MAGNETIC CORE FOR AN ELECTROMAGNETIC INDUCTION DEVICE, AN ELECTROMAGNETIC INDUCTION DEVICE COMPRISING THE SAME, AND A METHOD OF MANUFACTURING A MAGNETIC CORE

Abstract

A magnetic core for an electromagnetic induction device, comprising: a limb made of a grain-oriented material, a yoke made of an amorphous material, and an auxiliary joint member made of grain-oriented material, wherein the auxiliary joint member joints the limb with the yoke, wherein the grain orientation of the limb is perpendicular to the grain orientation of the auxiliary joint member.

Claims

1. A magnetic core for an electromagnetic induction device, comprising: a limb made of a first grain-oriented material, a yoke made of an amorphous material, and an auxiliary joint member made of a second grain-oriented material, wherein the auxiliary joint member joints the limb with the yoke, wherein a grain orientation of the limb is perpendicular to a grain orientation of the auxiliary joint member.

2. The magnetic core as claimed in claim 1, wherein the auxiliary joint member consists of the second grain-oriented material.

3. The magnetic core as claimed in claim 1, wherein the limb and the auxiliary joint member each comprises a plurality of laminated plates, wherein a joint between the auxiliary joint member and the limb is formed by the laminated plates of the auxiliary joint member being interleaved with the laminated plates of the limb.

4. The magnetic core as claimed in claim 1, wherein the yoke and the auxiliary joint member each comprises a plurality of laminated plates, wherein a joint between the auxiliary joint member and the yoke is formed by the laminated plates of the auxiliary joint member being interleaved with the laminated plates of the yoke.

5. The magnetic core as claimed in claim 1, wherein a joint between the auxiliary joint member and the limb is a mitre joint.

6. The magnetic core as claimed in claim 5, wherein an angle of the mitre joint is 45.

7. The magnetic core as claimed in claim 1, wherein a joint between the auxiliary joint member and the yoke is a butt-lap joint.

8. The magnetic core as claimed in claim 1, wherein the yoke has a larger cross-section than the limb.

9. An electromagnetic induction device comprising a magnetic core as claimed in claim 1.

10. The electromagnetic induction device as claimed in claim 9, wherein the electromagnetic induction device is a transformer or a reactor.

11. The electromagnetic induction device as claimed in claim 9, wherein the electromagnetic induction device is a high voltage electromagnetic induction device.

12. A method of manufacturing a magnetic core of an electromagnetic induction device, wherein the method comprises: jointing a limb made of grain-oriented material with an auxiliary joint member made of a grain-oriented material such that a grain-orientation of the limb is perpendicular to a grain-orientation of the auxiliary joint member, and jointing a yoke made of an amorphous material with the auxiliary joint member.

13. The method as claimed in claim 12, wherein the limb, the yoke and the auxiliary joint member each comprises a plurality of laminated plates, wherein the jointing of the auxiliary joint member and the limb includes interleaving the laminated plates of the auxiliary joint member with the laminated plates of the limb, and wherein the jointing of the auxiliary joint member and the yoke includes interleaving the laminated plates of the auxiliary joint member with the laminated plates of the yoke.

14. The method as claimed in claim 12, comprising performing an inclined cut of the auxiliary joint member with respect to its grain-orientation before the jointing, wherein the jointing of the limb and the auxiliary joint member forms a mitre joint.

15. The method as claimed in claim 12, comprising performing a perpendicular cut of the auxiliary joint member with respect to its grain-orientation before the jointing, wherein the jointing of the auxiliary joint member and the yoke forms a butt-lap joint.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which:

[0034] FIG. 1 schematically depicts a section of a corner portion of an example of a magnetic core;

[0035] FIG. 2 schematically depicts a section of a corner portion of another example of a magnetic core;

[0036] FIG. 3 schematically depicts an example of a magnetic core for a three-phase application;

[0037] FIG. 4 schematically shows a section of a side view of an electromagnetic induction device with the magnetic core having been made visible; and

[0038] FIG. 5 is a flowchart of a method of manufacturing a magnetic core.

DETAILED DESCRIPTION

[0039] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

[0040] FIG. 1 depicts an upper left corner of an example of a magnetic core 1 for an electromagnetic induction device such as a power transformer, a distribution transformer or a reactor.

[0041] The magnetic core 1 comprises an upper yoke 3, a limb 5, and an auxiliary joint member 7. Although not shown in the drawing, the magnetic core also comprises a lower yoke and another limb which are identical to the upper yoke 3 and the limb 5, at least concerning material type and jointing.

[0042] The yoke 3 is made of an amorphous material. In particular, the yoke 3 may consist of an amorphous material. The material may for example be amorphous steel. The yoke 3 comprises a plurality of laminated plates or ribbons. Each plate is preferably made of amorphous material.

[0043] The limb 5 is made of a grain-oriented material. In particular, the limb 5 may consist of a grain-oriented material. The grain-oriented material may for example be silicon steel. The grain-orientation of the limb 9 may have a first orientation as shown by arrows G1, preferably parallel with the longitudinal direction of the limb 9.

[0044] The limb 5 comprises a plurality of laminated plates. Each plate is preferably made of grain-oriented material.

[0045] The auxiliary joint member 7 is made of a grain-oriented material. In particular, the auxiliary joint member 7 may consist of a grain-oriented material. The grain-oriented material may for example be silicon steel. The grain-orientation of the auxiliary joint member 7 may have a second orientation as shown by arrows G2, preferably parallel with the longitudinal direction of the yoke 3 and perpendicular to the first orientation. The grain orientation of the auxiliary joint member 7 and the grain orientation of the limb 5 are hence preferably perpendicular.

[0046] The auxiliary joint member 7 comprises a plurality of laminated plates. Each plate is preferably made of grain-oriented material.

[0047] The auxiliary joint member 7 joints the yoke 3 with the limb 5. The auxiliary joint member 7 hence connects the yoke 3 with the limb 5. The auxiliary joint member 7 is arranged between the yoke 3 and the limb 5. The auxiliary joint member 7 may have a polyhedral shape and the yoke 3 may be joined with a first face of the auxiliary joint member 7, and the limb 5 may be joined with a second face of the auxiliary joint member 7 adjacent to the first face.

[0048] The auxiliary joint member 7 and the yoke 3 are jointed by interleaving of the laminated plates/ribbons of the yoke 3 with the laminated plates of the auxiliary joint member 7. The frictional forces thus obtained hold the auxiliary joint member 7 and the yoke 3 together.

[0049] The auxiliary joint member 7 and the limb 5 are jointed by interleaving of the laminated plated of the limb 5 and the laminated plates of the auxiliary joint member 7. The frictional forces thus obtained hold the auxiliary joint member 7 and the limb 5 together.

[0050] The yoke 3 may have a greater cross-sectional area than the limb 3, preferably at a cross-section taken anywhere along the longitudinal extension of the yoke 3. The cross-sectional area of the yoke 3 may be selected such that is compensates for the lower saturation point of the amorphous material compared to the grain-oriented material of the limb 5 so that the yoke 3 will not become saturated during normal operation.

[0051] The joint between the auxiliary joint member 7 and the limb 5 may be a mitre joint or a step-lap mitre joint. The angle of the mitre joint or step-lap mitre joint may for example be about 45, for example 45 plus/minus 1-2, or it may be exactly 45. The angle is the angle between the first face and the second face of the auxiliary joint member 7.

[0052] Due to the angled structure of the joint between the auxiliary joint member 7 and the limb 5 and due to their perpendicular grain orientation, the magnetic flux will essentially not cross the grain orientation of the limb 5 or the auxiliary joint member 7. Instead, there will an essentially perpendicular flow direction change at the joint, where the magnetic flux continues to follow the grain orientation of the auxiliary joint member 7.

[0053] The joint between the auxiliary joint member 7 and the yoke 3 may be a butt-lap joint. The yoke 3 hence has a straight cut end face 3a which is perpendicular to the direction of longitudinal extension of the yoke 3.

[0054] In the example in FIG. 1, the yoke 3 has a greater cross-sectional area than the limb 5 and thus the auxiliary joint member 7 has a trapezoidal shape seen from the side.

[0055] As shown in FIG. 1, windings 9 may be provided around the limb 5 of the magnetic core 1.

[0056] FIG. 2 shows another example of a magnetic core. Magnetic core 1 is very similar to the magnetic core 1 in FIG. 1. The auxiliary joint member 7 is however cut with an angle that differs from the 45 or about 45 angle shown in FIG. 1. In the example in FIG. 2 the angle of the mitre joint or step-lap mitre joint may for example be in the range of 20<<45 and 45<<70.

[0057] FIG. 3 schematically shows an example of magnetic core 1 for a three-phase application. The magnetic core 1 is configured to be used in a three-phase electromagnetic induction device. The magnetic core 1 comprises two limbs 5 arranged laterally and a limb 5 arranged between the two lateral limbs 5. The three limbs 5, 5 are arranged parallel with each other. The cross-sectional dimension of all three limbs 5, 5 may be the same until they start to taper. All three limbs 5, 5 are made of a grain-oriented material with their grain orientation being parallel with their longitudinal extension. The limbs 5, 5 may be made of laminated plates.

[0058] Additionally, the yoke 3 comprises a first yoke member 4a and a second yoke member 4b. Each of the first yoke member 4a and the second yoke member 4b is made of amorphous material. The first yoke member 4a is connected to the left hand side limb 5 as described above, via an auxiliary joint member 7 or 7. The second yoke member 4b is connected to the right hand side limb 5 as described above, via an auxiliary joint member 7 or 7.

[0059] The magnetic core 1 furthermore includes an additional auxiliary joint member 7. The auxiliary joint member 7 is configured to provide a connection between the limb 5, in the following referred to as central limb and the first yoke member 4a and the second yoke member 4b.

[0060] The central limb 5 has tapering end portions. The upper such tapering end portion can be seen in FIG. 3. According to the example in FIG. 3, the tapering shape is symmetrical with respect to the central longitudinal axis of the limb 5. The tapering end portion is triangular or pyramid-shaped and forms the shape of an isosceles triangle. The top angle , of the triangle may be equal to the twice the angle of the mitre joint or step-lap mitre joint of the limbs 5/auxiliary joint members 7.

[0061] The auxiliary joint member 7, in the following referred to as central auxiliary joint member is configured to receive the tapering end portion of the central limb 5. To this end, the central auxiliary joint member 7 has a cut-out which corresponds to the shape of the triangular tapering end portion.

[0062] The central auxiliary joint member 7 is made of grain-oriented material. The grain orientation is perpendicular to the grain orientation of the central limb 5.

[0063] The central auxiliary joint member 7 may be a single piece formed by laminated grain oriented plates extending between the first yoke member 5a and the second yoke member 4b, or two or more pieces formed of laminated grain oriented laminated plates, whereby for example two pieces may be jointed along a vertical line intersecting the apex of the top angle . The jointing may be made by interleaving of the laminated plates of the two or more pieces.

[0064] The laminated plates of the central auxiliary joint member 7 may be interleaved with the laminated plates of the first yoke portion 4a and with the laminated plates of the second yoke portion 4b. The central auxiliary joint member 7 may thereby be jointed with the first yoke portion 4a and the second yoke portion 4b. Similarly, the laminated plates of the central auxiliary joint member 7 may be interleaved with the laminated plates of the central limb 5.

[0065] In the example in FIG. 3, the angle may for example be 45 or it may differ from 45. the angle may for example be in the range of 20<<45 and 45<<70.

[0066] FIG. 4 schematically shows an example of an electromagnetic induction device 11. The electromagnetic induction device 11 may for example be a transformer such as a power transformer or a distribution transformer, or a reactor.

[0067] The electromagnetic induction device 11 may for example a high voltage electromagnetic induction device such a high voltage direct current (HVDC) electromagnetic induction device, or a medium voltage electromagnetic induction device.

[0068] The electromagnetic induction device 11 comprises the magnetic core 1, windings 9 and 10 wound around limbs 5, and bushing 13 of which only one is shown, electrically connected to respective windings 9, 10.

[0069] The example in FIG. 4 shows a two-phase electromagnetic induction device 11, but the magnetic core 1 could alternatively be provided with further limbs for additional electrical phases, e.g. for three-phase applications.

[0070] FIG. 5 shows a flowchart of a method of manufacturing the magnetic core 1, 1.

[0071] In a step a) the auxiliary joint member 7, 7 is cut with an inclined cut relative to its grain orientation to obtain the second face which is to be jointed with the limb 5. The auxiliary joint member 7, 7 is also cut with a perpendicular cut relative to its grain orientation to obtain the first face which is to be assembled with the yoke 3. The angle is formed between the first face and the second face. The two cuts may be performed in any order.

[0072] In a step b) the auxiliary joint member 7, 7 is jointed with the limb 5. In particular, laminated plates of the auxiliary joint member 7, 7 are interleaved with laminated plates of the limb 5. In this manner, the mitre joint or step-lap mitre joint is formed.

[0073] In step c) the auxiliary joint member 7, 7 is jointed with the yoke 3. In particular, laminated plates of the auxiliary joint member 7, 7 are interleaved with laminated plates of the yoke 3. In this manner, the butt-lap joint is formed. It is to be noted that steps b) and c) may be performed in any order.

[0074] The above steps a)-c) are performed for all the auxiliary joint members 7, 7 included in the magnetic core 1, 1.

[0075] The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.