Method of manufacturing a magnetic circuit loop

Abstract

A method of manufacturing a magnetic circuit loop for a polyphase transformer from a magnetic strip, the method comprising the steps of: a) providing a magnetic strip having a constant width in the form of a cylindrical roll extending along a longitudinal axis; b) manufacturing first and second half-rolls by cutting the roll into segments, the two half-rolls having a longitudinal axis, each comprising a respective boundary surface formed once the half-roll is separated from the other half-roll, the roll being cut obliquely with respect to the longitudinal axis such that the first half-roll comprises a first loop whose boundary surface oriented outward with respect to its longitudinal axis: while the boundary surface of the second half-roll is oriented oppositely to that of the first half-roll; c) aligning the first and second half-rolls to form two loops, comprising at least one sub-step of counter-unwinding and rewinding the second half-roll on a mandrel.

Description

Technical Field

[0001] The present invention relates to magnetic circuits for magnetic induction devices such as three-phase power transformers, and more particularly to a method for manufacturing a circuit for constituting such magnetic circuits. Background Technology

[0002] A power transformer includes a magnetic circuit, commonly referred to as a magnetic core, and a coil assembly placed around the magnetic circuit to ensure inductive coupling.

[0003] Referring to Figure 1, the magnetic circuit 2 of the three-phase transformer 1 can be in the form of a three-dimensional prismatic cage in a known manner, which is formed by the combination of three loops 3 arranged side by side in a triangular formation extending at a 60° angle to each other. These loops 3 are prismatic, that is, each has a generally rectangular outline, and are shaped such that each loop has an inclined engagement surface 4 extending at a 30° angle relative to the extending plane of the corresponding loop. The loops 3 form a magnetic circuit 2 in pairs 6 at their joints, and coil assemblies 7 are placed around each column. In fact, the assembly of the coil assemblies results in each loop 3 being divided into two half-loops, each half-loop taking the form of the letter U, and each half-loop including two cut surfaces that are then reconstructed as a whole through the coil assembly by keeping the cut surfaces face to face.

[0004] Circuit 3 is typically fabricated by stacking layers of magnetic material. One method manufacturers use to obtain such a stack is to wrap a magnetic strip around a rectangular cross-section mandrel.

[0005] To define the inclined joint surface 4 when manufacturing the circuit 3 by winding the strip, a first method known in the art involves adjusting the strip width upstream of the winding around a rectangular cross-section mandrel by laser cutting. However, in practice, using this method reveals the appearance of burrs, i.e., excess material irregularly formed along the cut edge, which is a source of short circuits and unwanted spaces between layers once the winding is made.

[0006] As shown in Figure 2, an alternative method for pre-cut strips involves winding a magnetic strip 8 of constant width around a rectangular cross-section mandrel, and then chamfering the edges, denoted as H, by machining, electro-erosion, or waterjet cutting. This method overcomes the surface defects observed when laser-cutting strips, but still always results in costly material fragments in the same way. This method, which is both lossy and time-consuming, therefore seems perfect.

[0007] Therefore, the purpose of this invention is to provide a manufacturing solution for magnetic circuit loops that can limit material waste and overall manufacturing costs. Summary of the Invention

[0008] Therefore, the present invention relates to a method for manufacturing a magnetic circuit loop for a multiphase transformer using magnetic strips, the method comprising at least the following steps:

[0009] a) Provide a magnetic strip of constant width in the form of a cylindrical roller extending along the longitudinal axis;

[0010] b) Cut the roller into segments to extract first and second half-rollers having a longitudinal axis, each of the first and second half-rollers including a corresponding boundary surface formed once the first and second half-rollers are separated from the other half-roller, the roller being cut obliquely relative to the longitudinal axis such that the boundary surfaces are oriented in opposite directions: the first half-roller includes a boundary surface oriented outward relative to its longitudinal axis, while the second half-roller includes a boundary surface oriented inward relative to its longitudinal axis.

[0011] c) Aligning the first and second half-rolls to form two loops, including at least one sub-step of unrolling in reverse on the mandrel and rewinding the second half-roll.

[0012] For this solution, compared to the manufacturing of circuits according to the prior art, the material fragments and therefore manufacturing costs are limited, as the prior art requires forming the coil on the mandrel and then performing edge chamfering.

[0013] The present invention also relates to a method of manufacturing a loop thus defined, wherein aligning the first and second half-rolls c) includes a sub-step of straightening a convex surface that appears at the end of the step of reverse unfolding and rewinding the second half-roll on the mandrel, the convex surface corresponding to the profile of the boundary surface at the end of the reverse unfolding and rewinding sub-step, such that the boundary surface orientation of the straightened second half-roll corresponds to the edge surface orientation of the first half-roll.

[0014] The present invention also relates to a loop manufacturing method thus defined, comprising a sub-step of hollowing out the boundary surface of a second half-roll before a sub-step of reverse unwinding and rewinding on a mandrel, the hollowing sub-step preventing the appearance of a convex surface corresponding to the boundary surface profile after reverse rewinding, such that the orientation of the boundary surface of the second half-roll at the end of reverse unwinding and rewinding on the mandrel corresponds to the edge surface profile of the first half-roll.

[0015] The invention also relates to a method of manufacturing a loop, which is thus defined as an additional step d) of shape transition after the step of aligning the first and second half-rollers, the shape transition step d) comprising vertically unfolding and rewinding the first and second half-rollers on another mandrel having a non-circular cross section.

[0016] The present invention also relates to a method of manufacturing a circuit as defined theretherein, wherein another mandrel has a generally rectangular cross-section.

[0017] The present invention also relates to a method for manufacturing a circuit as defined herein.

[0018] The mandrel has a non-circular cross-section; and

[0019] The step of aligning the first and second half-rolls includes additional sub-steps of vertically unfolding and rewinding the first half-roll on the mandrel.

[0020] The present invention also relates to a method of manufacturing a circuit as defined theretherein, wherein the mandrel has a generally rectangular cross-section.

[0021] This invention also relates to a method for manufacturing the magnetic circuit of a multiphase transformer, comprising:

[0022] - Manufacture at least three circuits according to the circuit manufacturing method defined herein.

[0023] - An end-to-end arrangement of loops used to form a closed profile, with the loops contacting each other at their boundary surfaces.

[0024] The present invention also relates to a method for manufacturing a power transformer, the power transformer comprising a magnetic circuit having a three-dimensional cage shape, the magnetic circuit being formed by a plurality of loops arranged end-to-end along a closed profile, and two loops of the plurality of loops being manufactured according to a loop manufacturing method thus defined. Attached Figure Description

[0025] Figure 1, which has already been described, is a schematic perspective view of a three-phase transformer including the magnetic circuit and coil assembly;

[0026] Figure 2, which has already been described, is a partial schematic perspective view of the magnetic circuit;

[0027] Figure 3 illustrates the steps of manufacturing a roller by winding a magnetic stripe onto a cylindrical mandrel, based on which a circuit is manufactured;

[0028] Figure 4 illustrates the steps of cutting the roller in Figure 3 into segments;

[0029] Figure 5 is a schematic diagram of the first and second half-rolls obtained at the end of the segmentation step;

[0030] Figure 6 illustrates the steps of vertically unfolding and rewinding the first half-roll on a rectangular cross-section mandrel;

[0031] Figure 7 and

[0032] Figure 8 illustrates the steps of unrolling and rewinding the second half-roll in the reverse direction on a circular cross-section mandrel;

[0033] Figure 9 illustrates the steps for straightening a convex surface;

[0034] Figure 10A illustrates the step of hollowing out the second half of the roller to prevent convexity from forming;

[0035] Figure 10B illustrates the steps of simultaneously cutting the roll of Figure 3 into segments to form the first and second half rolls and hollowing out the second half roll to prevent convex surface association.

[0036] Figure 11 shows the steps of reverse unfolding and rewinding the second half-roll on the rectangular cross-section mandrel after the hollowing step;

[0037] Figure 12 is a flowchart of two possible methods for manufacturing a circuit according to the present invention;

[0038] Figure 13 shows the relationship between the spindle diameter and the cutting angle. Detailed Implementation

[0039] The method according to the present invention aims to optimize the loop 3 of the magnetic circuit 2 of FIG1, which is made of magnetic stripe.

[0040] The idea behind this invention is to improve compatibility with machining operations applied to circular contours of components, relative to machining operations applied to non-circular contours (e.g., the rectangular contour of loop 3).

[0041] Regarding this principle, the manufacturing method of the circuit 3 according to the present invention begins with step A, which involves winding a magnetic strip 13 with a constant thickness and width around a first mandrel 12 having a circular cross-section and a longitudinal axis X to form a roller with a cylindrical cross-section / profile, which is labeled as 11 in FIG3.

[0042] Then, in the segmentation step, two half-rolls 14 and 16 of complementary shape and equal volume are removed from roll 11 by advantageously using a parallel lathe labeled B. At the end of the method, these two half-rolls 14 and 16 will become two loops 3 of the magnetic circuit.

[0043] For this purpose, the roller 11 is held on either side of its longitudinal end by a gripper with a concentric clamping function on the workpiece holder of a parallel lathe. This assembly is driven to rotate by the spindle, and the longitudinal axis X of the roller corresponds to the rotation axis of the spindle.

[0044] Step B, the segmentation process, involves machining a groove of constant width from the outer contour of roller 11 as roller 11 rotates about its longitudinal axis X, through which a cutting tool, indicated by 17 in Figure 4, passes. The cutting tool moves linearly along a drive direction Y extending at an angle θ relative to the longitudinal axis X. After segmentation, first and second half-rollers 14, 16 with corresponding longitudinal axes X14, X16 are subsequently obtained. The invention advantageously drives roller 11 in the direction of rotation, which tends to tighten the helix formed by the winding of the magnetic strip 13, thereby eliminating strip deformation during the segmentation process.

[0045] Due to step B, which involves cutting into segments, each of the resulting two half-rollers 14 and 16 includes a corresponding boundary surface marked 14a and 16a formed by the cutting tool, as shown in Figure 4. These boundary surfaces 14a and 16a are truncated conical and extend at equal angles relative to the entire plane of the respective half-rollers 14 and 16.

[0046] Referring to Figure 4, the first half-roll 14 has a boundary surface 14a referred to as the "outer" or "outward" boundary surface because any vector V14 perpendicular to this surface does not intersect the longitudinal axis X14; while the boundary surface 16a of the second half-roll 16 in the opposite direction is referred to as the "inner" or "recessed" boundary surface because any vector V16 perpendicular to this surface intersects the longitudinal axis X16. Furthermore, step B, which involves cutting into segments, is performed such that the longitudinal extent of the first half-roll 14 measured at its inner and outer circumferences corresponds to the longitudinal extent of the second half-roll 16 at its outer and inner circumferences, respectively. In other words, the cross-section of the second half-roll 16 corresponds to the cut and inverted cross-section of the first half-roll 14.

[0047] Step B, which involves cutting into segments, is easy to implement and is particularly suitable for processing components with circular profiles. It can form truncated conical boundary surfaces 14a and 16a, each of which is designed to become an inclined engagement surface 4 of the loop 3 with a rectangular profile as shown in FIG. 1. After the segmenting step, the first and second half-rolls 14 and 16 are shaped to conform to the structure of the loop 3.

[0048] In the examples of Figures 1 and 2, each loop 3 has an inclined engagement surface 4 extending at a 30° angle relative to the loop plane. In this respect, the invention wisely specifies:

[0049] - The diameter of the first mandrel 12 used to form the roller 11 corresponds to the inner profile length of the loop 3.

[0050] - Adjust the length of the magnetic strip 13 used so that the roller 11 has a thickness equal to that of the loop 3 to be formed. Furthermore,

[0051] - The value of the cutting angle θ, measured relative to the longitudinal axis X of roller 11, is 60°.

[0052] Based on this, referring to Figures 6 to 9, the forming of the loop 3 according to a first embodiment of the method according to the invention will be described. The first half-roller 14 has a cross-section corresponding to the cross-section of the loop 3 shown in Figure 1, particularly relative to its boundary surface 14a, but has a circular profile, i.e., different from the expected rectangular profile. In this respect, the operation for forming the loop 3 on the first half-roller 14 includes a single shape transition from a circular profile to a rectangular profile.

[0053] Therefore, the method steps associated with the first loop 3 of the magnetic circuit manufactured by the first half-roller 14 include unrolling it to rewind it around the second mandrel 15, the second mandrel 15 being:

[0054] - The circumference is equal to the diameter of the first circular mandrel 12 used to form the roller 11; and

[0055] - The cross section corresponds to the inner contour of loop 3, which is usually rectangular, in accordance with the example in Figure 1.

[0056] The rewinding is performed vertically, so that the layers of magnetic strip 13 are stacked identically. In other words, as shown in FIG6, the layer that defines the outer periphery of the first half-roller 14 with its circular outline still corresponds to the layer that defines the outer periphery of the loop 3 thus obtained.

[0057] Regarding the second half-roller 16, its cross-section and shape are different from the expected cross-section and shape of the loop 3 shown in Figure 1.

[0058] In this respect, the present invention provides a segment transition step to make the second half-roll 16 equivalent to the first half-roll 14 in its post-cut state, which is performed before the shape transition step to obtain the second loop 3. This segment transition step is formed in two consecutive sub-steps labeled C2 and D2. Referring to Figures 7 and 8, the first sub-step C2 includes unfolding the second half-roll 16 by simultaneously rewinding the second half-roll 16 in reverse around a third mandrel 18 having a circular profile and a diameter equal to that of the mandrel 12 used for the first time to form a roll 11. Unlike vertical rewinding, this reverse rewinding results in the magnetic strip layers 13 being stacked in reverse. Specifically, the strip layer defining the outer periphery of the second half-roll 16 at the end of the cutting step corresponds to the layer defining the inner periphery of the second half-roll in its state at the end of the first step, labeled 16'.

[0059] Referring to Figure 7, a convex surface K and stripes or grooves J have been observed at the end of sub-step C2. These stripes J are caused by the reversal of the cutting angle of the magnetic stripe layer 13. Regarding the convex surface K, it is caused by the difference between the lengths of the magnetic stripe 13 observed before sub-step C2 and the following:

[0060] - A first length measured from point A to point B, where points A and B are located on boundary surface 16a, at the outer periphery of the cross-section of the second half-roller 16 and the centerline T, respectively.

[0061] - The second length measured from point B to point C, which is located on the boundary surface 16a and at the inner circumference of the second half-roller 16.

[0062] By considering points A', B', and C' corresponding to points A, B, and C respectively, once reverse rewinding occurs, i.e. at the end of sub-step C2, the discovered length difference results in more magnetic stripe layers 13 separating points A' and B' after sub-step C1 compared to the magnetic stripe layers separating points B' and C', thus forming a convex surface K.

[0063] In this regard, it should be understood that the first sub-step C2 does not allow the cross-section of the first half-roll 14 to be found, and the second sub-step D2 aims to correct said cross-section. This second sub-step D2 includes the advantageous operation of straightening the convex surface K using a parallel lathe and an enveloping machining tool 19, which is linearly displaced at an angle θ along an inclined plane relative to the axis of half-roll 16'. Removing this convex surface K results in the second half-roll (labeled 16' at this stage) being substantially aligned with the first half-roll 14.

[0064] Assuming that the first step of forming the second half-roll 16 is often equivalent to the first half-roll 14, the next step of forming the second half-roll corresponds to the described step C1 to obtain loop 3, that is, a shape transition formed by vertical rewinding on a second mandrel 15 of a generally rectangular cross section.

[0065] At the end of step B, which involves cutting into segments, the forming circuit 3 by the second half-roller 16 has been explained above according to the first embodiment of the invention. This first embodiment removes the convex surface K by machining, which appears after reverse rewinding (sub-steps C2 and D2) due to the truncated conical feature of the boundary surface 16a.

[0066] Alternatively, according to the second embodiment, the method aims to prevent the appearance of a convex surface K by hollowing out the boundary surface 16a of the second half-roll 16, so that reverse rewinding produces a substantially straight rather than curved generator surface. As understood, the second embodiment of the method differs from the first embodiment in terms of the shaping of the second half-roll 16.

[0067] More specifically, and referring to Figure 10A, the forming of the second half-roll 16 according to the second embodiment is ensured in two consecutive steps. Advantageously, the first step, including hollowing out the boundary surface 16a to produce an anti-convex surface, is implemented by straightening with a parallel lathe inducing rotation of the second half-roll 16 about its axis X16, and the envelope machining tool moving along a curve to perform the machining.

[0068] At the end of the first step, marked E, the second step F includes unfolding the second half-roller by simultaneously rewinding the second half-roller, marked 16”', around the second mandrel 15, which has a generally rectangular cross-section as previously described. As understood, the trajectory of the control tool 20 is such that the anti-convex surface, marked 16a”', originating from its channel, cancels out the difference in the initial magnetic strip length 13 as described at the bottom of Figure 7.

[0069] At the end of step F, the second half-roller generally corresponds to loop 3 as illustrated in Figure 1, but is locally distinguished by a serrated, rough mating surface, specifically including a generator surface marked R with a basic straight line. This identifying characteristic stems from the reversal of the cutting angle of the magnetic stripe layer 13 after reverse rewinding, which results in the appearance of stripe J.

[0070] In practice, when forming the magnetic circuit 2 of the three-phase transformer 1 as shown in Figure 1, there is no restriction on using a loop with a serrated joint surface rather than a smooth joint surface. Since the magnetic flux does not circulate from one loop to another within the framework of this magnetic circuit 2, it is not necessary to strictly ensure the flat support contact of the joint surface 4 of the parallel loop 3.

[0071] However, without departing from the scope of the invention, it is conceivable to provide additional steps aimed at straightening stripe J to precisely conform to the morphology of loop 3 shown in Figures 1 and 2. In this case, the second half-roller 16 may need to be slightly longer when cutting into segments to compensate for the material removal being performed.

[0072] In practice, the boundary surface 16a can be hollowed out directly during the process of cutting the roller 11 into segments to prevent the appearance of a convex surface. In other words, according to the second embodiment of the invention, steps B and E can be combined. This feature is particularly advantageous when separating the two half rollers 14 and 16 becomes too restrictive at the end of step B, which is necessary for implementing step E, which involves hollowing out the boundary surface 16a as shown in FIG. 10A. Referring to FIG. 10B, the association between step B and the first step E (labeled BE) is generally implemented in a similar manner to step B of the segmentation shown in FIG. 4, but is distinguished by the tools used and the cutting operation.

[0073] More specifically, the cutting tool labeled 21, relative to its head—that is, from its active portion to the cutting of the material—is different from the tool 20 used in step B, as shown in the figure, for cutting into segments. The tool 20 used in step B has a beveled head that extends continuously by forming an end at the end of the tool, without creating any discontinuity in the extension of the rod supporting the head. The head of tool 21 also has a beveled head extending in the extension of the rod to form a first end 21a at the end of the tool, and protrudes laterally by forming a second end 21b at the joint.

[0074] Similar to tool 20 in step B, tool 21 is displaced linearly along the driving direction Y, which extends at an angle θ relative to the longitudinal axis X, in step BE. Furthermore, the orientation change of tool 21 around the second end 21b creates a pivot point that displaces only along the driving direction Y, such that:

[0075] -Through the channel at the second end, the boundary surface 14a of the first half-roller 14 is formed as a truncated cone; and

[0076] - The convex surface 16a” of the second half roller 16” is formed by the channel of the first point 21a, and the first point smoke curve moves when the orientation of the tool 21 changes.

[0077] The method according to the invention is explained in the case of manufacturing a pair of prismatic loops 3 using two half-rollers 14 and 16 having cylindrical profiles and inverted cross sections, wherein the half-rollers are removed from the roller 11 of the magnetic strip 13 by being cut into segments. Referring to the schematic flowchart of FIG12, the manufacturing of the first loop is based on a single-shape transition operation C1, which includes vertically unfolding and rewinding the half-roller 14 on a mandrel 15 having a generally rectangular cross section, while the manufacturing of the other loop can be performed according to two protocols, the two protocols being:

[0078] - A cross-sectional transition and shape transition need to be applied to the other half-roller 16, which for each protocol means the steps of reverse unwinding and rewinding C2,F;

[0079] The approaches used to address loop inconsistency issues through the presence of a convex surface K differ significantly: one protocol requires step D2 to remove the convex surface K by machining it once it appears during reverse rewinding C2, while the other protocol, conversely, requires anticipating and overcoming the appearance of this convex surface K by forming a hollow anti-convex surface upstream of the reverse rewinding step F. The anti-convex surface can be formed after the segmentation step B in step E, associated with aligning the first and second half-rolls, or simultaneously with the segmentation in step BE.

[0080] To limit the number of operations and the amount of debris, the present invention wisely implements the machining steps D2, E of the proposed protocol by turning the half roll 16 before rewinding it on a mandrel 15 with a generally rectangular cross section.

[0081] The method with the fewest steps involves sorting steps A, B, BE, F, and then C1.

[0082] To manufacture loop 3 of Figure 1, different steps of the method according to the invention have been described by taking into account certain dimensional standards, namely:

[0083] - The first, second, and third mandrels 12, 15, and 18 have the same diameter as the inner circumference of loop 3.

[0084] - Adjust the length of the magnetic strip 13 used so that the thickness of the roller 11 is equal to that of the circuit 3 to be formed.

[0085] - The value of angle θ is 60°.

[0086] Regarding the second mandrel 15 with a basic rectangular cross-section, it should be understood that, as the final target mandrel, the half-roll is wound around it to adopt the shape of loop 3, and its circumference must correspond to the inner loop circumference. However, based on the existence of the geometric link diameter angle θ, which will be generally explained below with reference to FIG13, the present invention is not limited to conforming to the above-mentioned diameter criteria regarding the first and third mandrels 12 and 18 and the cutting angle value θ.

[0087] Figure 13 illustrates a “control” configuration conforming to the aforementioned dimensional standards. This control configuration includes a first mandrel M, the diameter of which corresponds to the inner circumference of loop 3 in Figure 1, and which carries a half-roller P cut into segments at a 60° angle. By applying the method described in this stage, the half-roller P becomes the loop defined in Figure 1. Dimension J will be labeled, corresponding to the distance that separates the length projected onto the mandrel from the boundary surface formed by the segmentation.

[0088] The first configuration differs from the control configuration in that it has a mandrel M1 with a larger diameter than the control mandrel M, which carries a half-roller P1 formed by a belt of the same length as that used in the control configuration (by taking into account the material drop after cutting into segments), to present a belt volume equal to that of the control half-roller P. By applying this method, the loop 3 shown in Figure 1 can be formed, wherein the cutting angle θ1 of the loop 3 is less than 60° and is defined to conform to dimension J.

[0089] The second construction differs from the control construction in that it has a mandrel M2 with a smaller diameter than the control mandrel M, which carries a half-roller P2 formed by a belt of the same length as that used in the control construction. A loop 3 according to FIG. 1 can also be formed by applying the method according to the invention, wherein the cutting angle θ2 of the loop is greater than 60° and is defined to conform to dimension J.

[0090] As understood, the flexibility of implementing the method according to the invention is confirmed by allowing adjustment of the angle values ​​θ in steps B and D2 and the diameters of the first and third mandrels 12, 18 introduced in steps A and C2 to manufacture the loop 3 according to FIG1.

[0091] It should also be noted that the method according to the invention is not limited to manufacturing a circuit with the specific configuration of FIG1.

[0092] In fact, it should be understood that the method according to the invention is not limited to manufacturing a loop having a mating surface extending at a 30° angle relative to the loop plane by limiting the angle θ only as needed.

[0093] Similarly, without departing from the scope of the invention, virtually any type of loop 3 shape can be considered. Specifically, this means that a mandrel with a cross-section adapted to the shape of the loop to be manufactured can be used instead of the second rectangular cross-section mandrel 15.

[0094] In particular, it is possible to consider using the method according to the invention, i.e. without involving the second rectangular cross-section mandrel 15, to manufacture a loop with a circular profile.

[0095] Moreover, the present invention provides the possibility of enriching the method with additional machining operations, which are advantageously performed in turning, for example by longitudinal turning and straightening, for example for defining the corner surfaces marked 14b, 16b in the examples of Figures 4 and 5, which are also shown in Figure 1 but not labeled.

[0096] In particular, the corner surface marked 14b can be easily straightened in step B. The corner surface marked 16b can be easily straightened in step D2, and is more difficult to straighten in step B or E due to the anti-convex surface. In the case of forming the corner surface marked 14b, the anti-convex surface is not necessary because it is not very obvious in the magnetic circuit 1 assembly of FIG1 and is external.

[0097] Finally, the invention is described with the case where the roller 11, made of magnetic strip 13, is divided into two half-rollers 14, 16 of equal volume. In this case, it should be understood that the width and length of the magnetic strip 13 used to form the roller 11 are defined with respect to the dimensions of the circuit to be manufactured. Since a three-phase transformer comprises three circuits, it is conceivable to dimension the roller 11 so that several pairs, each formed by the first and second complementary half-rollers 14, 16, can be judiciously extracted from it. Specifically, when it is desired to manufacture at least two circuits, applying the method according to the invention can limit manufacturing costs.

Claims

1. A method for manufacturing a circuit (3) of a magnetic circuit (2) for a multiphase transformer using magnetic strips (13), the method comprising at least the following steps: a) Provide a magnetic strip (13) in the form of a cylindrical roller (11) extending along the longitudinal axis (X) of the roller. b) The roller (11) is cut into segments to extract a first half-roller (14) and a second half-roller (16) having a longitudinal axis (X14) of a first half-roller and a longitudinal axis (X16) of a second half-roller, wherein each half-roller includes a corresponding boundary surface (14a; 16a) formed once the half-roller is separated from the other half-roller, wherein the roller is cut obliquely relative to the longitudinal axis (X) of the roller such that the orientations of the boundary surfaces (14a; 16a) are opposite: the first half-roller (14) includes a boundary surface (14a) oriented outward relative to the longitudinal axis (X14) of the first half-roller, while the second half-roller (16) includes a boundary surface (16a) oriented inward relative to the longitudinal axis (X16) of the second half-roller. c) Aligning the first half-roller (14) and the second half-roller (16) to form two loops (3), including at least one sub-step of unrolling in reverse and rewinding the second half-roller on a mandrel.

2. The method according to claim 1, wherein, Step c) of aligning the first half-roller (14) and the second half-roller (16) includes a sub-step of straightening the convex surface (K) that appears at the end of the step of rewinding and unwinding the second half-roller (16) on the mandrel, wherein the convex surface (K) corresponds to the profile of the boundary surface (16a) at the end of the rewinding and unwinding sub-step, such that the direction of the boundary surface (16a) of the straightened second half-roller (16) corresponds to the direction of the boundary surface (14a) of the first half-roller (14).

3. The method according to claim 1, comprising a sub-step of hollowing out the boundary surface (16a) of the second half-roll (16) before the sub-step of reverse unfolding and rewinding on the mandrel, wherein, The hollowing step prevents the appearance of a convex surface (K) that corresponds to the profile of the boundary surface (16a) after reverse rewinding, such that the direction of the boundary surface (16a) of the second half-roll (16) at the end of reverse unwinding and rewinding on the mandrel corresponds to the profile of the boundary surface (14a) of the first half-roll (14).

4. The method according to claim 2, comprising an additional step d) of shape transition after the step of aligning the first half-roller (14) and the second half-roller (16), wherein, Step d) of the shape transition includes vertically unfolding and rewinding the first and second half-rollers on another mandrel with a non-circular cross-section.

5. The method according to claim 4, wherein, The other mandrel has a generally rectangular cross-section.

6. The method according to claim 3, in, The mandrel has a non-circular cross-section; and Step c) of aligning the first half-roller (14) and the second half-roller (16) includes the sub-steps of vertically unfolding and rewinding the first half-roller (14) on the mandrel.

7. The method according to claim 6, wherein, The mandrel has a generally rectangular cross-section.

8. The method according to claim 1, wherein, The circuit is prismatic and has a generally rectangular outline.

9. A method for manufacturing a magnetic circuit (2) for a multiphase transformer, comprising: - Use the method according to claim 1 to manufacture at least three loops (3). - The loop (3) is arranged end-to-end to form a closed profile.

10. A method for manufacturing a power transformer, wherein, The power transformer includes a three-dimensional cage-shaped magnetic circuit (2), wherein the magnetic circuit is formed by a plurality of loops (3) arranged end-to-end along a closed profile, wherein at least two loops (3) of the power transformer are manufactured according to the method of claim 1.

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