ELECTRICAL CURRENT SENSOR

• US 20100301852A1
• Filed: 01/21/2009
• Published: 12/02/2010
• Est. Priority Date: 01/25/2008
• Status: Active Grant

• Current Assignee: LEM International SA (LEM Holding SA)
• Original Assignee: Liaisons Electroniques-Mecaniques LEM SA
• Inventors: Schlafli, Dominik, Teppan, Wolfram
• Granted Patent: US 8,618,796 B2
• Time in Patent Office: Days
• US Class Current: 324/253
• CPC Class Codes: G01R 15/18 using inductive devices, e.g. transformers
• 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
• CPC Class Codes: G01R 15/186 using current transformers with a core consisting of two or more parts, e.g. clamp-on type G01R15/142 - G01R15/16 take precedence; tong testers G01R1/22

Abstract

Closed-loop current sensor comprising a magnetic circuit, a magnetic field sensor, and a compensation circuit configured to generate a magnetic field opposing a magnetic field created by an electrical current to be measured flowing in one or more primary conductors (10) extending through a central opening (38) of the magnetic circuit. The magnetic circuit comprises a magnetic core (4) made of at least two core parts (28a, 28b) assembled together to form a substantially closed magnetic circuit, wherein a second branch (32) of the magnetic circuit comprises inner (40a, 40b) and outer (42a, 42b) wall portions joined by one or more lateral wall portions (46a, 46b, 46a′, 46b′) at least partially surrounding a cavity portion (44) receiving the magnetic field sensor (8) therein, the lateral and outer wall portions extending from one or both lateral edges of the inner wall portion.

Claims

1. A closed-loop current sensor comprising a magnetic circuit, a magnetic field sensor, and a compensation circuit configured to generate a magnetic field opposing a magnetic field created by an electrical current to be measured flowing in one or more primary conductors (10) extending through a central opening (38) of the magnetic circuit, the magnetic circuit comprising a magnetic core (4) made of at least two core parts (28a, 28b) assembled together to form a substantially closed magnetic circuit, wherein a second branch (32) of the magnetic circuit comprises inner (40a, 40b) and outer (42a, 42b) wall portions joined by one or more lateral wall portions (46a, 46b, 46a′

, 46b′

) at least partially surrounding a cavity portion (44) receiving the magnetic field sensor (8) therein, the lateral and outer wall portions extending from one or both lateral edges of the inner wall portion.

2. Sensor according to claim 1 wherein said second branch of the magnetic circuit comprises one or more extensions (50, 50′

) extending from inner, lateral or outer wall portions of a magnetic core part overlapping one or more corresponding wall portions of another magnetic core part.

3. Sensor according to claim 1 or 2 wherein there are lateral wall portions (46a, 46b, 46a′

, 46b′

) on either side of the cavity portion (44).

4. Sensor according to any one of the preceding claims wherein the magnetic circuit comprises an air-gap between free end edges of the inner, outer or lateral wall portions.

5. Sensor according to any one of the preceding claims wherein the magnetic core parts are sheet metal stamped and formed parts.

6. Sensor according to any one of the preceding claims wherein the magnetic core has a substantially parallelepipedic shape with opposed side branches (34, 36) joining opposed first and second branches, the first and second branches being split in respective core parts.

7. Sensor according to the preceding claim wherein the first and second branches of the magnetic core are inserted in cavities (38, 56) of coil supports (14a, 14b) of the compensation circuit.

8. Sensor according to the preceding claim wherein the secondary circuit comprises a pair of coils (16a, 16b), one wound around each coil support.

9. Sensor according to claim 7 or 8 wherein the side branches of the magnetic circuit interconnecting the opposed first and second branches each comprise a reinforcement (60) in the form of a stamped ridge or embossing.

10. Sensor according to any one of the preceding claims wherein the magnetic field sensor comprises a dielectric support (19), a fluxgate core (18) mounted thereon and a fluxgate coil (20) wound around the support and fluxgate core and wherein electrical terminals are securely fixed to the dielectric support, the terminals comprising coil connection portions for electrical connection to ends of the fluxgate coil and terminal portions (76) for connection of the magnetic field detector to a circuit board (26).

11. Sensor according to any one of the preceding claims wherein the circuit board is adjacent respective ends of first and second coils of the compensation circuit.

12. Sensor according to any one of the preceding claims comprising one or more essentially U-shaped primary conductor portions extending partially around a branch of the magnetic circuit receiving the magnetic field sensor.

13. Sensor according to the preceding claim comprising a housing with a plurality of preformed primary conductor guide cavities extending between opposed lateral faces of the housing through a central opening of the magnetic circuit, for insertion of one or more primary conductor portions therethrough.

14. Sensor according to the preceding claim wherein the primary conductors or groups of primary conductors carrying different primary currents are separated by a spacing resulting from leaving at least one pre-formed housing cavity (82) therebetween free.

15. Sensor according to any one of the preceding claims wherein the housing comprises guide slots (84) along the lateral faces of the housing for positioning lateral branches (22) of the primary conductor portions.

16. Sensor according to the preceding claim wherein each U-shaped primary conductor portion is bent so that it extends through a guide slot positioned in a plane orthogonal to a mounting face that is offset from a plane parallel thereto extending through the corresponding preformed cavity through which the U-shaped primary conductor extends.

21. Sensor according to any one of claims 17 to 20 comprising any one or more of the further features of the sensor according to any one of claims 1 to 12.

23. Sensor according to the preceding claim comprising any one or more of the further features of the sensor according to any one of claims 1 to 16.

17. A current sensor comprising a housing, a magnetic circuit with a central opening, a magnetic field sensor, and one or more essentially U-shaped primary conductor portions extending partially around a branch of the magnetic circuit, wherein the housing comprises a plurality of preformed primary conductor guide cavities extending between opposed lateral outer faces of the housing through the central opening of the magnetic circuit, the preformed primary conductor guide cavities configured for insertion, after assembly of the magnetic field sensor and magnetic circuit in the housing, of said one or more primary conductor portions therethrough, and wherein the sensor has less primary conductor portions than preformed primary conductor guide cavities.

18. Sensor according to the preceding claim wherein the housing comprises guide slots along the lateral faces of the housing for positioning lateral branches of the primary conductor portions.

19. Sensor according to claim 17 or 18 wherein the primary conductors or groups of primary conductors are separated by a spacing resulting from leaving at least one pre-formed housing cavity (82) therebetween free.

20. Sensor according to the preceding claim wherein each U-shaped primary conductor portion is bent so that it extends through a guide slot positioned in a plane orthogonal to a mounting face that is offset from a plane parallel thereto extending through the corresponding preformed guide cavity through which the U-shaped primary conductor extends.

22. A closed-loop current sensor comprising a housing, a magnetic circuit, a magnetic field sensor, and a compensation circuit configured to generate a magnetic field opposing a magnetic field created by an electrical current to be measured flowing in one or more primary conductors extending through a central opening of the magnetic circuit, the magnetic circuit comprising a magnetic core made of at least two core parts assembled together to form a substantially closed magnetic circuit having a substantially parallelepipedic shape with opposed side branches joining opposed first and second branches, the compensation circuit comprising a signal processing circuit (12), a coil (16a) surrounding the first branch of the magnetic circuit, and a coil (16b) surrounding the second branch of the magnetic circuit, the coils being mounted on respective coil supports (14a, 14b), wherein the signal processing circuit comprises a circuit board positioned along a face of the sensor at an end of the coils, substantially orthogonal to a mounting face (5) of the sensor and wherein the second branch (32) of the magnetic circuit comprises inner (40a, 40b) and outer (42a, 42b) wall portions at least partially surrounding a cavity portion (44) with an open end adjacent the circuit board allowing the magnetic field sensor (8) to be insertably received therein in a direction orthogonal to the circuit board.