DEVICE FOR THE INSULATED MEASUREMENT OF CURRENT AND A METHOD FOR THE INSULATED DETERMINATION OF CURRENT

• US 20150233977A1
• Filed: 05/01/2015
• Published: 08/20/2015
• Est. Priority Date: 11/02/2012
• Status: Active Grant

• Current Assignee: SiEVA, Doo
• Original Assignee: SiEVA, Doo
• Inventors: PLATISE, Uros
• Granted Patent: US 9,927,464 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 15/08 Circuits for altering the measuring range
• 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 15/20 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
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/20 using transductors , i.e. a magnetic core transducer the saturation of which is cyclically reversed by an AC source on the secondary side

Abstract

The invention relates to a device for the isolated measurement of current, comprising a magnetic core that has an opening through which a primary conductor extends, and at least one measurement region that has at least two openings which divide each measurement region into at least three adjacent flux paths. The device additionally comprises a compensator winding that is wound about parts of the core outside of the at least one measurement region, at least two flux paths of the same measurement region, around which at least one exciter winding is wound, as well as at least one measurement winding that is wound about parts of said at least one measurement region. The invention also relates to a method for determining current in an isolated manner using an afore-mentioned device.

Claims

1. A device (1) for measuring current, comprising:

a magnetic core (2) with

an opening (3) through which a primary conductor (L₁) is routed, and

at least one measuring region (4) with at least two openings (5), which subdivide the measuring region (4) into at least three adjacent flux paths (R_1a, R_1b, R₂, R_2a, R_2b);

a compensating winding (L_C), which is wound around parts of the core (2) outside the measuring region (4);

at least two flux paths (R_1a, R_1b, R_2a, R_2b) of the same measuring region (4), wound by at least one exciter winding (L_S);

at least one measuring winding (L_M), which is wound around parts of the measuring region (4).

2. A device (1) according to claim 1,

characterized in that

the device (1) has

a measuring region (4) with two openings (5) subdividing the measuring region (4) into at least three adjacent flux paths (R_1a, R_1b, R₂),

one exciter winding (L_S) wound with different orientation around two flux paths (R_1a, R_1b) and

one measuring winding (L_M) wound around the other flux path (R₂).

3. A device (1) according to claim 1,

characterized in that

the device (1) has

two measuring regions (4) with respectively two openings (5) subdividing the measuring regions (4) into three adjacent flux paths (R_1a, R_1b, R₂),

two exciter windings (L_S) wound with different orientation around respectively two flux paths (R_1a, R_1b) of the measuring regions (4),

one measuring winding (L_M) wound around the other flux path (R₂) of one of the measuring regions (4) and/or

one measuring winding (L_M) wound around the other flux path (R₂) of the other measuring region (4).

4. A device (1) according to claim 1,

characterized in that

the device (1) has

a measuring region(4) with three openings (5) subdividing the measuring region (4) into a first pair of adjacent flux paths (R_1a, R_1b) and a second pair of adjacent flux paths (R_2a, R_2b) and

two exciter windings (L_S) wound with different orientation around respectively one pair of adjacent flux paths (R_1a, R_1b, R_2a, R_2b) .

5. A device (1) according to claim 4,

characterized in that

one measuring winding (L_M) is wound around the first pair of adjacent flux paths (R_1a, R_1b) and/or

one measuring winding (L_M) is wound around the second pair of adjacent flux paths (R_2a, R_2b).

6. A device (1) according to claim 4,

characterized in that

the middle of the openings (5) has a larger extent that the flux paths (R_1a, R_1b, R_2a, R_2b) and thereby

defines a first common extension (R₁) of the first pair of adjacent flux paths (R_1a, R_1b) and

a second common extension (R₄) of the second pair of adjacent flux paths (R_2a, R_2b),

one measuring winding (L_M) is wound around the first common extension (R₁) and/or

one measuring winding (L_M) is wound around the second common extension (R₄).

7. A device (1) according to one of claims 1 to 6,

characterized in that

the at least one exciter winding (L_S) is connected to a modulator unit (M).

8. A device (1) according to claim 7,

characterized in that

a demodulator (D) is connected to the at least one measuring winding (L_M) and can be synchronized with the modulator unit (M).

9. A device (1) according to claim 8,

characterized in that

an integrator (I) is connected to the demodulator (D).

10. A device (1) according to one of claims 1 to 9,

characterized in that

an output (A) is connected directly or indirectly via a first operational amplifier (G) to the compensating winding (L_C).

11. A device (1) according to one of claims 9 or 10,

characterized in that

the integrator (I) is connected to the compensating winding (L_C).

12. A device (1) according to claim 10,

characterized in that

the integrator (I) is connected to a second operational amplifier (K), which is connected to the compensating winding (L_C) and the first operational amplifier (G).

13. A device (1) according to one of the preceding claims, characterized in that the measuring winding (L_M) comprises an analog-to-digital converter (6).

14. A device (1) according to one of claims 10 to 13, characterized in that the first operational amplifier (G) and the second operational amplifier (K) are implemented together as digital and analog components.

15. A method for determining current using a device (1) according to one of the preceding claims, with the following process steps:

Passing a primary current (I₁) through the primary conductor (L₁) and thereby inducing a magnetic flux in the core (2);

Passing a compensating current (I_C) through the compensating winding (L_C) and thereby inducing a magnetic flux in the core, in order to counteract the magnetic flux induced by the primary conductor (L₁);

Periodically energizing the at least one exciter winding (L_S) and thereby, to the extent energized, inducing a magnetic flux in at least two flux paths (R_1a, R_1b, R_2a, R_2b) wound by the at least one exciter winding (L_S) and thereby modulating the said flux paths (R_1a, R_1b, R_2a, R_2b) magnetically;

Sensing, by means of the at least one measuring winding (L_M), the change of the magnetic flux between various energization conditions of the exciter winding (L_S), in order to tap a demodulation signal for regulation of the magnetic flux induced by the compensating winding (L_C);

Setting the compensating current (I_C) to a value such that the change of magnetic flux sensed by the measuring winding (L_M) is minimized;

Measuring the compensating current (I_C);

Calculating the primary current (I₁) from the compensating current (I_C).

16. A method according to claim 15,

characterized in that

two exciter windings (L_S) are operated in opposition.

17. A method according to claim 15 or 16,

characterized in that,

by means of the demodulator (D), the ends of the measuring winding (L_M) are connected alternately to the input of the integrator (I).

18. A method according to claim 17,

characterized in that

the demodulator (D) is synchronized with the modulator unit (M).

19. A method according to claim 17 or 18,

characterized in that

the output signal of the demodulator (D) is converted by means of the integrator (I) into the compensating current (I_C).

20. A method according to claim 17 or 18,

characterized in that

the output signal of the demodulator is converted into the compensating current (I_C) by means of the integrator (I) and the second operational amplifier (K), which receives a feedback signal from the first operational amplifier (G).

21. A method according to one of claims 15 to 20, characterized by measurement of the inductance of the at least one exciter winding (L_S) and generation of a signal that indicates whether or not the respective measured inductance lies within a specified range.

23. A magnetic switch (S) according to claim 19,

characterized in that

one exciter winding (L_S) is wound with different orientation around two flux paths (R_1a, R_1b, R_2a, R_2b).

22. A magnetic switch (S) of a magnetic core (2) with a measuring region (4) that has at least two openings (5) that subdivide the measuring region (4) into at least three adjacent flux paths (R_1a, R_1b, R₂, R_2a, R_2b), with the following features:

at least one exciter winding (L_S) is connected to a modulator unit (M),

either one exciter winding (L_S) is wound around two flux paths (R_1a, R_1b, R_2a, R_2b) of the measuring region (4), or two exciter windings (L_S) are wound around respectively one of the flux paths (R_1a, R_1b, R_2a, R_2b) of the measuring region (4) and

the at least one exciter winding (L_S) can be energized periodically by means of the modulator unit (M) in order, to the extent that it is energized, to induce a magnetic flux in the two flux paths (R_1a, R_1b, R_2a, R_2b) wound by the at least one exciter winding (L_S).