Non-intrusive power monitor

• US 20050275397A1
• Filed: 06/15/2004
• Published: 12/15/2005
• Est. Priority Date: 06/15/2004
• Status: Active Grant

• Current Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Original Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Inventors: Lightbody, Simon H., Gunn, Colin N., Huber, Benedikt T., Teachman, Michael E.
• Granted Patent: US 7,265,533 B2
• Time in Patent Office: Days
• US Class Current: 324/126
• CPC Class Codes: G01R 15/142 Arrangements for simultaneous measurements of several parameters employing techniques covered by groups G01R15/14 - G01R15/26
• CPC Class Codes: G01R 15/16 using capacitive devices
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• CPC Class Codes: G01R 21/06 by measuring current and voltage G01R21/08 - G01R21/133 take precedence
• CPC Class Codes: H05K 1/0268 for electrical inspection or testing
• CPC Class Codes: H05K 1/0393 Flexible materials H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: H05K 2201/051 Rolled

Abstract

Systems and methods for monitoring power in a conductor. A flex circuit may include multiple layers including a voltage sensing layer, a coil layer, and a ground layer. The coil layer includes traces that form a coil structure around a conductor when the flex circuit is wrapped around the conductor. The coil layer generates a voltage that may be integrated to determine a current in the conductor. When the flex circuit is wrapped around the conductor, the voltage sensing layer is closest to the conductor. The voltage sensing layer forms a capacitor with the conductor. Using an adjustable capacitive voltage divider, the voltage of the conductor may be determined from a voltage signal received from the voltage sensing layer.

Claims

1. A flex circuit for use in measuring at least one of a voltage and a current in a conductor, the flex circuit comprising:

a voltage sensing layer including a conductive plane, wherein the voltage sensing layer forms a first capacitance with a conductor when the flex circuit is wrapped around the conductor, wherein a voltage signal from the voltage sensing layer is used to determine a voltage of the conductor; and

a coil layer having a plurality of traces formed therein, wherein the plurality of traces form a coil structure around the conductor when the flex circuit is wrapped around the conductor, wherein a voltage signal from the coil layer is used to determine a current of the conductor.

2. A flex circuit as defined in claim 1, further comprising a ground layer including a conductive plane, wherein the coil layer is disposed between the voltage sensing layer and the ground layer.

3. A flex circuit as defined in claim 1, wherein the coil layer comprises a first layer of traces and a second layer of traces.

4. A flex circuit as defined in claim 3, wherein the first layer of traces and the second layer of traces are electrically connected to form a single conductive path through the first layer and the second layer.

5. A flex circuit as defined in claim 3, wherein the coil layer further comprises:

a plurality of vias disposed on a first end of the flex circuit; and

a plurality of vias disposed on a second end of the flex circuit that is opposite the first end.

6. A flex circuit as defined in claim 5, wherein the plurality of vias disposed on the first end and the plurality of vias on the second end each electrically connect the traces in the first layer with traces in the second layer.

7. A flex circuit as defined in claim 5, wherein the voltage sensing layer is insulated from the coil layer.

8. A flex circuit as defined in claim 5, wherein the coil layer is insulated from the ground layer.

9. A power monitoring system for monitoring electrical characteristics of a conductor through which electrical power is supplied to a load, the system comprising:

a flex circuit having a plurality of layers, wherein the flex circuit is operative to be coupled with a conductor such that a plurality of traces in the flex circuit form a coil structure around the conductor; and

a module that receives signals produced by the flex circuit, wherein the module processes the signals to determine at least one of a voltage, a current, and an amount of energy delivered to a load through the conductor.

10. A power monitoring system as defined in claim 9, wherein the plurality of layers in the flex circuit further comprises:

a voltage sensing layer including a conducting plane that is nearest the conductor when the flex circuit is coupled with the conductor, wherein the voltage sensing layer forms a first capacitance with the conductor;

a current sensing layer including a coil layer adjacent to the voltage sensing layer, wherein the coil layer includes one or more layers of conductive traces; and

a ground layer adjacent to the coil layer.

11. A power monitoring system as defined in claim 10, wherein the coil layer provides a voltage signal to the module, the module integrating the voltage input to determine a current of the conductor.

12. A power monitoring system as defined in claim 10, wherein the voltage sensing layer provides a voltage signal that is used by the module to determine a voltage of the conductor.

13. A power monitoring system as defined in claim 10, wherein the coil layer further comprises a plurality of traces in one or more layers.

14. A power monitoring system as defined in claim 10, wherein the flex circuit further comprises first vias on one end of the flex circuit and second vias on a second end of the flex circuit opposite the first end, wherein the first vias and the second vias electrically connect traces in a first layer of the coil layer with traces in a second layer of the coil layer.

15. A power monitoring system as defined in claim 14, wherein the plurality of traces includes the traces in the first layer and the traces in the second layer such that the plurality of traces forms a single conductive path in the coil layer.

16. A power monitoring system as defined in claim 10, wherein the module further comprises a switched capacitor bank coupled to a first capacitance between the voltage sensing layer and the conductor.

17. A power monitoring system as defined in claim 16, wherein the switched capacitor bank further comprises a plurality of switches controlled by a processor such that a capacitance of the switched capacitor bank can be adjusted, thereby enabling the module to perform autoranging and autodetection of the voltage of the conductor.

18. A power monitoring system as defined in claim 16, wherein the module uses the switched capacitor bank to determine a value of the first capacitance.

19. The power monitoring system as defined in claim 16, wherein the module uses the switched capacitor bank to determine a value of the first capacitance in combination with a capacitance between the ground layer of the flex circuit and a ground of the load.

20. The power monitoring system as defined in claim 18, wherein the module uses the value and the capacitance of the switched capacitor bank to determine the voltage on the conductor.

21. A power monitoring system for monitoring voltage and or current in a conductor that provides electrical power to a load, the power monitoring system comprising:

a module;

a flex circuit coupled to the module, the flex circuit having a voltage sensing layer and a coil layer, wherein the flex circuit is configured to wrap around a conductor;

a first input in the module that receives a first voltage signal from the voltage sensing layer, the module identifying a voltage of the conductor from the first voltage signal; and

a second input in the module that receives a second voltage signal from the coil layer, wherein the module integrates the second voltage signal to determine a current of the conductor.

22. A power monitoring system as defined in claim 21, wherein the first input further comprises an amplifier that is coupled to a power meter integrated circuit adapted to convert the voltage signal to the voltage of the conductor, wherein the second input further comprises an amplifier that is coupled to the power meter integrated circuit that is adapted to integrate the second voltage signal to produce the current of the conductor.

23. A power monitoring system as defined in claim 22, the module further comprising a processor that is coupled to the power meter integrated circuit via one or more control lines.

24. A power monitoring system as defined in claim 23, the module further comprising a port for exporting at least one of the voltage of the conductor, the current of the conductor, the power flow in the conductor and the energy flow in the conductor to a display.

25. A power monitoring system as defined in claim 21, the module further comprising a communications port for exporting at least one of the voltage of the conductor, the current of the conductor, the power flow in the conductor and the energy flow in the conductor to a remote device.

26. A power monitoring system as defined in claim 21, the flex circuit further comprising a ground layer arranged next to the coil layer such that the coil layer is between the coil layer and the voltage sensing layer.

27. A power monitoring system as defined in claim 21, wherein the coil layer further comprises a single conductive path that forms a coil structure when the flex circuit is wrapped around the conductor such that the coil layer generates the second voltage signal in response to magnetic flux.

28. A power monitoring system as defined in claim 21, wherein the coil layer further comprises a first layer of traces and a second layer of traces.

29. A power monitoring system as defined in claim 28, wherein the flex circuit further comprises a first end having first vias and a second end having second vias, wherein the first vias and the second vias electrically connect the first layer of traces with the second layer of traces to form a single conductive path in the coil layer.

30. A power monitoring system as defined in claim 21, the module further comprising a switched bank of capacitors controlled by a processor, wherein the switched bank of capacitors enables the module to determine a capacitance between the voltage sensing layer and the conductor and a capacitance between the ground layer and a ground of a load.

31. A power monitoring system as defined in claim 21, further comprising a high gain circuit coupled to the second voltage signal, wherein the high gain circuit produces a square wave used for frequency measurement.

32. A flex circuit that can removably wrap around a conductor to monitor at least one of a voltage and a current of the conductor, the flex circuit comprising:

a voltage sensing layer that is adjacent an insulation of a conductor when the flex circuit is wrapped around the conductor;

a ground layer arranged over the voltage sensing layer; and

a plurality of traces arranged in one or more layers between the voltage sensing layer and the ground layer, wherein the plurality of traces form a single conductive path that forms a coil structure when the flex circuit is wrapped around the conductor.

33. A flex circuit as defined in claim 32, wherein the plurality of traces are insulated from the voltage sensing layer and the ground layer.

34. A flex circuit as defined in claim 32, further comprising first vias on a first end and second vias on a second end, wherein the first vias and the second vias electrically connect traces in a first layer with traces in a second layer.

35. A flex circuit as defined in claim 34, further comprising a first connector on the first end that is adapted to couple with a second connector on the second end to secure the flex circuit around the conductor.

36. A flex circuit as defined in claim 35, wherein the flex circuit has a width that is selected to substantially match a circumference of the conductor.

37. A method for monitoring electrical power in a conductor, the method comprising:

forming a voltage sensing layer of a flex circuit, the first layer including a conductive plane;

forming a coil layer in the flex circuit, wherein the coil layer includes a plurality of traces that form a single conductive path in the flex circuit and that form a coil structure when the flex circuit is wrapped around a conductor; and

insulating the coil layer from the voltage sensing layer.

38. The method as defined in claim 37, further comprising:

forming a ground layer of the flex circuit over the coil layer such that the coil layer is between the voltage sensing layer and the ground layer, wherein the ground layer includes a conductive plane; and

insulating the coil layer from the ground layer.

39. The method as defined in claim 38, further comprising:

encircling the conductor with the flex circuit;

monitoring a first voltage on the voltage sensing layer, wherein the first voltage is indicative of the voltage on the conductor;

monitoring a second voltage output from the coil layer, wherein the second voltage is indicative of the current flowing in the conductor.

40. A power monitoring system for monitoring at least one power parameter in a conductor that provides electrical power to a load, the power monitoring system comprising:

a metallic layer operative to be wrapped around a conductor while remaining electrically insulated from the conductor;

a capacitor bank coupled between the metallic layer and a ground point, the capacitor bank operative to apply different capacitances between the metallic layer and the ground point;

a processor operative to adjust the capacitance of the capacitor bank, the processor operative to measure voltages across the capacitor bank for at least two different capacitances and operative to calculate the voltage on the conductor therefrom.

41. The power monitoring system as defined in claim 40 wherein the ground point is a system ground.

42. The power monitoring system as defined in claim 41 further comprising a communications circuit coupled to the processor and operative to transmit the measured voltage via at least one of a wired and a wireless communications link.

43. The power monitoring system as defined in claim 40 further comprising a second metallic layer forming a capacitance from the ground point to a system ground.

44. The power monitoring system as defined in claim 40 further comprising a communications circuit coupled to the processor and operative to transmit the measured voltage via at least one of a wired and a wireless communications link.

45. A method for monitoring at least one of a voltage and a current in a conductor that is connected with a load, the method comprising:

forming a first capacitance between a voltage sensing layer of a flex circuit and a conductor;

forming a coil-like structure around the conductor using a plurality of traces formed in a coil layer of the flex circuit;

receiving a first voltage signal from the voltage sensing layer to determine a voltage of the conductor; and

receiving a second voltage signal from the coil layer to determine a current in the conductor.

46. A method as defined in claim 45, further comprising insulating the coil layer from the voltage sensing layer.

47. A method as defined in claim 45, further comprising forming a second capacitance between a ground layer of the flex circuit and a ground of the load.

48. A method as defined in claim 45, wherein forming a first capacitance further comprises coupling the flex circuit to the conductor by wrapping the flex circuit around the conductor.