WO2011107693A2

WO2011107693A2 - Polyphase polydiscoid electric machine comprising magnets

Info

Publication number: WO2011107693A2
Application number: PCT/FR2011/050381
Authority: WO
Inventors: Julien Jac; Nicolas Philippe Ziegler
Original assignee: Erneo
Priority date: 2010-03-04
Filing date: 2011-02-24
Publication date: 2011-09-09
Also published as: FR2957208B1; WO2011107693A3; FR2957208A1

Abstract

The invention relates to a polydiscoid electric machine comprising magnets, comprising a number M of even phases, a plurality of discoid rotors arranged coaxially along an axis of rotation, a plurality of pairs of stators consisting of a first stator and a second stator arranged either side of a rotor, said stators comprising a number Ns of pairs of teeth and windings, according to which the windings of a stator are monophase, said first stators and second stators of a pair of stators being out-of-phase by an angle essentially equal to ±90/Ns degrees, and the second stator of a pair of stators and the first stator of the following pair of stators along the axis of rotation are out-of-phase by an angle essentially equal to ±180/(M∙Ns) degrees.

Description

"Polydiscooid Polyphase Magnetic Electric Machine"

Technical area

The present invention relates to a polyphase electrical machine with disc rotors.

The field of the invention is more particularly, but in a nonlimiting manner, that of discoidal permanent magnet electric machines of high reliability for applications with high volume and / or mass performance, for embedded systems applications in particular.

State of the art

In embedded systems, for example for the aeronautical field or that of land vehicles, the most sought-after electric motorization architectures are those which have the best mass and / or volume performances, as well as a high reliability. In this context, the architectures of disco electric polyentrefers offer interesting possibilities.

These machines generally consist of a plurality of disk-shaped rotors which are arranged along the axis of rotation between stators. The rotors support permanent magnets while the stators comprise teeth facing the rotors, separated by notches into which windings are inserted. The spaces between the stators and the rotors constitute the air gaps.

In particular, WO 96/29774 is known from Lipo et al. which discloses a polydiscoid machine consisting of two stators surrounding a rotor. The stators comprise teeth around which coils corresponding to two phases are wound. According to the embodiments described, each stator supports the windings of one or both phases. The stators are arranged so that the teeth of one face the notches of the other. The rotor is made up of tangentially and alternately oriented magnets, between which are inserted elements made of magnetic material.

Also known is WO 2008/003990 to Lamperth et al. which discloses a polydiscoid machine consisting of a plurality of rotors alternating with stators. The rotors are provided with magnets oriented in the axial direction, alternating polarity. The stators are provided with teeth separated by notches. The teeth are provided with isthms to minimize the reluctance of the magnetic circuit. Each stator comprises coils powered by three phases inserted in the notches.

In order to produce high power electrical machines, it is known to combine a plurality of stators and rotors along the axis of rotation, which is made particularly easy by the discoid structure of the assembly. Such solutions are in particular described in WO 96/29774 and WO 2008/003990. We thus find an alternation of rotors framed by stators. The stators which are not at the ends are in fact constituted by two stators each facing a rotor.

However, these solutions of the prior art do not constitute more than the juxtaposition of elementary machines consisting of two stators flanking a rotor, stacked along the axis of rotation. In particular, the phase distribution is identical between similar stators of the elementary machines, and no particular angular relationship is established between these elementary machines, which are simply most often arranged in the same orientation.

These solutions are unsatisfactory for applications in aeronautics in particular, requiring both high mass and / or volume performance, high reliability and minimal torque ripples. In fact, apart from the power which is actually the sum of the contributions of the elementary machines, the other characteristics are not better than those of each of these elementary machines, and notably:

The number of phases is limited to that which can be reasonably implemented at the level of one elementary machine, for example two in WO 96/29774 and three in WO 2008/003990, respectively. However, it is well known that an increase in the number of phases of an electric machine makes it possible on the one hand to reduce the amplitudes of the torque ripples and on the other hand to push back the rank of the harmonics of torque at the origin of the ripples. . As a result, the torque ripple characteristics can not be optimal in a machine using only a small number of phases; - In order to guarantee maximum reliability and dependability, it is preferable to limit the number of phases per stator. Indeed, unless the coils of the respective phases are physically close to each other, there is less risk that the failure of a winding (for example excessive heating due to a short circuit) does not lead to the failure of the windings. 'another. From this point of view, the ideal configuration is one phase per stator. But if, as in WO 96/29774, there is a juxtaposition of independent machines with a rotor, the total number of phases is limited to two, with consequent unsatisfactory torque ripple characteristics;

- If a phase of a basic machine fails, the torque characteristic of this elementary machine is strongly affected, resulting in a significant impact in terms of ripple and power loss, especially on the torque characteristic of the machine. system as a whole, which typically consists of two or three elementary machines. The fault tolerance of the assembly is therefore limited.

The object of the present invention is to provide a polydiscoïd electrical machine having high mass and / or volume performances, reduced torque ripples and significantly improved reliability and fault tolerance.

Presentation of the invention

This objective is achieved with a polydiscooid magnets electric machine comprising:

an M number of even phases, greater than two,

a plurality of disc-shaped rotors arranged coaxially along an axis of rotation in a substantially identical angular orientation, which rotors comprise a plurality of magnets,

a plurality of pairs of stators arranged coaxially along the axis of rotation, constituted by a first and a second stator arranged on either side of a rotor, which stators comprise a number Ns of pairs of teeth, which teeth facing the rotors and being separated by notches, which notches include coils,

characterized in that

the windings of a stator are single-phase, the machine comprising at least as many stators as there are phases, said first and second stators of a pair of stators are out of phase by an angle substantially equal to ± 90 / Ns degrees, and

the second stator of a pair of stators and the first stator of the next pair of stators along the axis of rotation are out of phase by an angle substantially equal to ± 180 / (M-Ns) degrees.

According to embodiments:

the winding of the stators may comprise a stack of substantially electrically conductive elements separated by substantially insulating elements, arranged so as to constitute a serpentine surrounding several teeth, which coil is inserted into the notches and passing alternately along the the outer face and the inner face relative to the axis of rotation of said teeth,

the coil may comprise a stack of sheets cut so as to fit into the notches between the stator teeth,

the rotors may comprise a plurality of pairs of magnets, which magnets are oriented substantially parallel to the axis of rotation and of alternating polarity,

the rotors can comprise a number of pairs of magnets identical to the number of pairs of teeth of the stators,

the rotors may comprise a plurality of magnets of orientation substantially parallel to the axis of rotation and of identical polarity, alternating with elements made of magnetic material,

the rotors may comprise a plurality of magnets of substantially perpendicular orientation and tangential to the axis of rotation, alternating with elements made of magnetic material, which magnets are arranged in such a way that two magnets surrounding a member made of magnetic material are opposite polarity;

the magnets can be held by a support of substantially non-magnetic material having through openings in which said magnets are embedded,

the magnets can be held by disks of substantially non-magnetic material bonded on either side of the rotors,

second and first adjacent stators can be made in the same mechanical element of which they constitute two faces, the stators can be made in sheet windings in which the notches are machined,

the stators may be made of a SMC type material (in English: "Soft Magnetic Composite").

In contrast with the devices of the prior art such as for example that described in WO 96/29774, the electric machine according to the invention does not constitute a simple juxtaposition of several two-phase machines but a polyphase electrical machine comprising a high number of phases. The overall design and structure of the machine are optimized for the total number of phases actually implemented, which determines in particular the relative angular orientations of the rotors.

The high number of phases and the mechanical and electrical phase shifts of the phases relative to one another, in particular because of the relative arrangement of the stators, make it possible on the one hand to obtain a substantial reduction in the amplitude of the torque ripples. and on the other hand to push back the rank of the harmonics of torque at the origin of the undulations.

The high number of phases also contributes to the objective of increasing the reliability of operation, thanks precisely to the segmentation of the power between the phases. Indeed, a defect leading to a loss of phase induces a loss of power even lower than the number of phases is important.

The stators have only one phase, which makes it possible physically to decouple the phases from each other, and in particular to limit the risks of propagation between phases of defects of electrical or thermal origin (excessive heating, short circuits). Moreover, the magnetic architecture is such that the mutual inductances between phases are very weak and therefore the phases are also decoupled magnetically.

In addition, always with a view to increasing the reliability of operation, the phases of the machine can be advantageously powered by single-phase bridge inverters, which eliminates the risk of propagation of any electrical fault at within the power inverter.

In another aspect, there is provided an electrical machine comprising a plurality of polydiscooid electric magnets according to the invention, arranged along the axis of rotation so that the angular orientations of a second stator constituting the end of one of said machines, and a first stator constituting the adjacent end along the axis of rotation of another of said machines are out of phase by an angle substantially equal to ± 180 / (M-Ns) degrees.

It is also proposed an electrical machine comprising a plurality of polydiscooid electric magneto machines according to the invention, arranged along the axis of rotation so that the angular orientations of a second stator constituting the end of one of said machines, and a first stator constituting the adjacent end along the axis of rotation of another of said machines, are substantially identical.

Description of the Figures and Embodiments

Other advantages and particularities of the invention will appear on reading the detailed description of implementations and non-limiting embodiments, and the following appended drawings:

FIG. 1 illustrates an embodiment of a polydiscooid electric machine with magnets according to the invention,

FIG. 2 illustrates an embodiment of the stator of an electric machine according to the invention,

FIG. 3 illustrates an embodiment of the rotor of an electric machine according to the invention,

FIG. 4 illustrates the relative angular positioning of the stators and rotors in an electric machine according to the invention, as seen along its periphery,

FIG. 5 illustrates a second embodiment of the stator of an electric machine according to the invention,

FIG. 6 illustrates a third embodiment of the stator of an electric machine according to the invention,

FIG. 7 illustrates a mode of combination of electrical machines according to the invention,

FIG. 8 illustrates another mode of combination of electrical machines according to the invention.

With reference to FIG. 1, a polydiscooid electric machine with magnets according to the invention consists of a plurality of disc-shaped rotors 2, coaxially mounted and integral with a shaft, or axis of rotation 3. rotors 2 are arranged between stators 1, each rotor 2 being thus framed by a pair of stators la and lb.

With reference to FIG. 2, the stators 1 comprise, on their portion facing the rotor 2, teeth 10 separated by notches 11 in which coils 4 circulate. The coils 4 of a stator 1 correspond to a phase of the machine. In other words, each stator 1 only supports one phase 4, which physically separates the windings phases to prevent the failure of one of them affects the others.

The winding 4 of a phase of a stator 1 is made in the form of a coil disposed in the notches 11 between the teeth 10. This coil consists of a stack of layers of material substantially electrically conductive, substantially isolated from each other. It travels all the slots of the stator, so as to constitute the equivalent of a winding of the same polarity surrounding a tooth 10 on two of the stator. The electrical connection between the coils of the coils, constituted by the successive layers, is made at the ends 12.

The coil is made by a stack of copper sheets, cut to the desired shape and electrically isolated. This embodiment of the winding allows a considerable simplification of the manufacturing operations of the electric machine according to the invention, since the assembly of the winding 4 in the stator 1 can be reduced to an insertion operation of the complete pre-assembled coil.

The coil-shaped prefabricated winding 4 also has the advantage of making it possible to adapt to the shape of the magnetic circuit, for example by allowing variations in the current density. It also allows better heat dissipation and a better notch filling coefficient. This serpentine winding 4 requires open notches 11 (that is to say for example teeth without isthmus) to be able to be inserted, but the use of a high number of phases in the electric machine according to the invention makes it possible to limit the torque ripples induced by the opening of these notches 11.

The stators 1 are made by a winding of magnetic sheets, in which the notches 11 are then machined. This configuration is more favorable for operations at high frequencies since it It is possible to implement thinner sheets. Indeed, the thickness of the rolled sheets can go down to 0.1 mm or even 0.05 mm, unlike stacked sheets whose thicknesses are generally greater than or equal to 0.2 mm.

With reference to FIGS. 3 and 4, the rotors 2 comprise magnets 20 which are arranged in such a way that their magnetic field (or their axis of magnetization) is parallel to the axis of rotation and their alternating polarity. Thus, a rotor 2 alternately comprises on its periphery magnets 20a of alternating polarity 25 with magnets 20b of the opposite polarity. The number of magnets 20 of the rotors 2 is identical to the number of teeth 10 of the stators 1.

The magnets 20 are in the form of a portion of disks. They are fixed on the rotors 2 by means of discs 21 of substantially non-magnetic material of small thickness, glued on either side of these rotors 2 so as to maintain them. This method of attachment allows a simplified manufacture of the device while ensuring a very good resistance to radial stresses due to the centrifugal force.

The elements (stators 1 and rotors 2) of the electric machine according to the invention are arranged in angular orientations which allow both:

to minimize the magnetic couplings between elements, so as to minimize the impact of the failure of one element on the others,

to minimize the amount of magnetic field in the magnetic yokes 27 of the stators, so as to limit the iron losses and / or the mass, and

- To minimize the ripples of the couple while pushing them to high harmonics.

Thus, the rotors 2 are disposed in a substantially identical angular orientation 26, that is to say with the magnets of the same polarity of all the rotors substantially aligned along the axis 3 of the machine. In this way, the amount of magnetic field created by the magnets closing in the magnetic yokes 27 of the intermediate stators is reduced, which makes it possible to reduce the iron losses or the mass.

The stators la and lb disposed on either side of a rotor 2 are out of phase by an angle Φϊ substantially equal, in absolute value, to 90 / Ns degrees, Ns being the number of pairs of teeth. In this way, the magnetic couplings within the module consisting of the stators 1a and 1b and the rotor 2 are minimized.

The stators lb and the facing two consecutive rotors 2 are out of phase by an angle Oe substantially equal, in absolute value, to 180 / (M-Ns) degrees, M being the number of phases of the machine. This angle Oe is determined to be the smallest angle allowing a homogeneous angular distribution, over 360 degrees, of the phases of a machine that would have 2-M phases (instead of M phases).

In this way :

an M-phase machine is obtained whose torque ripples are pushed back to the 2-M harmonic of the fundamental frequency,

- The amount of magnetic field created by the windings 4 and closing in the magnetic yokes 27 of the intermediate stators lb, the is effectively reduced.

These intermediate stators 1, that is to say placed between two successive rotors 2, consist of the assembly of two stator elements 1a, 1b.

The magnetic architecture thus obtained is such that mutual inductances between phases are very weak. The phases are thus also decoupled magnetically. In the case illustrated in Figures 1 and 4, the orientations of the angles Φϊ and Oe are in opposite directions. It is however important to note that all the orientation combinations of these angles Φϊ and Oe are usable within the scope of the invention.

According to the embodiments, an electric machine according to the invention can be made with any number of phases, for example four, six, eight, ten, twelve or fourteen phases.

The embodiment illustrated in FIG. 1 concerns a machine comprising five pairs of teeth (Ns = 5) and four phases (M = 4), whose phase shifts between stators are substantially equal to Oi = 90 ° / Ns and

Oe = -45 ° / Ns, respectively. In this example, the angular positions of the stators, relative to the first stator, are as follows:

{0; 90 / Ns; 45 / Ns; 135 / Ns} degrees.

As explained above, substantially equivalent embodiments could be for example substantially according to one of the sets angular orientations, in absolute value, relative to the first stator, according to:

{0; 90 / Ns; 135 / Ns; 225 / Ns} degrees, or

{0; 90 / Ns; 135 / Ns; 45 / Ns} degrees.

For six phases, therefore six stators 1 and three rotors 2, the phase shifts between stators are substantially equal, in absolute value, at Φϊ = 90 ° / Ns and Oe = 30 ° / Ns respectively. The embodiments of the machine may for example be substantially in accordance with one of the sets of angular orientations, in absolute value, relative to the first stator, as follows:

{0; 90 / Ns; 60 / Ns; 150 / Ns; 120 / Ns; 210 / Ns} degrees,

{0; 90 / Ns; 120 / Ns; 210 / Ns; 240 / Ns; 330 / Ns} degrees,

{0; 90 / Ns; 120 / Ns; 30 / Ns; 60 / Ns; 150 / Ns} degrees, etc.

It is also possible to have several stators with the same angular orientation.

The angular positions of the stators relative to the first stator as defined above constitute the mechanical phase shifts of the electric machine.

For correct operation, the windings 4 of the stators 1 must be powered by electrical signals whose electrical phase shifts are substantially equal to the mechanical phase shifts of the stators they feed multiplied by Ns.

According to embodiments, it may be advantageous to combine several electrical machines according to the invention along an axis of rotation, in particular to increase power and / or reliability.

With reference to FIG. 7, it is possible in particular to combine two electrical machines according to the invention 40 and 41 so that the angular orientations of the second stator lb constituting the end of one of said machines 40, and the first stator constituting it. the adjacent end along the axis of rotation 3 of the other machine 41, is also out of phase with an angle of an angle Oe substantially equal, in absolute value, to 180 / (M-Ns) degrees. A 2-phase machine is thus produced, which must be powered by control electronics also at 2-M electrical phases, at least if the angular positions of all the stators 1 are different. This solution therefore requires more control electronics complex. However, it has the advantage of allowing the implementation of all the 2-M electrical phases equitably distributed over 360 degrees corresponding to the angular positions of the stators with phase shifts Φϊ and Oe, in which case it is possible to achieve a balanced control in which the sum of the currents of the electrical phases is zero, which makes it possible to have a floating neutral. The machine can then be powered with 2-M electrical phases with a conventional 2-M arm inverter.

Of course it is possible to combine more than two electrical machines according to the invention in this way.

It is also possible to combine several electrical machines according to the invention with M phases or 2-M phases along an axis of rotation, according to configurations of number of phases and various control, for example:

- several machines comprising the same number of phases, powered by the same electronics or separate electronics,

several machines comprising a different number of phases.

With reference to FIG. 8, it may then be advantageous to combine them so that the last stator lb of a machine 40 and the first stator la of the next machine 41 to which it is attached have substantially the same angular orientation. This makes it possible to further minimize the field in the intermediate yokes 27 between two machines 40, 41. Moreover, when the combined machines 40 and 41 comprise stators 1 of similar angular orientation, the control can be carried out by an inverter which comprises the number of phases of a machine, or at least one inverter driven by a number of control signals equivalent to the number of phases of a machine.

According to variant embodiments:

- The windings 4 of the stators 1 may comprise several coils, each arranged around a group of teeth 10 different from said stator 1;

- The windings 4 of the stators 1 may comprise several coils, each surrounding all or part of the teeth 10 of the stator 1, and being manufactured separately and stacked on top of each other in the notches 11;

The windings 4 of the stators 1 may consist of coils individually surrounding one tooth 10 out of two; The windings 4 of the stators 1 may consist of coils individually surrounding all the teeth 10;

- The stators 1 can be made of a material of the SMC type (in English: "Soft Magnetic Composite"), which has the advantage of better heat dissipation (due to its isotropic nature in particular) and high frequency performance (greater than 1500 Hz) interesting;

- Maintaining the magnets 20 on the rotors 2 can be provided by a substantially non-magnetic material support and preferably electrically non-conductive, such as for example Dacron®, another plastic material, or ceramic). Openings are provided in this support, in which the magnets are embedded and fixed (for example by gluing);

- The rotors 2 may comprise a substantially disk-shaped central magnetic yoke on which are fixed, on either side and vis-à-vis, magnets 20;

With reference to FIG. 5, a magnet 20 of two of the rotor 2 can be replaced by an element made of a substantially magnetic material 30, in which case the rotor 2 comprises an alternation of magnets 20 and elements made of magnetic material 30, which magnets 20 being arranged such that their magnetic field (or their axis of magnetization) is substantially parallel to the axis of rotation 3 and their identical polarity;

With reference to FIG. 6, the rotor 2 can comprise an alternation of magnets 20 and magnetic material elements 30, which magnets 20 are arranged in such a way that their magnetic field (or their axis of magnetization) is substantially perpendicular and tangential to the axis of rotation 3, and two magnets 20 flanking a magnetic material member 30 are of opposite polarity, so as to constitute a flux concentration pattern;

- The stators 1 intermediate, that is to say placed between two successive rotors 2, can be made on the basis of a single piece or the same mechanical element having teeth 10 and notches 11 on both sides , then equivalent to the stators lb and la respectively. Of course, the invention is not limited to the examples that have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

Claims

A polydiscoid magnets electric machine comprising:

an M number of even phases, greater than two,

a plurality of disc-shaped rotors (2) arranged coaxially along an axis of rotation (3) in a substantially identical angular orientation, which rotors comprise a plurality of magnets (20),

a plurality of pairs of stators (1a, 1b) arranged coaxially along the axis of rotation (3), constituted by a first (1a) and a second stator (1b) arranged on each side and other of a rotor (2), which stators (1) comprise a number Ns of pairs of teeth (10), which teeth (10) face the rotors (2) and are separated by notches (11), which notches comprising coils (4),

characterized in that

the windings (4) of a stator (1) are single-phase, the machine comprising at least as many stators (1) as there are phases,

said first (1a) and second (1b) stators of a pair of stators are out of phase by an angle substantially equal to ± 90 / Ns degrees, and

the second stator (1b) of a pair of stators and the first stator (1a) of the next pair of stators along the axis of rotation (3) are out of phase by an angle substantially equal to ± 180 / ( M-Ns) degrees.

2. Electrical machine according to claim 1, characterized in that the winding (4) of the stators (1) comprises a stack of substantially electrically conductive elements separated by substantially insulating elements, arranged so as to constitute a coil surrounding several teeth, which coil is inserted into the notches (11) and passing alternately along the outer face and the inner face relative to the axis of rotation (3) of said teeth (10).

3. Electrical machine according to claim 2, characterized in that the coil (4) comprises a stack of cut sheets so as to be inserted into the notches (11) between the teeth (10) of the stator (1).

4. Electrical machine according to one of the preceding claims, characterized in that the rotors (2) comprise a plurality of pairs of magnets (20a, 20b), which magnets (20) being oriented substantially parallel to the axis rotation (3) and alternating polarity (25).

5. Electrical machine according to claim 4, characterized in that the rotors (2) comprise a number of pairs of magnets (20a, 20b) identical to the number of pairs of teeth (10) of the stators (1).

6. Electrical machine according to one of claims 1 to 3, characterized in that the rotors (2) comprise a plurality of magnets (20) oriented substantially parallel to the axis of rotation (3) and polarity ( 25), alternating with elements of magnetic material (30).

7. Electrical machine according to one of claims 1 to 3, characterized in that the rotors (2) comprise a plurality of magnets (20) oriented substantially perpendicular and tangential to the axis of rotation (3), alternating with magnetic material elements (30), which magnets (20) are arranged in such a way that two magnets (20) surrounding a magnetic material element (30) are of opposite polarity (25).

8. Electrical machine according to one of claims 4 to 7, characterized in that the magnets (20) are held by a substantially non-magnetic material support having through openings in which said magnets (20) are embedded.

9. Electrical machine according to one of claims 4 to 8, characterized in that the magnets (20) are held by discs (21) of substantially non-magnetic material glued on either side of the rotors (2).

10. Electrical machine according to one of the preceding claims, characterized in that second (Ib) and first (the) stators adjacent are formed in the same mechanical element which they are two faces.

11. Electrical machine according to one of the preceding claims, characterized in that the stators (1) are made in sheet windings in which the notches (11) are machined.

12. Electrical machine according to one of claims 1 to 10, characterized in that the stators (1) are made of a material type SMC (in English: "Soft Magnetic Composite").

Electrical machine comprising a plurality of electrical machines (40, 41) according to one of the preceding claims, arranged along the axis of rotation (3) so that the angular orientations of a second stator (Ib). constituting the end of one of said machines (40), and a first stator (la) constituting the adjacent end along the axis of rotation (3) of another of said machines (41), are out of phase an angle substantially equal to ± 180 / (M-Ns) degrees.

Electric machine comprising a plurality of electrical machines (40, 41) according to one of the preceding claims, arranged along the axis of rotation (3) such that the angular orientations of a second stator (Ib). constituting the end of one of said machines (40), and a first stator (1a) constituting the adjacent end along the axis of rotation (3) of another of said machines (41), are substantially identical.