Stator of a rotary electrical machine, comprising foldable constrictions

Abstract

Disclosed is a stator (1) of a rotary electrical machine, comprising a stator mass (3) having a plurality of slots (10) and a winding in the slots (10), the winding comprising bundles of round wires (6), at least one slot (10) or each of the slots comprising a plurality of round wires (6) which follow one another circumferentially, and at least one slot (10) or each of the slots being open towards an air gap in the machine and comprising two foldable constrictions (20) that partially close the corresponding slot (10).

Description

[0001] Description

[0002] Title: Stator of a rotating electrical machine comprising foldable isthmuses

[0003] Technical field

[0004] The present invention relates to rotating electrical machines and more particularly to the stators of such machines.

[0005] Prior art

[0006] In known stators, the stator yoke provides fully open or semi-open slots towards the air gap, so as to allow the insertion of windings. Generally, the semi-open slots accommodate loosely arranged electrical conductors of circular cross-section, while the fully open slots accommodate neatly arranged electrical conductors of rectangular cross-section.

[0007] Fully open slots are characterized by the fact that they open into the stator bore over their entire width, whereas semi-open slots, which also open into the bore, do so only through a significantly narrower opening. This restriction corresponds to a local widening of the teeth located on either side of the slot; these parts are commonly called slot isthmuses.

[0008] To hold the conductors in the notch, one can use either a rigid wedge, with a rectangular profile, which slides into grooves specially designed for this purpose in the teeth, or a flexible wedge, of the "paper insulation" type with a curved profile, which is inserted between the conductors and the isthmuses.

[0009] Stators are known in which the slots can be closed with non-magnetic shims. However, such shims may come loose and interfere with the operation of the machine.

[0010] Patent application EP 1 283 583 relates to a stator comprising wires having a width substantially equal to the notch width. This stator is intended for a low voltage alternator such as 12 V or 24 V.

[0011] There is a need for an easy-to-assemble rotating electrical machine stator that allows efficient slot filling while ensuring satisfactory electromagnetic performance. There is also a need to further improve electrical machine stators, particularly to reduce torque ripples.

[0012] Summary of the invention

[0013] The invention aims to meet this need and achieves this, according to one of its aspects, by means of a stator for a rotating electrical machine, comprising a stator mass having a plurality of notches and a winding arranged in the notches, the winding comprising bundles of round wires, at least one notch, or even each of the notches, comprising several round wires succeeding one another circumferentially, and at least one notch, or even each of the notches, being open towards an air gap of the machine and comprising two foldable isthmuses partially closing the corresponding notch.

[0014] The stator has a stator mass which can be made by stacking magnetic sheets, the notches being made by cutting the sheets. The closing of the notches on the air gap side is obtained by the foldable isthmuses which can be made in one piece with the rest of the sheets forming the stator mass.

[0015] Alternatively, the stator mass may be produced at least partially by an additive manufacturing technique, in particular by powder sintering and machining. The stator may comprise a plurality of stacked wafers, each produced by additive manufacturing.

[0016] The stator according to the invention may be without added magnetic shims. This eliminates the risk of the shims closing the slots becoming detached.

[0017] The presence of the semi-closed notches by the foldable isthmuses makes it possible to mechanically strengthen the stator and reduce vibrations. This results in a minimized cogging torque effect. This stator makes it possible to significantly reduce electromagnetic disturbances linked to the presence of the openings of the notches opening onto the air gap in the prior art.

[0018] Furthermore, because the notches are semi-closed by the foldable isthmuses, the risk of impregnation varnish leaking into the air gap is reduced. This reduces the amount of varnish or resin lost and the cleaning operations required.

[0019] The stator mass may comprise teeth arranged between the notches. Thus, each notch is semi-closed on the air gap side by two foldable isthmuses connected to two consecutive teeth of the stator mass. By "foldable isthmus" is meant that an isthmus comprises a bridge of material connecting it to the tooth which is deformable, so as to allow a change in the orientation of the isthmus relative to the corresponding tooth. The foldable isthmus may be movable between a first position in which it extends into the bore of the stator, and a second position in which it partially closes the opening of the notch, and extends in the extension of an edge of the tooth defining the bore of the stator.

[0020] The foldable isthmuses are arranged at the foot of the corresponding tooth. The foldable isthmuses are integral with the adjacent teeth. Each tooth may have at least one foldable isthmus, in particular two foldable isthmuses.

[0021] Two consecutive teeth are connected on the opposite side by a yoke. The yoke is made in one piece with the teeth. The stator is therefore without a yoke attached to a toothed crown.

[0022] At least one notch, or even each of the notches, may be open towards the stator bore. At least one notch, or even each of the notches, may have several round wires following one another radially.

[0023] The winding consists of round wires. A diameter of the round wires can be between 0.8 and 2 mm. The diameter of the wires is small compared to the size of a slot. A ratio of the wire diameter to a slot width can be less than 0.5, better still less than 0.6, even better still less than 0.7, or even less than 0.8, or even less than 0.9.

[0024] The round wires can be arranged roughly staggered in the corresponding notch.

[0025] The stator slots may accommodate a superposition of bundles corresponding to different phases; the bundles of the different phases may be insulated by thin insulators, from each other and from the stator mass. The bundles may consist of a variable number of turns; the turns may comprise a variable quantity of wires in parallel, and these wires in parallel may be a mixture of different diameters.

[0026] Statement of the invention

[0027] At least one foldable isthmus, preferably all foldable isthmuses, may have a length greater than 2 mm, preferably greater than 2.5 mm, or even greater than 3 mm. At least one foldable isthmus, preferably all foldable isthmuses, may have a length less than 10 mm, preferably less than 9 mm, or even less than 8 mm. At least one foldable isthmus, preferably all foldable isthmuses, may have a length corresponding to 20 to 45% of the width of the notch. The length of the foldable isthmuses may be quite significant, since in their folded position, the foldable isthmuses almost completely close the notches.

[0028] At least one foldable isthmus, preferably all foldable isthmuses, can be connected to the corresponding tooth by a bridge of material delimited by a cutout made on the side of the notch. The presence of the cutout makes it possible to facilitate the folding of the corresponding foldable isthmus to partially close the notch.

[0029] When the bendable isthmus is bent, it extends in line with the edge of the corresponding tooth defining the stator bore.

[0030] The cutout may be generally triangular in cross-section, especially when the isthmus is unfolded. The cutout forms a notch at the base of the foldable isthmus, which helps to fold it after inserting the wires. It may be triangular or of any other shape.

[0031] The two foldable isthmuses partially closing a notch may provide a notch opening between them. A width of the notch opening provided between the two foldable isthmuses of the notch may be, when the isthmuses are folded, less than 40% of the width of the notch, better still less than 30%, being for example of the order of 20% of the width of the notch. This narrowing of the opening is particularly advantageous because

[0032] 11 contributes to the improvement of the stator output waveforms.

[0033] For example, an opening whose width is slightly larger than the air gap is a good compromise. The width of the slot opening can be, when the isthmuses are bent, larger than the air gap width. In this configuration, the signal quality can be improved, without unnecessarily short-circuiting part of the magnetic flux in the stator.

[0034] The two foldable isthmuses partially closing a notch may provide a notch opening between them. A width of the notch opening provided between the two foldable isthmuses of the notch may be, when the isthmuses are unfolded, greater than 60% of the width of the notch, better still greater than 70%, being for example of the order of 80% of the width of the notch. For a known semi-closed notch, the ratio may be of the order of 50%. At least one notch, better still all the notches, may have a flat bottom. The edge of the notch defining the bottom of the notch may be at least partially rectilinear.

[0035] At least one notch, preferably all notches, may have two radial edges parallel to each other. The notches may be substantially rectangular in shape.

[0036] At least one tooth, preferably all teeth, may have two radial edges converging in the direction of the machine's axis of rotation.

[0037] A ratio of the surface area of ​​a notch to the section of the wires of the notch may be less than 2.5, or even strictly less than 2.5, in particular less than 2.4, or even less than 2.3, better still less than 2.2, being for example of the order of only 2.

[0038] Reducing this ratio can allow the stator designer to better optimize its design. For example, for a given wire cross-section, and with the same flux density in the stator mass, the mass of the stator mass could be reduced by around 10%. The quality of heat exchange between the wires and the stator mass can be significantly improved, which can promote better cooling of the coils.

[0039] By alleviating the dimensional dependency connecting the wires and the slot opening, it is possible to significantly reduce the latter and improve the performance of the magnetic circuit.

[0040] Furthermore, the increase in the occupancy density within a slot is also advantageous with regard to a step of impregnating the coils with impregnation varnish. Indeed, the empty space between the wires is less important thanks to the invention, therefore the quantity of varnish necessary to fill this void is less. In addition, this makes it possible to promote the maintenance of the varnish in the slots until the polymerization step. By increasing the filling of the slot, the maintenance of the varnish in the slot by capillary effect is promoted, and the risk of hot spots appearing in the winding is minimized.

[0041] The invention also relates, independently or in combination with the above, to a rotating electrical machine comprising a stator as described above and a rotor. The machine may be an alternator. It may be an alternator producing a voltage greater than 100 V, better still greater than 200 V, for example greater than 300 V, being for example of the order of 400 V or more.

[0042] The delivered voltage can be alternating. It can be three-phase. The different phases can be distributed in the slots. The winding can have a shortened pitch.

[0043] The power supplied can be in the order of a few kVA to several MVA.

[0044] The stator according to the invention can advantageously be wound for different voltages, frequencies, and powers.

[0045] The invention also relates, independently or in combination with the above, to a method of manufacturing a stator of a rotating electrical machine as described above, in which bundles of round wires are inserted into the notches of the stator by introducing them radially into the corresponding notches starting from one of the axial ends of the machine, with a longitudinal translation.

[0046] Wire bundles can be wound into closed turns, similar in shape to rectangles with rounded corners, thus forming coils. There can be continuity between the different coils of the same phase when forming the windings. There can be either single coils or a string of coils.

[0047] Coils can be formed on winding forms. The winding forms used can be configured to guide and hold the wire bundles, while keeping the coil heads free. This allows for much better control over the arrangement of the wires in the bundles. The winding forms can have grooves to receive the wires. They can be U-shaped in cross-section. These grooves, which receive the wires, can have a width equivalent to, or even slightly less than, the width of a slot.

[0048] In the insertion step, the coils are inserted into the stator bore opposite their respective slots, and the wires of the bundles are inserted into the slot through the slot opening. The introduction of a bundle is done gradually by stripping the wires through the opening. The diameters of the wires that constitute the bundle are smaller than the slot opening width.

[0049] However, since the foldable isthmuses are in the open position, the slots are almost completely open to the stator bore. This results in a much less chaotic distribution of wires within the slots than in a conventional semi-open slot.

[0050] The coils may first be lightly engaged in the bore of the stator mass by one of the axial ends of the machine on the side opposite their final position, so that the beginning of the bundles enters the slot between the isthmuses. A small part of the bundles are then in the slot, and the rest are waiting in front of the stator mass. The bundles are then translated longitudinally towards the opposite side of the stator mass. In this movement, the part of the bundles which are outside the stator mass slide into the slots, and the front parts of the bundles which pass through the slot opening finally emerge at the downstream end of the stator mass. At the end of this translation, the bundles are inside the slots.

[0051] In total, the filling of a notch can be carried out by installing the notch bottom insulators, then by inserting a first bundle, then if necessary by installing inter-bundle insulators, then by inserting a second bundle, and finally by installing notch closing insulators.

[0052] This operation is repeated as many times as necessary to enter the different coils.

[0053] In the process, sheets may be pre-cut to form the stator mass, the sheets having foldable isthmuses extending into the stator bore.

[0054] When cutting the poles, the isthmuses are opened, being unfolded. They may have edges converging towards the axis of rotation of the machine.

[0055] The foldable isthmuses may not be tangential to the bore to form the boundary between the inside of the slot and the central bore of the sheet metal. Their orientation is rather radial and they extend into the bore. They are connected to the teeth by a geometry that will subsequently favor their change of position. Their length can also be quite significant, since in their future folded position, the foldable isthmuses will almost completely close the slots. The foldable isthmuses, which can extend the radial edges of the slots into the bore, do so at a non-zero angle that allows the slot opening to be slightly reduced. The stator mass can be formed from a strip of sheet metal cut into sectors, each sector having one or more slots and / or one or more teeth.Alternatively, a sheet of the stator mass may be formed from a plurality of sectors assembled together, each sector comprising one or more notches and / or one or more teeth.

[0056] A sector may have cooling channels or cooling fins. When cutting, the isthmuses of one sector may be cut between cooling fins of another sector. Before cutting, they can thus be nested.

[0057] In the method, at least one bendable isthmus, better all the bendable isthmuses, can form before bending a non-zero angle with the radial edges of the corresponding notch. The angle can be between 5° and 45°, better between 10° and 40°, or even between 15° and 35°, even better between 20° and 30°. The angle can be sufficiently small so as not to disturb the arrangement of the wires during their insertion. Furthermore, the angle can nevertheless be sufficient so that the isthmuses can retain the notch closing insulators.

[0058] In the process, after inserting the wire bundles, the foldable isthmuses can be folded in order to pack the round wires and partially close the stator notches.

[0059] The foldable isthmuses are folded so that they are in line with the stator teeth. The contour of the stator at its bore can be cylindrical or substantially cylindrical. Once folded, the foldable isthmuses do not form any reliefs in the air gap.

[0060] During the insertion stage, the wires have more space than the space in the notch alone. In fact, they also have space provided by the isthmuses opened before folding. Folding the isthmuses thus forces the wires to pack into the notch, the space provided by the isthmuses opened before folding then no longer being available.

[0061] When the round wires are packed into the corresponding notch, the round wires can be arranged in a roughly staggered pattern, given their circular cross-section. They are pushed by the internal edges of the isthmuses. The bulging of the wires is reduced.

[0062] Brief description of the drawings The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which:

[0063] [Fig 1] Figure 1 shows a schematic and partial cross-section of a notch in a stator according to the invention.

[0064] [Fig 2] Figure 2 shows a schematic and partial cross-section of the notch in Figure 1 with the foldable isthmuses unfolded.

[0065] [Fig 3 a] Figure 3 a shows in cross-section, schematically and partially, the notch of Figure 1, superimposed on a notch of the prior art.

[0066] [Fig 3b] Figure 3b shows in cross-section, schematically and partially, the notch of Figure 1 with the foldable isthmuses unfolded, superimposed on a notch of the prior art.

[0067] [Fig 4a] Figure 4a shows a schematic and partial cross-section of the notch in Figure 1 with the foldable isthmuses unfolded.

[0068] [Fig 4b] Figure 4b is a view similar to Figure 4a of a notch of the prior art.

[0069] [Fig 5] Figure 5 is a view similar to Figure 2 of an alternative embodiment.

[0070] [Fig 6] Figure 6 illustrates the method of manufacturing a stator according to the invention.

[0071] Detailed description

[0072] In the drawing, the actual respective proportions of the various constituent elements have not always been respected, for the sake of clarity.

[0073] Figure 1 illustrates a notch 10 of stator 1 of a rotating electrical machine, with a stator mass 3 and a winding 5 arranged in the notch 10.

[0074] The winding 5 comprises bundles of round wires 6, the notch 10 comprising, as illustrated, several round wires 6 succeeding one another circumferentially and radially. A diameter of the round wires 6 can be of the order of 1 mm. It can be seen that the diameter of the wires 6 is small compared to the size of the notch 10. A ratio of the diameter d of wires to a width Le of the notch can be of the order of 10, the width Le of the notch being approximately 10 mm. It can also be seen that the round wires 6 are arranged substantially in a staggered pattern in the corresponding notch. The notch 10 receives a superposition of two bundles corresponding to two different phases, the bundles of the two phases being insulated, from each other and from the stator mass 3, by thin insulators 12.

[0075] The notch 10 is open towards an air gap of the machine and the bore of the stator, and comprises two foldable isthmuses 20 partially closing it. The notch having come by cutting the sheets, the closing of the notches on the side of the air gap is obtained by the foldable isthmuses 20 which came in one piece with the rest of the sheets forming the stator mass 3.

[0076] The notch 10 has a flat bottom. The edge 13 of the notch defining the bottom of the notch is straight, with rounded corners. The notch 10 also has two radial edges 14 parallel to each other. The notch 10 is thus of substantially rectangular shape.

[0077] The stator mass 3 comprises teeth 8 arranged between the notches 10. Thus, each notch 10 is semi-closed on the air gap side by two foldable isthmuses 20 connected to two consecutive teeth 8 of the stator mass 3. The foldable isthmuses 20 are arranged at the foot of the corresponding tooth 8. The foldable isthmuses 20 are in one piece with the adjacent teeth 8. Each tooth 8 comprises two foldable isthmuses 20.

[0078] Each isthmus 20 comprises a bridge of material 21 connecting it to the tooth 8 which is deformable, so as to allow a change in the orientation of the isthmus relative to the corresponding tooth. The foldable isthmus 20 is movable between a first position illustrated in Figure 2 in which it extends into the bore of the stator, and a second position illustrated in Figure 1 in which it partially closes the opening of the notch 10, and extends in the extension of an edge of the tooth 8 defining the bore of the stator.

[0079] The material bridge 21 is delimited by a cutout 22 made on the side of the notch 10, which makes it possible to promote the folding of the corresponding foldable isthmus 20 to partially close the notch 10. The cutout 22 is in this example in cross-section of generally triangular shape. The cutout 22 forms a notch at the base of the foldable isthmus 20, which makes it possible to promote its folding after the insertion of the wires. It can be triangular or of any other shape, as illustrated by way of example in Figure 5, where the cutout 22 is a little deeper.

[0080] The foldable isthmus 20 has in the example described a length Li of approximately 4 mm, or approximately 40% of the notch width. The length of the foldable isthmuses 20 can be quite large, since in their folded position, the foldable isthmuses 20 almost completely close the notches 10.

[0081] The two foldable isthmuses 20 partially closing the notch 10 form between them a notch opening 30, a width If of the notch opening 30 formed between the two foldable isthmuses 20 of the notch being, when the isthmuses are folded as illustrated in figures 1 and 3a, of the order of 20% of the width Le of the notch.

[0082] The two foldable isthmuses 20 partially closing a notch 10 provide between them a notch opening 35, a width lo of the notch opening 35 provided between the two foldable isthmuses of the notch being, when the isthmuses are unfolded as illustrated in Figure 4a and 3b, of the order of 80% of the width Le of the notch. For a known semi-closed notch, the ratio can be of the order of 50%, as illustrated in Figure 4b.

[0083] We will now describe the manufacturing process of stator 1.

[0084] First, laminations are cut to form the stator mass 3, the laminations having foldable isthmuses 20 extending into the bore of the stator, as illustrated in Figure 3b. When cutting the poles, the isthmuses 20 are opened, being unfolded. The foldable isthmuses are not tangential to the bore to form the boundary between the interior of the notch and the central bore of the lamination. Their orientation is rather radial and they extend into the bore.

[0085] The foldable isthmuses, which extend the radial edges of the notches in the bore, do so with a non-zero angle y which makes it possible to reduce the notch opening 35. The foldable isthmuses 20 thus form, before folding, a non-zero angle y with the radial edges 14 of the notch 10. The angle y is of the order of 22°.

[0086] Subsequently, bundles of round wires 6 are inserted into the notches 10 of the stator by introducing them radially into the corresponding notches starting from one of the axial ends of the machine, with a longitudinal translation, as illustrated in Figure 6. Since the foldable isthmuses 20 are in the open position, the notches are almost completely open on the bore of the stator. Also, a distribution of the wires within the notches is obtained which is much less chaotic than in a conventional semi-open notch, as illustrated in Figure 2.

[0087] The coils may first be lightly engaged in the bore of the stator mass by one of the axial ends of the machine on the side opposite their final position, so that the beginning of the bundles enters the slot between the isthmuses. A small part of the bundles are then in the slot, and the rest are waiting in front of the stator mass. The bundles are then translated longitudinally towards the opposite side of the stator mass. In this movement, the part of the bundles which were outside the stator mass slide into the slots, and the front parts of the bundles which passed through the slot opening finally emerge at the downstream end of the stator mass. At the end of this translation, the bundles are inside the slots.

[0088] In total, the filling of a notch 10 is carried out by laying the notch bottom insulators 12, then by inserting a first bundle, then if necessary by laying inter-bundle insulators, then by inserting a second bundle, and finally by laying notch closing insulators.

[0089] After inserting the bundles of wires 6, the foldable isthmuses 20 are folded in order to pack the round wires 6 and partially close the notches 10 of the stator 1, to obtain the configuration of figure 1.

[0090] The foldable isthmuses 20 are folded so as to be in line with the teeth 8 of the stator 1. The contour of the stator 1 at the level of its bore is cylindrical or substantially cylindrical in shape. Once folded, the foldable isthmuses 20 do not form any reliefs in the air gap.

[0091] During the insertion step, the wires 6 have a larger space than the space of the notch 10 alone. Indeed, they also have a space provided by the open isthmuses 20 before folding. The folding of the isthmuses 20 thus forces the wires 6 to pack into the notch, the space provided by the open isthmuses before folding then no longer being available.

[0092] When the round wires 6 are packed into the corresponding notch, the round wires can be arranged in a roughly staggered pattern, given their circular cross-section. They are pushed by the internal edges of the isthmuses. The bulging of the wires is reduced.

Claims

Claims 1. Stator (1) of a rotating electrical machine, comprising a stator mass (3) having a plurality of notches (10) and a winding arranged in the notches (10), the winding comprising bundles of round wires (6), at least one notch (10), or even each of the notches, comprising several round wires (6) succeeding one another circumferentially, and at least one notch (10), or even each of the notches, being open towards an air gap of the machine and comprising two foldable isthmuses (20) partially closing the corresponding notch (10), at least one foldable isthmus, better all the foldable isthmuses, being configured to form before folding a non-zero angle with the radial edges of the corresponding notch, the angle being between 5° and 45°.

2. Stator according to the preceding claim, at least one foldable isthmus, better all the foldable isthmuses (20) having a length (Li) greater than 2 mm.

3. Stator according to one of the preceding claims, at least one foldable isthmus (20), better all the foldable isthmuses, being connected to the corresponding tooth by a material bridge (21) delimited by a cutout (22) made on the side of the notch (10).

4. Stator according to the preceding claim, the cutout (22) being in cross section of general triangular shape, in particular when the isthmus (20) is unfolded.

5. Stator according to one of the preceding claims, the two foldable isthmuses (20) partially closing a notch (10) provide between them a notch opening (30), a width of the notch opening provided between the two foldable isthmuses of the notch being, when the isthmuses are folded, less than 40% of the width of the notch, better still less than 30%, being for example of the order of 20% of the width of the notch.

6. Stator according to one of the preceding claims, the two foldable isthmuses (20) partially closing a notch (10) provide between them a notch opening (35), a width of the notch opening provided between the two foldable isthmuses of the notch being, when the isthmuses are unfolded, greater than 60% of the width of the notch, better still greater than 70%, being for example of the order of 80% of the width of the notch.

7. Stator according to one of the preceding claims, at least one notch (10), better all the notches, having a flat bottom (13).

8. Stator according to one of the preceding claims, at least one notch (10), better all the notches, having two radial edges (14) parallel to each other.

9. Stator according to one of the preceding claims, at least one tooth (8), better all the teeth, having two radial edges converging in the direction of the axis of rotation of the machine.

10. Stator according to one of the preceding claims, a ratio of the surface area of ​​a notch (10) to the section of the wires of the notch being less than 2.5, or even strictly less than 2.5, in particular less than 2.4, or even less than 2.3, better still less than 2.

2.

11. Rotating electrical machine (1) comprising a stator (2) according to one of the preceding claims and a rotor.

12. Method for manufacturing a stator of a rotating electrical machine according to any one of claims 1 to 10, in which bundles of round wires (6) are inserted into the notches of the stator by introducing them radially into the corresponding notches starting from one of the axial ends of the machine, with a longitudinal translation, method in which at least one foldable isthmus forms before folding a non-zero angle with the radial edges of the corresponding notch, the angle being between 5° and 45°.

13. Method according to the preceding claim, in which sheets are first cut to form the stator mass (3), the sheets comprising foldable isthmuses (20) extending into the bore of the stator.

14. Method according to the preceding claim, in which all the foldable isthmuses form, before folding, a non-zero angle (y) with the radial edges (14) of the corresponding notch (10).

15. Method for manufacturing a stator of a rotating electrical machine according to any one of claims 1 to 10, in which bundles of round wires (6) are inserted into the notches of the stator by introducing them radially into the corresponding notches starting from one of the axial ends of the machine, with a longitudinal translation, method in which, after insertion of the bundles of wires (6), the foldable isthmuses (20) are folded in order to pack the round wires (6) and partially close the notches (10) of the stator.

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