and third and fourth voltage-sensing conductors.

9. The apparatus of claim 1 including a Y-junction interconnecting conductors of said contacting cable section and said canceling cable section, said Y-junction directly connecting first and second voltage-sensing conductors to third and fourth voltage-sensing conductors, said Y-junction transposing connections between first and second current-carrying conductors and third and fourth current-carrying conductors.

10. Apparatus of claim 1 including a zero-coupling cable section interposed between said contacting cable section and said measuring circuitry, said zero-coupling cable section comprising current-carrying and voltage-sensing conductors and characterized by negligible mutual inductance coupling between its said current-carrying conductors and its said voltage-sensing conductors.

11. A low-inductance cable for implementing Kelvin connections to positive and negative terminals of an electrochemical cell or battery comprising:

a first cable section adapted to couple to a positive terminal with a first current-carrying conductor and a first voltage sensing conductor and to couple to a negative terminal with a second current-carrying conductor and a second voltage-sensing conductor, said second current-carrying and voltage-sensing conductors spaced apart from said first current-carrying and voltage-sensing conductors,

a second cable section comprising a third current-carrying conductor, a third voltage-sensing conductor, a fourth current-carrying conductor, and a fourth voltage-sensing conductor, said fourth current-carrying and voltage sensing conductors spaced apart from said third current-carrying and voltage-sensing conductors; and

,

a cable junction interposed between said first cable section and said second cable section, said cable junction interconnecting said first and fourth current-carrying conductors, said second and third current-carrying conductors, said first and third voltage-sensing conductors, and said second and fourth voltage-sensing conductors.

13. The low-inductance cable of either claim 11 or claim 12 wherein said first current-carrying and voltage-sensing conductors, said second current-carrying and voltage-sensing conductors, said third current-carrying and voltage-sensing conductors, and said fourth current-carrying and voltage-sensing conductors comprise four pairs of insulated wires.

14. The low-inductance cable of claim 13 wherein wires of each said pair are twisted together.

15. The low-inductance cable of either claim 11 or claim 12 wherein said first current-carrying and voltage-sensing conductors, said second current-carrying and voltage-sensing conductors, said third current-carrying and voltage-sensing conductors, and said fourth current-carrying and voltage-sensing conductors comprise four shielded coaxial cables.

16. The low-inductance cable of claim 15 wherein current-carrying and voltage-sensing conductors of said first cable section couple through a distributed mutual inductance given by equation (6) and current-carrying and voltage-sensing conductors of said second cable section couple through a distributed mutual inductance given by equation (7).

12. A low-inductance cable for implementing Kelvin connections to positive and negative terminals of an electrochemical cell or battery comprising:

a first cable section adapted to couple to a positive terminal with a first current-carrying conductor and a first voltage sensing conductor and to couple to a negative terminal with a second current-carrying conductor and a second voltage-sensing conductor, said second current-carrying and voltage-sensing conductors spaced apart from said first current-carrying and voltage-sensing conductors,

a second cable section comprising a third current-carrying conductor, a third voltage-sensing conductor, a fourth current-carrying conductor, and a fourth voltage-sensing conductor, said third current-carrying and voltage sensing conductors spaced apart from said fourth current-carrying and voltage-sensing conductors; and

,

a cable junction interposed between said first cable section and said second cable section, said cable junction interconnecting said first and fourth voltage-sensing conductors, said second and third voltage-sensing conductors, said first and third current-carrying conductors, and said second and fourth current-carrying conductors.

17. A connecting cable for providing Kelvin connections to a positive terminal and a negative terminal of an electrochemical cell or battery comprising:

a first cable section adapted to couple to said positive terminal with first and second conductors and to couple to said negative terminal with third and fourth conductors, said third and fourth conductors spaced apart from said first and second conductors,

a second cable section comprising fifth, sixth, seventh, and eighth conductors, said seventh and eighth conductors spaced apart from said fifth and sixth conductors,

a third cable section comprising ninth, tenth, eleventh, and twelfth conductors, said eleventh and twelfth conductors spaced apart from said ninth and tenth conductors,

a first cable junction interposed between said first cable section and said second cable section, said first cable junction interconnecting said first and eighth conductors, said second and sixth conductors, said third and seventh conductors, and said fourth and fifth conductors; and

a second cable junction interposed between said second cable section and said third cable section, said second cable junction interconnecting said fifth and tenth conductors, said sixth and eleventh conductors, said seventh and twelfth conductors, and said eighth and ninth conductors.

18. The connecting cable of claim 17 wherein said first and second conductors, said third and fourth conductors, said fifth and sixth conductors, and said seventh and eighth conductors comprise four pairs of insulated wires.

19. The connecting cable of claim 18 wherein insulated wires of each said pair are twisted together.

20. The connecting cable of claim 17 wherein said first and second conductors, said third and fourth conductors, said fifth and sixth conductors, and said seventh and eighth conductors comprise conductors of four shielded coaxial cables.

21. The connecting cable of claim 17 wherein said ninth and tenth conductors and said eleventh and twelfth conductors comprise two pairs of twisted insulated wires.

22. The connecting cable of claim 17 wherein said ninth and tenth conductors and said eleventh and twelfth conductors comprise conductors of two shielded coaxial cables.

23. The connecting cable of claim 20 wherein coaxial cable shields couple to coaxial cable center conductors through distributed mutual inductances given by equation (6) in cable section 1 and by equation (7) in cable section 2.

24. The connecting cable of claim 22 wherein coaxial cable shields couple to coaxial cable center conductors through distributed mutual inductance given by equation (7).

25. A cable for implementing Kelvin connections to first and second terminals of an electrochemical cell or battery comprising:

a first cable section adapted to couple to said first terminal with a conductor pair comprising a current-carrying conductor and a voltage-sensing conductor and to couple to said second terminal with another conductor pair comprising a current-carrying conductor and a voltage-sensing conductor,

a second cable section comprising two spaced-apart conductor pairs, each said pair comprising a current-carrying conductor and a voltage-sensing conductor; and

,

a cable junction interconnecting conductors of said first and second cable sections, said cable junction transposing connections such that conductors in each pair in said first cable section couple to conductors in different pairs in said second cable section.

26. The cable of claim 25 wherein said conductor pairs in said first and second cable sections comprise pairs of insulated wires.

27. The cable of claim 26 wherein insulated wires of each said pair are twisted together.

28. The cable of claim 25 wherein said conductor pairs in said first and second cable sections comprise shielded coaxial cables.

29. The cable of claim 28 wherein current-carrying conductors couple to voltage-sensing conductors in said first cable section through distributed mutual inductance given by equation (6) and current-carrying conductors couple to voltage-sensing conductors in said second cable section through distributed mutual inductance given by equation (7).

30. A low-inductance cable for implementing Kelvin connections to first and second terminals of an electrochemical cell or battery comprising:

a first cable section adapted to couple to said first terminal with one pair of conductors and to couple to said second terminal with another pair of conductors,

a second cable section comprising two spaced-apart pairs of conductors,

a third cable section comprising two spaced-apart pairs of conductors,

a first cable junction interconnecting conductors of said first and second cable sections, said first cable junction transposing connections such that conductors in each pair in said first cable section couple to conductors in different pairs in said second cable section; and

,

a second cable junction interconnecting conductors of said second and third cable sections, said second cable junction transposing connections such that conductors in each pair in said second cable section couple to conductors in different pairs in said third cable section.

31. The low-inductance cable of claim 30 wherein said pairs of conductors in said first and second cable sections comprise pairs of insulated wires.

32. The low-inductance cable of claim 31 wherein wires in each said pair are twisted together.

33. The low-inductance cable of claim 30 wherein said pairs of conductors in said first and second cable sections comprise shielded coaxial cables.

34. The low-inductance cable of claim 30 wherein said pairs of conductors in said third cable section comprise pairs of insulated wires twisted together.

35. The low-inductance cable of claim 30 wherein said pairs of conductors in said third cable section comprise shielded coaxial cables.

36. The low-inductance cable of claim 33 wherein mutual inductance coupling between coaxial cable shields and center-conductors is given by equation (6) in said first section and by equation (7) in said second section.

37. The low-inductance cable of claim 35 wherein mutual inductance coupling between coaxial cable shields and center-conductors is given by equations (7) in said third section.