Wound rotor with means for cooling the rotor windings

Abstract

Wound rotor with means for cooling the rotor windings The invention relates to a wound rotor (1) for an electrical machine, comprising: - a rotating shaft (3), - a rotor body (2) integral with the rotating shaft (3), comprising a plurality of magnetic poles (20a, 20b, 20c, 20h) provided with windings (8a, 8b) extending from one axial end of the rotor body (2) to an opposite axial end, the wound rotor (1) comprising a cooling channel (9) extending in the rotating shaft (3), and the rotor body (2) comprising a passage (4) capable of supplying cooling liquid to at least one of the windings (8a, 8b), the passage (4) extending in the rotor body (2) while being connected to the cooling channel (9), and opening onto a wall (25) of the rotor body (2) extending between the two axial ends of the rotor body (2). (Figure 1)

Description

Title of the invention: Wound rotor with means for cooling the rotor windings

[0001] The present invention relates to the fields of electrical engineering and mechanics, and more specifically concerns a wound rotor for an electrical machine, finding an advantageous application in the automotive field.

[0002] Electric and hybrid electric vehicles use electric motors to provide their propulsion or traction. In order to increase the power density of such an electric motor, with a view to reducing its size for equal electrical power, it is necessary to ensure effective cooling of its electrical conductors when current flows through them.

[0003] Indeed, the greater the intensity of the current flowing through these electrical conductors, the greater the losses by Joule effect and the increase in temperature of the motor windings, such a rise in temperature being able to degrade the operation of the electric motor if the heat generated by these thermal losses is not quickly evacuated. This is why certain electric traction or propulsion machines comprising windings are cooled by a liquid such as oil. In such an electric machine, the liquid circulates in a closed loop in a cooling circuit passing through the electric machine in which the liquid sprays the windings of the machine for example using oil injectors fixed on a casing of the electric machine.

[0004] When the electrical machine has a wound rotor, it is difficult to cool the rotor windings since these windings rotate during operation of the electrical machine. Only the winding heads are therefore generally well cooled, which does not allow uniform cooling of the rotor windings and is detrimental to the efficiency of the electrical machine.

[0005] The present invention aims to remedy at least in part the aforementioned drawbacks by providing a wound rotor and an electrical machine comprising such a wound rotor, which allow homogeneous cooling of the rotor windings and improve the efficiency of the electrical machine.

[0006] To this end, the invention provides a wound rotor for an electric machine, comprising - a shaft rotating around an axis of rotation of the wound rotor, - a rotor body secured to the rotating shaft, comprising a plurality of magnetic poles provided with windings extending from one axial end of the rotor body to an opposite axial end of the rotor body, the wound rotor being characterized in that it comprises a cooling channel extending in the rotating shaft, and in that the rotor body comprises a passage capable of supplying cooling liquid to at least one of the windings, the passage extending in the rotor body while being connected to the cooling channel, and opening onto a wall of the rotor body extending between the two axial ends of the rotor body.

[0007] It should be noted that in this patent application, the term "axial" (or "axially", "axial", "axial") refers, unless otherwise stated, to a direction parallel to the axis of rotation of the rotor of the electric machine. Similarly, the term "radial" (or "radially", "radial", "radial") refers, unless otherwise stated, to a direction orthogonal to the axis of rotation of the rotor of the electric machine, and secant to this axis of rotation, while the terms "angular" (or "angularly") or "ortho-radial" (or "ortho-radial / radially / radial") refer, unless otherwise stated, to a direction orthogonal to the axial direction and to a radial direction, this orthogonal direction being in fact rotating around the axis of rotation of the rotor.

[0008] The wound rotor therefore comprises several windings distributed angularly around the rotor body, the turns of the windings forming a radial magnetic field exchange surface with a stator, and extending from one axial end to the other of the rotor body, leaving coil heads protruding on either side of the rotor body on these axial ends, which can be insulated from the rotor body by winding supports made of insulating material.

[0009] The cooling channel preferably extends axially in the rotating shaft and is for example supplied from a fixed part of an electrical machine comprising the wound rotor, by a cooling liquid. The passage connected to the cooling channel in the rotating shaft is hollowed out in the rotating shaft then in the rotor body so as to open onto a substantially cylindrical wall of the rotor body, the latter having a generally cylindrical shape, its two axial ends forming bases of this generally cylindrical shape.

[0010] Thanks to the invention, the liquid does not reach the rotor windings via the winding heads, but reaches an axially more centered part of the rotor body, which facilitates its distribution from one axial end of the rotor body to the other, and therefore allows more uniform cooling of the rotor windings.

[0011] Of course, preferably several passages are dug from the cooling channel to the windings, so as to also angularly homogenize the cooling of the rotor windings.

[0012] The coolant is for example a liquid such as oil.

[0013] In one embodiment of the invention, the magnetic poles project from a cylindrical central portion of the rotor body, and each comprise a foot extending radially from the cylindrical central portion, each winding being wound around the foot, and the passage opens between two feet of two magnetic poles, the wall of the rotor body being formed by the cylindrical central portion.

[0014] The cylindrical central portion of course designates a substantially cylindrical central portion, the external walls of this portion being able to deviate slightly from a cylindrical shape, for example by comprising grooves.

[0015] In this embodiment of the invention, the wound rotor is a salient pole rotor, the space between the two feet forming a notch. The passage therefore opens into the notch, in which the cooling liquid is guided partly axially along wires of at least one of the windings surrounding one of the feet, these wires extending axially in the notch. This embodiment allows the cooling liquid leaving the passage to cool, for example, two rotor windings simultaneously.

[0016] In an alternative embodiment of the invention, a winding notch being formed by at least the wall of the rotor body and the two feet, the windings in the notch each being protected by an insulating jacket, the passage opens into the winding cavity through one of the insulating jackets.

[0017] In this embodiment variant, there are therefore two insulating jackets in the notch, for example in the form of spindles, one of the spindles housing the wires of the winding surrounding one of the feet, these wires extending axially in the notch, and the other spindle housing the wires of the winding surrounding the other of the feet, these wires extending axially in the notch. These insulating jackets open axially on either side of the rotor body, at the axial ends thereof. Each insulating jacket is perforated at the passage to allow the coolant to penetrate into the insulating jacket, which forms a coolant channel opening at the axial ends of the rotor body. In this embodiment variant, the rotor comprises for example a passage at each notch of the wound rotor, each passage bringing coolant to a different winding.Optionally, the rotor has two passages at each notch, each winding then being cooled on either side of the foot which it surrounds by two different passages.

[0018] Alternatively, in a main embodiment of the invention, the two magnetic poles each comprise a head covering the foot and extending on either side of the foot, a first winding cavity being formed by the wall, a first of the feet and its head, and a second winding cavity being formed by the wall, a second of the feet and its head, and the winding in each of the first and second winding cavities is protected by the same insulating jacket, the passage opening into an opening in the insulating jacket, the opening being located between the two winding cavities.

[0019] In this main embodiment variant, the notch between the two feet forms two winding cavities, the winding wires present in the notch being protected from the rotor body, generally made of magnetic steel, by the same insulating jacket covering at least part of the walls of the notch, this insulating jacket however being perforated at the level of the opening allowing the arrival of cooling liquid through the passage. The separation of the windings in the insulating jacket can be achieved by the shape of the insulating jacket, which for example comprises a fold separating the two windings. A wedge for holding the windings is for example inserted into this fold.

[0020] The insulating jacket opens axially on either side of the rotor body, at the axial ends thereof. The opening in the insulating jacket allows the coolant to penetrate therein and form a coolant channel opening at the axial ends of the rotor body. In this main embodiment variant, the rotor comprises, for example, a passage at each notch of the wound rotor, each passage spraying coolant onto the wires present in the notch of the two windings.

[0021] According to an advantageous and optional characteristic of this main embodiment of the invention, the windings in the first and second cavities are separated by a fold in the insulating jacket receiving a wedge for holding the windings, the holding wedge comprising two faces coming to bear against each of the windings by means of the insulating jacket, the faces being connected to each other by an edge radially facing the opening at a distance from the latter, thus allowing the passage of the cooling liquid between the edge and the wall of the rotor body.

[0022] This feature allows the coolant, leaving the passage through the opening of the insulating jacket, to be distributed equally between the first and second cavities thanks to the edge of the holding wedge, which cuts in two the flow of coolant arriving from the passage. This wedge is for example of triangular section, extends axially along the rotor body and is for example held radially by the heads of the magnetic poles, which each partly cover a face of the wedge connecting the two faces arranged to support the windings in the notch. It is possibly axially perforated to receive a tie rod for fixing a ring for holding the winding heads of the rotor. Of course, preferably each notch comprises such a holding wedge and such an insulating jacket.

[0023] According to an optional and advantageous characteristic of the invention, the passage opens into a groove in the wall of the rotor body. This groove allows the cooling liquid to flow more easily along the winding wires. When a retaining shim is used, the groove serves in particular to ensure clearance between the retaining shim and the rotor wall into which the passage opens. Alternatively, the passage opens onto a counterbore in the rotor body wall.

[0024] According to another optional and advantageous characteristic of the invention, the passage extends radially from the cooling channel to the wall of the rotor body. The passage is for example rectilinear and formed by a drilling from the wall of the rotor body to the cooling channel, after assembly of the rotor body on the rotating shaft.

[0025] Preferably, the passage opens onto the wall of the rotor body in a portion of the wall of the rotor body, axially centered relative to the rotor body. For example, the passage opens equidistant from the axial ends of the rotor body, facilitating the homogeneity of the distribution of the coolant in the axial direction.

[0026] The wound rotor preferably comprises several passages, each opening between each pair of adjacent magnetic poles. This ensures uniform cooling of the rotor in the angular direction. The passages are preferably structurally identical in each of the envisaged embodiments. For example, they are hollowed out in the same ortho-radial plane, or are axially offset from each other.

[0027] The passages pass through, for example, teeth formed inside the cylindrical central portion, the teeth allowing the rotor body to be secured to the rotating shaft by shrinking or fitting. Indeed, in order to save material, the rotor body is not necessarily solid and in certain cases contains teeth allowing it to be secured to the rotating shaft. The teeth are then preferably arranged angularly, each equidistant from two adjacent feet, and alternate, for example, between a shrinking tooth and an anti-rotation tooth.

[0028] Finally, the invention also relates to an electrical machine comprising a wound rotor according to the invention, in which the cooling channel comprises an inlet orifice at the end of the rotating shaft, centered around the axis of rotation of the rotating shaft, and in which means for supplying cooling liquid to the wound rotor are arranged on a fixed part of the electrical machine opposite the inlet orifice, the means for supplying cooling liquid being capable of receiving the cooling liquid and propelling it into the inlet orifice of the cooling channel.

[0029] The supply means are for example a projection nozzle or a jet fixed opposite the inlet orifice of the cooling channel. The latter is for example non-opening opposite the inlet orifice and supplies cooling liquid to several radial passages supplying the different notches of the body. rotor.

[0030] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0031] [Fig-1] is an ortho-radial sectional view of a wound rotor according to the invention, in an embodiment of the invention,

[0032] [Fig.2] is an enlargement of a portion of [Fig.l] at the level of notches of wound rotor winding, and

[0033] [Fig.3] is an axial sectional view of the wound rotor of [Fig.l], the section being made in the middle of a winding notch.

[0034] According to an embodiment of the invention shown in Figures 1 to 3, a wound rotor 1 according to the invention is intended to cooperate with a stator (not shown) of an electrical machine according to the invention. The electrical machine is radial flux in this embodiment of the invention, and the wound rotor 1 is a salient pole rotor, here comprising eight salient poles, including the magnetic poles 20h, 20a, 20b and 20c, which follow one another in the clockwise direction in [Fig.l].

[0035] The wound rotor 1 comprises a rotating shaft 3, mounted to move about an axis of rotation X (referenced [Fig.3]), and a rotor body 2 secured by shrink fitting to the rotating shaft 3. The rotor body 2 is made of a stack of magnetic steel sheets, forming the cores of the magnetic poles of the wound rotor 1 which project from a cylindrical central portion 22 of the rotor body 2.

[0036] In order to facilitate the hooping of the rotating shaft 3 in the rotor body 2, recesses are made on the internal periphery of the rotor body 2, leaving between them hooping teeth 24 allowing the hooping of the rotating shaft 3 in the rotor body 2, and anti-rotation teeth 26 fitting into axial grooves 32 formed on the surface of the rotating shaft 3. The anti-rotation teeth 26 prevent the rotor body 2 from rotating around the rotating shaft 3. The rotor body 2 comprises an alternation of hooping teeth 24 and anti-rotation teeth 26, and here comprises four hooping teeth 24 and four anti-rotation teeth 26, these teeth 24, 26 being angularly regularly distributed around the rotating shaft 3. The latter therefore has four axial grooves 32.

[0037] Of course, the wound rotor may be of a different design from that described here, the rotor body being able to be assembled on the rotating shaft other than by shrink fitting, and not include a stack of sheets but a different assembly to form the magnetic poles.

[0038] Each magnetic pole of the wound rotor 1 comprises a foot extending radially from the cylindrical central portion 22, a winding wound around the foot, and a head covering the foot by extending ortho-radially on either side of the foot. Thus the magnetic pole 20a comprises a foot 21a, around which a winding 8a is wound, and a head 23a whose ortho-radial extensions radially hold the winding 8a on either side of the foot 21a. Similarly the magnetic pole 20b comprises a foot 21b, around which a winding 8b is wound, and a head 23b whose ortho-radial extensions radially hold the winding 8b on either side of the foot 21b.

[0039] More precisely, each foot projecting from a wall 25 of the cylindrical central part 22 of the rotor body 2, a winding notch is formed between each pair of adjacent feet, and each winding notch comprises two winding cavities each receiving a separate winding. Each winding cavity is delimited by: - a part of the wall 25 of the cylindrical central part 22, this part of the wall 25 extending axially along the notch while being connected to a magnetic pole foot, - a wall of this magnetic pole foot, connected to the part of the wall 25, - and a wall of an ortho-radial extension of the head covering this foot, and coming to overhang the part of the wall 25.

[0040] In particular, the magnetic pole 20a comprises a first winding cavity 121a in the notch 12a between the magnetic poles 20h and 20a. This first winding cavity 121a is delimited by a part of the wall 25 of the cylindrical central part 22 located in the notch 12a, a wall of the foot 21a forming a lateral wall of the notch 12a, and a wall 230a of an ortho-radial extension of the head 23a, located opposite the winding 8a. The first winding cavity 121a therefore houses the wires of the winding 8a which are arranged axially in the notch 12a between the magnetic pole 20a and the magnetic pole 20h.

[0041] The magnetic pole 20a comprises symmetrically in the notch 12b located on the other side of the foot 21a relative to the notch 12a, that is to say between the magnetic pole 20a and the magnetic pole 20b, a second winding cavity 122b delimited by a part of the wall 25 of the cylindrical central part 22 located in the notch 12b, a wall of the foot 21a forming a lateral wall of the notch 12b, and a wall 232a of an ortho-radial extension of the head 23a, located opposite the winding 8a. The second winding cavity 122b therefore houses the wires of the winding 8a which are arranged axially in the notch 12b included between the magnetic pole 20a and the magnetic pole 20b.

[0042] Similarly, the magnetic pole 20b comprises a first winding cavity 121b in the notch 12b between the magnetic poles 20a and 20b. This first winding cavity 121b is delimited by a part of the wall 25 of the cylindrical central part 22 located in the notch 12b, a wall of the foot 21b forming a wall lateral of the notch 12b, and a wall 230b of an ortho-radial extension of the head 23b, located opposite the winding 8b. The first winding cavity 121b therefore houses the wires of the winding 8b which are arranged axially in the notch 12b between the magnetic pole 20a and the magnetic pole 20b.

[0043] The magnetic pole 20b comprises symmetrically in the notch 12c included located on the other side of the foot 21b relative to the notch 12b, that is to say between the magnetic pole 20b and the magnetic pole 20c, a second winding cavity 122c delimited by a part of the wall 25 of the cylindrical central part 22 located in the notch 12c, a wall of the foot 21b forming a lateral wall of the notch 12c, and a wall 232b of an ortho-radial extension of the head 23b, located opposite the winding 8b. The second winding cavity 122c therefore houses the wires of the winding 8b which are arranged axially in the notch 12c included between the magnetic pole 20b and the magnetic pole 20c.

[0044] The wires of separate windings present in each notch are electrically insulated from the magnetic steel of the rotor body 2 by an insulating jacket formed of two insulating papers 5 and 6. A shim 7 in each notch holds the wires of the separate windings in their respective winding cavities, bearing against the ortho-radial extensions of the magnetic pole heads partly delimiting these winding cavities.

[0045] As visible in [Fig.3], the wedge 7 extends axially along each magnetic pole from one axial end of the rotor body 2 to the other. In a plane perpendicular to the axis of rotation X, the wedge 7 is of substantially triangular section, and comprises: - a first face, the ends of which are each compressed by an ortho-radial extension of a pole head, for example in the notch 12b this first face is held by the ortho-radial ends 232a and 230b,

[0046] - a second face bearing against the winding wires present in a first winding cavity in the notch, for example against the wires of winding 8b in notch 12b, and

[0047] - a third face bearing against the winding wires present in a second winding cavity in the notch, for example against the wires of winding 8a in notch 12b.

[0048] The wires in the winding cavities are however electrically insulated from the shim 7, for example made of aluminum or synthetic polymer material (plastic), by a first insulating paper 6. The shim 7 therefore has a peak, between the second and third faces of the shim 7, which is located opposite the wall 25 of the rotor body 2 but at a distance from it, between the two winding cavities of the notch. As visible in [Fig. 3], tie rods 11 pass through the shims and make it possible to fix to the ex- axial ends of the rotor body 2, a crown 10 for holding the winding heads.

[0049] The second insulating paper 5 covers in each notch, the wall 25 of the rotor body 2 at the bottom of the notch as well as the side walls of the notch, formed by the feet of magnetic poles on either side of the notch, and the walls of the ortho-radial extensions of the pole heads partly delimiting the winding cavities present in the notch. The first insulating paper 6 partly covers these walls of ortho-radial extensions, over the second insulating paper 5, and comes to cover the wires of the windings between each winding cavity of the notch and the shim 7 present in the notch. In other words, the first insulating paper 6 has a fold into which the shim 7 is inserted, this fold separating the two winding cavities in the notch.

[0050] According to the invention, the rotating shaft 3 comprises a cooling channel 9, visible [Fig. 3] and extending axially in the rotating shaft 3. In this embodiment of the invention, the cooling channel 9 is hollowed out in the center of the rotating shaft 3 and only opens at one end thereof. Thus, the opening of the cooling channel 9 at the end of the rotating shaft 3 makes it possible to supply the cooling channel 9 with cooling liquid by spraying oil into this opening when the wound rotor is in operation. The cooling liquid is a liquid such as oil.

[0051] Furthermore, in this embodiment of the invention, the cooling channel 9 communicates, inside the rotating shaft with several passages 4 extending radially in the rotating shaft 3 then in the rotor body 2 up to the wall 25 of the rotor body 2, between each notch of the rotor body 2. These passages 4 are formed by drillings in the rotor body 2, once the rotor body 2 is assembled on the rotating shaft 3. They are made in the same ortho-radial plane which makes it possible not to modify the axial position of the machine used for these drillings, but as a variant the passages are axially offset from each other.

[0052] The junction between the passages 4 and the cooling channel 9 is made in a central portion of the rotating shaft 3 relative to the axial dimension thereof. Similarly, the passages 4 being here rectilinear and orthogonal to the axis of rotation X, they open onto an axially centered portion of the wall 25 of the rotor body 2, and open angularly between a first winding cavity and a second winding cavity in each notch. It should be noted that in order to ensure that each passage 4 is hollowed out in the material of the rotor body 2, the passages 4 are hollowed out in the hooping teeth 24 or the anti-rotation teeth 26, which implies that the hooping teeth 24 and the anti-rotation teeth 26 are each angularly arranged between two winding cavities of a notch, being radially distant from these cavities.

[0053] The passages 4 each open into a groove 250 (referenced [Fig.2]) made on the wall 25 of the rotor body 2 in each notch. As can be seen in particular in level of the notch 12b, the second insulating paper 5 of the insulating jacket in the notch 12b is perforated at the level of the opening of the passage 4, to allow the coolant leaving the groove 250 to pass into the insulating jacket. The groove 250 provides a space between the opening of the passage 4 and the shim 7 as well as the windings 8a and 8b, which allows the coolant to be better distributed axially along the winding wires in the notch 12b. In addition, the edge formed by the shim 7 between its second and third faces makes it possible to separate the flow of coolant coming from the groove 250 in two to distribute it homogeneously in each of the winding cavities present in the notch 12b.

[0054] It should be noted that the wall 25 of the rotor body 2 is not exactly cylindrical in the notches, in particular in order to hold the wires in each winding cavity by faces forming a right angle. The groove 250 prevents two lower faces of the two winding cavities in the notch from joining together to form a peak, and allows the shim 7 to remain at a distance from the wall 25 of the rotor body 2.

[0055] Thanks to the cooling channel 9 and the passages 4, the coolant arriving in the cooling channel 9 is distributed in each passage 4 to the eight insulating jackets of the wound rotor, in which the coolant circulates along the winding wires present in each first and each second winding cavity in each notch, to the axial ends of the rotor body 2. The coolant then falls into an oil reservoir present in the electrical machine integrating the wound rotor, and is returned by a circulation pump to a supply channel located opposite the opening of the cooling channel 9, to supply it.

[0056] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different variant embodiments of the invention envisaged in this application can be combined to achieve the invention, insofar as these variants are not incompatible with each other.

Claims

Claims

1. Wound rotor (1) for an electrical machine, comprising: - a rotating shaft (3) about an axis of rotation (X) of the wound rotor (1), - a rotor body (2) integral with the rotating shaft (3), comprising a plurality of magnetic poles (20a, 20b, 20c, 20h) provided with windings (8a, 8b) extending from one axial end of the rotor body (2) to an opposite axial end of the rotor body (2), the wound rotor (1) being characterized in that it comprises a cooling channel (9) extending in the rotating shaft (3), and in that the rotor body (2) comprises a passage (4) capable of supplying cooling liquid to at least one of the windings (8a, 8b), the passage (4) extending in the rotor body (2) while being connected to the cooling channel (9), and opening onto a wall (25) of the rotor body (2) extending between the two axial ends of the rotor body (2).

2. A wound rotor (1) according to claim 1, wherein the magnetic poles (20a, 20b) project from a cylindrical central portion (22) of the rotor body (2), and each comprise a foot (21a, 21b) extending radially from the cylindrical central portion (22), each winding (8a, 8b) being wound around the foot (21a, 21b), and wherein the passage (4) opens between two feet (21a, 21b) of two magnetic poles (20a, 20b), the wall (25) of the rotor body (2) being formed by the cylindrical central portion (22).

3. Wound rotor (1) according to claim 2, wherein a winding notch is formed by at least the wall (25) of the rotor body and the two feet (21a, 21b), the windings (8a, 8b) in the notch each being protected by an insulating jacket, the passage opens into the winding cavity through one of the insulating jackets.

4. A wound rotor (1) according to claim 2, wherein the two magnetic poles (20a, 20b) each comprise a head (23a, 23b) covering the foot (21a, 21b) and extending on either side of the foot (21a, 21b), a first winding cavity (121b) being formed by the wall (25), a first of the feet (21b) and its head (23b), and a second winding cavity (122b) being formed by the wall (25), a second of the feet (21a) and its head (23a), and wherein the winding (8a, 8b) in each of the first and second winding cavities (121b, 122b) is protected by the same insulating jacket, the passage (4) opening into an opening in the insulating jacket, the opening being located between the two winding cavities (121b, 122b).

5. A wound rotor (1) according to claim 4, wherein the windings (8a, 8b) in the first and second winding cavities (121b, 122b) are separated by a fold in the insulating jacket receiving a holding wedge (7) for the windings, the holding wedge (7) having two faces bearing against each of the windings (8a, 8b) via the insulating jacket, the faces being connected together by an edge radially facing the opening at a distance therefrom, thus allowing the passage of the cooling liquid between the edge and the wall (25) of the rotor body (2).

6. Wound rotor (1) according to any one of claims 1 to 5, in which the passage (4) opens into a groove (250) of the wall (25) of the rotor body (2).

7. A wound rotor (1) according to any one of claims 1 to 6, wherein the passage (4) extends radially from the cooling channel (9) to the wall (25) of the rotor body (2).

8. Wound rotor (1) according to any one of claims 1 to 7, in which the passage (4) opens onto the wall (25) of the rotor body (2) in a portion of the wall (25) of the rotor body (2) centered axially relative to the rotor body (2).

9. Wound rotor (1) according to any one of claims 2 to 8, comprising several passages (4) each opening between each pair of adjacent magnetic poles (20a, 20b, 20c, 20h).

10. An electrical machine comprising a wound rotor (1) according to any one of the preceding claims, wherein the cooling channel (9) comprises an inlet orifice at the end of the rotating shaft (3), centered around the axis of rotation (X) of the rotating shaft, and wherein means for supplying cooling liquid to the wound rotor (1) are arranged on a fixed part of the electrical machine opposite the inlet orifice, the means for supplying cooling liquid being capable of receiving the cooling liquid and propelling it into the inlet orifice of the cooling channel (9).

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