EP2817868A1

EP2817868A1 - Rotor of a rotating machine with flux concentration

Info

Publication number: EP2817868A1
Application number: EP13713998.6A
Authority: EP
Inventors: Michael Leo Mcclelland; Xavier JANNOT; Michel Labonne
Original assignee: Moteurs Leroy Somer SAS
Current assignee: Moteurs Leroy Somer SAS
Priority date: 2012-02-20
Filing date: 2013-02-19
Publication date: 2014-12-31
Also published as: WO2013124787A1; FR2987184A1; CN104126266A; FR2987184B1; US20150171684A1

Abstract

The present invention relates to a rotor (1) of a rotating electric machine with flux concentration, comprising: -a rotor body (3) comprising recesses (8), and -permanent magnets (7) arranged in the recesses (8) of the rotor body (3), said permanent magnets being arranged in the shape of a V oriented towards the air gap, each V defining an elementary polar portion, at least two consecutive elementary polar portions having an identical polarity.

Description

ROTOR OF ELECTRICAL ROTARY MACHINE

CONCENTRATION OF FLOW

The present invention relates to rotating electrical machines, including synchronous machines, including motors, and more particularly the rotors of such machines. The invention is concerned with permanent magnet and flux concentration rotors. The flux concentration rotors comprise a rotor mass in which permanent magnets are housed, the latter being engaged in housings oriented most often radially.

Electrical machines are known having permanent non-radial magnets, arranged for example in V or U, as in patents EP 1 414 130, US 6 984 909, US 6 836 045, US 6 794 784, US 6 909 216, US 5,955,807, and US patent application 2008/231135.

Thanks to the concentration of flux in the poles, the induction obtained in the gap is greater than the induction in the magnets. The induction obtained in the gap can depend strongly on the circumferential position.

In the application US 2007/014850 and in the international application WO 2010/039786, the permanent magnets are arranged in two concentric layers.

In known rotors, in order to obtain sufficient induction levels in the air gap and to have compact machines, it may be necessary to use magnets with a high energy density, which is therefore expensive. Indeed, such magnets are made with rare earths.

In other machines, low-energy magnets made of ferrite are used, but such machines have the disadvantage of requiring high polarity or very large diameter rotors to obtain induction levels in the air gap. comparable to what can be achieved with magnets with high volumic energy.

A machine with high polarity requires high frequencies, which results in significant losses in the motor in the form of losses iron and in the inverter in the form of switching losses. Such machines with high polarity and with low energy density magnets are therefore used at limited speeds. Thus, rotors of rotating flow-rate electrical machines do not make it possible to supply machines with relatively low polarity, for example less than six, with efficient use of magnets, in particular ferrite magnets and / or low-density magnets. 'energy.

There is therefore a need to benefit from a rotating electric machine rotor allowing a more efficient use of the magnets in particular ferrite magnets and / or low energy density, and possibly with a polarity that is not necessarily high. .

The invention aims to meet all or part of this need and it succeeds, according to one of its aspects, with a rotating electric machine rotor flux concentration, comprising:

a rotor mass comprising housings, and

permanent magnets arranged in the housings of the rotor mass, the permanent magnets being arranged in V oriented towards the air gap, each V defining an elementary polar part, at least two consecutive polar elementary parts having an identical polarity.

The rotor mass defines elementary pole portions each disposed between magnets which are symmetrically polarized relative to each other and which make it possible to effectively concentrate the flux of the magnets. Thanks to the elementary polar parts, the invention makes it possible to improve the induction obtained in the air gap whatever the circumferential position.

Several consecutive polar elementary parts define by juxtaposition a main pole of the rotor. The number of elementary polar parts in a main pole is greater than or equal to two, being for example two, three, four or five. When the number of elementary polar parts is equal to two, the magnets defining the same pole are arranged in the form of W. At least three consecutive polar elementary parts may have an identical polarity, or even at least four consecutive polar elementary parts, or even five consecutive polar elementary parts.

Thanks to the arrangement of the magnets in the rotor mass, sufficient induction levels in the air gap are obtained even with a relatively low rotor polarity, for example less than 6, while not necessarily using magnets with high volumetric energy, such as magnets made of rare earths, but on the contrary low energy density, for example made of ferrite. The cost of the rotor can thus be reduced. In addition, the polarity of the rotor can be reduced if the application requires it. In fact, the rotor according to the invention makes it possible to increase the level of induction in the gap without increasing the polarity and by using magnets with a low energy density.

By "V-oriented gap" means that the V is open towards the air gap. A V can be formed by two consecutive permanent magnets when moving circumferentially. Alternatively, a V may be formed by more than two permanent magnets when moving circumferentially, in particular by four permanent magnets, two magnets for example forming each branch of V. Such a segmentation of magnets can improve circulation flow into the rotor mass and / or introduce bridges to stiffen it.

A branch of a V may be formed of several magnets, for example two. Two magnets of a branch of the V can be aligned. In a variant, the magnets forming a branch of a V may each extend along an axis, the two axes forming an angle α between them. This angle may be between 0 ° and 45 °.

The permanent magnets may be rectangular in cross section. Alternatively, the width of a magnet taken in cross section perpendicular to the axis of rotation may taper when moving towards the air gap. The permanent magnets may be generally trapezoidal in cross section. In another variant, the magnets may be in curvilinear cross section, for example of ring-shaped shape.

Two consecutive magnets of two consecutive polar elementary parts of identical polarities can form a V oriented towards the axis of rotation. When moving circumferentially, the disposition of the consecutive magnets may be identical when moving from one V to another V of the same pole to a V of a pole of opposite polarity. Thus, two consecutive magnets of two consecutive polar elementary portions of opposite polarities can also form a V oriented towards the axis of rotation.

Alternatively, the disposition of the consecutive magnets may be different than one goes to a V of the same pole or that one goes to a V of a pole of opposite polarity. it can optimize the circulation of the flow in the rotor mass. By way of example, two consecutive magnets of two consecutive polar elementary portions of opposite polarities may extend substantially parallel to each other. Such an arrangement of the magnets makes it possible to optimize the circulation of the flux in the rotor mass.

The thickness of the rotor mass between two consecutive magnets of two consecutive polar elementary parts of opposite polarities may be less than 5 mm, or even 3 mm, better still less than 1.5 mm.

In another variant, the same magnet can participate in two consecutive V at a time, in particular two V of two poles of opposite polarities. The magnet can in this case be for example twice as large in cross section as a magnet participating only one V.

A housing may extend radially over a length greater than the radial length of the corresponding magnet in cross section. The shape of the cross-sectional housing can be chosen to optimize the waveform of induction in the gap. For example, at least one end of the housing in cross section perpendicular to the axis of rotation may be of triangular shape, or both ends may be of triangular or curved shape, or in the form of an arc. When the magnet is inserted into the corresponding housing, the part (s) of the housing without magnet at one of its ends or ends may be in the form of a right triangle or rounded. For two consecutive dwellings, the hypotenuses of the two right triangles or the curved located closer to the gap can be arranged opposite to each other. Such a shape makes it possible to better guide the magnetic flux towards the gap. For two consecutive dwellings, the hypotenuses of the two right triangles or the roundings located closest to the axis of rotation can be arranged face to face.

Permanent magnets can form a number of V between 8 and

24, or between 12 and 20, for example 16. It may be possible to determine for a given rotor an optimum number of V to maximize the production of the flux in the air gap depending on the polarity of the rotor and the geometric dimensions of the last. The optimum number of V for a given polarity may, for example, be greater than the optimum number of V for a polarity greater than the given polarity.

The number of rotor poles may be less than or equal to 8, or less than or equal to 6, being for example equal to 4. Thanks to the invention, it is possible to provide a low rotor. polarity, for example at only two poles, while achieving an effective flux concentration. There is not necessarily a frequency limit of use, and the rotor according to the invention can be used while being powered by an electronic power inverter, while limiting the losses iron to the motor and the losses by switching in the inverter.

The permanent magnets of the rotor can be made at least partially of ferrite. They may for example not contain rare earths, or at least contain less than 50% rare earth en masse.

The rotor may comprise a shaft extending along an axis of rotation. The shaft may be made of a magnetic material, which advantageously makes it possible to reduce the risk of saturation in the rotor mass and to improve the electromagnetic performances of the rotor. The shaft may comprise a magnetic sleeve in contact with the rotor mass, the sleeve being mounted on an axis, magnetic or not.

The rotor mass extends along the axis of rotation and is arranged around the shaft. The shaft may comprise torque transmission means for driving in rotation of the rotor mass.

The rotor mass may be formed entirely by an assembly of rotor plates each monobloc or by a winding of a sector band. Thus, the rotor may be devoid of reported pole pieces, and the construction of the rotor is simplified.

The stack of magnetic sheet layers may comprise a stack of magnetic sheets, each in one piece, each sheet forming a layer of the stack.

As a variant, the stack of magnetic sheet layers may comprise one or more magnetic sheet (s) wound on it (s) itself, each sheet being able to form several layers of the stack, according to the number of turns on which it is rolled up on itself.

A sheet may comprise a succession of sectors connected by material bridges. Material bridges can form the bottom of a housing of a permanent magnet, on the side of the gap.

Each sector can correspond to an elementary polar part. A sheet may comprise a number of sectors equal to the number of elementary polar parts, or alternatively to the number of poles of the rotor. A sheet may have a number of sectors greater than the number of elementary polar parts of the rotor, for example a multiple of the number of elementary polar parts of the rotor, two sectors of the same sheet that can be superimposed on one another when the sheet is wound to form the mass rotor.

For example, each rotor plate is cut from a sheet of magnetic steel, for example steel 0.1 to 1.5 mm thick. The sheets can be coated with an electrical insulating varnish on their opposite faces before assembly within the stack. The insulation can still be obtained by a heat treatment of the sheets.

Alternatively, the rotor mass may comprise polar parts independent of each other. Each pole piece may be formed of a stack of magnetic sheets.

At least one of the housings may be of oblong shape, preferably elongated in a rectilinear direction. Preferably, all the housings are oblong, elongate in a rectilinear direction. Alternatively, the housing can be elongate in a curved direction, for example in a circular arc.

The distribution of the housings is advantageously regular and symmetrical, facilitating the cutting of the rotor sheet and the mechanical stability after cutting when the rotor mass consists of a superposition of rotor plates.

The number of housings and magnets depends on the polarity of the rotor. The rotor mass may comprise any number of dwellings, for example between 4 and 96 dwellings, better still between 8 and 40 dwellings, or even between 16 and 32 dwellings.

Magnets can be buried in the rotor mass. In other words, the magnets are covered by the layers of magnetic sheets at the gap. The surface of the rotor at the air gap can be entirely defined by the edge of the magnetic sheet layers and not by the magnets. The housing does not open then radially outward.

The rotor mass may comprise one or more holes to lighten the rotor, to allow its balancing or for the assembly of the rotor plates constituting it. Holes may allow the passage of tie rods now integral with the sheets.

The sheet layers can be snapped onto each other. The housings can be filled at least partially with a non-magnetic synthetic material. This material can lock in place the magnets in the housing and / or increase the cohesion of the sheet package.

The rotor mass may comprise, where appropriate, one or more reliefs contributing to the proper positioning of the magnets, especially in the radial direction.

The rotor mass may have an outer contour which is circular or multilobed, a multi-lobed shape may be useful for example to reduce torque ripples or harmonics of current or voltage.

The rotor can receive an outer ring, which surrounds the package of sheets. This can reduce the width of the material bridge connecting two consecutive sectors.

The rotor can be cantilevered or not.

The rotor can be made of several rotor pieces aligned in the axial direction, for example three pieces. Each piece can be angularly shifted relative to other adjacent pieces ("step skew" in English).

The invention further relates to a rotating electrical machine, such as a synchronous motor or a synchronous generator, comprising a rotor as defined above. The rotor can be inside or outside.

The use of an outer rotor can prevent possible saturation between consecutive magnets of the same polarity, which could occur with an inner rotor. It can thus have a magnetic induction in the larger gap. On the other hand, in an outer rotor configuration, there is more room to arrange the magnets, which makes it easier to increase the flux concentration factor in the gap.

This machine may comprise a stator with concentrated or distributed winding.

The rotor can have as many main poles as the stator.

The invention will be better understood on reading the following detailed description, nonlimiting exemplary embodiments thereof, and on examining the appended drawing, in which:

FIG. 1 is a schematic and partial cross-sectional view of a machine comprising a rotor produced in accordance with the invention;

FIG. 2 represents a detail of embodiment of FIG. 1, and - Figures 3 to 11 and 5a are views similar to Figure 2, illustrating alternative embodiments.

FIG. 1 illustrates a rotary electrical machine 10 comprising a rotor 1 and a stator 2.

The stator 2 comprises for example a concentrated or distributed winding. This stator makes it possible to generate a rotating magnetic field driving the rotor in rotation, in the context of a synchronous motor, and in the case of an alternator, the rotation of the rotor induces an electromotive force in the stator windings.

The rotor 1 shown in FIGS. 1 and 2 comprises a rotor magnetic mass 3 extending axially along the axis of rotation X of the rotor, this rotor mass being for example formed by a stack of magnetic sheets 4 stacked along the X axis, the sheets being for example identical and superimposed exactly. They can be held together by clipping, rivets, tie rods, welds or any other technique. Alternatively, the rotor mass may comprise at least one magnetic sheet wound on itself. The magnetic sheets are preferably magnetic steel. All grades of magnetic steel can be used.

The rotor mass 3 comprises a central opening 5 for mounting on a shaft 6. The shaft 6 may, in the example considered, be made of a non-magnetic material, for example non-magnetic stainless steel or aluminum.

The rotor 1 comprises a plurality of permanent magnets 7 arranged in corresponding housings 8 of the rotor magnetic mass 3. The permanent magnets 7 are arranged in V oriented towards the gap. Each V defines an elementary polar part 9, two consecutive polar elementary parts 9 having an identical polarity. These two polar elementary parts 9 define in the example in question a magnetic pole of the rotor. Two consecutive magnets 7 of the same magnetic pole and the same elementary polar part have the same polarities on their facing faces.

The two branches of the V form in the example described an angle γ between 10 ° and 90 °. In addition, the V may extend over a radial height L of between 5 and 25 cm. The height L can be 30% to 80% of the radius of the rotor, measured between the axis of rotation and the gap. As a variant, three consecutive polar elementary parts may have an identical polarity, as illustrated in FIG. 4, or even four consecutive polar elementary parts, as illustrated in FIG. 5, or even five consecutive polar elementary parts, as illustrated in FIG. In each of these figures, there is illustrated a main magnetic pole of a rotor according to the invention.

FIG. 4 also illustrates the drawing of the magnetic field lines of a pole of the rotor, and in FIG. 5 an example of the choice of the orientation of the magnetization of the magnets for a main magnetic pole. of the rotor.

In the example illustrated, the permanent magnets 7 are generally rectangular in cross section, but it is not beyond the scope of the present invention if they are of a different shape, for example trapezoidal, as illustrated in FIG. In this figure, it is seen that the width / of a magnet taken in cross section perpendicular to the axis of rotation tapers when one is heading towards the air gap.

The magnets may be made of ferrite or alternatively of rare earths, for example of neodymium or other type. Preferably, the magnets are made of ferrite.

In the illustrated examples, two consecutive magnets of two consecutive polar elementary parts of identical polarities also form a V oriented towards the axis of rotation.

In addition, in the exemplary embodiments illustrated in FIGS. 4 to 6, two consecutive magnets of two consecutive polar elementary portions of opposite polarities also form a V oriented towards the axis of rotation.

It may of course be otherwise, and in the embodiment illustrated in Figure 1, two consecutive magnets of two consecutive polar elementary portions of opposite polarities extend substantially parallel to each other. Such an arrangement of the magnets makes it possible to optimize the circulation of the flux in the rotor mass.

The thickness e of the rotor mass between two consecutive magnets of two consecutive V of opposite polarities is between 1.5 and 5 mm, in the example described.

In a variant embodiment illustrated in FIG. 3, the same magnet participates in two Vs of two poles of opposite polarities at a time. In the example described, the magnet is twice as wide in cross-section as a magnet participating in only one V. In the examples illustrated in Figures 4 to 6, the end 8a of the housing 8 closest to the axis of rotation is triangular in cross section perpendicular to the axis of rotation.

In the example illustrated in FIGS. 2, the housings defining each of the branches of the same V communicate by their end 8a closest to the axis of rotation.

As a further variant or additionally, the two ends 8a and 8b of each housing 8 are of triangular shape, as illustrated in FIG.

The end 8b of the housing 8 may alternatively further comprise a curved edge, for example in an arc-in-circle, as shown in Figure 5a.

In the examples just described, a V is formed by two consecutive permanent magnets when moving circumferentially. Of course, it is not beyond the scope of the present invention if it is otherwise, and if for example a V is formed by more than two permanent magnets when moving circumferentially. Each branch of a V may for example be provided by several permanent magnets, including two or even three or four. In an exemplary embodiment, a V may be formed in particular by four permanent magnets, two magnets forming for example each leg of the V, as illustrated by way of example in FIG. 7. The magnets forming a branch of a V may be extend each along an axis, the two axes making an angle a between them. This angle may be between 0 ° and 90 °.

Alternatively, a branch of a V may be formed with a single magnet having two rectilinear portions inclined relative to each other by an angle a, as shown in FIG. 9.

In another variant, the magnets may be curvilinear, as illustrated in FIG.

A synthetic material can be injected into the housings 8, so as to block the magnets in the housing 8 and / or ensure the cohesion of the sheet package. The material used is for example an epoxy resin or a thermoplastic material. The locking of the magnets 7 can also be effected by clamping under the action of the centrifugal force.

In all the examples which have just been described, the rotor is internal, but it is not beyond the scope of the present invention if the rotor is outside. For exemple, FIG. 11 illustrates a machine 10 comprising an inner stator 2 and an outer rotor 1.

Of course, the invention is not limited to the embodiments which have just been described.

For example, the sheets can be made with holes to allow the passage of connecting rods of the laminations of the rotor mass.

The phrase "with one" should be understood as being synonymous with "having at least one".

Claims

Rotating flow rate electric machine rotor (1), comprising:

a rotor mass (3) comprising housings (8), and

permanent magnets (7) arranged in the housings (8) of the rotor mass (3), the permanent magnets being arranged in V oriented towards the air gap, each

V being formed by more than two permanent magnets (7) and defining an elementary polar part (9), at least two consecutive polar elementary parts (9) having an identical polarity.

Rotating flow electric machine rotor (1), comprising:

a rotor mass (3) comprising housings (8), and

V defining an elementary polar part (9), at least two consecutive polar elementary parts (9) having an identical polarity, the width (e) of a magnet taken in cross section perpendicular to the axis of rotation thinner when the we are heading towards the air gap.

Rotor (1) of a flow-rate rotating electrical machine, comprising:

a rotor mass (3) comprising housings (8), and

permanent magnets (7) arranged in the housings (8) of the rotor mass (3), the permanent magnets being arranged in V oriented towards the gap, each V defining an elementary polar part (9), at least two parts elementary pole poles (9) having the same polarity, the permanent magnets being curvilinear in cross section.

Rotating flow electric machine rotor (1), comprising:

a rotor mass (3) comprising housings (8), and

permanent magnets (7) arranged in the housings (8) of the rotor mass (3), the permanent magnets being arranged in V oriented towards the air gap, each V defining an elementary polar part (9), at least two consecutive polar elementary parts (9) having an identical polarity,

the rotor being outside the machine.

5. Rotor according to any one of claims 2 to 4, wherein a V is formed by two permanent magnets (7) consecutive when moving circumferentially.

6. Rotor according to any one of the preceding claims, wherein a V is formed by four permanent magnets, two magnets forming each branch of V.

7. Rotor according to any one of the preceding claims, at least three consecutive polar elementary parts (9) having an identical polarity, or even at least four consecutive polar elementary parts, or even five consecutive polar elementary parts.

8. Rotor according to any one of the preceding claims, wherein the permanent magnets (7) are rectangular in cross section.

A rotor according to any one of claims 1 to 7 except claim 2, wherein the width (e) of a magnet taken in cross section perpendicular to the axis of rotation tapers when we go towards the air gap.

10. Rotor according to any one of claims 1 to 7 with the exception of claim 3, wherein the permanent magnets are in curvilinear cross section.

1. A rotor according to any one of the preceding claims, wherein the consecutive magnets (7) of two consecutive polar elementary parts (9) of identical polarities form a V oriented towards the axis of rotation.

12. Rotor according to any one of the preceding claims, wherein the consecutive magnets (7) of two polar elementary portions (9) consecutive opposite polarities form a V oriented towards the axis of rotation.

13. Rotor according to any one of the preceding claims, wherein the consecutive magnets (7) of two consecutive polar elementary parts (9) of opposite polarities extend substantially parallel to each other.

14. Rotor according to the preceding claim, wherein the thickness (e) of the rotor mass (3) between the consecutive magnets (7) of two consecutive V of opposite polarity is less than 5 mm, better still less than 1.5 mm .

15. Rotor according to any one of the preceding claims, wherein at least one housing (8) extends radially over a length greater than the radial length of the corresponding magnet, in cross section.

16. Rotor according to any one of the preceding claims, wherein at least one end (8a, 8b) of the housing (8) in cross section perpendicular to the axis of rotation is triangular or curved, better the two ends ( 8a, 8b) are of triangular or curved shape.

17. Rotor according to any one of the preceding claims, wherein the permanent magnets form a number of V between 8 and 24, better between 12 and 20, in particular 16.

18. Rotor according to any one of the preceding claims, having a number of poles less than or equal to 8, see less than or equal to 6.

19. Rotor according to any one of the preceding claims, wherein the permanent magnets are made at least partially of ferrite.

20. Rotor according to any one of the preceding claims, comprising a plurality of rotor pieces aligned in the axial direction and angularly offset relative to each other.

21. A rotating electric machine comprising a rotor according to any one of the preceding claims.

22. Rotating electric machine comprising a rotor according to any one of the preceding claims with the exception of claim 4, the rotor being external.