TORIC MAGNETIC CORE INDUCTIVE FILTERING DEVICE

Abstract

The invention relates to an inductive type filtering device comprising: • a first toroidal magnetic core (11) without air gap formed around a central recess (12), • a first electrical conductor (15) formed of turns wound around the first magnetic core (11) without passing through the central recess (12), in which no electrical conductor passes through the central recess (12).

Description

Preferably, the characteristic dimension of the coil is substantially equal to a largest external dimension of the magnetic core carried by the direction. Advantageously, the device further comprises a second toroidal magnetic core formed around a second central recess, the first magnetic core being arranged inside the second central recess, so that the second toroidal magnetic core closes a magnetic circuit formed by the first magnetic core. An air gap may be present between the first magnetic core and the second magnetic core. The device then advantageously comprises at least one magnetic or non-magnetic shim arranged in the air gap. Advantageously, the device further comprises a second electrical conductor formed of turns wound around the second magnetic core. Advantageously, no electrical conductor passes through the second central recess, the turns of the second electrical conductor being wound around the second magnetic core without passing through the second central recess. The first toroidal magnetic core is wound around a first axis. The first electrical conductor is wound around the first axis. The second toroidal magnetic core is wound around a second axis; the first and second axes are advantageously substantially perpendicular or parallel. The first magnetic core is advantageously made of nanocrystalline material. The central recess of the first magnetic core is advantageously filled with a magnetic material. The device may comprise several first toroidal magnetic cores formed around a central recess, and several first electrical conductors each formed of turns wound around one of the first magnetic cores without passing through the central recess of the first magnetic core around which the first electrical conductor in question is wound. The first magnetic cores are arranged inside the central recess of the second magnetic core. The device according to the claim may further comprise a third toroidal magnetic core disposed within the second central recess, the first magnetic cores being disposed between the second magnetic core and the third magnetic core. The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawing in which: Figures 1 and 2 represent two embodiments of coils wound around a toroidal magnetic core and in accordance with the invention; Figures 3 and 4 show two variants of the embodiment of Figure 2; Figures 5a, 5b, 6a and 6b respectively represent the use of the coils of Figures 1 and 2 in more complex filtering devices; Figure 7 shows an example of use of one of the filtering devices of Figures 3 or 4; Figure 8 represents a variant of the device of Figure 3; Figure 9 represents another variant of a device according to the invention. For the sake of clarity, the same elements will have the same references in the different figures. Figure 1 shows a first embodiment of a filtering device 10 comprising a toroidal magnetic core 11 without an air gap formed around a central recess 12. The magnetic core 11 is cylindrical in shape and extends around an axis 13. The central recess 12 also extends along the axis 13. The filtering device 10 comprises an electrical conductor 15 formed of turns wound around the magnetic core 11. The electrical conductor 15 may have a flat section, for example in the form of a strip or a braid that is wound around the magnetic core 11 by stacking the turns one on top of the other. Alternatively, the electrical conductor 15 may have a circular section. The turns may be arranged side by side in one or more layers. The electrical conductor 15 may be made of different metal alloys, such as copper or aluminum alloys. The presence of a central recess 12 makes it easier to produce the magnetic core, particularly when it is made of nanocrystalline material due to the fact that this material is manufactured as a ribbon wound around the central recess 12. Conventionally, in the presence of a central recess 12, the turns of a filtering device are formed by passing through the central recess 12. This makes it possible to close the magnetic circuit. On the contrary, and in an unconventional manner, the invention proposes to wind the turns of the electrical conductor 15 around the core magnetic circuit 11 without passing through the central recess 12. Taken in isolation, the filtering device 10 comprises an open magnetic circuit, which, a priori, is less efficient than a closed magnetic circuit. On the other hand, this makes it possible to wind the turns of the electrical conductor 15 much more simply without passing through a central recess. In the variant of Figure 1, the winding of the turns of the electrical conductor 15 is done around the axis 13. The invention is well suited to a magnetic core 11 made of nanocrystalline ferromagnetic material. It is also possible to make the magnetic core 11 in other types of ferromagnetic materials. It is possible to fill the central recess 12 with a ferromagnetic material in order to take advantage of the free volume left in the central recess to further increase the inductance value of the electrical conductor 15. The filling material may be of a different type from that used for the magnetic core 11. In Figure 1, the filling of the central recess 12 is carried out by means of balls 16 made of ferromagnetic material. Other shapes may be used to fill the central recess 12. Figure 2 shows a second embodiment of filtering device 20 comprising a toroidal magnetic core 21 without air gap formed around a central recess 22. The magnetic core 21 is also of cylindrical shape extending around an axis 23. The central recess 22 extends along the axis 23. The notion of cylindrical shape must be understood in the broad sense, that is to say a shape developed from any curve and a generatrix resting on the curve. To obtain the central recess 22, the curve is closed. The presence of a closed curve facilitates the production of the magnetic core from ribbons wound following the shape of the closed curve. In the example of Figure 2, the curve is substantially rectangular and the generatrix of the cylindrical shape is a direction carried by the axis 23. Any other shape of curve is of course possible within the scope of the invention. The filtering device 20 comprises an electrical conductor 25 formed of turns wound around the magnetic core 21. Unlike the filtering device 10 where the conductor 15 is wound around the axis 13 along which the central recess 12 extends, the electrical conductor 25 is wound around the magnetic core 21 along an axis 26 substantially perpendicular to the axis 23. In the example shown, where the closed curve is substantially rectangular, the axis 26 is parallel to the greatest length of the rectangle. Alternatively, it is possible to wind the turns of the conductor 25 around an axis parallel to the shortest length of the rectangle. However, a winding axis of the turns parallel to the greatest length of the rectangle allows, for the same number of turns, to wind them closer to the magnetic circuit and thus increase the self-induction value of the filtering device 20. As with device 10, it is possible to fill the central recess 22 with a ferromagnetic material. As with the embodiment of Figure 1, the magnetic core 21 may be made of nanocrystalline ferromagnetic material or other types of ferromagnetic materials. The magnetic cores 11 and 21 may be made without an air gap, which is well suited to nanocrystalline ferromagnetic material, or by means of cut and assembled cores, which is suitable for other types of ferromagnetic materials. The choice may be made depending on the availability of cut or uncut magnetic cores on the market. The filtering devices 10 and 20 shown in Figures 1 and 2 each comprise a single winding formed respectively by the conductors 15 and 25. Alternatively, still within the scope of the invention, several windings can be formed around the same magnetic core in order to couple these windings. Figure 3 shows in section a variant of the device 20 in which the conductor 25 is produced by means of a strip 27 wound around the magnetic core 21. The greatest length, denoted I of the cylindrical section of the central recess 22 extends along the axis 26. The fact of winding the strip 27 around the magnetic core 21 without crossing the central recess 22 makes it possible to choose a strip 27 whose width denoted L is greater than the length I of the central recess 22. This makes it possible to make the best use of the external length of the magnetic core 21 along the axis 26. In the example shown, the width of the strip 27 is equal to the external length of the magnetic core 21. The self-induction value obtained by winding the strip 27 is thereby increased. Figure 4 shows in section another variant of the device 20 in which the conductor 25 is produced by means of an electrical conductor 25 with a circular section and marked 28. The length of the coil produced by winding the conductor 28 is defined along the axis 26. In the example shown, the length of the coil is equal to the external length of the magnetic core 21. The length of the coil is therefore also marked L in Figure 4 and is also greater than the length I of the central recess 22. The self-induction value obtained by winding the conductor 28 is also increased. In Figure 4, the conductor 28 forms a single layer of turns. The coil thus formed can of course comprise several layers of turns. More generally, a characteristic dimension L of the coil produced by winding the electrical conductor 25 is greater than the largest dimension I of the cylindrical section of the central recess 22, the two dimensions being carried by the same direction, in this case the axis 26. This characteristic is also verified for the embodiment shown in Figure 1. Preferably, the characteristic dimension L of the coil is substantially equal to the largest external dimension of the magnetic core always measured along the axis 26 so that the magnetic flux present inside the coil is guided as much as possible by the magnetic core. Figures 5a and 5b show the use of the device 10 of Figure 1 in a more complex filtering device 30. The filtering device 30 comprises a toroidal magnetic core 31 without an air gap formed around a central recess 32. The first device 10 is arranged inside the central recess 32 so that the magnetic core 31 closes a magnetic circuit formed by the magnetic core 11. The magnetic core 31 is also cylindrical in shape extending around an axis 33 perpendicular to the plane of Figure 3. The cylindrical shape is based on a substantially rectangular closed curve. The axis 13 around which the turns of the electrical conductor 15 are wound is substantially perpendicular to the axis 33. The magnetic core 11 may be in contact with the magnetic core 31 at two opposite sides of the curve substantially rectangular. Air gaps 34 and 35 are formed at each of the contacts between the two magnetic cores 11 and 31. It is possible to place in one of the air gaps or possibly in both, a shim 36 which may be magnetic or non-magnetic. A magnetic shim 36 makes it possible to fill the functional clearance between the two magnetic cores 11 and 31 by best channeling the magnetic flux generated by the turns of the conductor 25. On the contrary, a non-magnetic shim 36 makes it possible to leave a non-magnetic air gap and thus to control the value of the saturation current and to limit the variation of the value of the inductance. More precisely, as long as the magnetic core 11 is not saturated, the inductance value remains constant. If the intensity of the current flowing in the electrical conductor 15 increases so as to saturate the magnetic core 11, the inductance value decreases.The fact of interposing a non-magnetic 36 shim makes it possible to increase the intensity of the current beyond which saturation is reached. It is possible to complete the device 30 with another electrical conductor 37 formed of turns wound around the magnetic core 31. In Figure 5a, the winding of the turns of the electrical conductor 37 can, this time, be carried out in a conventional manner by crossing the central recess 32 of the magnetic core 31. Here again one or more windings can be formed around the magnetic core 31. Alternatively, or in addition, as shown in Figure 5b, the electrical conductor 37 can be wound around the magnetic core 31 in an unconventional manner, that is to say without crossing the central recess 32. Figures 6a and 6b show the use of the device 20 of Figure 2 in a filtering device 40 similar to the filtering device 30. The filtering device 40 contains the magnetic core 31 and possibly the electrical conductor 37 wound in a conventional manner, as shown in Figure 6a. As previously, alternatively or in addition, as shown in Figure 6b, the electrical conductor 37 can be wound around the magnetic core 31 in an unconventional manner. The axis 26 around which the turns of the electrical conductor 25 are wound is substantially perpendicular to the axis 33. One or more shims 36 may be arranged in one or more of the air gaps 34 and 35. As with the magnetic cores 11 and 21, the magnetic core 31 can be made without an air gap, i.e. uncut. Alternatively, the magnetic core 31 can be made from cut cores, which is advantageous in the case where the electrical conductor 37 is wound in a conventional manner. The assembly of the magnetic core 31 is then carried out after insertion of the coil of the conductor 27 on the cut parts. In the devices shown in Figures 5b and 6b, no electrical conductor passes through the central recess 32. Winding the electrical conductor 37 in an unconventional manner makes it possible to increase its characteristic dimension, as described with the aid of Figures 3 and 4. Figure 7 represents an example of use of one of the filtering devices 10 or 20. These devices can be implemented for common mode and differential filtering at the output of a converter 45 delivering a DC voltage between two outputs 46 and 47. The common mode filtering can be carried out by means of two windings 48 and 49 each connected in series with one of the two outputs 46 and 47. The two windings 48 and 49 are wound in the same direction, for example in a conventional manner, and / or in a non-conventional manner, around the magnetic core 31 like the electrical conductor 37. The differential filtering can be carried out by means of a winding 50 connected in series on one of the outputs, for example the output 46. The winding 50 can be formed by the electrical conductor 15 wound around the magnetic core 11. Other components, such as capacitors, can complete the filtering example described with the aid of the figure 7.Many other types of winding connections are of course possible to provide filtering at the output of a converter. Figure 8 represents a variant of the device of Figure 3 comprising several devices 10 arranged inside the central recess 32 of the magnetic core 31 to form a filtering device 55. The different devices 10 are all arranged between two opposite faces of the central recess 32. A shim 36 may be arranged between each of the magnetic circuits 11 and the magnetic circuit 31. Several devices 20 or other similar devices may be implemented in place of the different devices 10. The filtering device 55 may also comprise a conductor 37 wound around the magnetic core 31 and / or in an unconventional manner. Figure 9 shows another variant of a filtering device 60 according to the invention and comprising several devices 10, three in the example shown. The magnetic core 31 is here replaced by two toroidal magnetic cores 61 and 62 without air gap each formed around a central recess, respectively, 63 and 64. The two magnetic cores 61 and 62 are nested. More specifically, the central recess 63 of the magnetic core 61 is configured to contain the magnetic core 62. The devices 10 are arranged inside the central recess 63 between the two magnetic cores 61 and 62. In the example shown, the two magnetic cores 61 and 62 both have a cylindrical shape developed from a triangular curve shown in the plane of Figure 9 and a generatrix perpendicular to the plane of Figure 9. The triangular curves are equilateral and the sides of the triangles of each of the magnetic cores 61 and 62 face each other.A device 10 is arranged between the parallel faces of each of the two triangles. The closing of each of the magnetic circuits 11 of the devices 10 is partly achieved by the magnetic core 61 and partly by the magnetic core 62. A shim 36 may be arranged between each of the magnetic circuits 11 and one of the magnetic circuits 61 and 62. As previously, filtering devices 20 may replace the filtering devices 10. It is of course possible to have more than one device 10 between two parallel faces of each of the triangles. A triangle arrangement is, for example, suitable for filtering a three-phase network. Other forms of magnetic cores are also conceivable within the scope of the invention. Windings similar to winding 37 may be arranged around one or both of the magnetic cores 61 and 62 in a conventional or unconventional manner.

Claims

CLAIMS 1. Filtering device comprising: • a first toroidal magnetic core (21) without air gap formed around a central recess (22), • a first electrical conductor (25) formed of turns wound around the first magnetic core (21) without passing through the central recess (22), wherein no electrical conductor passes through the central recess (12, 22), wherein the first toroidal magnetic core (21) is wound around a first axis (23), wherein the first electrical conductor (25) is wound around an axis (26) substantially perpendicular to the first axis (23).

2. Device according to claim 1, in which a characteristic dimension (L) of a coil produced by winding the first electrical conductor (15, 25) is greater than the largest dimension (I) of a cylindrical section of the central recess (12, 22), the characteristic dimension (L) and the largest dimension (I) of the cylindrical section being carried by the same direction (26).

3. Device according to claim 2, in which the characteristic dimension (L) of the coil is substantially equal to a largest external dimension (L) of the magnetic core (11, 21) carried by the direction (26).

4. Device according to one of the preceding claims, further comprising a second toroidal magnetic core (31, 61) formed around a second central recess (32, 62), the first magnetic core (11, 21) being arranged inside the second central recess (32, 62), so that the second toroidal magnetic core (31, 61) closes a magnetic circuit formed by the first magnetic core (11, 21).

5. Device according to claim 4, in which an air gap (34, 35) is present between the first magnetic core (11, 21) and the second magnetic core (31, 61), the device further comprising at least one magnetic or non-magnetic wedge (36) arranged in the air gap (34, 35).

6. Device according to any one of claims 4 or 5, further comprising a second electrical conductor (37) formed of turns wound around the second magnetic core (31, 61).

7. Device according to claim 6, in which no electrical conductor passes through the second central recess (32, 62), the turns of the second electrical conductor (37) being wound around the second magnetic core (31, 61) without passing through the second central recess (32, 62).

8. Device according to any one of claims 4 to 7, in which the second toroidal magnetic core (31) is wound around a second axis (33) and in which the first and second axes are substantially parallel.

9. Device according to one of the preceding claims, in which the first magnetic core (11, 21) is made of nanocrystalline material.

10. Device according to one of the preceding claims, in which the central recess (12, 22) of the first magnetic core (11, 21) is filled with a magnetic material (16).

11. Device according to any one of claims 4 to 10 as a claim dependent on claim 4, comprising several first toroidal magnetic cores (11, 21) formed around a central recess (12, 22), and several first electrical conductors (15, 25) each formed of turns wound around one of the first magnetic cores (11, 21) without passing through the central recess (12, 22) of the first magnetic core (11, 21) around which the first electrical conductor (15, 25) in question is wound, in which the first magnetic cores (11, 21) are arranged inside the central recess (32, 62) of the second magnetic core (31, 61).

12. Device according to claim 11, further comprising a 5 third toroidal magnetic core (62) arranged inside the second central recess (63), the first magnetic cores (10, 20) being arranged between the second magnetic core (61) and the third magnetic core (62).

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