METHOD FOR WELDING WITHOUT ADDITION OF MATERIAL

Abstract

The invention relates to a method for welding a plurality of strands (33) of one or more electrical conductors (22), comprising at least the following steps: (a) preparing the strands (33) to be welded such that at least the free ends (22a) of adjacent strands are axially offset by a non-zero distance d. (b) melting the free ends (22a) of the strands thus arranged in order to weld them without addition of material.

Claims

1. A method for welding a plurality of strands of one or more electrical conductors, each strand having a free end, the method comprising at least the following steps: (a) preparing the strands to be welded such that at least the free ends of adjacent strands are axially offset along the axis of elongation of the strands, by a non-zero distance d, (b) melting the free ends of the strands thus arranged in order to weld them without addition of material, wherein, step (b) forms a layer of melted material having a variable thickness (h) of greater thickness between 100% and 300% of a thickness (e) of a strand.

2. A method for welding a plurality of strands of one or more electrical conductors, comprising at least the following steps: (a) preparing the strands to be welded such that at least the free ends of adjacent strands are axially offset, along the axis of elongation of the strands, by a non-zero distance d and such that all the strands of one or more electrical conductors to be welded together are arranged symmetrically with respect to a plane of symmetry, and (b) melting the free ends of the strands thus arranged in order to weld them without addition of material.

3. The method according to claim 1, wherein the preparing step (a) is carried out by machining the strands to be welded.

4. The method according to claim 3, wherein the distance (d) is between 5% and 120% of the thickness (e) of a strand.

5. The method according to claim 1, wherein the distance (d) is between 5% and 50% of a width (L) of a section to be welded.

6. The method according to claim 1, wherein all the strands of one or more electrical conductors to be welded together are arranged symmetrically with respect to a plane of symmetry.

7. The method according to claim 1, wherein free ends of the strands of one or more electrical conductors to be welded together being are prepared so that all the free ends of the strands have the general shape of a step pyramid.

8. The method according to claim 1, wherein the melting step (b) is carried out by means of a heat source.

9. The method according to claim 8, wherein the heat source first heats the free end(s) of the strands of greater height during melting step (b).

10. A stator of a rotating electrical machine, comprising a stator mass comprising notches, each notch receiving one or more electrical conductors, an electrical conductor comprising one or more strands each having a free end, the free ends of the strands of one or more electrical conductors being welded together by the welding method according to claim 2, the layer of melted material having a variable thickness (h) of greater thickness between 100% and 300% of the thickness (e) of a strand.

11. The stator according to claim 10, wherein an outer surface of the layer of melted material has a convex portion.

12. The stator according to claim 10, wherein the layer of melted material has a variable thickness (h), of larger thickness greater than 1 mm.

13. The stator according to claim 10, wherein all the electrical conductors having a free end located at the same circumferential position about the axis of rotation of the machine, regardless of their radial position, are electrically connected together.

14. A rotating electrical machine comprising the stator according to claim 10 and a rotor.

15. A method for manufacturing a stator according to claim 10, the method comprising the following step: positioning the electrical conductors in the notches of the stator, this positioning step (c) taking place before the preparation (a) and melting (b) steps.

16. The method of claim 1 wherein the layer of material having melted has a thickness of between 120% and 200% of the thickness (e) of a strand.

17. The method of claim 3 wherein the distance (d) is between 10% and 100% of the thickness (e) of a strand or between 15% and 80% of the thickness (e) of the strand.

18. The method of claim 5 wherein the distance (d) is between 10% and 40% of the width (L) or between 15% and 23% of the width (L).

19. The method of claim 12 wherein the variable thickness (h) of the layer of melted material is greater than 1.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0110] The method and stator made in accordance with the method may be better understood upon reading the following detailed description, of non-limiting embodiments thereof, and on examining the appended drawings, in which:

[0111] FIG. 1 is a schematic, partial perspective view of a stator,

[0112] FIG. 2 is a schematic, partial perspective view of the stator of FIG. 1,

[0113] FIG. 3 is a detail perspective view of the stator of FIG. 1,

[0114] FIG. 4 is a partial view of the stator of FIG. 1 after preparation of the strands,

[0115] FIG. 5 is a partial view of the stator of FIG. 1 after melting of the free ends of the strands,

[0116] FIG. 6 is a sectional view of the strands of two electrical conductors welded together,

[0117] FIG. 7a is a sectional view of the strands of two electrical conductors to be welded arranged to have the shape of a regular step pyramid,

[0118] FIG. 7b is a view similar to FIG. 7a of an alternative embodiment,

[0119] FIG. 7c is a view similar to FIG. 7a of an alternative embodiment,

[0120] FIG. 8a is a view similar to FIG. 7a of an alternative embodiment,

[0121] FIG. 8b is a view similar to FIG. 7a of an alternative embodiment,

[0122] FIG. 8c is a view similar to FIG. 7a of an alternative embodiment, and

[0123] FIG. 9 is a view similar to FIG. 7a of an alternative embodiment.

DETAILED DESCRIPTION

[0124] FIGS. 1 to 5 show a stator 2 of a rotating electrical machine 1 also comprising a rotor, not shown. The stator makes it possible to generate a rotating magnetic field for driving the rotating rotor, in the context of a synchronous motor, and in the case of an alternator, the rotation of the rotor induces an electromotive force in the electrical conductors of the stator.

[0125] The examples illustrated below are schematic and the relative dimensions of the various component elements have not necessarily been observed.

[0126] The stator 2 comprises electrical conductors 22, which are arranged in notches 21 formed between teeth 23 of a stator mass 25. The notches 21 are closed.

[0127] The electrical conductors 22 comprise strands 33. The strands 33 have a generally rectangular cross-section, in particular with rounded corners. In the described example, the strands 33 are superimposed radially in a single row.

[0128] As shown in FIG. 3, thickness e of a strand 33 is its dimension in the radial direction of the machine. The width of a strand 33 is defined as its dimension in the circumferential direction about the axis of rotation of the machine. The width L of the section to be welded corresponds to the sum of the thicknesses e of each strand.

[0129] The electrical conductors 22 are for the most part in the form of pins, namely U or I pins, and which extend axially in the notches. A first electrical conductor housed in a first notch is electrically connected to a second electrical conductor housed in a second notch, at the outlet from said notches.

[0130] The first and second notches are non-consecutive. In the illustrated example, they are separated by 7 other notches. In a variant, the first and second notches are separated by 3, 4, 5, 6, 8, 9, 10 or 11 other notches, for example.

[0131] The electrical connection is formed on the electrical conductors just after they exit the two notches, at one axial end of the stator mass. The two electrical conductors each comprise an oblique portion 22b, which converge toward one another. The electrical connection between two conductors is done in a plane perpendicular to the axis of rotation of the machine, causing the free ends 22a of the strands of the two electrical conductors to melt.

[0132] In particular, FIG. 3 shows the free end surfaces 22a of the strands of the first and second electrical conductors intended to be prepared such that at least the free ends 22a of adjacent strands are axially offset by a non-zero distance d.

[0133] In the described embodiment, the preparation takes place by machining the strands.

[0134] FIG. 4 illustrates the free end surfaces 22a of the strands of the first and second electrical conductors 22 after a machining step. The end surfaces 22a are at different heights as a result of this machining step.

[0135] FIGS. 5 and 6 show the stator 2 after the step of melting the free ends 22a of the strands. Two electrical conductors 22 and 22′ have been welded together. The electrical conductor 22 comprises three strands 33a, 33b, 33c and the electrical conductor 22′ comprises three strands 33a′, 33b′, 33c′. A layer of melted material 13 ensures the electrical connection between the two electrical conductors 22 and 22′. The outer surface of this layer of melted material 13 is convex. In the example shown in FIG. 6, it is in the shape of a dome. The thickness h of the layer of melted material 13 is of the order of 3 mm. The smallest current flow section 14 is contained in the plane that separates the strands 33a and 33a′.

[0136] In order to implement the welding method, the strands can be prepared according to one of the arrangements illustrated in FIGS. 7a to 9.

[0137] In the embodiment shown in FIG. 7a, the free ends of the strands of the two electrical conductors 22, 22′ to be welded together are prepared so that all the free ends of the strands have the general shape of a step pyramid. The distance between two free ends 22a of two adjacent strands is denoted by d. In the illustrated embodiment, the electrical conductor 22 comprises three strands 33a, 33b, 33c and the electrical conductor 22′ comprises three strands 33a′, 33b′, 33c′. The distance d between the free ends of the strands 33a and 33a′ is zero. The distance d between the free ends of the strands 33a and 33b, 33b and 33c, 33a′ and 33b′ and 33b′ and 33c′ is non-zero. The strands 33a and 33a′ are the strands of greater height. The strands are prepared by being machined perpendicular to their axis of elongation. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to twice the value of the distance d.

[0138] In the embodiment shown in FIG. 7b, the strands are prepared so that the assembly has a triangular profile. The electrical conductors 22, 22′ have been machined obliquely. In the illustrated embodiment, the two electrical conductors 22, 22′ are machined along the same slope. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to twice the value of the distance d. In an embodiment that is not shown, the two electrical conductors 22, 22′ are machined along two different slopes.

[0139] In the embodiment illustrated in FIG. 7c, the strands are prepared such that the assembly exhibits a piecewise affine function profile. The affine function that represents the profile is increasing, then decreasing. Each strand is machined obliquely in isolation. Thus, each strand can be machined with a different slope from the others. The strands 33a, 33b, 33c of the electrical conductor 22 are machined in a direction opposite the strands 33a′, 33b′, 33c′ of the electrical conductor 22′. The difference in height between the free ends 22a of the highest strands 33a and 33a′ and the free ends 22a of the lowest strands 33c and 33c′ is between 1 and 2 mm. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to twice the value of the distance d.

[0140] In the embodiment illustrated in FIG. 8a, the strands are prepared so that the assembly has the shape of a staircase. In this embodiment, the free end 22a of a strand is offset by a distance d with respect to the adjacent strand. In the illustrated example, the distance d is constant. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to five times the value of the distance d.

[0141] In the embodiment illustrated in FIG. 8b, the strands are prepared so that the assembly has the shape of a bevel. In this case, all the strands of the two electrical conductors 22 and 22′ are machined obliquely in the same direction. All the free ends 22a then have the same slope. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to five times the value of the distance d.

[0142] In the embodiment illustrated in FIG. 8c, the strands are prepared such that the assembly exhibits a piecewise affine function profile. The affine function representing the profile is strictly increasing. In an embodiment that is not shown, it is strictly decreasing. Each free end 22a of the strand is machined obliquely and in isolation. Thus, each strand can be machined with a different slope from the others. All the free ends 22a of the strands are machined in the same direction. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to five times the value of the distance d.

[0143] In one embodiment shown in FIG. 9, the strands can be prepared so that all of the strands are arranged in the form of crenellations. The greatest thickness h of the layer of melted material that can be obtained when the strands are prepared according to this embodiment is equal to one times the value of the distance d.

[0144] Of course, the invention is not limited to the embodiments that have just been described, and the rotor associated with the described stator can be wound, with a squirrel cage or with permanent magnets, or else with variable reluctance.

[0145] In addition, the strands can be prepared in strand arrangements other than those illustrated.

[0146] The expression “comprising a” should be understood as being synonymous with “comprising at least one.”