CN111869064A

CN111869064A - Synchronous machine with wound inductor

Info

Publication number: CN111869064A
Application number: CN201880087417.2A
Authority: CN
Inventors: J-C.米波; Z-Q.朱; Z.吴; P-S.法拉
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2017-12-22
Filing date: 2018-12-20
Publication date: 2020-10-30
Anticipated expiration: 2038-12-20
Also published as: WO2019122737A1; FR3076113A1; FR3076113B1; CN111869064B

Abstract

A switched flux electric machine comprising adjacent first and second polarity portions, the upper face of the first polarity portion having a range γ r01 along the circumference of the rotor, the lower face of the first polarity portion having a range γ ri1, the upper face of the second polarity portion in the same pair having a range γ r02, the lower face of the second polarity portion having a range γ ri2, the two polarity portions being arranged such that the axial end surface of the first polarity portion faces the axial end surface of the second polarity portion, wherein γ ri1 < γ r01, γ r02 < γ ri2, and γ r01 ≈ γ r 02.

Description

Synchronous machine with wound inductor

Switched flux wound induction synchronous machines, which are used in particular for providing electrical or mechanical power in vehicles, are known from the prior art, for example from the publication Zhongze WU ICEMS 2016 "design and analysis of segmented stator wound field switched flux machines for electric vehicles". A switched flux synchronous rotating electrical machine connected to a shaft via bearings makes it possible to supply electrical power to supply electrical components of the vehicle or to supply mechanical power to drive the vehicle, i.e. to provide the proportional torque required by the vehicle's consumables. This type of machine can achieve higher levels of torque due to the larger total winding surface area.

This type of switched flux synchronous rotating electrical machine comprises a field stator and an armature stator, the two stators being positioned in a concentric radial arrangement about the axis of rotation Z, the field stator being internal to the armature stator, an air gap being defined between the two stators, in which a rotor is accommodated, a field stator formed by a stator main body including a plurality of teeth extending from the field stator main body toward the rotor, field windings wound on the plurality of teeth of the field stator, an armature stator formed by a stator main body, the stator body including a plurality of teeth extending from the armature stator body toward the rotor, armature windings wound on the plurality of teeth of the armature stator, and the rotor is free of windings or permanent magnets, the rotor being formed by an assembly of pairs of polar sections circumferentially arranged in an air gap facing each stator, the polar sections being separated by polar steps.

A disadvantage of this type of machine is that during the movement of the rotor relative to the excitation and armature stators, the modification of the field lines generates a destructive induced voltage at the excitation stator, generating losses and reducing the performance level of the machine. The aim is therefore to be able to optimize the torque produced by reducing the induced voltage.

Thus, in an electric machine such as the one forming the subject of the invention, a pair of polar portions comprises a first polar portion and a second polar portion adjacent to the first polar portion, each polar portion having substantially the form of a truncated pyramid, each polar portion positioned in the air gap having: two facing axial end surfaces along an axis of the motor, two facing spaces in a circumferential direction of the motor, two faces facing each other including an upper face facing the armature stator and a lower face facing the field stator, the upper face of the first polarity portion having a range along a circumference of the rotor defined by an opening angle γ r01 facing the face of the armature stator between a first left space and a first right space, the lower face of the first polarity portion having a range along the circumference of the rotor defined by an opening angle γ ri1 facing the face of the field stator between the first left space and the first right space, the upper face of the second polarity portion in the same pair having a range along the circumference of the rotor defined by an opening angle γ r02 facing the face of the armature stator between the second left space and the second right space, the lower face of the second polarity portion having a range along the circumference of the rotor, the range is defined by an opening angle γ ri2 facing the face of the excitation stator between a second left blank and a second right blank, the two polarity portions being arranged such that an axial end surface of the first polarity portion faces an axial end surface of the second polarity portion, the blanks of the first polarity portion being inclined such that: γ ri1 < γ r01, the blank of the second polarity portion is tilted such that: γ r02 < γ ri2, wherein γ r01 and γ r02 are the same size.

This type of machine has a simple design because it does not require slip rings, brushes, etc., the only movable part is the one that can move together with the polar part, it does not require any current limitation, and it is easy to assemble the polar part. In addition, by limiting the abrupt change in magnetic flux at the excited stator, the geometry and specific arrangement of the pairs of polar sections forming the rotor makes it possible to reduce destructive induced voltage harmonics. The inclination of the voids also helps to reduce abrupt changes in magnetic flux.

According to one embodiment, the motor is such that γ r01 ═ γ r02 ═ γ r0, γ r0 is the opening angle facing the armature stator, and the inequality is verified: 0.5 < Rri1 < 0.9, 0.9 < Rri2 < 0.95, and 0.7 < Rr0 < 0.75, wherein the angular polarity step is defined by: the polarity step is 360/Ner, where Ner denotes the number of teeth on the rotor, and Rr0 γ r 0/polarity step, Rr 1 γ ri 1/polarity step, and Rr 2 γ ri 2/polarity step.

According to one embodiment, the motor is such that Rri2 equals 0.95 and Rri1 equals 0.54.

According to one embodiment, for each polarity section, the two axial end faces are substantially parallel to each other and transverse to the upper and lower faces, for each polarity section the distance (i.e. the thickness) between the upper and lower faces is the same for both polarity sections, for each polarity section the distance (i.e. the depth) between the axial end faces is the same for both polarity sections, the left margin of the first polarity section has the same inclination angle in the opposite direction as the right margin of the first polarity section, and the right margin of the first polarity section has the same inclination angle in the opposite direction as the left margin of the second polarity section, the two polarity sections being positioned such that the upper face of the first polarity section is continuous with the upper face of the second polarity section along the axis of the electrical machine.

According to one embodiment, each polarity portion is substantially symmetrical, the two spaces of the first polarity portion are substantially inclined in two opposite directions by the same inclination angle ζ with respect to a plane transverse to the above, and the two spaces of the second polarity portion are also inclined in two opposite directions by the same inclination angle ζ.

According to one embodiment, the N pairs of polar sections are arranged in adjacent pairs along the axial direction of the electrical machine, two adjacent pairs of the N pairs being offset by a distance along the circumference of the rotor that is shorter than the first polarity step, the adjacent pairs being offset in pairs along the circumference of the rotor, the offset V between the first and last pairs of the N pairs of polar sections along the circumferential direction of the rotor being given by: v × N × 2 × p tan θ sk, where θ sk represents a torsion angle.

According to one embodiment, the electrical torsion angle T is contained in the interval [80 °, 90 ° ] and is advantageously about 84 ° for a machine comprising twelve teeth at each stator, independently of the number of pairs of polar sectors contained between ten and fourteen, given by: t θ sk X, where X is the number of pole pairs assigned to each stator.

According to one embodiment, the number of teeth of each stator is twelve and the number of pairs of polar portions is ten, for γ r0 contained in the interval (25 °, 27 °), the opening angle γ ri1 of the face facing the excitation stator of the first polar portion is contained in the interval (18 °, 32.4 °), advantageously about 19.4 °, and the opening angle γ ri2 of the face facing the excitation stator of the second polar portion is contained in the interval (32.4 °, 34.2 °), advantageously about 34.2 °.

The invention will be better understood upon reading the following description and examining the accompanying drawings. These figures are provided purely by way of illustration of the invention and are in no way limiting.

Fig. 1 shows a perspective view of a rotary electric machine in which a pair of polarity portions are enlarged;

FIG. 2 shows the magnetic flux lines at different positions of the rotor relative to the stator;

figures 3a and 3b show a pair of polar parts according to two perspective views;

FIG. 4 shows a pair of polar parts in the case of an asymmetrical polar part;

FIG. 5 shows the decay of the induced voltage due to the coupling of the polar parts;

FIGS. 6a and 6b show the induced voltage of the 6 th harmonic with or without polar partial coupling;

FIG. 7 shows the case of twisting;

fig. 8 shows the influence of the torsion angle on the induced voltage.

The rotating electric machine shown in fig. 1 includes: a fixed excitation stator 12 supporting excitation; and an armature stator 11, which is also fixed. The two

stators

11, 12 are fitted in a concentric radial arrangement around the axis of rotation Z as the axis of the machine and are separated by an air gap. The rotor 20 is mounted for rotation about an axis of rotation X in the air gap between the two fixed stators.

The excitation stator 12 made of soft magnetic material has a stator main body and teeth extending radially from the stator main body. The field winding 102 is wound on each tooth of the field stator. The field winding 102 has a DC field current passing through it. The DC current is designed to polarize the legs of the stator and act as an inductor. The excitation coil is coupled to produce a predetermined number of poles.

The rotor 20, which is located radially between the field stator 12 and the armature stator 11, is formed of polar portions circumferentially arranged in the air gap. The polar portion is made of a soft ferromagnetic material. The polar part is mounted on a movable ring support. The movable support is made of a non-magnetic and non-conductive material, such as stainless steel or plastic.

The rotor 20 faces the teeth of the exciting stator 12. The rotor also faces the armature stator 11.

The armature stator 11 is formed of a stator body and teeth extending radially from the armature stator body toward the rotor 20. An armature winding 101 is wound on each tooth of the armature stator 11. The armature stator has an AC field current passing therethrough.

In this embodiment, the electrical machine will advantageously comprise one or more electrically conductive coil phases. In the embodiment shown in fig. 1, this would be a three-phase motor, a configuration of this type being advantageous in terms of control and stability.

In these machines, the torque performance level will be improved, especially when the number of poles and polar sections verifies one of the following equations: ns-pl + ph or ns-ph-pl or ns-pl-ph, where ns is the number of pole part pairs in the rotor, ph is the number of pole pairs in the armature stator, pl is the number of pole pairs in the excitation stator. When one of these equations is validated, each stator has the same number X of pole pairs on both sides of the rotor in its interaction with the rotor. By adjusting the magnetic flux density, the pair of polar parts 21 of the rotor thus make it possible to transform each stator into a stator with a different number of poles.

The field density in the air gap has many harmonics and one of the largest harmonics generated in the air gap between the rotor 20 and the armature stator 11 is typically a harmonic of the order pl-ph or pl + ph.

The number of poles on the stator is limited by the choice of windings and their power supply.

Numerically, for the machine shown in fig. 1, in which the rotor 20 comprises ten polar sections 21, the number of poles will therefore be chosen such that the excitation stator has 8 poles (pl-4) and the armature stator has 12 poles (ph-6). In the air gap on the armature stator side, the rotor 20 converts the magnetic flux of the excitation stator having 8 poles to the armature stator having 12 poles: ns-pl-4-6, which corresponds to the number of pole pairs ph in the armature stator. In the air gap on the excitation stator side, the rotor 20 converts the magnetic flux of the excitation stator having 12 poles to the excitation stator having 8 poles: ns-ph 10-6 4, which corresponds to the number of pole pairs pl in the excitation stator.

In operation, a DC current generates a magnetization at each branch of the excitation stator 12, alternately corresponding to a north pole and a south pole, by passing through the coils of the excitation stator 12. Thus, a rotating magnetic field is generated in the air gap by the interaction between the magnetization of the excited stator and the polar part of the rotor 20, which magnetizes the facing teeth of the excited stator 12. The armature stator 11 through which the AC current passes generates a variable rotating field that interacts with the previous rotating field to generate torque. The interaction between these two fields results in field lines as shown in figure 2.

Rotation of the rotor 20 (i.e. the opposed polarity portions) relative to the

stators

11, 12 produces a change in the flux path through the field coils depending on the position of the polarity portions.

In the case of the electric machine shown in fig. 1, the number of teeth on the field stator is the same as the number of teeth on the armature stator, wherein each tooth of the field stator 12 faces a notch defined between two teeth of the armature stator 11, and the paired pole portions are located between the field stator and the armature stator.

Fig. 2 shows the magnetic flux to which the armature stator 11 is subjected depending on the position of the rotor 20 in the case of the electrical machine shown in fig. 1. During the rotation of the rotor 20, the magnetic flux to which the armature stator 11 is subjected passes through a maximum positive value and a minimum negative value, which corresponds to a condition in which it is advantageous for the magnetic flux to pass through one or the other of the polar portions around the stator.

Considering a part of the electrical machine in which the teeth of the armature stator are between two consecutive teeth of the field stator, when the rotor 20 is in a state in which the polar portion 21 faces both the teeth of the field stator and the teeth of the armature stator (θ ═ 0 ° or 180 °), the magnetic flux circulates through the armature stator 11. This corresponds to the magnetic flux limit experienced by the armature stator. When the polar portion 21 faces the notch between two teeth of the excitation stator 12 and faces the tooth of the armature stator 11 (θ ═ 90 °), the magnetic flux circulates directly between the polar portion 21 and two consecutive teeth of the excitation stator. This corresponds to zero flux experienced by the armature stator 11. When two adjacent polar portions face two consecutive teeth of the excitation stator, while the teeth of the armature stator concerned do not face any polar portion (θ ═ 270 °), the magnetic flux circulates directly through two teeth adjacent to the teeth of the armature stator concerned, which are subjected to zero magnetic flux. As a variant, the number of teeth on the two stators will be different.

Depending on time, this type of flux variation through the exciter coil generates an induced voltage at the terminals of the exciter coil.

The axial direction Z of the motor is a direction according to the axis of the motor. The circumferential direction is the direction following the circumference of the rotor in a plane transverse to the axis Z of the motor. The radial direction of the motor is the direction given by the radius of the rotor in a plane transverse to the axial direction Z.

In this machine, shown in perspective in fig. 1, each

polar part

22, 23 is in the form of a truncated pyramid with six faces facing in pairs as shown in fig. 3. Each polar part is advantageously substantially symmetrical.

Each polar part is placed in the air gap between the two

stators

11, 12 so that both faces face the stators. These two faces are an upper face and a lower face, where the

upper face

220, 230 faces the armature stator, and the

lower face

221, 231 faces the field stator 12. These two faces are slightly curved so as to follow the very small curvature of the stator. The two faces are substantially parallel to each other, facing in a radial direction. The two upper and lower surfaces are separated by a thickness e.

The other two faces facing in the axial direction Z are the two axial end faces 224, 225, 234, 235. The two axial end faces are substantially transverse to the upper and lower faces and parallel to each other. The two axial end faces are separated by a depth p.

The last two faces facing each other in the circumferential direction are the blanks of the polar portions 21. Left and

right blanks

222, 232, 223, 233 are defined with respect to the displacement direction along the circumference of the rotor. The voids are inclined in opposite directions relative to a plane transverse to the upper, lower and axial faces. The inclined spaces of the truncated pyramid participate in the attenuation of the induced voltage caused by the sudden change in magnetic flux.

As shown in fig. 3a, the extent of the first polarity portion 22 in the circumferential direction is given by the angle determined from the center of the motor. Both faces of the polar portion 21 facing the stator do not have the same extent along the circumference. The upper face of the first polarity portion 21 has a range along the circumference of the rotor, which is defined between the first left margin and the first right margin by an opening angle γ r01 facing the face of the armature stator. The lower face of the first polarity portion has an extent along the circumference of the rotor, which is defined between the first left margin and the first right margin by an opening angle γ ri1 of the face facing the excitation stator. The two different opening angles γ ri1, γ r01 that define the geometry of the first polar portion validate the equation γ ri1 < γ r01, which defines the tilt angle of the left and right blanks of the first polar portion.

A second adjacent polar section 23 having a similar geometry to the first polar section will also have the form of a truncated pyramid with the same thickness e and the same depth p.

The upper face 230 of the second polarity portion has a range along the circumference of the rotor defined between the second left margin 232 and the second right margin 233 by an opening angle γ r02 facing the face of the armature stator. The lower face 231 of the second polarity portion has an extent along the circumference of the rotor, which is defined between the second left margin 232 and the second right margin 233 by an opening angle γ ri2 facing the face of the exciting stator. The two different opening angles γ ri2, γ r02 that define the geometry of the second polarity portion validate the equation γ ri2 > γ r02, which defines the tilt angle of the left and right blanks of the second polarity portion.

Advantageously, the two spaces of a single polar section are inclined substantially by the same angle ζ in two opposite directions.

As a variant, the two blanks are inclined by two different angles ζ 1 and ζ 2.

According to a preferred embodiment, the angles γ r01, γ r02 will be substantially the same as γ r0, wherein the upper side of the first polarity portion has substantially the same dimensions as the upper side of the second polarity portion.

Thus, the opening angle of the two polar portions of a single pair will verify the following equation:

γri1＜γr0＜γri2

thus, the two

polar parts

22, 23 will be two head-to-tail truncated pyramids, wherein the first polar part corresponds to the pyramid oriented towards the inside of the motor and the second polar part corresponds to the pyramid oriented towards the outside of the motor.

The two polar portions are arranged such that the rear axial end surface of the first portion 225 faces the front axial end surface of the second polar portion 234. Thus, the two end surfaces are in contact on all the end surfaces of the first polar part, the two upper faces of the two polar parts forming a rectangle with a width of 2 × p and a longitudinal extent along the circumference of the machine corresponding to the angle γ r0 (fig. 3 b).

The two

polar parts

22, 23 are advantageously glued to each other at these end surfaces. This makes it possible to prevent an adverse leakage of magnetic flux between the two polarity portions.

Thus, the two polar parts of the pair form a block of thickness e and depth 2 × p, hollowed out in a portion of its depth in the axial and circumferential directions.

As a variant, it is possible to machine a pair of polar portions 21 in a single piece, i.e. by machining a single piece of material in order to form the two adjacent polar portions.

According to the variant shown in fig. 4, when the two spaces of a single polar section have different inclination angles ζ 1 and ζ 2, the polar section is therefore asymmetric, and the other polar section of the pair will reproduce the same asymmetry. Thus, as shown in fig. 4, the two polarity portions will be arranged such that the left blank of the first polarity portion having the inclination angle ζ 1 will have the same inclination angle ζ 1 as the right blank of the second polarity portion, but in opposite directions. The right blank of the first polarity portion of the inclination angle ζ 2 will have the same inclination angle as the left blank of the second polarity portion.

As a variant, the two axial end faces do not have to be transverse to the upper and lower faces, but are inclined with respect to a direction transverse to the upper and lower faces.

Depending on the geometry of the motor, the angular polarity step is defined by:

the polarity step size is 360/Ner, where Ner represents the number of pairs of polar sections in the case described herein.

The parameters of the polar part coupling are set by the following equation:

rr0 ═ γ r 0/polarity step size

Rri1 ═ γ ri1 per polarity step

Rri2 ═ γ ri2 per polarity step

The coupling will be particularly effective in the configuration where the equation validates the following inequality:

0.5＜Rri1＜0.9

0.9＜Rri2＜0.95

0.7＜Rr0＜0.75

in particular in the case where Rri2 equals 0.95 and Rri1 equals 0.54, the coupling will be optimal independently of the number of teeth on the two stators (11, 12), which corresponds to the angular condition for obtaining optimal coupling, independently of the number of teeth on the stators.

Instead, and instead of the conventional simple polar parts known in the prior art, the insertion of pairs of polar parts 120 of this type will make it possible to eliminate the sudden transition of magnetic flux between each

stator

11, 12 and the rotor 20 when the rotor moves facing the stator and facing the teeth of the stator and the notches defined between the teeth of the stator. In effect, the second polarity portion produces a supplementary magnetic flux that is offset by 180 ° with respect to the magnetic flux produced by the first polarity portion, so that the two fluxes compensate each other, resulting in a zero sum, as shown in fig. 5.

For a machine geometry corresponding to fig. 1, where the number of teeth on the field stator is the same as the number of twelve teeth on the armature stator, and for a rotor comprising ten pairs of polar sections, the sudden change in the magnetic flux trajectory experienced by the field coil during the motion of the rotor, depending on the position of the polar sections with respect to the two stators, will generate an induced voltage and hence a harmonic of the DC excitation signal, the dominant harmonic of which in this configuration will be the 6 th order harmonic (fig. 5).

By increasing the pair-polar portion 21 as described above, a significant reduction in peak-to-peak voltage will be observed, particularly for this 6 th harmonic, while maintaining a higher level of average torque of the motor. In the case of polar parts with the following dimensions, the 6 th harmonic will be greatly attenuated: γ r0 ═ 25.2 °, γ ri1 ═ 19.5 °, γ ri2 ═ 35 °, as shown in fig. 6a and 6 b.

According to a variant, the polar part of the air gap can be replaced by a polar part of the N pairs. A plurality of paired polarity sections will be adjacent in pairs in the axial direction Z of the electric machine. Two adjacent pairs of polar sections 21 will be offset in the circumferential direction of the rotor. According to Z, the trailing axial end face 235 of the second polar part of a first pair is partially glued onto the leading axial end face 224 of the first polar part of an adjacent pair. The offset between two consecutive pairs will advantageously be regular.

As shown in fig. 7, a twist angle θ sk may be defined that will define the overall offset of the plurality of pairs of juxtaposed polar portions with respect to the direction Z, i.e., the offset between the first and last pairs of the plurality of pairs in the circumferential direction. By reducing the effect of harmonics 6 in the induced voltage, the torsion will also possibly suppress the magnetic flux.

The depth of the N pairs of polar portions along the rotation axis Z is denoted by P, and each pair has the characteristics described previously, P ═ N × 2 × P.

Therefore, the twisting parameter V in the circumferential direction is given by V ═ P tan θ sk.

Thus, the offset in the circumferential direction between two pairs of consecutive polar sections will be given by v 2p tan θ sk. According to a variant, it will be possible to take into account irregular offsets between adjacent pairs of polar portions.

The twisting makes it possible to suppress the magnetic flux by making it more sinusoidal and to limit the effect of the major harmonics.

The mechanical torsion angle θ sk is related to the electrical torsion angle T by the following equation:

t θ sk X, where X is the number of pole pairs assigned to each stator.

In the case of a previous electric machine comprising 12 teeth on each stator, with a number of pairs of polar sectors comprised between 10 and 14, the electric torsion angle will advantageously be comprised in the interval [80 °, 90 ° ], and in particular will be about 84 °, as shown in fig. 8. This provides an optimum angle without unduly reducing torque while limiting the effect of harmonic 6.

In the case of an electrical machine comprising a field stator and an armature stator each having 12 teeth and a rotor comprising 11 pairs of polar sections, the 6 th harmonic will be greatly attenuated in the case of polar sections having the following dimensions: γ r0 is 23 °, γ ri1 is 15 °, and γ ri2 is 31 °.

In this type of configuration, the peak-to-peak voltage is greatly reduced while maintaining a higher level of average torque of the motor.

In the case of an electrical machine comprising a field stator and an armature stator each having 12 teeth and a rotor comprising 13 pairs of polar sections, the 6 th harmonic will be greatly attenuated in the case of polar sections having the following dimensions: γ r0 is 19.4 °, γ ri1 is 21.5 °, and γ ri2 is 27 °.

In the case of an electrical machine comprising a field stator and an armature stator each having 12 teeth and a rotor comprising 14 pairs of polar sections, the 6 th harmonic will be greatly attenuated in the case of polar sections having the following dimensions: γ r0 is 18 °, γ ri1 is 14.5 °, and γ ri2 is 24 °.

The reduction in the peak-to-peak voltage of this harmonic is shown in figures 6a and 6b for a system with 12 teeth on the stator and 11, 13 or 14 teeth on the rotor.

In all the foregoing, the polar parts of the rotor will typically be made of soft magnetic material, such as FeSi, FeCo or FeNi ferromagnetic steel plates.

The dimensions will be such that p is typically about 35mm and e is typically about 6 mm.

Claims

1. Switched flux synchronous rotating machine comprising a field stator (12) and an armature stator (11), the two stators (11, 12) being positioned around a rotation axis (Z) in a concentric radial arrangement, the field stator (12) being internal to the armature stator (11), an air gap being defined between the two stators, in which a rotor (20) is housed,

The excitation stator (12) is formed by a stator body including a plurality of teeth extending from the excitation stator body toward the rotor (20), an excitation winding (102) wound on the plurality of teeth of the excitation stator,

the armature stator (11) is formed of a stator body including a plurality of teeth extending from the armature stator body (11) toward the rotor (20), an armature winding (101) wound on the plurality of teeth of the armature stator,

said rotor (20) being free of windings or permanent magnets, said rotor (20) being formed by an assembly of pairs of polar sections (21) arranged circumferentially in an air gap facing each stator, said polar sections being separated by polar steps,

the method is characterized in that:

a pair of polar portions (21) comprising a first polar portion (22) and a second polar portion (23) adjacent to the first polar portion, each polar portion having substantially the form of a truncated pyramid,

each polarity portion positioned in the air gap has: two facing axial end surfaces along an axis of the electric machine, two facing blanks along a circumferential direction of the electric machine, two faces facing each other, the two faces including an upper face facing the armature stator and a lower face facing the excitation stator,

The upper face of the first polarity portion (220) has a range defined between a first left margin (222) and a first right margin (223) by an opening angle γ r01 facing the face of the armature stator along the circumference of the rotor,

the lower face of the first polarity portion (221) has an extent along the circumference of the rotor defined between a first left margin (222) and a first right margin (223) by an opening angle γ ri1 facing the face of the excitation stator,

the upper face of the second polarity portion (230) of the same pair has a range along the circumference of the rotor defined between a second left margin (232) and a second right margin (233) by an opening angle γ r02 facing the face of the armature stator,

the lower face of the second polarity portion (231) has an extent along the circumference of the rotor defined between a second left margin (232) and a second right margin (233) by an opening angle γ ri2 facing the face of the excitation stator,

the two polarity sections (22, 23) are arranged such that the axial end surface of the first polarity section faces the axial end surface of the second polarity section,

the spaces of the first polarity portion are inclined such that: γ ri1 < γ r01, the voids of the second polarity portion being inclined such that: gamma r02 < gamma ri2,

Wherein, the sizes of the gamma r01 and the gamma r02 are the same.

2. The electric machine of claim 1, wherein γ r01 ═ γ r02 ═ γ r0, wherein γ r0 is the opening angle facing the armature stator, and verifies the inequality:

0.5＜Rri1＜0.9，

0.9＜Rri2＜0.95

and Rr0 is more than 0.7 and less than 0.75,

wherein the angular polarity step is defined by:

a polarity step of 360/Ner, where Ner represents the number of teeth on the rotor,

and:

rr0 ═ γ r 0/polarity step size

Rri1 ═ γ ri1 per polarity step

Rri2 ═ γ ri2 per polarity step.

3. The electric machine of claim 2, wherein Rri1 equals 0.54 when Rri2 equals 0.95.

4. The electric machine according to any of claims 1 to 3, wherein for each polar section (22, 23) two axial end faces are substantially parallel to each other and transverse to the upper and lower faces,

the distance between said upper and lower faces is called the thickness (e) for each polar part and is the same for both polar parts,

the distance between said axial end faces is called the depth (p) for each polar part and is the same for both polar parts,

the left spaces (222) of the first polarity portion have the same inclination angle in the opposite direction as the right spaces (223) of the first polarity portion, and the right spaces (232) of the first polarity portion have the same inclination angle in the opposite direction as the left spaces (233) of the second polarity portion,

The two polarity portions are positioned such that an upper face of the first polarity portion (220) is continuous with an upper face of the second polarity portion (230) along an axis of the electric machine.

5. The electric machine of claim 4, wherein:

each of the polar portions is substantially symmetrical in that,

the two spaces (222, 223) of the first polarity portion are inclined in two opposite directions by substantially the same inclination angle ζ with respect to a plane transverse to the upper face,

the two spaces (232, 233) of the second polarity portion are also inclined in two opposite directions by the same inclination angle ζ.

6. The electric machine according to any of claims 1 to 5, wherein the N polar portion pairs are arranged in adjacent pairs along an axial direction of the electric machine,

two adjacent ones of the N pairs are offset along the circumference of the rotor by a distance shorter than the first polarity step,

the adjacent pairs are offset in pairs along the circumference of the rotor,

an offset V in the circumferential direction of the rotor between the first and last of the N pairs of polar sections is given by:

v is N × 2 × p tan θ sk, where θ sk represents a twist angle, and p represents a depth of the polar portion along the axis (Z).

7. The electric machine according to claim 6, wherein the electric twist angle T is contained in the interval [80 °, 90 ° ],

And advantageously about 84 deg. for a machine comprising twelve teeth at each stator (11, 12), independently of the number of pairs of polar sectors comprised between ten and fourteen,

the electrical twist angle T is given by: t θ sk X,

where X is the number of pole pairs assigned to each stator.

8. The electrical machine according to any of claims 1 to 7, wherein the number of teeth of each stator (11, 12) is twelve and the number of pairs of polar portions is ten, for γ r0 contained in the interval (25 °, 27 °), the opening angle γ ri1 of the face of the first polar portion facing the excitation stator is contained in the interval (18 °, 32.4 °), advantageously about 19.4 °, and the opening angle γ ri2 of the face of the second polar portion facing the excitation stator is contained in the interval (32.4 °, 34.2 °), advantageously about 34.2 °.