MAGNETIC CLOSING CORE

Abstract

A magnetic core (12), particularly for a voltage transformer, comprising: a first part (14) having a U- or E-shaped cross-section, including a first substantially rectangular plate (30) from which extend at least two parallel lateral walls (22, 24), the free edges of which form first bearing surfaces (38, 42); a second part (16) comprising a second plate (36) of identical dimensions to the first plate (30); and at least one second bearing surface (44) resting on the first bearing surfaces (38, 42) of the first part (14), wherein the first and second parts (14, 16) are joined by means of male / female assemblies (46) interposed between the bearing surfaces (38, 42, 44). For the abbreviated version: Figure 4.

Description

Title of the invention: MAGNETIC CORE WITH OPTIMIZED CLOSURE Technical field of the invention

[0001] The invention relates to a magnetic core for a magnetic circuit implemented in an electrical transformer and a method of manufacturing such a core. Technical background

[0002] A magnetic circuit consists of a magnetic core, generally made of ferromagnetic material, through which a magnetic field flux circulates.

[0003] The magnetic field is generally created either by windings surrounding the magnetic circuit and crossed by currents, or by permanent magnets contained in the magnetic circuit.

[0004] When several windings are wound around the same magnetic core, they constitute magnetically coupled circuits.

[0005] This is particularly the case for static transformers, which comprise at least two primary and secondary coils whose windings are arranged around the same magnetic core. In such a static transformer, the energy is transferred from a primary magnetic circuit to a secondary magnetic circuit via the magnetic core which constitutes the transformer frame.

[0006] The magnetic core is closed on itself so as to constitute at least one magnetic loop allowing the field lines to be closed on themselves. For this, the magnetic core comprises at least one branch on which each of the two coils is wound, and this core is closed on itself. The coils can be wound on the same branch or on two separate branches of the core.

[0007] There are different types of magnetic cores, such as toroidal cores, O-cores, EE-type cores and EL-type cores.

[0008] Type O cores comprise a first part having a U-shaped section comprising two parallel walls, and a second part having a U-shaped or I-shaped section covering this first part.

[0009] The cores of type El or type EE, for their part, comprise a first part having an E-shaped section comprising two parallel walls and a middle wall. In the case of a core of type El, the core comprises a second part shaped in the form of a plate having an I-shaped section and covering the first part. In the case of a core of type EE, the core comprises a second part having an E-shaped section also comprising two parallel walls and a middle wall resting head to tail on the walls of the first part. In both cases, these cores are particularly particularly advantageous because they allow the two coils to be placed on the middle wall(s) and the field lines to be looped symmetrically on either side of this middle wall via the side walls.

[0010] A problem arises regarding the closing of the magnetic circuit in the case of magnetic cores of type O, El or EE.

[0011] There are currently various technical solutions for ensuring that the second part is maintained on the first part.

[0012] A first solution consists of holding the second part against the first part by means of a housing enclosing the two parts. In addition to the fact that this solution is bulky and involves expensive machining, it requires control of the clamping force of the housing, otherwise the core will be damaged.

[0013] A second solution consists of gluing the second part onto the first part. This design has many disadvantages because there are very few glues available for this type of application. In addition, since the glue does not have constant mechanical characteristics as a function of temperature, its temperature resistance can lead to a significant variation in the air gap between the first and second parts, which has the consequence of degrading the performance of the magnetic circuit.

[0014] A third solution consists of ensuring a strapping of the two parts. This solution also does not guarantee the air gap between the first and second parts and it can also cause the appearance of an electric arc in the event of rupture of the strapping. Summary of the invention

[0015] The invention overcomes the aforementioned drawbacks by proposing a fixing of the first and second parts by means of at least one male-female assembly.

[0016] For this purpose, the invention proposes a magnetic core, in particular for a voltage transformer, comprising: - a first part made of ferromagnetic material, which extends along a general axis X and which has, transversely to this axis X, a U-shaped or E-shaped section, this first part comprising: • a first, substantially rectangular plate, • at least two parallel side walls, extending along the X axis perpendicularly from two opposite edges of the first plate, these side walls being formed in one piece with the first plate, and having free edges which are substantially parallel to the first plate and which form first bearing surfaces, and - a second part made of ferromagnetic material which extends along the general axis X and which presents transversely to this axis X, a I-shaped or E-shaped section, this second part comprising a second plate of dimensions identical to the first plate, and at least one second bearing surface resting on the first bearing surfaces of the first part.

[0017] More specifically, the first and second parts are assembled by means of male / female assemblies which are interposed between each of the first bearing surfaces and the at least one second bearing surface.

[0018] The invention advantageously makes it possible to guarantee reliable fixing of the second part to the first part, making it possible to maintain a reduced air gap.

[0019] According to other characteristics of the core: - each male / female assembly comprises on the one hand at least one first bore which has an axis perpendicular to the first and second plates and which is formed in one of the first and second parts, and on the other hand at least one column of the same diameter as a diameter of said first bore, this column extending from the other of the first and second parts and being received in said first bore, - the column is in one piece with the first or second part from which it extends, - the column is further received in a second bore which is formed in the first or second part from which it extends and which projects out of said second bore, - the second bore is blind or through and the column consists of a dowel, - the dowel is made of a ferromagnetic or plastic material, - the second bore is through, the column consists of a screw which passes through said second bore, and the first bore has a tapping complementary to a thread of said screw, - the screw is metallic or made of plastic material, - the magnetic core is of type El and: • the first part has an E-shaped section with the two identical parallel side walls and it further comprises a middle wall which is identical, parallel, and equidistant from the two side walls, this middle wall extending along the X axis perpendicular to the first plate, and being formed in one piece with the first plate, and comprising a free edge which is substantially parallel to the first plate and which also forms a first bearing surface, • the second part has an I-shaped section and is shaped into a plate, one face of which facing the first part forms the second support surface resting on the first support surfaces, - the first bores are formed in the side and middle walls of the first part and open into the bearing surfaces of said side and middle walls, - a single male / female assembly is interposed between each of the first and second bearing surfaces, - the single male / female assembly is interposed between the middle of each of the side and middle walls and the second plate.

[0020] The invention also relates to a method of manufacturing a magnetic core of the type described above, comprising at least the following steps: a. manufacture the first and second parts by additive manufacturing, b. produce the female parts of the male / female assemblies, c. insert the male parts of the male / female assemblies to fix the first and second parts to each other.

[0021] According to a first variant of this method, step b) is carried out simultaneously with step a) by additive manufacturing.

[0022] According to a second variant of this method, step b) is carried out after step a) by removing material. Brief description of the figures

[0023] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - [Fig.l] [Fig.l] is a schematic perspective view of a transformer having an O-type magnetic core; - [Fig.2] [Fig.2] is a schematic perspective view of a transformer comprising a magnetic core of type El or EE; - [Fig.3] [Fig.3] is a schematic sectional view of a magnetic core of type El; - [Fig.4] [Fig.4] is a schematic perspective view of a core ma El type genetics according to a first embodiment of the invention; - [Fig.5] [Fig.5] is a schematic perspective view of a magnetic core of type El according to a second embodiment of the invention; - [Fig.6] [Fig.6] is a schematic perspective view of a magnetic core of type El according to a third embodiment of the invention; - [Fig.7] [Fig.7] is a block diagram illustrating the manufacturing steps of a first method of manufacturing the magnetic core according to the invention; and - [Fig.8] [Fig.8] is a block diagram illustrating the manufacturing steps of a second method of manufacturing the magnetic core according to the invention. Detailed description of the invention

[0024] Two examples of transformers 10 are shown schematically in Figures 1 and 2.

[0025] The transformer 10 of [Fig. 1] is a so-called O-type transformer because it comprises a core 12 having a general O-shaped section making it possible to close the magnetic circuit of this transformer. The core 12 comprises a first part 14 made of ferromagnetic material having a U-shaped section and a second part 16 made of ferromagnetic material having an I-shaped section. Coils 18 and 20 are wound on two side walls 22, 24 of the first part 14. The first and second parts 14, 16 are joined along an air gap 26, shown in strong lines.

[0026] The transformer 10 of [Fig.2] which has been shown with an air gap 26 in strong lines is a so-called El type transformer because it comprises a core 12 having a general section in the shape of an E and joined Is making it possible to close the magnetic circuit of this transformer. The core 12 comprises a first part 14 having an E-shaped section and a second part 16 having an I-shaped section. Coils 18 and 20 are wound on a middle wall 28 of the first part 14, this branch being equidistant from side walls 22, 24. The first and second parts 14, 16 are joined along the air gap 26, shown in strong lines.

[0027] [Fig.2] also represents a transformer 10 which may have an air gap 26' in dotted lines which is a so-called EE type transformer because it comprises a core 12 having a general section made in the form of two E joined head to tail which make it possible to close the magnetic circuit of this transformer. The core 12 comprises first parts 14 and second parts 16 both comprising E-shaped sections. Coils 18 and 20 are wound on a middle wall 28 of each of these parts 14, 16, this branch being equidistant from side walls 22, 24 of each of these parts 14, 16. The first and second parts 14, 16 are joined along the air gap 26', represented in dotted lines.

[0028] In the remainder of this description, the case of a core 12 of type El will be considered, but it will be understood that the present invention also applies to a core of type O or type EE.

[0029] [Fig. 3] represents a section of a magnetic core 12 of type El known from the state of the art and figures 4 to 6 represent perspective views of different cores 12 of type El according to the invention. These cores 12 are here called "planar" type (an English acronym for "plan") because the first part 14, which extends along an axis general X of elongation and which has transversely with respect to this axis X an E-shaped section, comprises a first plate 30 substantially rectangular extending along the general X axis of elongation, and two parallel side walls 22, 24 which also extend along the X axis of elongation but perpendicularly in a direction Z from two opposite edges 32, 34 of the first plate 30. The core also comprises a middle wall 28 which is identical, parallel, and equidistant to the two side walls 22, 24, and which also extends along the X axis of elongation perpendicularly in the direction Z to the first plate 30.

[0030] The core 12 therefore sees its largest dimension oriented along the elongation axis X.

[0031] It will be understood that this arrangement is in no way limiting of the invention and that the core could be of type O or EE without changing the nature of the invention, just as its elongation axis X could be oriented differently.

[0032] The second part 14 is also made of ferromagnetic material and extends along the general axis X. It has, transversely to this axis X, an I-shaped section, and, in the case of a core 12 of type El, it is formed of a second plate 36 of dimensions identical to the first plate 30.

[0033] It will be understood that in the case of an EE type core, the second part 14 would not be limited to a second plate 36 but it would also include side and middle walls.

[0034] In the example of core 12 of type El which has been shown here, the side walls 22, 24 and the middle wall 28 are formed in one piece with the first plate 30 and they comprise free edges substantially parallel to the first plate 30 which form first bearing surfaces 38, 40, 42 for the second part 16.

[0035] For this purpose, a turned face of the second plate 36 turned towards the first part 30 forms a second bearing surface 44 resting on the first bearing surfaces 38, 40, 42.

[0036] It can therefore be understood that maintaining the second bearing face 44 on the first bearing faces 38, 40, 42 is decisive with regard to obtaining an air gap 26 as small as possible. Typically an air gap value of 150 qm is an acceptable value for this type of application.

[0037] To achieve this aim, in accordance with the invention, as illustrated in FIGS. 4 to 6, the first and second parts 14, 16 are assembled by means of male / female assemblies 46 which are interposed between each of the first bearing surfaces 38, 40, 42 and the second bearing surface 44.

[0038] As illustrated in Figures 4 to 6, each male / female assembly 46 comprises on the one hand at least one first bore 48 which has an axis Z perpendicular to the first and second plates 30, 36 and which is formed in one of the first and second parts 12, 14.

[0039] Here, the core 12 comprises three male / female assemblies 46, the first bores 48 of which are formed in the first part 14. This configuration is not limiting of the invention as to the number of male / female assemblies 46 or as to the positioning of their first bores 48 on the first part 14 or the second part 16. The first bores 48 are formed in the lateral walls 22, 24 and middle walls 28 of the first part 14 and open into the bearing surfaces 38, 40, 42 of said lateral walls 22, 24 and middle walls 28.

[0040] According to the invention, each male / female assembly 46 comprises at least one column with a diameter corresponding to the corresponding bore 48, this column 50 extending from the other of the first and second parts 14, 16 and being received in the bore 48. In the three embodiments which have been shown in FIGS. 4 to 6, each column 50 extends from the second part 16.

[0041] According to a first embodiment of the invention which has been shown in [Fig. 4], each column 50 is in a single piece with the first or second part 14, 16 from which it extends, that is to say here the second part 16. For example, the second part 16 is produced by an additive manufacturing process and the column 50 is produced at the same time as the second part 16.

[0042] According to second and third embodiments which have been shown in figures 5 and 6, the column 50 is received in a second bore 52 which is formed in the first or second part from which it extends, here the second part 16, and it projects out of said second bore 52 to be able to be inserted into the first bore 48.

[0043] The second bore 52 may be a through bore, as shown in [Fig. 6], and in this case the pin 50 is shaped like a dowel. It allows the assembly of the first and second parts 14, 16 simply by aligning the second bores 52 with the first bores 48 and by introducing the pin 50 through the two bores 48, 52. The pin 50 is held in the bores 48, 52 with a tight fit.

[0044] The second bore can also be blind and in this case the pin 50, still shaped as a dowel, allows the assembly of the first and second parts 14, 16 simply by introducing the pins 50 in abutment in the second bores 52 then by introducing the pins 50 projecting out of the second bores 52 from the second bearing face 44, integral with the second part 16, into the first bores 48.

[0045] When they are shaped as dowels, the columns 50 can advantageously be made of a ferromagnetic or plastic material.

[0046] As illustrated in [Fig.6] which represents a third embodiment of the invention, when the second bore 52 is through, the column 50 can also be made up of a screw which passes through the second bore 52, and which is received in the first bore 48 which then comprises a tapping 54 complementary to a thread 56 of this screw. The column 50 is shaped in the form of a metal screw or a plastic material,

[0047] Whatever the embodiment envisaged, there is a great deal of latitude as to the number or positioning of the first bores 48 on the first part 14. In Figures 4 to 6, a single male / female assembly 46 is shown interposed between each of the first bearing surfaces 38, 40, 42 and the second bearing surface 44, but it will be understood that there could be a greater number.

[0048] Similarly, in this case, each single male / female assembly 46 is interposed between the middle of each of the side walls 22, 24 and middle 28 and the second plate 36, but it will be understood that the assemblies 46 can be arranged in other non-aligned arrangements, as long as these assemblies distribute the fixing points regularly.

[0049] As has been seen, the core 12 can advantageously be manufactured by an additive manufacturing process.

[0050] Also, as illustrated in Figures 7 and 8, the core 12 can be manufactured according to a method comprising the steps of: a. manufacturing the first and second parts 14, 16 by additive manufacturing, b. produce the female parts of the male / female assemblies 46, i.e. the bores 48, c. introducing the male parts of the male / female assemblies 46, i.e. the columns 50, to fix the first and second parts 14, 16 to each other.

[0051] According to a first variant of this method which is shown in [Fig.7], step b) is carried out simultaneously with step a) by additive manufacturing. In this case the first bores 48 are manufactured at the same time as the first part 14. The columns 50 are either independent, or as seen with reference to the first embodiment of the invention, also manufactured by additive manufacturing with the second part 16.

[0052] According to a second variant of this method, step b) is carried out after step a) by removing material. Once the first part 14 has been manufactured, it is machined to form the first bores 48.

[0053] The invention therefore makes it possible to propose a core 12 in two parts 14, 16 guaranteeing a reduced air gap 26.

Claims

Claims

1. Magnetic core (12), in particular for a voltage transformer, comprising: - a first part (14) made of ferromagnetic material, which extends along a general axis X and which has, transversely to this axis X, a U-shaped or E-shaped section, this first part (14) comprising: • a first plate (30) substantially rectangular, • at least two parallel side walls (22, 24), extending along the X axis perpendicularly from two opposite edges (32, 34) of the first plate (30), these side walls (22, 24) being formed in one piece with the first plate (30) and having free edges which are parallel to the first plate (30) and form first bearing surfaces (38, 42), and - a second part (16) made of ferromagnetic material which extends along the general axis X and which has, transversely to this axis X, an I-shaped or E-shaped section, this second part (16) comprising a second plate (36) of dimensions identical to the first plate (30), and at least one second bearing surface (44) resting on the first bearing surfaces (38, 42) of the first part (14), characterized in that the first and second parts (14, 16) are assembled by means of male / female assemblies (46) which are interposed between each of the first bearing surfaces (38, 42) and the at least one second bearing surface (44).

2. Magnetic core (12) according to the preceding claim, characterized in that each male / female assembly (46) comprises on the one hand at least one first bore (48) which has an axis (Z) perpendicular to the first and second plates (30, 36) and which is formed in one of the first and second parts (14, 16), and on the other hand at least one column (50) of the same diameter as a diameter of said first bore (48), this column (50) extending from the other of the first and second parts (14, 16) and being received in said first bore (48).

3. Magnetic core (12) according to claim 2, characterized in that the column (50) is in one piece with the first or second part (14, 16) from which it extends.

4. Magnetic core (12) according to claim 2, characterized in that the column (50) is received in a second bore (52) which is formed in the first or second part (14, 16) from which it extends and in that it projects out of said second bore (52) from the second bearing face (44).

5. Magnetic core (12) according to claim 4, characterized in that the second bore (52) is blind or through and in that the column (50) consists of a dowel.

6. Magnetic core (12) according to one of claims 3 or 4, characterized in that the dowel is made of a ferromagnetic or plastic material.

7. Magnetic core (12) according to claim 4, characterized in that the second bore (52) is a through bore, in that the column (50) is made up of a screw which passes through said second bore (52), and in that the first bore (48) comprises a tapping (54) complementary to a thread (56) of said screw.

8. Magnetic core (12) according to one of the preceding claims, characterized in that it is of type El and in that: - the first part (14) has an E-shaped section with the two identical parallel side walls (22, 24) and it further comprises a middle wall (28) identical, parallel, and equidistant to the two side walls (22, 24), this middle wall (28) extending along the X axis perpendicular to the first plate (30), and being formed in one piece with the first plate (30), this middle wall (28) comprising a free edge which is parallel to the first plate (30) and which also forms a first bearing surface (40), - the second part (16) has an I-shaped section and it is shaped into a plate (36) of which one face facing the first part (14) forms the second bearing surface (44) resting on the first surfaces support (38, 40, 42).

9. Magnetic core (12) according to the preceding claim, characterized in that the first bores (48) are formed in the side walls (22, 24) and middle walls (28) of the first part (14) and open into the bearing surfaces (38, 40, 42) of said side walls (22, 24) and middle walls (26).

10. Magnetic core (12) according to one of the preceding claims, characterized in that a single male / female assembly (46) is interposed between each of the first (38, 40, 42) and second (44) bearing surfaces.

11. A method of manufacturing a magnetic core (12) according to one of claims 1 to 10, characterized in that it comprises the following steps: a. manufacturing the first and second parts (14, 16) by additive manufacturing, b. producing the female parts of the male / female assemblies (46), c. introducing the male parts of the male / female assemblies (46) to fix the first and second parts (14, 16) to each other.

12. Method for manufacturing a magnetic core (12) according to the preceding claim, characterized in that step b) is carried out simultaneously with step a) by additive manufacturing.

13. Method of manufacturing a magnetic core (12) according to claim 11, characterized in that step b) is carried out after step a) by removing material.

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