Axial-flux electric traction machine

Abstract

The invention relates to an axial-flux electric machine (10) rotating about an axis of rotation (X) and comprising: - at least one rotationally mobile homopolar rotor (11) having p poles and comprising: • an annular disc (15) having an axis of symmetry coincident with the axis of rotation (X), • p / 2 upper studs (16) and p / 2 lower studs (17), p being an even whole number, the upper studs (16) being radially further from the axis of rotation (X) than the lower studs (17), the lower studs (17) and the upper studs (16) alternating circumferentially, - at least one concentric rotor winding (20) mounted radially between the upper studs (16) and the lower studs (17), the upper studs (16) and the lower studs (17) not axially facing the rotor winding (20), the upper studs (16) and the lower studs (17) being able to be polarized under the effect of a rotor current (Ir) circulating in the rotor winding (20) so as to form p poles of the rotor (11), and - at least one stator (12), fixed in terms of rotation, comprising at least one stator coil (30), characterized in that the rotor winding (20) is fixed in rotation.

Description

[0001] Description

[0002] Title of the invention: ELECTRIC AXIAL FLUX TRACTION MACHINE

[0003] Technical field of the invention

[0004] The invention relates to a rotating axial flux electric traction machine for a motor vehicle. The invention finds particularly advantageous applications for the propulsion of low-power electric vehicles, in particular between 4kW and 5kW. The invention can thus advantageously be implemented in particular with low-power four-wheeled electric vehicles ("microcars" in English), two-wheeled vehicles such as motorcycles, or heavy quadricycles. The invention also applies to powers of 100 kW to 400 kW at high voltage, for example greater than 400 V.

[0005] Technological background

[0006] Almost all known systems for the traction of electric vehicles are based on alternating current motors, either permanent magnet synchronous or asynchronous.

[0007] Propulsion systems for electric vehicles are also known based on brushed DC motors with separate excitation. Motor control essentially consists of power adjustment on the armature (the usual speed control method for a brushed DC motor) supplemented by continuous flux variation on the inductor. Since such control is free of jolts, handling is often considered disconcerting, even unpleasant, by drivers who enjoy dynamic driving.

[0008] Known from JP 2019 129638 A, CN 105 356 701 B and CN 202 856 578 U are axial flux electrical machine armatures comprising polyphase power windings, with alternating current where the electromechanical energy conversion takes place.

[0009] Also known from the prior art are axial flux electrical machines whose inductor and armature are opposite each other in the axial direction as described in French application 1750497 filed on January 17, 2017. These axial flux electrical machines have the advantage of being axially compact. In this configuration, it is known that the rotor can be of the homopolar claw type as illustrated in Figure 1. The rotor 11 described here comprises a single rotating rotor winding 12 regardless of the number of poles p of the rotor. The claws, forming the different poles p of the rotor, are divided into two groups of different polarities, a first group and a second group. The two groups are circumferentially alternated.

[0010] The rotor 11 of Figure 1 comprises an annular disc 13 from which the claws extend.

[0011] Each claw of the first group, also called first claw 14, has a first axial base 15 which extends from an inner periphery of the disc and a first claw beak extending radially outwards.

[0012] Each claw of the second group, also called second claw 18, has a second axial base 19 which extends from an outer periphery of the disc and a second claw beak 20 extending radially inwards.

[0013] The rotating rotor winding 12 is mounted axially between the disc 13 and the claw tips 15, 20 and radially between the first bases 15 and the second bases 19.

[0014] The claws are polarized under the effect of the current flowing in the rotor winding 12 so as to form the p poles of the rotor.

[0015] However, such a rotor structure with a rotating rotor winding is complex to manufacture and assemble. Machining the claw tips, mounting the rotor winding and installing the claws makes this type of inductor expensive.

[0016] Powering a rotating rotor winding requires the use of friction parts, such as rings and brushes, to power it. These friction parts wear out by definition and must be replaced.

[0017] Summary of the invention

[0018] The invention aims in particular to effectively remedy the aforementioned drawbacks by proposing an axial flux electric machine rotating around an axis of rotation characterized in that it comprises:

[0019] - at least one homopolar rotor, mobile in rotation, with p poles comprising: o an annular disc with an axis of symmetry coincident with the axis of rotation, op / 2 upper clamps and p / 2 lower clamps, p being an even integer, the upper clamps being radially further from the axis of rotation than the lower clamps, the lower clamps and the upper clamps being circumferentially alternated at least one concentric rotor winding mounted radially between the upper clamps and the lower clamps, the upper clamps and the lower clamps not being axially opposite the rotor winding, the upper clamps and the lower clamps being capable of being polarized under the effect of a rotor current circulating in the rotor winding so as to form p poles of the rotor, and

[0020] - at least one stator, fixed in rotation, comprising at least one stator coil,

[0021] The machine is remarkable in that the rotor winding is fixed in rotation.

[0022] The manufacture and assembly of the rotor are simplified and less expensive compared to the prior art illustrated. The assembly composed of the annular disc and the studs does not have an undercut area which complicates its manufacture, notably with a need for machining.

[0023] According to one aspect of the invention, there is no axial interlocking between the annular disc and the studs on the one hand and the rotor winding on the other hand.

[0024] Since the rotor winding is now fixed in rotation, it is no longer necessary to have friction parts to supply it with direct current, which greatly simplifies the electrical machine. Powering a fixed rotating winding is simpler than powering a rotating winding.

[0025] The electric machine has substantially identical performance compared to an identical machine comprising a rotor according to figure 1.

[0026] The lower studs and upper studs are circumferentially alternated when a lower stud is angularly framed by two upper studs, without regard to radial height.

[0027] A disc within the meaning of the invention means a circular or non-circular plate. A disc may, for example, have a polygonal outline.

[0028] According to one aspect of the invention, the rotor winding is axially opposite the annular disc in one of the two axial directions. According to one aspect of the invention, the studs form the poles of the rotor when the rotor winding is energized. Each pole comprises a single stud.

[0029] According to one aspect of the invention, the lower cleats extend from a radially inner periphery of the annular disc.

[0030] According to one aspect of the invention the upper cleats extend from a radially outer periphery of the annular disc.

[0031] According to one aspect of the invention, the upper studs and the lower studs form a single piece of the same material with the annular disc. This reduces the number of operations during assembly and simplifies the process. The annular disc, the upper studs and the lower studs form a single piece.

[0032] According to one aspect of the invention, the upper studs and the lower studs are trapezoidal in shape. Each upper stud and each lower stud have a radially cylindrical outer surface. Each upper stud and each lower stud have a radially cylindrical inner surface.

[0033] According to one aspect of the invention, the upper studs and the lower studs do not protrude radially from the annular disc.

[0034] According to one aspect of the invention, all the upper crampons and all the lower crampons associated with said rotor winding are on the same axial side of the annular disc.

[0035] According to one aspect of the invention, at least one of the upper clamps and the lower clamps may have an insert receiving a magnet. The magnet makes it possible to increase the intensity of the rotor field. The insert may be blind, in particular in the radial direction, in particular in the axial direction, in particular in the axial direction and the axial direction.

[0036] According to one aspect of the invention, all of the upper studs and all of the lower studs have a magnet.

[0037] According to one aspect of the invention, p is between two and thirty-two, in particular between four and sixteen. The rotor has a polar pitch equal to 2*TT / P, expressed in radians.

[0038] According to one aspect of the invention, the lower studs are all capable of having the same polarity and the upper studs are all capable of having the same polarity opposite to the polarity of the lower studs. All the lower studs may have the same shape. All the lower studs may be uniformly distributed in the circumferential direction.

[0039] According to one aspect of the invention, each lower stud has an external angular opening. The value of the external angular opening of the lower studs pi can be between 0.5*(polar pitch) and 0.95*(polar pitch).

[0040] According to one aspect of the invention, each lower stud has an inner angular opening. The value of the inner angular opening of the lower studs P2 may be between 0.5*(polar pitch) and 0.95*(polar pitch). For the lower studs, the outer angular opening may be greater than or equal to the inner angular opening. The lower studs may widen radially outward.

[0041] All upper studs can have the same shape. All upper studs can be evenly distributed in the circumferential direction.

[0042] According to one aspect of the invention, each upper stud has an external angular opening. The value of the external angular opening of the upper studs P3 can be between 0.5*(polar pitch) and 0.95*(polar pitch).

[0043] According to one aspect of the invention, each upper stud has an inner angular opening. The value of the inner angular opening of the upper studs P4 may be between 0.5*(polar pitch) and 0.95*(polar pitch). For the upper studs, the inner angular opening may be greater than or equal to the upper angular opening. The upper studs may widen radially inward.

[0044] According to one aspect of the invention, the annular disc may be hollow.

[0045] According to one aspect of the invention, the annular disc is mounted on a rotor shaft. The annular disc is, for example, sleeved or shrink-fitted.

[0046] According to one aspect of the invention, the annular disc has an outer radius. The value of the outer radius Rext may be between 10 cm and 40 cm, preferably between 10 cm and 20 cm, in particular 15 cm.

[0047] According to one aspect of the invention, the annular disc has an inner radius. The value of the inner radius Rint may be between 0.1 * Rext and 0.75 * Rext, in particular between 0.4 * Rext and 0.60 * Rext, for example 0.5 * Rext. According to one aspect of the invention, the radially outer surfaces of the upper studs are contiguous with the radially outer surface of the annular disc.

[0048] According to one aspect of the invention, the radially inner surfaces of the lower studs are contiguous with the radially inner surface of the annular disc.

[0049] According to one aspect of the invention, the rotor has an axial rotor dimension, the value Lz of which may be between 2cm and 10cm, in particular between 3cm and 5cm, for example 3.6cm. The annular disc has an axial thickness. The value of the axial thickness of the annular disc ez1 may be between 0.25*Lz and 0.4*Lz.

[0050] According to one aspect of the invention, each upper stud and each lower stud has an axial dimension. This axial dimension may be identical for each of the upper studs and each of the lower studs. The value of this axial dimension ez2 may be between 0.5*Lz and 0.75*Lz.

[0051] According to one aspect of the invention, the electrical machine has an upper radial air gap between the upper clamps and the rotor winding of between 0.1 mm and 1 mm.

[0052] According to one aspect of the invention, the electrical machine has a lower radial air gap between the lower clamps and the rotor winding of between 0.1 mm and 1 mm.

[0053] According to one aspect of the invention, the electrical machine has an axial air gap between the rotor winding and the annular disc. The radial air gap may be between 0.1 mm and 1 mm.

[0054] According to one aspect of the invention, the rotor winding is mounted on the stator. The fixed parts of the machine are thus shared, which avoids the need for a fixed part dedicated to the rotor winding.

[0055] According to one aspect of the invention, the electrical machine comprises a single rotor winding.

[0056] According to one aspect of the invention, the electrical machine may comprise a plurality of rotor windings supplied in parallel.

[0057] According to one aspect of the invention, the electrical machine comprises a casing. The rotor winding is carried by a rotor disc, the rotor disc and the stator are fixed to the casing. According to one aspect of the invention, the rotor disc is a part independent of the stator. The rotor disc may be non-magnetic.

[0058] According to one aspect of the invention, the stator comprises a printed circuit board "PCB". The printed circuit board may comprise at least one PCB layer comprising the stator coil.

[0059] According to one aspect of the invention, the printed circuit board "PCB" may comprise a plurality of PCB layers.

[0060] According to one aspect of the invention, each PCB layer comprises a plurality of stator coils. These stator coils may be coplanar and angularly and symmetrically spaced from each other.

[0061] According to one aspect of the invention, each stator coil is continuous and concentric in a single plane from an outermost stator coil portion to an innermost concentric stator coil portion.

[0062] According to one aspect of the invention, stator coils in adjacent PCB layers are circumferentially aligned with each other relative to the axis to define symmetrical stacks of stator coils in an axial direction.

[0063] According to one aspect of the invention, each stator coil includes a first terminal on the outer edge of the coil, a second terminal in the center of the stator coil.

[0064] According to one aspect of the invention, each stator coil may be connected directly to an adjacent stator coil on the same PCB layer. Each stator coil may be connected directly to a corresponding stator coil on another PCB layer.

[0065] According to one aspect of the invention, each stator coil has only two terminals, each coil being continuous and uninterrupted between its only two terminals.

[0066] According to one aspect of the invention, the rotor winding is fixed to the printed circuit board, for example overmolded.

[0067] According to one aspect of the invention, the stator comprises a plurality of teeth, the stator coil being wound around said teeth.

[0068] According to one aspect of the invention, the stator comprises a plurality of stator coils, each being wound on one of said teeth. According to one aspect of the invention, the rotor winding is traversed by the direct rotor current, and in that the at least one stator coil is traversed by a polyphase stator current system.

[0069] The rotor current does not change sign and is mainly used to set the flux level. Note that the rotor winding is not traversed by a polyphase current system during normal operation.

[0070] According to one aspect of the invention, the rotor winding is electrically connected to a control device. The control device may comprise a plurality of controllable switches in order to continuously vary the current in the winding. The switches may be Mosfets and / or diodes. The controllable switches may be arranged in an H-bridge.

[0071] According to one aspect of the invention, each rotor is axially framed by two stators. The rotor may comprise p / 2 upper studs and p / 2 lower studs on each of the two axial sides of the annular disc.

[0072] According to one aspect of the invention, each rotor may be associated with two rotor windings, each rotor winding being associated with an axial side of the annular disc.

[0073] According to one aspect of the invention, each stator is axially framed by two rotors. The two rotors can be associated with the same stator.

[0074] According to one aspect of the invention, the electric machine may have a mechanical nominal power of between 4 kW and 35 kW, being for example 4 kW, 8 kW, 15 kW, 25 kW or 35 kW, or the electric machine may have a mechanical nominal power of between 40 kW and 400 kW, being for example 40 kW, 80 kW, 100 kW, 150 kW, 180 kW, 200 kW, 300 kW or 400 kW.

[0075] This rotating electrical machine can be electrically powered from an electrical energy storage unit via an inverter / rectifier, this inverter / rectifier allowing, depending on whether the electrical machine operates as a motor or a generator, to charge an on-board network of the vehicle or to be electrically powered from this network.

[0076] The nominal voltage of the electrical energy storage unit may be 12 V, 48 V or have another value, for example another value greater than 300 V. The invention also relates to a motor vehicle characterized in that it comprises a rotating electrical machine as previously defined to propel said vehicle.

[0077] According to one embodiment, the electric traction machine is installed on a rear axle between a wheel and a differential of said motor vehicle. Alternatively, the electric machine may be installed directly in the wheel of the vehicle in a "wheel motor" type assembly.

[0078] According to one aspect of the invention, the motor vehicle may be a purely electric traction vehicle. According to one aspect of the invention, the vehicle may be a hybrid traction vehicle. Both thermal and electric.

[0079] According to one aspect of the invention, the motor vehicle may be an electric utility vehicle or a light truck. The electric machine according to the invention, of the axial type, makes it possible to obtain a higher mass power and higher continuous power than the electric machines according to the prior art. This electric machine is suitable for the driving profiles of utility vehicles transporting loads and requiring continuous electrical power.

[0080] Brief description of the figures

[0081] The invention will be better understood by reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.

[0082] Identical, similar or analogous elements retain the same reference from one figure to another.

[0083] [Fig. 1] is a perspective view of an example of a rotor according to the prior art.

[0084] [Fig. 2] is a schematic view of an exemplary motor vehicle according to the present invention.

[0085] [Fig. 3] is an exploded perspective view of an example of an electrical machine according to the invention.

[0086] [Fig. 4] is a perspective view of a rotor of the electric machine of Fig. 3.

[0087] [Fig. 5] is a front view of the rotor and rotor winding of Fig. 3. [Fig. 6] is a front view of an exemplary stator of the electrical machine according to the invention.

[0088] Detailed description of the invention

[0089] Figure 2 illustrates a motor vehicle according to an example of the invention comprising a rotating electrical machine 10 according to an example of the invention.

[0090] In the example considered, the motor vehicle is an electric vehicle EV comprising wheels 3 and the electric machine 10. The electric machine is configured to drive at least indirectly at least one of the wheels 3. The vehicle comprises a high-voltage power supply battery B, preferably a rechargeable battery, for supplying electrical energy to the machine. The battery B is for example a high-voltage power supply, in particular greater than 60V. The battery may also be a low-voltage battery, in particular 48V.

[0091] In the example considered, the electric machine 10 allows the EV vehicle to be moved alone and is installed on a rear axle 2 between a rear wheel 3 and a differential. Alternatively, the electric machine 10 could be installed on the front axle, not shown. Alternatively, the electric machine 10 could be installed in at least one wheel 3. In particular, one electric machine 10 is used in each rear wheel 3.

[0092] In the example described, the electrical machine 10 comprises at least one rotor, at least one rotor winding and at least one stator. These will be described in more detail in connection with the following figures.

[0093] In the example described, the stator is powered via an inverter / rectifier I configured to convert a direct voltage (DC) from the battery B into an alternating voltage (AC) in order to control the electrical machine 10. The stator is traversed by a polyphase, in particular three-phase, stator current system Is.

[0094] In the example considered, the rotor winding is also supplied by battery B by a direct rotor current Ir. The rotor winding is electrically connected to battery B.

[0095] In the example considered, the rotor winding is capable of continuously generating a rotor current from zero to a maximum value in order to vary the rotor flux

[0096] In the example considered, the rotor current Ir is independent of the stator current Is. Figure 3 now describes in detail an example of an axial flux machine 10 according to the invention which can equip the vehicle described in Figure 2. The electrical machine is axial flux and rotates around an axis X of rotation.

[0097] In the example considered, the rotor 11 is homopolar, is mobile in rotation and has p poles. The rotor 11 comprises an annular disc 15 with an axis of symmetry coincident with the axis X.

[0098] In the example considered, the rotor 11 also comprises p / 2 upper crampons 16 and p / 2 lower crampons 17. The upper crampons 16 are radially further from the X axis than the lower crampons 17.

[0099] The lower studs 17 and the upper studs 16 are circumferentially alternated. Each lower stud 17 is angularly framed by two upper studs 16, without taking into account the radial height.

[0100] P is an even integer. P is between two and thirty-two. Here sixteen. Rotor 11 has a polar pitch equal to 2*Pi / p, or TT / 8 radians for a polarity of 8, or .22.5 degrees.

[0101] In the example considered, the electrical machine 10 comprises at least one concentric rotor winding 20 mounted radially between the upper clamps 16 and the lower clamps 17. The upper clamps 16 and the lower clamps 17 are not axially opposite the rotor winding 20.

[0102] In the example considered, the upper clamps 16 and the lower clamps 17 are polarized under the effect of the rotor current Ir circulating in the rotor winding 20 so as to form the sixteen poles of the rotor 11. The lower clamps 17 all have the same polarity and the upper clamps 16 all have the same polarity opposite to the polarity of the lower clamps 17.

[0103] Each of the sixteen poles of the electrical machine 10 comprises a single clamp among the upper clamps 16 and the lower clamps 17.

[0104] In the example considered, the rotor winding 20 is fixed in rotation. The rotor winding 20 is carried by a rotor disc 21 itself fixed in rotation which is a part independent of the stator. In a variant not shown, the rotor winding is mounted on the stator. There is no rotor disc dedicated to fixing the rotor winding.

[0105] In the example considered, the rotor winding 20 is unique.

[0106] In the example considered, there is no axial interlocking between the annular disc and the studs on the one hand and the rotor winding on the other hand. The rotor winding 20 is axially opposite the annular disc 15 in one of the two axial directions, that is to say along the X axis. All the upper studs 16 and all the lower studs 17 associated with the rotor winding are on the same axial side of the annular disc 15.

[0107] In the example considered, the lower crampons 17 extend from a radially inner periphery 22 of the annular disc 15 and the upper crampons 16 extend from a radially outer periphery 23 of the annular disc 15. The upper crampons 16 and the lower crampons 17 do not protrude radially from the annular disc.

[0108] In the example considered, the upper crampons 16 and the lower crampons 17 are made of the same material as the annular disc 15. The annular disc 15, the upper crampons 16 and the lower crampons 17 thus form a single piece.

[0109] In the example considered, the upper studs 16 and the lower studs 17 are all trapezoidal in shape. Each upper stud 16 and each lower stud 17 has a radially outer cylindrical surface and has a radially inner cylindrical surface. The radially outer surfaces of the upper studs 16 are contiguous with the radially outer surface of the annular disc 15 and the radially inner surfaces of the lower studs 17 are contiguous with the radially inner surface of the annular disc 15.

[0110] In the example considered, all the lower studs 17 have the same shape and are distributed uniformly in the circumferential direction. Each lower stud 17 has an external angular opening pi whose value is between 0.5*(polar pitch) and 0.95*(polar pitch) and an internal angular opening P2 whose value is between 0.5*(polar pitch) and 0.95*(polar pitch). Here pi and P2 are equal.

[0111] In the example considered, all the upper studs 16 have the same shape and are distributed uniformly in the circumferential direction. Each upper stud 16 has an outer angular opening P3 whose value is between 0.5*(polar pitch) and 0.95*(polar pitch) and an inner angular opening P4 whose value is between 0.5*(polar pitch) and 0.95*(polar pitch). Here P4 is larger than P2. The upper studs widen radially inwards.

[0112] In the example considered, the annular disc 15 is hollow. The annular disc is mounted on a rotor shaft, not shown, for example fitted or shrink-fitted.

[0113] In the example considered, the annular disc has an external radius Rext whose value is between 10 cm and 40 cm, preferably between 10 cm and 20 cm, in particular 15 cm and an internal radius Rint whose value is between 0.1 *Rext and 0.75*Rext, in particular between 0.4*Rext and 0.60*Rext, for example 0.5*Rext.

[0114] In the example considered, the rotor 11 has an axial rotor dimension, the value Lz of which can be between 2cm and 10cm, in particular between 3cm and 5cm, for example 3.6cm. The annular disc 15 also has an axial thickness ez1 of which the value is between 0.25*Lz and 0.4*Lz.

[0115] In the example considered, each upper stud 16 and each lower stud 17 has an identical axial dimension ez2 whose value is between 0.5*Lz and 0.75*Lz.

[0116] In the example considered, the electrical machine 10 has an upper radial air gap 25 between the upper clamps 16 and the rotor winding 20 of between 0.1 mm and 1 mm.

[0117] In the example considered, the electrical machine 10 has a lower radial air gap 26 between the lower clamps 17 and the rotor winding 20 of between 0.1 mm and 1 mm.

[0118] In the example considered, the electrical machine has an axial air gap of between 0.1 mm and 1 mm between the rotor winding and the annular disc.

[0119] In the example considered, the rotor disk 21 and the stator can be fixed to a casing of the electrical machine 10. An example of stator 12 is described with reference to FIG. 6.

[0120] In the example considered, the stator 12 is fixed in rotation and comprises a plurality of stator coils 30 and a printed circuit board "PCB" 31. The printed circuit board may comprise a plurality of PCB layers. Each PCB layer comprises a plurality of coplanar stator coils 30, angularly and symmetrically spaced from one another. In the example considered, each stator coil 30 is continuous and concentric in a single plane from an outermost stator coil portion to an innermost concentric stator coil portion.

[0121] In the example considered, stator coils in adjacent PCB layers are circumferentially aligned with each other relative to the axis to define symmetrical stacks of stator coils in an axial direction.

[0122] In the example considered, each stator coil 30 is connected directly to an adjacent stator coil on the same PCB layer.

[0123] In an example not shown, the rotor winding 20 can be mounted on the stator 12. The rotor winding can be overmolded or soldered onto the printed circuit board 31. In such a variant, the electrical machine 10 does not have a rotor disk.

[0124] In a variant not shown, the stator comprises a plurality of coils, each being wound on one of said teeth.

[0125] In an example not shown, the machine may comprise a single stator 12 surrounded by two rotors 11.

[0126] In an example not shown, the electrical machine 10 comprises a plurality of rotors 11, each rotor 11 being axially framed by two stators 12. The rotors 11 can then comprise the upper clamps 16 and the lower clamps 17 on each of the two axial sides of the annular disc 15. Each rotor 11 can be associated with two rotor windings 20, each rotor winding being associated with an axial side of the annular disc.

[0127] Of course, the preceding description has been given by way of example only and does not limit the scope of the invention, which would not be exceeded by replacing the various elements with any other equivalents.

[0128] Identical, similar or analogous elements retain the same reference from one figure to another.

Claims

CLAIMS 1. Electrical machine (10) with axial flux rotating around an axis of rotation (X) comprising: - at least one homopolar rotor (11), mobile in rotation, with p poles comprising: o an annular disc (15) with an axis of symmetry coincident with the axis of rotation (X), op / 2 upper clamps (16) and p / 2 lower clamps (17), p being an even integer, the upper clamps (16) being radially further from the axis of rotation (X) than the lower clamps (17), the lower clamps (16) and the upper clamps (17) being circumferentially alternated, at least one concentric rotor winding (20) mounted radially between the upper clamps (16) and the lower clamps (17), the upper clamps (16) and the lower clamps (17) not being axially opposite the rotor winding (20), the upper clamps (16) and the lower clamps (17) being capable of being polarized under the effect of a rotor current (Ir) flowing in the rotor winding (20) so as to form p poles of the rotor (11), and - at least one stator (12), fixed in rotation, comprising at least one stator coil (30), characterized in that the rotor winding (20) is fixed in rotation.

2. Electrical machine (10) according to the preceding claim, characterized in that the lower crampons (17) extend from the radially inner periphery (22) of the annular disc (15) and in that the upper crampons (16) extend from a radially outer periphery (23) of the annular disc (15).

3. Electrical machine (10) according to any one of the preceding claims, the electrical machine (10) having an upper radial air gap (25) between the upper clamps (16) and the rotor winding (20) of between 0.1 mm and 1 mm and a lower radial air gap (26) between the lower clamps (17) and the rotor winding (20) of between 0.1 mm and 1 mm.

4. Electrical machine (10) according to any one of the preceding claims, characterized in that the rotor winding (20) is mounted on the stator (12). Electrical machine (10) according to any one of the preceding claims, characterized in that the electrical machine (10) comprises a casing, the rotor winding (20) is carried by a rotor disc (21), the rotor disc (21) and the stator (12) being fixed on the casing. Electrical machine (10) according to any one of the preceding claims, the stator (12) comprising a printed circuit board "PCB" (31), the printed circuit board (31) comprising at least one PCB layer comprising said stator coil (30). Electrical machine (10) according to any one of claims 1 to 5, the stator comprising a plurality of teeth, the stator coil being wound around said teeth. Electrical machine (10) characterized in that the rotor winding (20) is traversed by the continuous rotor current (Ir), and in that the at least one stator coil (31) is traversed by a polyphase current system (Is).Motor vehicle (EV) characterized in that it comprises an electric machine (10) as defined according to any one of the preceding claims to propel said vehicle. Motor vehicle (EV) according to the preceding claim, characterized in that the electric machine is installed on a rear axle (2) between a wheel (3) and a differential of said motor vehicle (25).

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