Current sensor and measuring system comprising such a current sensor

Abstract

The invention relates to a current sensor (6; 6') and a measuring system comprising such a current sensor. The current sensor comprises: an insulating substrate (10) having a central opening; a winding surrounding the central opening and comprising a coil (12, 14) wound around a portion of the insulating substrate; wherein the current sensor comprises at least one ferromagnetic layer (40, 42) incorporated in the portion of the insulating substrate, the coil (12, 14) surrounding the ferromagnetic layer.

Description

Technical Field

[0001] The invention relates to a current sensor and a measuring system comprising such a current sensor. Background Art

[0002] A Rogowski winding is a current sensor capable of measuring the intensity of an alternating current flowing through an electrical conductor.

[0003] Such sensors generally include a wound coil defining a closed contour around a central opening through which an electrical conductor is received. Current flowing through the electrical conductor induces a voltage between the terminals of the coil.

[0004] Rogowski coils can be manufactured on a printed circuit board (PCB). For example, an insulating substrate is pierced by a plurality of metallized through holes arranged in a predetermined pattern on the face of the substrate and positioned to define a closed contour around a central opening. A series of metallized holes and conductive traces formed on the layers of the substrate together define a conductive path forming a winding of the coil.

[0005] Printed circuit board Rogowski windings (PCB Rogowski coils) have the particular advantage of being relatively simple and inexpensive to manufacture on an industrial scale. They are also easy to miniaturize.

[0006] One disadvantage of these sensors is that they have a low gain (e.g., about 10 μV per ampere), which makes it difficult to detect small changes in current in an electrical conductor. This limitation is unacceptable in some applications, for example, when such sensors are used as current sensors in electrical protection devices in power distribution equipment.

[0007] Therefore, there is a need for current sensors, particularly Rogowski coils for printed circuit boards, that overcome these disadvantages. Summary of the invention

[0008] According to a first aspect of the present invention, a current sensor comprises:

[0009] - an insulating substrate having a central opening;

[0010] - a winding surrounding the central opening and comprising a coil wound around a portion of the insulating substrate;

[0011] The current sensor comprises at least one ferromagnetic layer incorporated in a portion of an insulating substrate, and the coil surrounds the ferromagnetic material layer.

[0012] According to some advantageous but not essential aspects, such a current sensor may combine one or more of the following features, alone or in any technically feasible combination:

[0013] - the coil comprises a plurality of coil parts electrically connected in series, the coil parts being rectilinear in shape and arranged to form a quadrilateral closed contour around a central opening.

[0014] - The ferromagnetic layer is common to all coil parts.

[0015] - said ferromagnetic layer is divided into several parts, each part being associated with one of said coil parts.

[0016] The ferromagnetic layer comprises a sublayer of an alloy of iron and nickel and two sublayers of copper stacked on both sides of the sublayer of the alloy of iron and nickel.

[0017] - The alloy of iron and nickel is FeNi36 alloy.

[0018] - the thickness of the ferromagnetic layer is greater than or equal to 150 μm.

[0019] -The Rogowski winding also includes an additional coil, which is wound around another part of the substrate and offset in a direction perpendicular to the plane of the substrate, the two coils are interlaced and electrically connected in series, and wherein an additional ferromagnetic layer is incorporated in the other part of the insulating substrate, and the additional coil surrounds the additional ferromagnetic layer.

[0020] - the substrate comprises a through hole perpendicular to the plane of the substrate, and the ferromagnetic layer is separated from the through hole by a buffer area devoid of ferromagnetic material.

[0021] - The substrate is a printed circuit board comprising one or more stacked layers of cured polymer material.

[0022] According to another aspect of the present invention, a measurement system comprises a current sensor as described above and an electronic processing circuit configured to process a signal measured by the current sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention will be better understood and further advantages thereof will become more apparent from the following description of an embodiment of a current sensor, given by way of example only and with reference to the accompanying drawings.

[0024] [ Figure 1 ] Figure 1 is a schematic diagram of a measurement system including a current sensor according to some embodiments of the present invention;

[0025] [ Figure 2 ] Figure 2 is a schematic diagram of a current sensor according to a first embodiment of the present invention;

[0026] [ Figure 3 ] Figure 3 yes Figure 2A schematic cross-sectional view of a current sensor;

[0027] [ Figure 4 ] Figure 4 FIG. 1 is a schematic diagram of a current sensor according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0028] Figure 1 A measuring system 2 for measuring the intensity of an electric current flowing through an electrical conductor 4 , such as a cable, a wire or a busbar, is shown.

[0029] In this case, the system 2 comprises a current sensor 6 and an electronic processing circuit 8 connected to the current sensor 6 and configured to process the signal measured by the current sensor 6 .

[0030] According to some embodiments, the current sensor 6 comprises a Rogowski coil comprising a coil defining a closed contour around a central opening 7 through which the conductor 4 is received. The ends of the winding are connected to inputs of a processing circuit 8 .

[0031] For example, the closed contour takes the shape of a polygon, in particular a quadrilateral, such as a square. As a variant, other shapes are conceivable, such as a circle or an ellipse.

[0032] According to some examples, the current flowing through the electrical conductor induces a voltage between the terminals of the coil. This voltage is proportional to the time derivative of the intensity of the current flowing through the conductor 4.

[0033] The processing circuit 8 is, for example, configured to calculate the value of the current based on the voltage signal delivered as an output from the current sensor 6 .

[0034] According to some embodiments, the current sensor 6 and the processing circuit 8 may be mounted on the same printed circuit board.

[0035] A first embodiment of the current sensor 6 is Figure 2 and 3 Shown in.

[0036] The current sensor 6 comprises a substrate 10 , which is preferably planar in shape.

[0037] Figure 2 The height of the current sensor 6 in a geometrical plane parallel to the substrate 10 is shown, thus showing the appearance of the sensor 6 on the upper face of the substrate 10. However, the substrate 10 itself is not shown to facilitate the understanding of the drawing. Figure 3 , a portion of the current sensor 6 is shown in a cross-sectional view perpendicular to the plane of the substrate 10 .

[0038] Preferably, the substrate 10 is electrically insulating.

[0039] According to some examples, substrate 10 is a printed circuit board that includes one or more layer stacks of a cured polymer material such as FR-4 epoxy.

[0040] For example, the substrate 10 may be manufactured by laminating multiple layers of a fiber braid pre-impregnated with resin, by depositing material, by additive manufacturing, or by any other suitable method.

[0041] According to some embodiments, the Rogowski winding includes at least one coil 12 wound around a portion of a substrate 10 .

[0042] For example, the electrical conductor is wound in turns on one or more layers of the substrate 10 .

[0043] According to some examples, the coil 12 at least partially penetrates the substrate 10, for example by means of a metallized hole (also referred to as a “through hole”) that penetrates the substrate 10 and enters the substrate 10 through at least a portion of its thickness and in a direction perpendicular to the plane of the substrate 10. The coil 12 also includes a conductive trace, for example made of a metal such as copper, which extends on one or more layers of the substrate 10, for example in a direction parallel to the plane of the substrate 10.

[0044] In other words, the coil 12 is formed by a combination of metallized holes extending perpendicular to the plane of the substrate 10 and conductive traces extending on the various layers of the substrate 10 .

[0045] Generally speaking, the term "Rogowski coil" does not imply a specific shape of turns, which may be circular, oval, polygonal or any other shape. In the exemplary embodiment described, the shape of the turns is polygonal, such as rectangular or square.

[0046] Preferably, a portion of the coil 12 is exposed to the exterior face of the substrate 10 , as will be described in more detail below.

[0047] According to one or more embodiments, the coil 12 includes a plurality of coil portions 16 , 18 , 20 , 22 electrically connected in series.

[0048] In the example shown, the coil parts 16, 18, 20, 22, also called coil segments, are rectilinear and arranged to form a quadrilateral closed contour around the central opening. For example, the closed contour is located in the center of the central opening.

[0049] For example, four coil portions 16, 18, 20, 22 are arranged end to end at right angles around a central opening, parallel to the plane of the substrate, while being connected only by a portion of the wire forming the winding.

[0050] In the embodiment shown, the Rogowski coil advantageously comprises a combination of two coils: a second coil 14 electrically connected in series with a first coil 12 .

[0051] However, according to some alternative embodiments, it is provided that the Rogowski coil may comprise only one coil. Thus, one or the other of the coils 12 and 14 may be omitted.

[0052] According to other variations, other additional coils may be associated in a similar manner to form a Rogowski coil.

[0053] In the example shown, the coils 12 and 14 are wound on different portions of the substrate 10 and are interleaved with each other.

[0054] For example, the term “staggered” is understood to mean that, over at least a portion of the length of the closed profile, the respective turns of the coils 12 and 14 are arranged alternately.

[0055] Preferably, the portion of the substrate 10 is offset in a direction perpendicular to the plane of the substrate 10 .

[0056] exist Figure 3 In the example shown, the turns of the first coil 12 are surrounded by a first portion of the substrate 10 formed between the upper face of the substrate 10 and the interface 26 between the sublayers of the substrate through a hole or opening (e.g., a blind hole or a through hole extending downwardly into the substrate 10 perpendicular to the plane of the substrate 10). The coil 12 is exposed to the upper face of the substrate 10.

[0057] For example, the interface 26 lies in a geometric plane parallel to the plane of the substrate 10. Figure 3 In the figure, the interfaces 26 are shown at an enlarged interval to facilitate understanding of the drawing. However, in reality, the sub-layers of the substrate are in direct contact at these interfaces.

[0058] In a similar manner, the turns of second coil 14 surround a second portion of substrate 10 formed between the lower face of substrate 10 and an interface 24 between a sublayer similar to interface 26 by passing through holes extending between interface 24 and the lower face of substrate 10 .

[0059] In this example, the interface 24 is located above the interface 26. The coil 14 is exposed to the lower face of the substrate 10.

[0060] According to some embodiments, the additional coil 14 includes coil portions similar to the coil portions 16 , 18 , 20 , 22 of the coil 12 .

[0061] Preferably, if Figure 2 As shown, these portions of coil 14 are aligned or overlapped with corresponding coil portions 16 , 18 , 20 , 22 of coil 12 in a direction perpendicular to the plane of substrate 10 .

[0062] According to some alternative embodiments, the through hole 28 may be formed in the substrate 10 , for example by piercing the entire thickness of the substrate 10 in a direction perpendicular to the plane of the substrate 10 .

[0063] Optionally, when the through hole is near the coil, the metal pads 30 , 36 are deposited on the through hole on the upper and lower faces of the coil. For example, the pads are arranged at the interface 24 or 26 .

[0064] Preferably, the metal pads are made of copper. According to one manufacturing method given by way of example, the metal pads 30, 36 are manufactured before assembling the substrate 10 by depositing a metal layer on the base stack of layers of the substrate. Next, the metal layer is etched in a predetermined pattern to form the pads 30 and 36, which are then covered with the other layers of the substrate 10. When the substrate 10 is subsequently rolled to complete the manufacture of the sensor 6, the layers come into contact at the interfaces 24 and 26, respectively, and fill the voids left by the metal removed by etching.

[0065] In the example shown, the through-hole 28 is arranged near the coil 12. A metal pad 30 is arranged in the interface 26, in which the inner face of the coil 12 is arranged.

[0066] For example, the metal pad is circular or square, and is arranged around the cross section of the through hole 28 in the interface 26 .

[0067] Preferably, the metal pads 32 are disposed at the upper and lower ends of the through holes 28 on the upper and lower surfaces of the substrate 10 , respectively.

[0068] In the example shown, similar to the through-hole 28, the second through-hole 34 is arranged near the second coil 14. A metal pad 36 similar to the metal pad 30 is arranged in the interface 24.

[0069] These examples are not limiting and other through-holes may be configured differently.As a variant, through-holes 28, 34 may be omitted.

[0070] According to some particularly advantageous embodiments, the current sensor 6 comprises at least one ferromagnetic layer 40 , 42 incorporated in the portion of the or each insulating substrate 10 surrounded by the or each coil, such that the coil surrounds the ferromagnetic layer.

[0071] In the example shown, the first ferromagnetic layer 40 is incorporated within the portion of the first substrate 10 that is surrounded by the first coil 10 , between the upper face of the substrate 10 and the interface 24 .

[0072] The second ferromagnetic layer 42 is incorporated within the portion of the second substrate 10 that is surrounded by the second coil 14 , between the lower face of the substrate 10 and the interface 26 .

[0073] By adding such a ferromagnetic layer, the gain of the current sensor 6 is increased. Ultimately, this may improve the accuracy of the current measurement performed by the measurement sensor 6 and the measurement system 2.

[0074] In a non-limiting example given by way of illustration, the inventors have observed that, with the aid of an embodiment of the invention, the measurement gain of the current sensor 6 can be improved by a factor of five or more compared to known printed circuit board Rogowski windings, for example obtaining a gain greater than or equal to 80 μV per ampere.

[0075] The increase in gain is particularly advantageous when the sensor 6 is used as a current sensor in an electrical protection device within an electrical distribution device. In particular, the electrical protection device must be able to trip quickly once an electrical fault is detected. However, certain signal processing devices, such as passive integrators, introduce signal attenuation, which may negatively affect the signal in the case where the current sensor exhibits a low gain, thereby compromising the ability of the processing circuit 8 to detect electrical faults. The use of a digital integrator will only cause a small attenuation of the measured signal, but has the disadvantage of introducing a large amount of waiting time, so that the protection device will not be able to react quickly enough when an electrical fault event is detected. In contrast, with the aid of the sensor 6, the processing circuit 8 may include a simple passive integrator, which is simpler to manufacture and can avoid the above-mentioned problems.

[0076] As a variant, the number of ferromagnetic layers may be different, for example, selected according to the number of coils 12 or 14. It will therefore be understood that in a variant in which coil 14 is omitted, layer 42 may also be omitted.

[0077] Preferably, each coil 12 or 14 surrounds only one ferromagnetic layer.

[0078] In practice, the first coil 12 intersects the first ferromagnetic layer 40. The second coil 14 intersects the second ferromagnetic layer 42. Preferably, the coils 12 and 14 are not in electrical contact with the ferromagnetic layers 40 and 42.

[0079] According to some examples, ferromagnetic layers 40 and 42 are identical.

[0080] Preferably, ferromagnetic layers 40 and 42 are similar or identical in size and geometric arrangement, such as being aligned or overlapping relative to each other in a direction perpendicular to the plane of substrate 10 .

[0081] In the following, only the ferromagnetic layer 40 is described in detail, but the teachings can be transposed to the ferromagnetic layer 42 .

[0082] According to some embodiments, the ferromagnetic layer 40 includes a sublayer 44 of an alloy of iron and nickel and two sublayers 46 , 48 of copper stacked on both sides of the sublayer 44 .

[0083] An example of an iron and nickel alloy is the FeNi36 alloy, also known by the registered trademark “Invar.” This alloy advantageously makes it possible to obtain good magnetic properties while exhibiting mechanical properties that are advantageous for the construction and strength of the substrate 10 .

[0084] The ferromagnetic layer 40 may be formed by depositing a material, or constructed in the form of a plate that is incorporated into the substrate 10 during its manufacturing process.

[0085] As a variant, other materials may be used to form the ferromagnetic layer 40, for example a ferromagnetic metal alloy.

[0086] According to some embodiments, the ferromagnetic layer 40 is greater than or equal to 150 μm, or greater than or equal to 250 μm.

[0087] In the example shown, the ferromagnetic layer 40 is arranged between a first sublayer 41 of the substrate 10 and a second sublayer 43 of the substrate. The interface 24 is formed between the second sublayer 43 and the core layer of the substrate 10. With respect to the interface 26, a similar arrangement is used for the ferromagnetic layer 42.

[0088] In one non-limiting example given by way of illustration, the total thickness of the substrate 10 measured in a direction perpendicular to the plane of the substrate 10 may be between 0.1 cm and 1 cm.

[0089] According to some embodiments, when one or more vias 28 , 34 pass through the substrate 10 , the ferromagnetic layer 40 may be laterally separated from the vias 28 , 34 by a buffer region 50 devoid of ferromagnetic material.

[0090] It should be understood that the buffer region 50 is arranged in line with the ferromagnetic layer 40 .

[0091] According to some examples, buffer region 50 may be filled with an electrically insulating material or formed by a void in ferromagnetic layer 40. In other words, ferromagnetic layer 40 is not in electrical contact with vias 28 and 34. The void may be obtained by piercing the ferromagnetic layer or by etching the ferromagnetic layer.

[0092] For example, the size of the buffer region 50 is determined so that the distance between the side edge of the through hole 28, 34 and the ferromagnetic material of the ferromagnetic layer 40 closest to the side edge (the distance is measured in a direction parallel to the plane of the substrate 10) is greater than or equal to 25% of the width of the through hole 28, 34.

[0093] In one non-limiting example given by way of illustration, the width of the through hole 28 is equal to 650 μm. On each side of the through hole 28 , the width of the buffer region 50 is greater than or equal to 200 μm.

[0094] Figure 4A current sensor 6' according to a second embodiment is shown. Similar elements of the current sensor 6' to those of the first embodiment have the same reference numerals and are referred to as such whenever reference is made above. Figure 2 and Figure 3 The description provided can be transposed here and will not be described in detail.

[0095] The current sensor 6 ′ is substantially the same as or similar to the current sensor 6 , and in particular includes a plurality of coil portions 14 , 18 , 20 , and 22 .

[0096] The current sensor 6 ′ differs from the current sensor 6 in particular in that each ferromagnetic layer 40 , 42 is divided in the plane of the ferromagnetic layer into a plurality of parts which are preferably electrically insulated from one another and each of which is associated with one of the coil parts 14 , 18 , 20 and 22 .

[0097] In the example shown, the plate 40 is divided into four sections 60 , 62 , 64 and 66 associated with the coil sections 18 , 20 , 22 and 16 , respectively.

[0098] It will be appreciated that portions 60 , 62 , 64 and 66 are electrically insulated from one another, such as by being separated in the plane of ferromagnetic layer 40 by a layer of non-magnetic material or by an electrically insulating material, such as similar to buffer region 50 described above.

[0099] In this case, the expression “associated with the coil portion” should be understood to mean that the corresponding coil portion surrounds the ferromagnetic layer portion and is aligned with the ferromagnetic layer portion in a direction perpendicular to the plane of the substrate 10 .

[0100] In practice, each portion of the ferromagnetic layer 40 , 42 is associated with only one of the coil portions 16 , 18 , 20 and 22 .

[0101] Dividing the ferromagnetic layer in this way advantageously makes it possible to avoid premature magnetic saturation of the ferromagnetic layer when the current flowing through the conductor 4 reaches high values. However, the advantages offered by the presence of the ferromagnetic layer in terms of gain are retained.

[0102] In this case as well, the embodiment is not limited by the number of coil sections 16 , 18 , 20 , and 22 or the number of ferromagnetic layer sections 40 , 42 .

[0103] Although not shown in detail, it will be appreciated that the same applies to layer 42, which itself is divided in a similar manner.

[0104] Advantageously, the magnetic layer portions 60, 62, 64 and 66 can be formed by depositing magnetic layers similar to the layers 40 and 42 during the manufacture of the substrate, and then cutting through these layers by piercing the substrate with the aid of a perforation tool. For example, a plurality of holes are pierced perpendicularly to the plane of the substrate in the corners of the layers to form air gaps defining the portions 60, 62, 64 and 66. This method makes it possible to cut through both ferromagnetic layers of the stack simultaneously in the same way, thereby obtaining portions 60, 62, 64 and 66 of the same size for both ferromagnetic layers. In addition, the width of the air gap can be easily adjusted by choosing a thicker or thinner perforation tool, thereby making it possible to easily adjust the gain value of the sensor.

[0105] The above-described embodiments and modifications may be combined with each other to produce new embodiments.

Claims

1. A current sensor (6; 6'), comprising: - an insulating substrate (10) having a central opening; - a winding surrounding the central opening and comprising a coil (12, 14) wound around a portion of the insulating substrate; The current sensor comprises at least one ferromagnetic layer (40, 42) incorporated in the portion of the insulating substrate, the coil (12, 14) surrounding the ferromagnetic layer; The Rogowski winding further comprises an additional coil (14), the additional coil (14) being wound around another portion of the substrate and offset in a direction perpendicular to the plane of the substrate (10), the two coils (12, 14) being staggered and electrically connected in series, and the additional ferromagnetic layer (42) being incorporated into the other portion of the insulating substrate, the additional coil (14) surrounding the additional ferromagnetic layer.

2. The current sensor (6; 6') according to claim 1, wherein: The coil (12) comprises a plurality of coil sections (16, 18, 20, 22) electrically connected in series, the coil sections being rectilinear in shape and arranged to form a quadrilateral closed contour around a central opening.

3. The current sensor (6) according to claim 2, wherein: The ferromagnetic layers (40, 42) are common to all coil sections.

4. The current sensor (6') according to claim 2, wherein: The ferromagnetic layer is divided into several portions (60, 62, 64, 66), each portion being associated with one of the coil portions (16, 18, 20, 22).

5. A current sensor (6; 6') according to any one of the preceding claims, wherein The ferromagnetic layer (40, 42) includes a sublayer (44) of an alloy of iron and nickel and two sublayers (46, 48) of copper stacked on both sides of the sublayer of the alloy of iron and nickel.

6. The current sensor (6; 6') according to claim 5, wherein: The alloy of iron and nickel is FeNi36 alloy.

7. A current sensor (6; 6') according to any one of the preceding claims, wherein The thickness of the ferromagnetic layer (40, 42) is greater than or equal to 150 μm.

8. A current sensor (6; 6') according to any one of the preceding claims, wherein The substrate (10) includes through holes (28, 34) perpendicular to the plane of the substrate, and the ferromagnetic layers (40, 42) are separated from the through holes (28, 34) by a buffer region (50) free of ferromagnetic material.

9. A current sensor (6; 6') according to any one of the preceding claims, wherein The substrate (10) is a printed circuit board, which comprises one or more stacked layers of cured polymer material.

10. A measuring system (2), characterized in that It comprises a current sensor (6; 6') according to any one of the preceding claims, and an electronic processing circuit (8) configured to process the signal measured by the current sensor (6; 6').

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