US-12618876-B2 - Superparamagnetic transducer and corresponding magnetic field flow sensor for measuring a direct current

US12618876B2US 12618876 B2US12618876 B2US 12618876B2US-12618876-B2

Abstract

A super-paramagnetic material transducer includes: a rigid body with a longitudinal central axis and two planar surfaces at each of the opposite ends of the body in the direction of the longitudinal central axis, both of these planar surfaces being substantially perpendicular to the longitudinal central axis; and at least one support channel formed in the body and in which a super-paramagnetic coil is housed, the support channel extending parallel to the longitudinal central axis and opening onto both planar surfaces. The super-paramagnetic coil is formed by a core made of super-paramagnetic around which at least one electrical conductor is wound. Furthermore, a feedback winding formed by an electric conductor is wound on the external surface of the body and along the longitudinal central axis.

Inventors

Christian Kern

Assignees

SOCOMEC

Dates

Publication Date: 20260505
Application Date: 20231123
Priority Date: 20221222

Claims (10)

1 . A magnetic field flow sensor for measuring a direct current, formed by at least one super-paramagnetic material transducer intended to be subjected to an external magnetic field to be measured induced by a current traversing a primary conductor formed by at least one electrical conductor of which at least a portion extends along an axis, characterised in that the sensor comprises at least: a super-paramagnetic material transducer comprising: at least one super-paramagnetic coil formed by a core with a longitudinal axis made of super-paramagnetic material around which at least one electrical conductor is wound, along the longitudinal axis; and at least one feedback winding; a rigid body with a longitudinal central axis, and two planar surfaces at each of the opposite ends of the body in the direction of the longitudinal central axis, both of these planar surfaces being substantially perpendicular to the longitudinal central axis; at least one support channel formed in the body and in which the super-paramagnetic coil is housed, the support channel extending parallel to the longitudinal central axis and opening onto both planar surfaces; and characterised in that the feedback winding is formed by an electrical conductor wound onto the outer surface of the body and along the longitudinal central axis, said transducer having two opposite free ends along the longitudinal central axis, the super-paramagnetic transducer being formed by the feedback winding coupled to said at least one super-paramagnetic coil extending between both free ends; and wherein said sensor comprises: a magnetic circuit having at least two planar surfaces parallel to one another and perpendicular to the longitudinal central axis, both planar surfaces being positioned opposite the respective free ends of the super-paramagnetic transducer; and in that said sensor is positioned relative to said primary conductor such that said axis is perpendicular to the longitudinal axis and parallel to said planar surfaces.
2 . The magnetic field flow sensor according to claim 1 , characterised in that the transducer further comprises several distinct support channels, each channel housing a super-paramagnetic coil, the support channels extending parallel to the longitudinal central axis and being arranged in the body around the longitudinal central axis, each channel opening at both planar surfaces of the body.
3 . The magnetic field flow sensor according to claim 1 , characterised in that the core of said at least one super-paramagnetic coil has a cross-section of less than or equal to 5 mm 2 , and a super-paramagnetic material volume concentration of less than 10%.
4 . The magnetic field flow sensor according to claim 1 , characterised in that both planar surfaces form an external volume with the external surface of the body, the feedback winding being contained in this external volume.
5 . The magnetic field flow sensor according to claim 1 , characterised in that the body is formed by a first sub-structure comprising said at least one support channel and a second hollow sub-structure comprising both planar surfaces as well as the external surface supporting the feedback winding, the first sub-structure being inserted into the hollow volume of the second sub-structure, said at least one support channel being open radially towards the external surface of the body of the first sub-structure and opening at both ends of said body of the first sub-structure.
6 . The magnetic field flow sensor according to claim 1 , characterised in that for a primary conductor comprising: a primary conductor referred to as an “outward” conductor, for the flow of a current in a direction along the axis; and a primary conductor referred to as a “return” conductor, for the flow of a current in the opposite direction; the super-paramagnetic transducer is arranged between both of the primary outward and return conductors along a lateral axis perpendicular to the longitudinal central axis and to the axis, the magnetic circuit surrounding the assembly of primary outward and return conductors and super-paramagnetic transducer, forming a field flow contour perpendicular to the flow direction of the currents.
7 . The magnetic field flow sensor according to claim 6 , characterised in that for outward and return primary conductors formed by both branches of a single electrical conductor having a substantially U-shaped profile, the super-paramagnetic transducer is arranged between both branches.
8 . The magnetic field flow sensor according to claim 1 , characterised in that, for a single primary conductor, two super-paramagnetic transducers are arranged on either side of the primary conductor and extend parallel along the longitudinal central axis, and the magnetic circuit comprises two plates forming both planar surfaces, one of the plates being positioned opposite the free ends of both super-paramagnetic transducers, and the other plate being positioned opposite the other free ends of both super-paramagnetic transducers.
9 . The magnetic field flow sensor according to claim 1 , characterised in that, for three primary conductors, the sensor comprises two super-paramagnetic transducers positioned alternately with said primary conductors along a lateral axis perpendicular to the longitudinal central axis and to the axis, the magnetic circuit surrounding the assembly formed by the three primary conductors and both super-paramagnetic transducers.
10 . The magnetic field flow sensor according to claim 1 , characterised in that the sensor further comprises a Hall effect sensor and/or Rogowski coils around each primary conductor.

Description

TECHNICAL FIELD The present invention relates to the field of non-contact measurement of an electric current flowing in a conductor by measuring the flow of the magnetic field induced by this current. The invention relates more particularly to a super-paramagnetic transducer and a magnetic field flow sensor incorporating at least one transducer made of a super-paramagnetic material, suitable for measuring direct current. PRIOR ART To measure a current I, different physical principles can be used to generate a physical quantity representative of this current I. For example, the magnetic sensors implement transducers which are sensitive to magnetic quantities, such as the flow of the magnetic field, induced by the current to be measured. In particular, current sensors are known, implementing the so-called Néel® effect technology described, for example, in the document FR2891917. The distinctive feature of this technology is based on the use of a transducer consisting of coils whose cores are made of a composite loaded with nano-particles having super-paramagnetic properties (SPM). Conventionally, such a super-paramagnetic transducer (SPM) is formed by a wired conductor wound around and along a flexible and elongated magnetic core. The winding created along the magnetic core provides a dual function as both excitation and measurement coil. It is nevertheless customary to implement suitable feedback means to maintain the flow of the magnetic field in the core at a substantially zero value. The excitation coil may be used to provide the feedback function, but it is also possible to provide a specific winding superimposed on the excitation winding to act as a feedback coil. The use of this type of transducer has the advantage of not having a magnetic offset, because an SPM material has the distinctive feature of being free of hysteresis. However, the characteristics of SPM materials are such that it is necessary to make a compromise between measurement dynamics and sensitivity. In fact, the M(H) magnetisation of an SPM material substantially follows a Langevin function. FIG. 1 shows the relationship between primary field H(A/m) and measured field Hmes(A/m) with an open loop sensor based on a known SPM material. In the case illustrated in FIG. 1, it is observed that the linearity range is very small, and that the relationship is not bijective, each measured field value being able to correspond to two primary field values. In the example shown in FIG. 1, the linearity range, and therefore the measurement range, is limited to Hmax=1100 A/m. Thus, the use of SPM material having a low Hmax value, for example, 1100 A/m, makes it possible to have a good level of sensitivity, but the measurement range remains restricted, and is therefore not suitable for measuring the flow of the field having a large field variation along the measurement contour. The use of materials having a higher Hmax value, for example, 10 kA/m, to have a greater linearity range, will however reduce the sensitivity of the transducer, and is therefore not suitable for measuring small currents. Document EP 3 477 311 B1 proposes a current sensor comprising a magnetic circuit formed around a primary conductor, a probe coil arranged on the magnetic circuit, and a secondary winding that generates, in the magnetic circuit, a magnetic field in a direction that is opposite to a direction of a magnetic field generated by the flux of the primary current. This current sensor is relatively large, and does not make it possible to make any sufficiently precise measurement(s). The document US 2012/038360 A1 proposes a sensor of the current flowing in an electrical conductor. This sensor comprises a super-paramagnetic core that forms a closed circuit comprising a “U”-shaped core and a hoop, these two elements being detachable in order to be able to insert the conductor inside the magnetic circuit. This sensor, in order to operate, requires a core with a large cross-section, and also a high concentration of SPM material, i.e., a large quantity of SPM material that makes it a very expensive solution. Document WO 2022/129732 A1 proposes a current sensor comprising a pair of coils each comprising a super-paramagnetic core. The sensor also comprises three means for energising the coils with current, which is heavy to manufacture. In addition, the precision of the measurements of such a sensor is not satisfactory. SUMMARY OF THE INVENTION The present invention therefore aims to propose an alternative configuration of direct current or direct magnetic field flow sensor, made of SPM. In particular, the present invention aims to propose a configuration that takes advantage of the interesting characteristics of SPM transducers with zero-field flow, mainly their absence of magnetic offset, while having a reduced bulk and a cost-effective solution. SPM Transducer Thus, the invention provides an SPM super-paramagnetic material transducer comprising: at least one SPM coil formed b