Miniature arc fault current sensor and systems

• US 10,288,668 B2
• Filed: 02/10/2016
• Issued: 05/14/2019
• Est. Priority Date: 02/11/2015
• Status: Active Grant

• Current Assignee: Pulse Electronics Incorporated (Yageo Corporation)
• Original Assignee: Pulse Electronics Incorporated (Yageo Corporation)
• Inventors: Roemer, Glenn, Jin, Fuxue, Machado, Russell, Hamilton, Bruce
• Primary Examiner(s): Koval, Melissa J
• Assistant Examiner(s): Nguyen, Trung
• Application Number:
  US15/040,390
• Publication Number:
  US 20160231375A1
• Time in Patent Office: 1,189 Days
• Field of Search: 324537, 324500, 32475001, 324521, 324552, 324600, 324519, 324617, 324622, 324683, 324709, 324 66, 32475017, 32475428, 324548, 324658, 324661, 324 7666
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

An arc fault sensor disposed on a circuit board proximate to a current carrying trace. The arc fault sensor includes a magnetic flux concentrator (MFC). The MFC includes a first flange and a second flange that are joined by a center post. Each of the first and second flanges have a cross sectional area that is larger than the center post. A sense coil winding is wound around the center post. The arc fault sensor generates an output voltage that is proportional to a rate of change of current in the current carrying conductor. For a given diameter of the sense coil winding, the output voltage is enhanced by the ratio of the cross-sectional areas of the flanges relative to the cross-sectional area of the center post. Methods of manufacturing and utilizing the aforementioned arc fault sensor are also disclosed.

Claims

1. A compact arc fault sensor for sensing a varying current in a current carrying conductor on a circuit board having an upper surface that supports the current carrying conductor, the varying current creating a varying magnetic field that circulates around the current carrying conductor, the compact arc fault sensor comprising:

a magnetic flux concentrator having a lower flange, an upper flange, and a center post disposed between the upper flange and the lower flange, the lower flange for mounting proximate to the upper surface of the circuit board whereby the lower flange defines an edge that is proximate to an edge of the current carrying conductor carrying the varying current to be measured, the lower flange and the upper flange each having a larger lateral cross-sectional area than a lateral cross-sectional area of the center post as measured along a plane that is parallel to a portion of the upper surface whereby the circulating magnetic field passes through the upper and lower flanges and is concentrated along the center post; and

a sense coil wound around the center post and having terminals that provide an output voltage that is proportional to the rate of change of the current in the current carrying conductor to allow a very compact sense coil winding to output a voltage that is substantially enhanced by the ratio of the cross-sectional areas of the flanges relative to the cross sectional area of the center post.

2. The sensor of claim 1, wherein the lower flange is configured for mounting directly to the upper surface of the circuit board.

3. The sensor of claim 1, wherein the sensor includes an outer housing that surrounds at least a portion of the magnetic flux concentrator.

4. The sensor of claim 3, wherein the housing includes a housing portion between the lower flange and the upper surface of the circuit board.

5. The sensor of claim 3, wherein the housing includes a middle portion that is disposed between the upper and lower flanges wherein at least a portion of the sense coil winding is between the middle portion of the housing and the center post.

6. The sensor of claim 1, wherein the sense coil winding includes two terminals for soldering to the upper surface of the circuit board.

7. A compact sensor for sensing a varying current in a current carrying conductor formed upon a circuit board, the circuit board having an upper surface defining an XY plane, the sensor comprising:

a magnetic flux concentrator having a lower flange, an upper flange, and a center post between the upper flange and the lower flange, the lower flange for mounting proximate to the upper surface of the circuit board whereby the lower flange defines an edge that is proximate to an edge of the trace, the magnetic flux concentrator extending along a Z-axis that is normal to the XY plane, the lower flange, the center post, and the upper flange arranged along the Z-axis and each defining a projected lateral area relative to the XY plane, the projected lateral area of each of the lower flange and the upper flange are greater than the projected lateral area of the center post whereby a magnetic flux passing through the upper and lower flanges is concentrated in the center post; and

a sense coil wound around the center post and configured to provide a voltage output proportional to a rate change of magnetic flux passing through the center post which is enhanced by the magnetic flux concentrator.

8. The sensor of claim 7, wherein the lower flange is configured for mounting directly to the upper surface of the circuit board.

9. The sensor of claim 7, wherein the sensor includes an outer housing that surrounds at least a portion of the magnetic flux concentrator, the outer housing includes a housing portion between the lower flange and the upper surface of the circuit board.

10. The sensor of claim 7, wherein outer dimensions of the sensor fit within a cube having outer dimensions of less than 10 millimeters along the X, Y, and Z axes.

11. The sensor of claim 7, wherein a magnetic flux field strength passing through the center post is at least double that of the flanges in order to enable a very compact arc fault sensor.

12. The sensor of claim 7, wherein the projected area of the upper flange and the lower flange are each at least two times the projected area of the center post of the magnetic flux concentrator.

13. The sensor of claim 7, wherein the projected area of the upper flange and the lower flange are each at least three times the projected area of the center post of the magnetic flux concentrator.

14. The sensor of claim 7, wherein the projected area of the upper flange and the lower flange are each at least four times the projected area of the center post of the magnetic flux concentrator.

15. A compact arc fault sensor system for sensing a varying current in a current carrying conductor on a circuit board, the varying current creating a varying magnetic field that circulates around the current carrying conductor, the system comprising:

a compact arc fault sensor comprising;

a magnetic flux concentrator formed from a material having a relative permeability of at least 100 having a center post between two flanges including a first flange and a second flange, the compact arc fault sensor configured to be mounted to the circuit board such that a flux from the circulating magnetic field enters the first flange, passes through center post, and exits through the second flange; and

a sense coil winding disposed around the center post of the magnetic flux concentrator, the sense coil winding configured to output a voltage that is proportional to the rate of change of the varying current, the magnetic field strength is increased by the flux concentration between the two flanges to enable a compact sense coil winding to increase the output voltage for a given coil size;

wherein the current carrying conductor has a desired geometry with respect to the compact arc fault sensor.

16. The compact arc fault sensor system of claim 15, wherein the desired geometry comprises two portions of one or more circuit board traces that each run parallel with one another at least on a first and a second side of the compact arc fault sensor.

17. The compact arc fault sensor system of claim 16, wherein the desired geometry further comprises a third portion of the one or more circuit board traces that runs generally perpendicular to the two portions of the one or more circuit board traces.