FR2522189A1 - METHOD FOR PRODUCING AN ELECTRICAL TRANSFORMER, TRANSFORMER THUS PRODUCED AND WHEEL FOR THE WINDING - Google Patents

Abstract

1. A process for manufacturing a transformer comprising : a magnetic frame (1) having at least one core (2) and at least one yoke (3, 4) which cooperate to bound at least one substantially rectangular window (6) ; at least one high-voltage electrical circuit (13) ; and at least one low-voltage electrical circuit (11), in which process the magnetic circuit (1) is embodied, an insulating tube (9) is placed around the core (2) and is releasably connected at least one end to a demountable driving wheel (83) ; and the winding turns are wound by the tube (9) being rotated through the agency of the driving wheel (83), characterised in that the process starts from a plastics insulating tube (9) formed with at least one substantially axial slot (22), the slot (22) is opened for the core (2) to be placed in the tube (9), the slot (22) is closed and only then is the driving wheel (83) placed around the core (2) and rotatably connected to the annular end of the tube (9).

Description

The present invention relates to a method for producing a transformer

  electrical single-phase or polyphase more particularly of the kind in which the circuit

  magnetic defines at least one rectangular window.

  The invention also relates to a transformer

  performed according to the method below.

  It also relates to a wheel for winding

  this transformer according to the aforementioned method.

  In the transformers covered by the invention, the high and low voltage electrical circuits are wound around one or more insulating tubes, each in turn surrounding a magnetic core consisting of

  one of the branches of the magnetic circuit According to the

  Each circuit can have its core and its insulating tube, or there is only one core for each phase. Certain advantageous methods for producing such transformers, do not allow the magnetic circuit to be made around the electric windings. nor to put the electrical circuits on the magnetic cores at a certain stage of the realization of the magnetic circuit This is the case if the rectangular window magnetic circuit consists of one or more

  tapes rolled around the magnetic windows.

  According to such manufacturing methods, it is necessary to wind the electrical circuits around the core

  magnetic once the magnetic circuit is completed.

  To realize the electrical circuit, US Pat. No. 2,968,445 teaches placing a thin toothed wheel around the core carrying a cylindrical end-piece surrounding the core. The toothed-end gear assembly is assembled from two halves according to a joint plane. axial The toothed wheel is placed at one of the ends of the core, is rolled around the tip several layers of insulating paper to make the insulating tube, then

  the electrical circuits are wound around the insulating tube.

  The two halves of the toothed wheel are then disassembled, and the latter is removed by extracting the half-ends axially from the insulating tube. This method has the disadvantage that the paper or cardboard of which the tube is made is, despite all the precautions taken, a fragile material and lacking rigidity, likely to be the cause of insulation defects and thus involving large spaces However, we can not see which material other than cardboard could be used with greater success in the context of such a process. In addition, electrical circuits can not occupy the entire length of the core. , you have to reserve a certain length for the thickness of the toothed wheel, and still an extra length

  allowing then to extract the tip of the cardboard tube.

  In addition, the realization of the insulating tube is inconvenient and requires precautions as to the superposition

  correct and tight layers of paper.

  The object of the invention is to remedy these drawbacks by proposing a method according to which the electric windings are easy to use.

  place on the magnetic circuit and occupy almost

  the entire length of the core (s).

  The invention thus relates to a method for manufacturing a transformer comprising a magnetic frame comprising at least one core and at least one yoke which together define at least one substantially rectangular window, at least one high voltage electrical circuit and a low voltage electrical circuit. method, the magnetic circuit is made, an insulation tube is placed around the core, at least one end of which is removably coupled to a demountable drive wheel, and the electrical turns are wound by causing the insulation tube to rotate. via the drive wheel. According to the invention, the process is characterized

  rised from an insulating plastic tube

  as slit along at least one substantially axially directed line, in that the slit is moved to pass the magnetic core inside the tube, in that the slot is closed, and that at this stage only , the drive wheel is put in place around the core by mechanically coupling it to the annular end

insulation tube.

  Thus, the laying of the insulating tube is considerable-

  Simplified and it is both more rigid and better insulation It is no longer necessary that the drive wheel has a tip engaged inside.

  of the tube, so that at the end of winding, the driving wheel

  is easy to extract, and it is not necessary to provide extra kernel length for this

  effect The length of the kernel is therefore available in almost

all for windings.

  According to another aspect of the invention, the transformer made according to the above method, is characterized in that the insulating tube has only one slot and can move away elastically to allow

  to pass the magnetic core through the slot.

  The insulating tube can thus be made in one piece and its installation does not require any

fixing operation.

  According to a third aspect of the invention, the rotation drive wheel of the insulating tube for winding a transformer of the above kind, comprising two half-wheels intended to be assembled around the core, is characterized in that on its face facing the core, it has a bearing surface and centering on the insulating tube, an axial stop for the insulating tube, and means for coupling in rotation with the insulating tube. Thus, even with no end piece, toothed groove simultaneously ensures the axial and radial positioning

  and the rotational drive of the insulating tube.

  Other features and advantages of the invention

  will be apparent from the following description.

  In the accompanying drawings, given by way of non-limiting examples: FIG. 1 is a side elevational view of a three-phase transformer, according to the invention, the tank being cut along a plane parallel to the magnetic circuit plane;

  FIG. 2 is a view from above of the trans-

  formator of Figure 1, the lid of the tank being removed; FIG. 3 is an end view of the active part of the transformer of FIGS. 1 and 2, with section of the vessel in a plane parallel to that in the figure; Figure 4 is a view of the transformer in cross section along the plane IV-IV of Figure 1, on an enlarged scale; Figure 5 is a perspective view of the insulating tube for surrounding one of the cores; Figure 6 is a cross-sectional view of one of the cores with its insulating tube; Figure 7 is an exploded perspective view with cutaway, the insulating tube and a drive wheel for winding; FIG. 8 is a diagrammatic view in diagrammatic perspective view of a wedge for fixing the windings; FIG. 9 is a sectional view through FIG.

  the end of one of the nuclei, showing the tube that

  turn, and the two half-shims assigned to this end of the tube, one of these half-shims being mounted, the other during assembly; Figure 10 is a perspective view of the winding operation of the low voltage circuit; Figures 11a and 11b are bottom views of the two shims assigned to the upper end of any one of the three cores; Figures 12a and 12b are sectional views along the plane XII-XII of Figures 11a and 11b; Figures 13 and 14 are views according to Floches XIII and XIV of Figures 11a and 11b respectively; Fig. 15 is a side elevational view with cutouts of the transformer switching device with the covers of the thirds housings removed; Figure 16 is an end view of one of the housings of Figure 15, with cross section of the control rod; and FIG. 17 is an electrical diagram of the

switching device.

  In the example shown in the figures, the three-phase transformer is of the planar magnetic frame type 1 comprising three vertical rectilinear cores 2 whose lower and upper ends are respectively connected by an upper magnetic yoke 3 and

  a lower magnetic yoke 4 This definite structure

  nit between the three cores 2 two large windows

rectangular 6.

  The magnetic frame is made in known manner from rolled magnetic sheet metal strips It comprises a ring 7 rolled around each window 6 and a peripheral ring 8 surrounding the two rings 7

  At the same time each ring 7 or 8 having a semi-section

  octagonal, each ring 2 and each cylinder head 3 or 4

has the same octagonal section.

  As shown in FIG. 4, an insulating tube 9 is disposed coaxially and at a slight distance around each core 2. Given the electrical coupling of the transformer, each insulating tube 9 carries a low-voltage winding 11 made of aluminum strip. and a high-voltage winding 13 made of copper wire, coaxial with the tube 9 and the core 2. The two windings 11 and 13 extend over almost the entire length of the core 2, the high-voltage winding 13 being outside Between the windings 11 and 13 is disposed a conical annular insulating spacer, not shown, which allows the circulation

  insulating oil in the axial direction between the coils

Elements e.

  The active part of the transformer,

  that is to say the assembly consisting of the frame 1 and the electric windings 11, 13 is installed in a tank 14 containing insulating oil closed by an upper cover 16, and in which the cores 2 are vertical The bottom 17 of the tubiôrtequatretasas longitudinal 18 and two transverse battens 19 for receiving between them the magnetic frame 1

  and position it both in the long-term

  The same device is found under the cover 16 o rubber blocks 21 are further interposed between each pair of cleats

  18 and Box 1 to ensure the elastic positioning

  tick of the latter in the vertical direction.

  As shown schematically in Figure 5, the insulating tube 9 is made of plastic material and is split according to one of its generatrices 22 As shown in Figures 5 and 6, the profile of the slot 22 is sinuous, more precisely stepped , so that

  sufficiently lengthen the electrical leakage line

  staked by the slot to avoid any possibility of ignition between the electric windings and the

magnetic core 2.

  Along its generatrix 23 diametrically opposite the slot 22, the tube 9 has a thinning

forming hinge.

  At each of these annular ends, the insulating tube has two pins 26 arranged from

  and other of the slot 22 and adjacent thereto.

  Each tenon 26 has, on the side of the slot 22, a face 27 carried by a plane passing through the axis of the tube 22, so that when the slot 22 is closed, the two tenons 26 of one end are joined together on top, they

  then together have a substantially semicircular shape.

  As shown in FIG. 4, each annular end of the tube 9 protrudes axially from the windings 11

  and 13 over a length equal to the thickness of the tenons 26.

  In use, these are arranged laterally against the inner winding 11 The face 27 of the tenons 26

  is in-a plane perpendicular to the plane of the frame 1.

  Each annular end of the tube 9 is

  associated with an annular wedge 28 or 29 (FIG.

  between the annular ends of the electrical circuits

  11, 13 and the adjacent magnetic yoke 3 or 4.

  The shim 28, taken as an example, is shown very simply in FIGS. 8 and 9.

  comprises two semi-spacers 31, 32 of generally semi-

  circular In the example shown, the joint plane 33 between the demical 31 and 32 is carried by the plane

  longitudinal median CC of the frame 1 (Figure 9).

  On its annular face directed towards the core 2,

  the wedge has a bearing surface 34 whose contour corresponds to

  to the profile of the core 2, so that when the half-shims 31, 32 are assembled around it, the shim 28 has no freedom of radial movement or

rotating relative to the frame 1.

  In the example shown, the surface 34 is octagonal like the core 2 However, the oblique faces 36 of the surface 34 are recessed to avoid contact with the core 2, which simplifies the problems of centering Only the faces of the surface 34 that are parallel or perpendicular to the CC plane

  are in contact with the core 2 and ensure positioning.

  In use, the surface 34 is between the end

  annular tube 9 and the cylinder head 3 or 4 adjacent.

  The wedge 28 further has on its face facing the core a second bearing surface 37 axially closer to the windings Il and 13 than the face 34 The face 37, which is further from the axis of the core 2 than the face 34, is connected thereto by a shoulder 38 The face 37 'which is cylindrical and has a diameter equal to the outer diameter of the tube 9, bears on the outer face thereof and more specifically on the portion of the tube 9 which protrudes from the windings 11 and 13 The width of the surface 37 is equal to the length of the tube 9 which protrudes from the windings

11 and 13.

  In the offset position of 900 relative to the joint plane 33, the half-wedge 31 has a semicircular recess 39 whose shape corresponds to that of

two studs 26 assembled.

  In the zone between the two lines 41 (FIG. 9) which eliminate the zone in which the shim is interposed between the innermost strip of the yoke 3 or 4 and the windings 11 to 13, the UeAse Ure of the wedge 28 is equal to the distance separating

  service the windings 11 to 13 of a 3 or 4 adjacent tub.

  The holds 28, 29 made of

  injected plastic, thus ensuring both the position

  axial position, centering, and immobilisation in

  rotation of the windings 11 to 13 on the core 2.

  We will now describe in more detail a practical embodiment of the spacer 28 shown in FIGS.

Figures 11a to 14.

  As shown in particular in Figures 13 and 14, each half-wedge 31 or 32 comprises a web 43 which is substantially plane in the zone 40 of support against the magnetic yoke 3 or 4 On its face facing the windings 11,13, the sail 43 carries fins 44 located on either side of the central opening of the shim, and oriented perpendicular to the plane CC On the same face, the sail 43 also carries fins 46 parallel to the fins 44 and extending from the central opening of

the hold 28.

  The central opening of the wedge 28 is delimited by an octagonal cut of the web 43, the edge of which constitutes the bearing surface 34 against the

magnetic core 2.

  As shown in particular in Figures 11a, 11b, 13 and 14, the bearing surface 37 of the wedge 28 on the tube 9 is formed at the end of the fins

  46 directed towards the central opening of the hold 28.

  For this purpose, each of these ends forms a staircase constituted by a part of the face 36, a

  part of the shoulder 38 and part of the

face 37.

  On the half-wedge 31 only, the surface 37 further comprises a cylindrical threshold in the middle of which

is notched notch 39.

  In the zone 40 of the wedge 28, the sail 43 carries on its side facing the adjacent yoke 3 or 4, fins 48 oriented obliquely to the plane CC The orientation of the fins 48 carried by one of the half-shims 31, 32 on one side of the opening of the wedge 28 is symmetrical with respect to the plane CC of that carried by the other half-wedge 31 or 32 of the same

  side of the central opening of the hold 28, and is identi-

  than that of the fins 48 carried by the other half

  hold 31 or 32 on the other side of the central opening

from the hold 28.

  In addition, as shown in Figures 13 and 14, the fins 48 are lying in the direction of extraction of the half-shims, so that if one tends to extract the half-shims, they oppose this extraction while arching against the magnetic yoke

adjacent 3 or 4.

  Outside zone 40, sail 43 is

  curved (FIGS. 12 a to 14), in the opposite direction to the coils

11, 13.

  As shown in Figures 12a and 12b, the two half-blocks 31 and 32 are assembled in a stepped joint plane, in favor of the strength and accuracy of the assembly The fins 44 carried by each half hold 31 or 32 line up each with

  one of the fins 44 carried by the other half-hold.

  The fin 44 closest to the central opening of the wedge 28, called the fin 44a, is thicker than the others and is traversed by a bore, threaded with respect to the half-wedge 32, which makes it possible to screw together the two half-blocks 31, 32 by means of screws

in superpolyamide.

  1 1 Behind the two faces of the surface 34 which are parallel to the plane CC, the half-wedges 31, 32 have a rectangular notch 49 intended to reveal the side face of the windings 11 to 13 and allow the output connections Each half -cale 31 or 32 door on the opposite side to the windings

  11 to 13, a U-shaped mount 51 attached parsatranche to the sail 43.

  The central part of the frame is located between the opening

  center of the wedge 28 and the notch 49, while its two arms are directed away from the central opening Each of the branches of the frame 51 carries two snap holes 52 (Figure 122) The mount 51 of the half-wedge 32 serves to carry two supports 53, 54 intended to carry in turn coupling members

  between the low voltage windings of the transformer.

  As shown in FIG. 4, the support 53 carries a blade 56 electrically connected to the inner end of the winding 11. The end of the support 53 also carries a blade 57 electrically connected to the blade 56 and connecting it to a low voltage phase terminal 58 arranged on one of the end sidewalls of the tank 14 (FIG. 2). Two other blades 59 surrounded by insulation (FIG. 4) are mounted against the blade 57 and each connect the winding. 11 assigned to one of the other two cores 2 at a respective phase terminal

  next to terminal 58 (Figure 2).

  The support 54 carries a blade 62 connected to

  the other end of the winding 11 and a longitudinal blade

  Nale 63 electrically coupling the blades 62 of the three windings 11 of the transformer The blade 63 is electrically connected to a neutral terminal 64 arranged in

  transformer end below terminals 58 and 61 (Fig.

re 1).

  The frame 51 of the half-shim 31 bears no accessories By the notch 49 of this half-shim passes one of the end wires 66 of the high-voltage winding 13 Each of the wires 66 is connected directly to a terminal high voltage phase 67 (Figure 4) arranged in the lid 16 of the tank 14 just above

the notch 49 corresponding.

  At the end of the windings 11 and 13 directed towards the bottom of the tank 14, the wedge 29 carries a stacker

  68 being part of a switching device 69

  so much to adjust the transformation ratio of the transformer.

  The device 69 is shown schematically in FIG. 17 in which we see the three star-shaped windings 13 between each of the terminals 67 and a conductive rod 71 carrying a contact 72 in front of each of the windings 13. On the side of this rod, each winding 13 carries three output contacts 73, one connected to the end of the winding 13, the other connected to a turn located below this end and the third to a turn even further from the end of winding By moving the rod 71 in its longitudinal direction which corresponds to that of the transformer, the number of turns in service in each winding is adjusted and consequently, the ratio of

  transformation in the transformer.

  As shown in Figure 15, the contacts

  73 are arranged for each winding 13 in a bush 68.

  The conductive izinqle 71 is mounted between each of these cages 68 and a cover 74 which closes it (FIG. 16). In use, the trile is located

  between the windings 11, 13 and the bottom of the tank, next to the culase 4.

  At one of its ends, the rack 71 is connected to a cable 76 mounted in a sheath 77 and connected to a rotary control knob 78 placed under

the terminal 64 (Figure 1).

  At the same end, the rod 71 carries a rack 79 directed towards the bottom of the tank 14, which cooperates with a toothed wheel 81 to which is attached the end of a helical spring 82 (Figure 4) whose other end is fixed to the casing 68 The spring 82 constantly urges the pinion 81 in the direction of the tension of the cable 76, the settings being locked by a suitable device of known type provided for in FIG.

  the control button 78 (Figure 1).

  The manufacturing process will now be described.

  transformer above: First, rolls of magnetic sheet metal strips, the two inner rings 7 and then the outer ring 8 so as to complete the magnetic frame 1. Then, one of the cores 2 is placed around an insulating tube the slot 22, passing the core 2 through the slot 22 and closing again

  the slot 22 when the core 2 is in the tube 9.

  The hinge 23 allows the semi-cylindrical half-shells constituting the tube 9 to pivot with respect to

  the other during these operations.

  A driving gear 83 (FIGS. 7 and 10) is then placed at each end of the tube 9, formed of two half-wheels separated by a plane of joint passing substantially through the axis of the wheel 83. The two half-wheels are intended to be screwed to each other around the core 2 and

  of the end of the tube 9 to which the wheel 83 is affected.

  For this purpose, on either side of its central opening, the wheel 83 is provided with two bores 88 which pass through

  the joint plane 87 between the half-wheels 84 and 85.

  The bores 88 are threaded in the half-wheel 85 (whose teeth are not shown) and are embedded in a well 89 opening

  in the toothing (shown in part at 11 empt) the half-wheel 84.

  On its annular face directed towards the core 2, 1 4 the wheel 83 has a cylindrical surface 91 intended to bear all around the annular end of the tube 9 The axial dimension of the surface 91 corresponds to the length of tube 9 which must protruding from the windings 11, 13 In the offset position of 900 with respect to the joint plane 87, the half-wheel 8> 4 has a notch 92 intended to receive the two contiguous tenons 26. At its side, the half-wheel 85 presents opposite the notch 92, a radial groove 93 from the surface 91 to the

toothed circumference of the wheel 83.

  On the opposite side to the enrnulements, the surface 91 is bordered by a collar 9> 4 serving as a stop for the

insulating tube 9.

  Once the two wheels 83 are in plae (FIG. 10), three toothed satellites 96 are installed around each of them. For each wheel 83, one of the satellites 96 is coupled to a motor 97 'while the two others simply ensure the centering of the wheels 83 Among them, one door on the opposite side to the tube 9 a collar

  98 for axially positioning the wheels 83.

  The conductive strip 99 is then brought to the end of which a transverse conductive strip is attached which constitutes on each side of the strip 99 a blade 56 which is engaged in the groove 93 of the adjacent drive wheel 83 L '. one of the blades 56

  will then constitute the phase contact blade of the coil.

  (see figure> 4), while the other (not visible in figure 10), which can be much shorter, serves only to drive the

the wheels 83.

  The strip 99 consists of an aluminum strip covered with a sheet of insulating paper intended to electrically isolate the coil being produced from

the next turn.

  To promote the training of the band 99 by the wheels 83, it has stuck the departure thereof

with adhesive tape 101.

  When the low voltage winding 11 is finished, the end of the latter is fixed to the neutral coupling blade 63 (FIG. 4) which is engaged

  in the groove 93 of the wheel 83 (Figure 10).

  We then place around the coil 11

  an insulating plastic spacer (not shown

  known type, analogous to a scale

  curved to bring these two ends together.

  The winding 13 is then made around this spacer in a manner which, with regard to the arrangement of the turns and their mutual isolation,

  is similar to that described in US Patent 2,968,445.

  During the realization of the winding

  13, we connect the contacts 73 where it is planned.

  Once the winding 13 is over, we dismount

  the wheels 83, and in the same manner the rolls are

  around the other two nuclei 2.

  The wedges 28 and 29 are then placed around each core 2, the accessories 53 are installed,

  54, 68 (Figure 4) and the connections are made.

  The transformer which has just been described is thus particularly easy to produce, lightweight, compact and efficient In fact, the insulating tube 9 is very easy to put in place, and also allows to provide only a very small space between the 'winding

  In addition, thanks to this process of realization,

  windings using the tube 9, almost all

  the length of the cores 2 is occupied by the windings.

  The shims 28 and 29, which cooperates cleverly with the tube 9 alone ensure all the positioning functions of the windings relative to the magnetic frame 1 The very precise positioning ensured in this way reduces the safety margins provided for the spaces d insulation, which is advantageous

in lightness and performance.

  With the fins 44 and 46, and the curved parts of the sail 43 acting as oil baffles, a real oil circulation can be established

  by thermo-siphon between the windings.

  Of course, the invention is not limited to the example shown, many adjustments that can be made to this example, without departing from the scope of the invention. Thus, the invention can be applied to any mcnophase or polyphase transformer with window (s)

rectangular (s).

  It is not essential for the insulating tube to carry means for coupling in rotation with the drive wheels and the shims. This coupling could for example be effected by a thin projection carried by the wheels and shims and engaging in the slot 22.

  The insulating tube may consist of two completely separate shells It may instead

  only consist of an elastic shell without

  re. One could only provide a single drive wheel. It could also be provided that the high voltage circuit is wound directly around the core, while the low voltage circuit is wound around the

high voltage circuit.

Claims (7)

  A method for manufacturing a transformer comprising a magnetic frame (1) comprising at least one core (2) and at least one yoke (3, 4) which together define at least one substantially rectangular window (6), at least one high electrical circuit voltage (13) and at least one low-voltage electrical circuit (11), in which method the magnetic circuit (1) is produced, an insulating tube (9) is placed around the core (2) and removably coupled to it at least one of the ends to a demountable drive wheel (83), and the electrical turns are wound by causing the insulating tube (9) to rotate through the drive wheel (83), characterized in that what we start from an insulating tube (9) made of split plastic   in at least one substantially axial line (22)   in that the slot (22) is moved away from the magnetic core (2) to the inside of the tube (9), in that the slot (22) is closed and in that stage only we set up the drive wheel (83)   around the core (2) by coupling it in rotation at the end -   annular mite of the insulating tube (9).   2 Transformer made according to the method of claim 1, characterized in that e insulating tube (9) has only one slot (22) and can move elastically to allow to pass   the magnetic core (2) through the slot (22).   3 Transformer according to claim 2, characterized in that the insulating tube (9) comprises two half-cylindrical half-shells attached one   to the other by an axial thinning (23) forming a hinge.   4 Transformer conform to one of the   2 or 3, characterized in that the profile of the slot (22) is sinuous.   Transformer according to one of claims 2 to 4, characterized in that the insulating tube (9) at its end intended to be associated with the drive wheel (83) means (26) for coupling rotation with it. 6 Transformer according to claim, characterized in that the coupling means carried by the insulating tube (9) comprise two pins (26) arranged on each side of the slot (22) and adjacent thereto, these two tenons being adapted to engage a recess (92) of the drive wheel rotation (83).   7 Transformer conforming to one of the   5 or 6, characterized in that each end of the insulating tube (9) protrudes axially from electrical circuits (11, 13) which it carries, and is associated   an annular wedge (28, 29) interposed between the end   annular tee of the electric circuits (11, 13) and the yoke (3, 4), this wedge (28, 29) having on its face directed towards the core (2) two radially offset bearing surfaces (34, 37) l one (37) bearing on the insulating tube (9), and having means (39) capable of cooperating with the coupling means (26)   carried by the insulating tube (9) to immobilize this   ci in rotation about its axis parrappcxaux wedges (28,29),   the other (34) bearing on the magnetic core (2).   8 Rotating drive wheel of the insulating tube, for winding a transformer conforming to one   Claims 5 to 7, comprising two half-wheels   (84, 85) intended to be assembled around the core (2) characterized in that on its face facing the core (2), it has a bearing surface (91) and centering on the insulating tube (9) , an axial stop (94) for the insulating tube (9) and means (92) for coupling in rotation with the insulating tube (9).   9 Drive wheel according to the claim   8, characterized in that one of the half-wheels (85) has on its face facing the electrical windings (11, 13) a groove (93) directed radially for receiving during winding, at least one electrical coupling tab (56, 62) of at least one windings (11).