WO2019025349A1

WO2019025349A1 - Injected-cage rotor

Info

Publication number: WO2019025349A1
Application number: PCT/EP2018/070562
Authority: WO
Inventors: Sébastien Porcher; Nicolas NAY; Dany Prieto; François TURCAT
Original assignee: Moteurs Leroy-Somer
Priority date: 2017-07-31
Filing date: 2018-07-30
Publication date: 2019-02-07
Also published as: FR3069731B1; FR3069731A1

Abstract

Rotor of a rotary electric machine, comprising a bundle (2) of magnetic laminations (113), the magnetic laminations (113) comprising openings (3) forming slots (4) within the bundle (2), the bundle (2) comprising at least one keeper lamination (110) at one of its axial ends, bars (10) of a first electrically conducting material housed in at least part of the slots (4), these bars (10) coming to bear at one axial end against the said keeper lamination (110), with a second electrically conducting material (20) being injected into the slots (4).

Description

CAGE ROTOR INJECTED

The present invention relates to rotating electrical machines and more particularly the rotors of such machines.

Background

Asynchronous electric motors conventionally comprise a packet of magnetic sheets traversed by notches. Aluminum is injected under pressure to form bars which are connected to the outside of the sheet bundle by short-circuit rings.

To improve the electrical performance, it may be advantageous to further reduce the electrical resistivity of the bars by replacing the aluminum with copper. However, the melting temperature of copper being much higher than that of aluminum, it becomes difficult to inject copper into the notches.

A known solution is thus to introduce copper conductor bars into the notches and to inject aluminum under pressure to fill the space left free inside the notches by the bars.

Applications WO2011015494, WO2010100007, WO2009038678, US2011291516, WO2014067792, WO2011020788, WO2015071156, WO2012041943, JPH10234166, CN1925280, JPH11206080, JP2005278373, JPH1028360 disclose rotors whose laminations have notches receiving copper bars and in which aluminum is injected under pressure.

EP 2 728 718 discloses a rotor comprising conductive bars arranged in notches and aluminum injected into the notches. The sheets may comprise bearing units supporting the bars in the notches.

DE 10 2010 041796 discloses bundles of sheets having notches with a slope.

JP 2007/295756 discloses a rotor having conductive bars received in notches formed within a package of sheets. Expansion tools are used to push the bars against the radially outer surfaces of the notches.

WO2015 / 001601 discloses notches having, at shoulders, curved shapes convex to the radially inner direction, receiving copper bars and filled with aluminum around the bars. summary

A problem that arises during the injection of aluminum is the maintenance of the bars in the corresponding notches. This maintenance must not interfere with the realization of the rear short ring.

The invention responds to this need with a rotor of a rotating electrical machine, comprising:

a bundle of magnetic sheets, the magnetic sheets having perforations forming notches within the bundle, the bundle comprising at least one guard plate at one of its axial ends,

bars of a first electrically conductive material received in at least one part of the notches, these bars axially bearing at one end against said guard plate,

a second electrically conductive material injected into the notches. The presence of the guard plate (s) makes it possible to hold at least one end of these bars by pressing against the guard plate (s).

The guard plate or sheets are made with openings that allow the injection through them of the aluminum in the sheet package. Thus, the presence of the guard plates does not hinder beyond measure the injection of the second material, while ensuring an effective maintenance of the bars introduced into the notches until the injection operation.

The package of sheets may comprise at each of its axial ends a guard plate and the bars then bear at their axial ends against these guard plates.

The guard plate or plates may include openings allowing the injection of the second material into the notches and at least one relief superimposed at least partially on the bars to retain them axially.

This relief can be realized in various ways.

The guard plate (s) may comprise, in embodiments, two advances facing one notch receiving a bar. In alternative embodiments, the guard plate or plates comprise a notch material bridge receiving a bar.

The guard plate (s) may have the same thickness as the magnetic sheets or be thicker than the latter. The guard plate (s) may be in the same material or in a material different from that of the magnetic sheets.

The first material is preferably copper and the second material is preferably aluminum.

According to another of its aspects, the invention relates to a rotating electrical machine, comprising a rotor according to the invention, as defined above.

Description of figures

The invention will be better understood on reading the detailed description which follows, examples of non-limiting implementation thereof, and on examining the appended drawing, in which:

FIG. 1 schematically represents, in axial section, a rotor according to the invention,

FIGS. 2 to 7 show alternative embodiments of the guard plates and the rotor cage, and

- Figures 8A to 8D show alternative embodiments of the notches.

Rotor

FIG. 1 shows a rotor 1 according to the invention. This rotor 1 comprises a bundle of magnetic sheets 2, mounted on a shaft 9, for example made of steel, of axis X.

Package 2 is formed by the superposition of magnetic sheets 113 in which perforations 3 are cut.

The superposition of the openings 3 of the plates 113 forms, within the pack 2, notches 4 which extend longitudinally from one axial end of the pack 2 to the other. The notches 4 may be straight, that is to say that all the plates 113 are exactly superimposed without angular offset from one sheet 1 13 to the next. However, preferably, the plates 113 are superimposed by being angularly offset slightly from one sheet to the next so that the longitudinal axes of the notches 4 follow a helical path about the axis of rotation of the rotor, in a manner known in the art. itself.

In the example shown, all the plates 113 are identical and the openings 3 are also, so that the package 2 has identical notches 4. In variants, the package 2 is formed by assembling plates 113 which are not strictly identical in front view, of the front of the package 2, so that the section of a notch 4 may have a shape that varies when moving from the front end of the notch 4 at the rear end. In particular, the plates 113 may be identical when they are cut, but be assembled by turning some sheets relative to others, so that they generate an evolution of the section of the notch 4 when one moves along the axis of rotation.

The rotor 1 comprises bars 10 made of copper, introduced into the notches 4, and a material 20, such as aluminum, injected into the notches 4 in the space left free by the bars 10.

Short-circuit rings 120 and 130 are molded from aluminum at the ends of the pack of sheets 2. These rings 120 and 130 are in one piece with the aluminum cast in the notches 4.

Guard plates

Guard plates 110 are arranged at each end of the sheet 2 package. These guard plates 110 are configured to allow, on the one hand, the injection of aluminum into the notches 4 and, on the other hand, to retain the bars 10 axially. in the notches 4, the bars 10 bearing axially at their ends on the guard plates 110.

The guard plates 110 comprise openings 220 which allow injection through the guard plate 110 of the second material 20 into the pack 2 of sheets 113. Thus, the presence of the guard plates 110 does not hinder the injection too much. of the second material 20, while contributing to the effective maintenance of the bars introduced into the notches until the injection operation.

The guard plate or sheets 110 may comprise at least one retaining relief 221 superimposed at least partially on the bars 10 to retain them axially. This support relief 221 can be made in various ways.

In the example of FIG. 2, each guard plate 110 comprises perforations 220 that have the same shape as those 3 of the sheets of the pack 2, with the exception of two opposite projections 221a, which protrude on the long sides openings 3 and which are superimposed on the bars 10 introduced into the notches 4.

In the variant of Figure 3, each guard plate 110 has a material bridge 221b at the openings 220 which covers at least partially the copper rods 10. These openings 220 leave access to the notches 4 underlying the package 2, for the injection of the second material 20, namely aluminum in the example under consideration. The material bridge 221b can be located substantially at the interface between the aluminum and the copper, as illustrated in FIG. 3. As a variant, the material bridges 221b are offset radially inwards so as to be superposed exclusively on the copper bars, as shown in fig 4.

Notches without bars

In the variant illustrated in FIG. 5, the bars 10 are present in only part of the notches 4.

The absence of bars 10 in certain notches 4 keeps a larger total section for the passage of the injected aluminum, and thus facilitate the filling of the rear ring when the injection is done from the front.

The presence of bars of less electrical resistance material, such as copper, in some notches improves electrical performance. It is possible, by choosing the number of bars added, to optimize the increase of performances with regard to the cost of the machine, the copper being more expensive than the aluminum.

The rotor may have more notches 4 with bars 10 than slots without bar. In other variants, it is the opposite and the rotor has more notches without bar with bar.

Multiple arrangements of the bars 10 within the notches 4 are possible. For example, can be alternated in the circumferential direction a notch 4 without bar and a notch 4 with bar. It is also possible to alternate more generally no notches without bar with n ₂ notches with bar, ni and n ₂ being integers strictly greater than 1.

Hollow bars

In the variant of FIG. 5, the bars 10 are hollow and have a longitudinal internal cavity 17 which is filled by the second material 20.

The fact that the bars 10 are hollow further improves the filling of the cavity for molding the rear shorting ring, when the injection takes place from the front.

In addition, the total amount of copper used may be less, which reduces the cost of the machine.

The second material that is injected into the bars is protected from contact with the oxygen of the air by the material of the bars, except at the axial ends of the bars. them. In this way, the corrosion phenomena at the interface between the first and second materials are limited.

The bars 10 preferably have, in cross section, a closed contour, which may be non-circular.

Preferably, the second material 20 fills the notches also outside the bars, especially when the bars 10 do not occupy the entire section of the notches.

The bars 10, hollow or not, may extend over the entire radial dimension of the notches. In particular, the bars may have a cross section that is substantially the same shape as the notches.

Alternatively, the bars 10, hollow or not, have a radial dimension which is less than that of the notches.

All the notches in the rotor may have hollow bars with the second material injected therein. Alternatively, some notches may not have a bar, being in this case fully filled by the second conductive material. The rotor comprises for example more notches with bars than slots without bar, or vice versa.

Secondary notches

As illustrated in FIGS. 6 and 7, the openings can form, within the package, n main notches 4 as defined above and m secondary notches 40, radially inner with respect to the main notches, with n and m being non-zero integers and n> m.

Thanks to the secondary notches 40 of a larger passage section for the second conductive material, during the injection. The latter being injected from the front, the fact of having a larger passage section ensures faultless realization of the rear short ring.

The secondary notches 40 are disjoint from the main notches 4 in the example of FIG. 6.

In the variant illustrated in FIG. 7, each secondary notch 40 communicates with a main notch 4.

Each secondary notch 40 may be centered on a median plane of a main notch 4. The ratio ni m between the number of main notches 4 and the number of secondary notches 40 is for example equal to 2 or 3.

The secondary notches 40 preferably have an angular extent, measured around the center of the sheet bundle, greater than that of a main notch 4.

Notches with frictional reliefs

Some notches may have friction reliefs 5 arranged to frictionally retain the bars 10.

As illustrated in FIGS. 8A to 8D, at least part of the openings may present on at least part of their periphery frictional reliefs 5, the electrically conductive bars 10 received in the notches 4 bearing by at least one main face 11 against said reliefs.

These reliefs 5 can effectively maintain the bars 10 inside the sheet package. The reliefs 5 can be made very precisely during the cutting of the sheets, and allow a greater tolerance of bar manufacture.

In particular, when a material is injected into the notches 4 around the bars 10, the latter can remain motionless within the package. The reliefs 5 can also reduce the force to be exerted on the bars to insert them into the sheet package, reducing the contact area between the bars and the sheets.

The reliefs 5 can, by decreasing the contact area between the bars 10 and the plates, reduce the inter-bar currents flowing in the sheets and the corresponding energy loss by Joule effect.

The reliefs 5 are preferably present on opposite long sides 4a of the notches 4 which are oriented substantially radially. The conductive bars 10 bear against these reliefs 5 by two opposite main faces 11.

The reliefs may be in the form of bosses, distributed preferably over substantially the entire radial dimension of a bar 10.

The bosses 5 may have an amplitude h of between 0.2 and 0.4 mm, for example 0.3 mm, and have for example a radius of curvature R at their apex between 0.4 and 0.6 mm, for example 0.5mm, as shown in Figure 8A.

All the sheets of the packet can be identical or not. Notches with blocking reliefs

At least one sheet of the package may have at least one blocking relief 30 bearing against a radially outer end face 14 of a corresponding bar 10, the two opposite reliefs being each bearing against the same end face as shown in FIGS. 8A and 8C.

At least one sheet of the package may also have at least one blocking relief 31 bearing against a radially inner end face 13 of a corresponding bar, as illustrated in FIG. 8D. This locking relief 31 is preferably centered on the median plane of symmetry of the corresponding aperture.

Notches with separation reliefs

As illustrated in FIGS. 8B and 8D, separation reliefs 15 or 15a may extend within the openings and separate the notches 4 into first 6 and second 8 distinct compartments, the first compartments 6 being radially internal with respect to the second compartments. 8.

The conductive bars 10 of the first material can be arranged in the first or second compartments of at least a portion of the notches 4. The second electrically conductive material 20, different from the first, can then be arranged in the other compartments of these notches 4. The separation reliefs 15 or 15a which extend within the openings prevent the first and second materials from coming into contact. Thus, the potential phenomena of corrosion are eliminated.

The separation reliefs 15 or 15a may be of different shapes, being made by cutting with the material of the magnetic sheets.

In the example of FIG. 8B, the separation reliefs are material bridges 15 which separate each notch 4 into first and second non-communicating compartments 6 and 8.

In the variant of Figure 8D, the separation reliefs consist of advances 15a arranged opposite one another and which form between them a channel 16 sufficiently narrow to prevent contact between the first and second materials. For example, when the first compartments 6 are filled by molten aluminum injection, channels 6 having a width less than 0.6 mm and a height H less than 2 mm may be sufficient to prevent the aluminum enter the second compartments through the channels 6. The conductive bars 10 of the first material can be inserted into the first compartments 6, the first material being preferably copper, the second material 20 being injected into the second compartments 8, this second material preferably being aluminum. Such an embodiment is particularly suitable for a machine intended to be driven with a fixed frequency current. Indeed, when the motor is connected to the network, starting the motor requires a high current relative to the nominal point. As the ratio between the starting current and the nominal current is limited by the standards in force, the aim is to reduce it. At startup, the part of the notch that generates the electrical resistance is mostly the top of the notch, near the gap because of the skin effect. In order to limit this starting current, the resistance of the cage must increase. Thus, having the material of higher electrical resistivity closer to the air gap reduces the starting current.

In an alternative embodiment, the conductive bars 10 of the first material are inserted into the second compartments 8, this first material preferably being copper, the second material being injected into the first compartments 6, this second material preferably being aluminum. Such an embodiment is more particularly suitable for a motor connected to a drive, for a variable speed drive. In this case, the starting current is not a constraint. Positioning the material of lower electrical resistivity in the compartment closer to the air gap and optionally introducing an opening, especially in the form of a slot, on the side of the air gap which is devoid of electrically conductive material, allows to reduce the electrical losses. In addition, the presence of a bar in the upper part of the notch prevents the second material from flowing through the possible opening of the notch side of the air gap during injection.

Blocking elements

The machine may have pins or rivets 70 inserted into the notches in contact with the bars.

As illustrated in FIGS. 8A and 8C, these pins or rivets 70 are arranged in the bottom of the notches 4, to bear against the radially inner end face 13 of the bars 10.

The pins or rivets 70 may be conical. Rotor manufacturing

To manufacture the rotor, it is possible to cut the sheets 113 with a press equipped with a punch or with the laser and to form, during the cutting, perforations 3 corresponding to the main notches and, if necessary, to the secondary notches 40, and the bosses 5.

Then, the plates 113 are superimposed to form the package 2, then the bars 10 are inserted into the notches 4 by force. During insertion, the presence of the bosses 5 facilitates the advancement of the bars 10 within the pack 2 of sheets 13 and, if necessary, pins or rivets 70 are inserted into the bottom of the notches 4 to block the bars 10 before the injection. Once the bars 10 are put in place, it is possible to proceed in an injection press of the second material 20, namely aluminum. During the injection, the rings of short circuit are produced by molding.

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

For example, the notches may have other shapes, as well as the bars.

Other materials than copper and aluminum can be used.

Claims

Rotary electric machine rotor, comprising:

- a package (2) of magnetic sheets (113), the magnetic sheets (113) having openings (3) forming notches (4) within the package, the package comprising at least one guard plate (110) to the one of its axial ends,

- bars (10) of a first electrically conductive material received in at least a portion of the notches (4), these bars (10) bearing at one axial end against said guard plate (110),

a second electrically conductive material (20) injected into the notches (4).

2. Rotor according to claim 1, the package (2) having at each of its axial ends a guard plate (110) and the bars (10) bearing at their axial ends against said guard plates (110).

3. Rotor according to claim 1 or 2, the one or more guard plates (110) having openings (220) for injecting the second material (20) into the notches (4) and at least one relief (221a, 222b). ) superimposed at least partially on the bars to retain them axially.

4. Rotor according to claim 3, the one or more guard plates (110) having two advances (221a) facing each notch receiving a bar (10).

5. Rotor according to claim 3, the guard plate or plates having a bridge of material (222b) per notch receiving a bar.

6. Rotor according to any one of the preceding claims, the first material being copper.

7. Rotor according to any one of the preceding claims, the second material (20) being aluminum.

8. Rotating electric machine, comprising a rotor according to any one of the preceding claims.