Current sensor apparatus

• US 6,411,078 B1
• Filed: 01/20/2000
• Issued: 06/25/2002
• Est. Priority Date: 01/21/1999
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Nakagawa, Shiro, Tanaka, Katsuaki, Yabusaki, Katsumi, Itoh, Kazuyuki
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): LEROUX, ETIENNE PIERRE
• Application Number:
  US09/487,802
• Time in Patent Office: 887 Days
• Field of Search: 324/117.H, 324/117.R, 324/127, 324/244, 324/251, 324/253
• US Class Current: 324/117.00H
• CPC Class Codes: G01R 15/183 using transformers with a magnetic core
• CPC Class Codes: G01R 15/20 using galvano-magnetic devices, e.g. Hall-effect devices , i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices

Abstract

It is an object of the invention to provide a current sensor apparatus that reduces measurement errors resulting from variations in a position of a current path passing through the space inside a magnetic yoke. The current sensor apparatus comprises a ring-shaped magnetic yoke (2) surrounding a current path (1), part of the yoke having a gap (3), and a magnetic sensor element (4) placed in the gap (3) of the magnetic yoke (2). The magnetic sensor element (4) detects a magnetic field in the gap (3) generated by a current flowing through the current path (1) to measure the current flowing through the current path (1). The current sensor apparatus further comprises a magnetic field interrupter (5), placed between the current path (1) and the gap (3), for interrupting a magnetic field corresponding to a magnetic flux generated by the current passing through the current path (1) and not passing through the magnetic yoke (2), so that the magnetic field would not reach the magnetic sensor element (4).

Claims

1. A current sensor apparatus, comprising:

a ring-shaped magnetic yoke through which a magnetic flux generated by an electric current flowing through an electric current path passes, the yoke surrounding the electric current path, part of the yoke having a gap;

a magnetic sensor element placed in the gap of the magnetic yoke and provided for detecting a magnetic field in the gap generated by the current flowing through the current path;

a magnetic field interrupter, placed between the current path and the gap, for interrupting a magnetic field corresponding to a magnetic flux that is generated by the current passing through the current path and does not pass through the magnetic yoke, so that the magnetic field is cut off from the magnetic sensor element; and

a first magnetic path and a second magnetic path, through which the magnetic flux passing through the magnetic yoke passes divergently, wherein

the first magnetic path passes through the magnetic sensor element, and the second magnetic path passes through the magnetic field interrupter.

2. The current sensor apparatus according to claim 1 wherein the field interrupter is separated from the magnetic yoke.

3. The current sensor apparatus according to claim 1 wherein the field interrupter is integrated with the magnetic yoke.

4. The current sensor apparatus according to claim 3, wherein part of the field interrupter has another gap.

5. The current sensor apparatus according to claim 4, wherein a center position of the gap of the field interrupter is disposed offset from a straight line drawn through a center of the current path and a center of the gap of the magnetic yoke as viewed in cross-section.

6. The current sensor apparatus according to claim 1 wherein the field interrupter is made of a magnetic substance.

7. The current sensor apparatus according to claim 1 wherein the magnetic sensor element is a fluxgate magnetic sensor element.

8. A current sensor apparatus, comprising:

a ring-shaped magnetic yoke through which a magnetic flux generated by an electric current flowing through an electric current path passes, the yoke surrounding the electric current path, part of the yoke having a gap;

a magnetic sensor element placed in the gap of the magnetic yoke and provided for detecting a magnetic field in the gap generated by the current flowing through the current path;

a high frequency component detection coil for detecting a high frequency component of the current flowing through the current path; and

a first magnetic path and a second magnetic path, through which the magnetic flux passing through the magnetic yoke passes divergently, wherein

the first magnetic path passes through the magnetic sensor element, and the second magnetic path passes through the high frequency component detection coil.

9. The current sensor apparatus according to claim 8, further comprising an attenuation means for attenuating a frequency component of the magnetic flux passing through the first magnetic path that is higher than a specific cutoff frequency.

10. The current sensor apparatus according to claim 8 wherein the magnetic sensor element has a magnetic core placed in the gap and a sensor coil wound around the core and provided for detecting a magnetic field corresponding to the flux passing through the first magnetic path.

11. The current sensor apparatus according to claim 10, further comprising:

a drive means for driving the sensor coil by supplying an alternating excitation current that drives the core into a saturation region to the sensor coil; and

a measurement means for measuring the current passing through the current path by detecting variations in inductance of the sensor coil.

12. The current sensor apparatus according to claim 11, further comprising an attenuation means for attenuating a frequency component of the magnetic flux passing through the first magnetic path that is higher than a specific cutoff frequency, wherein the cutoff frequency is equal to or lower than a Nyquist frequency obtained from a frequency of the excitation current.

13. The current sensor apparatus according to claim 11 wherein the drive means has a series resonant circuit part of which is made up of the sensor coil and supplies a resonant current flowing through the series resonant circuit as the excitation current to the sensor coil.

14. The current sensor apparatus according to claim 11, further comprising a current supply means for supplying an electric current to the sensor coil, the current including a direct current and having a frequency different from a frequency of the excitation current.

15. The current sensor apparatus according to claim 14 wherein the current supply means supplies a negative feedback current to the sensor coil for negative feedback of an output of the measurement means to the sensor coil.

16. The current sensor apparatus according to claim 15 wherein the high frequency component detection coil forms a path for supplying the negative feedback current to the sensor coil.

17. The current sensor apparatus according to claim 11 wherein the measurement means has:

an inductance element connected to the sensor coil in series; and

a differentiation circuit for differentiating a voltage generated across the inductance element and outputting a signal responsive to the current flowing through the current path.

18. The current sensor apparatus according to claim 8, wherein the second magnetic path includes another gap.

19. The current sensor apparatus according to claim 8 wherein the second magnetic path is located between the current path and the first magnetic path.

20. The current sensor apparatus according to claim 10, further comprising a magnetic field interrupting member made of a magnetic substance and placed between the current path and the first magnetic path, the member interrupting a magnetic field corresponding to a magnetic flux that is generated by the current passing through the current path and does not pass through the magnetic yoke, so that the magnetic field is cut off from the magnetic sensor element, wherein the high frequency component detection coil is wound around the field interrupting member.

21. A current sensor apparatus comprising:

a ring-shaped magnetic yoke through which a magnetic flux generated by an electric current flowing through an electric path passes, the yoke surrounding the current path, part of the yoke having a gap;

a magnetic sensor element placed in the gap of the magnetic yoke and provided for detecting a magnetic field in the gap generated by the current flowing through the current path; and

a magnetic field interrupter, placed between the current path and the gap, for interrupting a magnetic field corresponding to a magnetic flux that is generated by the current passing through the current path and does not pass through the magnetic yoke, so that the magnetic field is cut off from the magnetic sensor element.

22. The current sensor apparatus according to claim 21 wherein the field interrupter is separated from the magnetic yoke.

23. The current sensor apparatus according to claim 21 wherein the field interrupter is integrated with the magnetic yoke.

24. The current sensor apparatus according to claim 23 wherein part of the field interrupter has another gap.

25. The current sensor apparatus according to claim 24 wherein a center position of the gap of the field interrupter is disposed offset from a straight line drawn through a center of the current path and a center of the gap of the magnetic yoke as viewed in cross-section.

26. The current sensor apparatus according to claim 21 wherein the field interrupter is made of a magnetic substance.

27. The current sensor apparatus according to claim 21 wherein the magnetic sensor element is a fluxgate magnetic sensor element.