Self powered current sensor

• US 6,417,661 B1
• Filed: 04/06/1999
• Issued: 07/09/2002
• Est. Priority Date: 08/28/1997
• Status: Expired due to Term

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: General Electric Company
• Inventors: Berkcan, Ertugrul, Seymour, Raymond Kelsey
• Primary Examiner(s): Sherry, Michael J.
• Assistant Examiner(s): TANG, MINH NHUT
• Application Number:
  US09/286,951
• Time in Patent Office: 1,190 Days
• Field of Search: 324/117.R, 324/127, 324/142, 324/126, 324/130, 324/133
• US Class Current: 324/117.00R
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• 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

Abstract

A self powered parallel bar current sensor for generating a signal which accurately represents current in a power line includes a power coil core having an opening extending therethrough, and a current sensing element including two substantially parallel sensing bars and a sensing coil. The sensing coil is disposed between the sensing bars, and the sensing bars and sensing coil extend through the power coil core opening. A reference coil may also be situated between the sensing bars. The current sensor is connected in series in the power line.

Claims

1. A self powered parallel bar current sensor for sensing current from a line current source, said bar current sensor comprising:

a power coil core having a power coil core opening extending therethrough; and

a current sensing element comprising two substantially parallel sensing bars and a sensing coil, each of said sensing bars having a first end electrically connected to each other and a second end electrically connected to each other, at least one of sensing bars extending through said power coil core opening, said sensing coil positioned between said sensing bars;

said current sensing element being adapted to be electrically coupled to said line current source, said sensing bars further being disposed with respect to said power coil such that current passing through said current sensing bars induces a voltage in said power coil, said power coil being electrically coupled to energize at least one sensing circuit component.

2. A self powered parallel bar current sensor in accordance with claim 1 wherein each of said sensing bars extends through said power coil core opening.

3. A self powered parallel bar current sensor in accordance with claim 1 wherein said power coil core further comprises a plurality of laminations.

4. A self powered parallel bar current sensor in accordance with claim 3 wherein said power coil core further comprises at least one power coil bobbin, one of said laminations extending through said bobbin.

5. A self powered parallel bar current sensor in accordance with claim 1 wherein said sensing element further comprises a reference coil, said reference coil extending through said opening adjacent said sensing coil.

6. A self powered parallel bar current sensor in accordance with claim 5 wherein said sensing coil comprises an assembly including a sensing coil portion, a feedback coil portion, and a sensing bobbin, said assembly being wound about said bobbin so that said feedback coil portion is between said sensing bobbin and said sensing coil portion.

7. A self powered parallel bar current sensor in accordance with claim 6 including an amplifier having an input coupled to said sensing coil portion and an output coupled to said feedback coil portion, said sensing coil portion being connected in series with said reference coil in a manner to provide the difference of voltages between said sensing coil portion and said reference coil.

8. A current sensing element for a current sensor for sensing current from a line current source, said current sensor including a power coil core having a power core opening extending therethrough, said current sensing element comprising:

two sensing bars;

each of said sensing bars having a first end and a second end, said first end of one of said sensing bars being secured to said first end of the other of said sensing bars, and said second end of one of the sensing bars being secured to said second end of the other of said sensing bars;

each of said sensing bars further having an intermediate segment, said respective intermediate segments being aligned along a respective axis oriented in a common direction such that the intermediate segments are disposed substantially parallel but separated from one another by a space; and

a sensing coil positioned between the sending bars, at least one of said sensing bars extending through the power coil core opening.

9. A current sensing element in accordance with claim 8 wherein both of said sensing bars extend through the power coil core opening.

10. A current sensing element in accordance with claim 8 wherein said sensing coil extends through the power coil core opening.

11. A current sensing element in accordance with claim 8 further comprising a reference coil situated adjacent said sensing coil.

12. A current sensing element in accordance with claim 8 wherein said sensing coil comprises an assembly including a sensing coil portion, a feedback coil portion, and a sensing bobbin, said assembly being wound about said bobbin so that said feedback coil portion is between said sensing bobbin and said sensing coil portion.

13. A method for assembling a current sensor for measuring current in a line source, the sensor including a power coil core having a power coil opening extending therethrough, and a sensing element including two substantially parallel sensing bars and a sensing coil, said method comprising the steps of:

positioning one of the parallel sensing bars to extend through the power coil opening;

electrically connecting a first end of each of said parallel bars to each other;

electrically connecting a second end of each of said parallel sensing bars to each other; and

positioning the sensing coil between the parallel sensing bars;

electrically coupling said power coil to at least one sensing circuit component such that current passing through said current sensing bars induces a voltage in said power coil to energize said at least one sensing circuit component.

14. A method in accordance with claim 13 including the additional step of positioning the other of the parallel sensing bars to extend through the power coil opening.

15. A method in accordance with claim 13, wherein the step of electrically connecting a first end of each of said parallel sensing bars to each other comprises electrically connecting the respective first ends of each of said parallel sensing bars to a first conductor bar;

and wherein the step of electrically connecting a second end of each of said parallel sensing bars to each other comprises electrically connecting the respective second ends of each of said parallel sensing bars to a second conductor bar.

16. A method in accordance with claim 13 wherein the sensing element further includes a reference coil, and wherein said method further comprises the step of positioning the reference coil between the parallel sensing bars.