WO2019025353A1

WO2019025353A1 - Squirrel-cage rotor

Info

Publication number: WO2019025353A1
Application number: PCT/EP2018/070568
Authority: WO
Inventors: Sébastien Porcher; Thierry VISSE; Stéphane BOULIN; 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: FR3069732A1; FR3069732B1

Abstract

The invention relates to the rotor of a rotating electrical machine, comprising: a stack (2) of magnetic laminations (113) defining slots (4); bars (10) of a first electrically conductive material, received in the slots (4); a second electrically conductive material (20), different from the first, injected into the slots (4); and pins (70) or rivets inserted into the slots (4) in contact with the bars (10).

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 having conductive bars arranged in notches. The rotor may comprise a deformable support device in the form of an aluminum wire extending from one end of the slots to the other.

DE 3043800 discloses a rotor having first bars of trapezoidal section and second bars of rectangular section disposed in the notches. An elastic member, for example in the form of a spring in the illustrated embodiments, can be inserted between the bottom of a notch and the second bar.

CN 201215905 discloses busbars received in notches formed within a bundle of sheets. The notches include a housing for receiving an elastic pin for clamping the bars.

JPH 1028360 discloses a rotor having aluminum coated copper bars received in the notches and aluminum injected into these notches.

summary One of the difficulties that arise during the injection of aluminum is the maintenance of the copper bars during the injection and / or before it.

The invention aims to remedy this difficulty and relates to an electric rotating machine rotor comprising:

a package of magnetic sheets defining notches,

bars of a first electrically conductive material received in the notches,

a second electrically conductive material, different from the first, injected into the notches,

pins or rivets inserted into the notches in contact with the bars.

The pins or rivets are preferably inserted between the bottom of the slots and the bars.

The pins or rivets hold the bars in place during the handling of the sheet bundle before the injection, and during the injection if necessary.

At least one shorting ring may be overmoulded on the pins or rivets, when the latter protrude from the sheet package. Thus, the pins or rivets remain completely integrated into the rotor after its manufacture.

The pins preferably have a conical shape to facilitate insertion of these into the notches. They can be striated or notched, if necessary, to improve their anchoring within the sheet package.

The package of sheets preferably has a thickness greater than the length of a pin or rivet. Thus, the pins or rivets only extend over a portion of the length of the package. The second material is preferably injected into the space behind the pins.

The rotor may have pins or rivets at only one end of the rotor.

Alternatively, the rotor has pins or rivets at each end of the rotor.

The pins can be solid, hollow and / or split.

When the pins are full, the interior space of the notches located behind the pins may not be filled by the second injected material. The pins are advantageously made to withstand the temperature during the injection of the second material. For example, the material of the pin may be aluminum, steel, stainless steel, or copper annealing.

The rivets are deformable to cause, by plastic deformation and / or elastic, the wedging bars in the notches. This solution is advantageous for large sheet metal.

Preferably, the magnetic sheets comprise a magnetic steel, for example iron / silicon, with its different shades. The thickness of each sheet is for example between 0.35mm and 0.65mm.

The subject of the invention is also a process for manufacturing a rotor as defined above, comprising the steps of:

- manufacture by punching or laser rotor laminations,

- forming the package of rotor plates by superimposing the magnetic sheets,

- insert bars of the first material into the notches of the sheet package,

- insert the pins or rivets in the notches to block the bars,

- inject the second material into the notches.

Description of figures

Other features and advantages of the present invention will emerge on reading the following detailed description, non-limiting examples of implementation thereof, and on examining the appended drawing, in which:

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

FIGS. 2A to 2D illustrate embodiments of notches,

FIGS. 3 to 5 represent alternative embodiments of rotor cages according to the invention,

FIG. 6 schematically represents, in axial section, a variant embodiment of the rotor according to the invention, and

FIGS. 7A to 7D illustrate alternative embodiments of pins or rivets.

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 sheets 113 are exactly superimposed without angular offset from one sheet 113 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 to 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.

Blocking elements

The machine comprises locking elements for example, as illustrated, in the form of pins 70 inserted in the notches in contact with the bars 10.

As illustrated in Figure 1, these pins 70 are preferably arranged in the bottom of the notches 4, to bear against the radially inner end face 13 of the bars 10. As illustrated, these pins preferably extend only on a part of the length of the package. The pins 70 may be conically shaped as illustrated.

In the example of Figure 1, the pins are hollow, which allows the injection of the second material 20 in the space 44 of the notches located behind the pins 70. Alternatively, these pins are solid, as shown in FIG. 7A.

When the pins are full, the second material can still be injected into the spaces behind the pins. For example as illustrated in Figures 2A to 2D, the shapes of the notches, and / or bars allow the injection of the second material behind the pins.

In the variants illustrated in FIGS. 7A to 7C, the pins have a generally cylindrical shape, with an end chamfer.

The dies may have a diameter D which decreases by approaching their end, as shown in Figures 7 A and 7B, to facilitate their introduction. The pins may be slit, as shown in Figures 7B and 7C.

In the variant of FIG. 7D, the locking elements are in the form of expandable rivets such as POP rivets.

Notches with frictional reliefs

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

As illustrated in FIGS. 2A to 2D, at least part of the openings may present on at least a portion of their periphery frictional reliefs 5, the electrically conductive bars 10 received in the notches 4 abutting by at least one main face 11 against said reliefs.

These reliefs 5 can help to effectively hold 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.

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, preferably extending 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 2A.

All the sheets of the packet can be identical or not.

Blocking reliefs

At least one sheet of the package may have at least one blocking relief 30 bearing against a radially outer end face of a corresponding bar, better two such opposing reliefs each bearing against the same end face, as represented in FIGS. 2A and 2D.

Notches with separation reliefs

As illustrated in FIGS. 2B and 2C, separation reliefs 15 or 15a can 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 may be arranged in the first or second compartments of at least a portion of the notches 4. The second electrically conductive material 20 may then be arranged in the other compartments of these notches 4. The separation reliefs 15 or 15a extending 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, 15a may be of different shapes, being made by cutting with the material of the magnetic sheets.

In the examples of FIGS. 7 and 8C, 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 2B, the separation reliefs are constituted by advances 15a disposed 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 w less than 0.6 mm and a height H less than 2 mm may be sufficient to prevent the aluminum 20 from entering the second compartments through the channels 6.

In the variant of FIG. 2C, the conductive bars 10 of the first material are inserted in the first compartments 6, the first material preferably being copper, the second material 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 in the eventual opening of the slot on the gap side during the injection.

Hollow bars

In the variants of FIGS. 2B and 2C, 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 thereof. 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.

The bars, hollow or not, can extend over at least the length of the package of sheets.

All the notches 4 of the rotor may have hollow bars 10 with the second material 20 injected therein. Alternatively, some notches 4 may not have a bar 10, being in this case completely filled by the second material 20. The rotor comprises for example more notches 4 with bars 10 than notches 4 without bar, or vice versa 10.

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 10 in a material of lesser electrical resistance 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 comprise more notches 4 with bars 10 than slots 4 without bar 10. In other variants, it is the opposite and the rotor has more notches without bar than bar.

Multiple arrangements of the bars 10 within the notches 4 are possible. For example, a notch barless and a bar notch may be alternated circumferentially. It is also possible to alternate more generally no notches without bar with n2 notches with bar, ni and n2 being integers strictly greater than 1.

Secondary notches

As illustrated in FIGS. 3 and 4, 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.

Bars 10 of the first electrically conductive material, preferably copper, are disposed in at least a portion of the main slots 4 and a second electrically conductive material 20, different from the first, preferably aluminum, is injected into the secondary slots 40.

Thanks to the secondary notches 40 of a larger passage section for the second conductive material 20, 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.

In the variant illustrated in FIG. 4, 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 n / 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.

Guard plates

The package 2 may comprise, as shown in FIG. 6, at least one guard plate 110 at at least one of its axial ends, preferably at each of the ends. Axial. Bars 10, better all the bars, bear against one axial end against this guard plate 110.

The presence of the guard plate (s) 110 makes it possible to hold the bars 10 at least at one end by pressing against the guard plate (s) 110.

At least one guard plate 110, and preferably each guard plate, is made with 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 guard plates 110 do not greatly interfere with the injection 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.

The or each support relief 221 may be formed by two facing advances, notch receiving a bar 10. These advances are superimposed on the bars. In alternative embodiments, the or each retaining relief 221 comprises a notch material bridge receiving a bar 10.

The pins 70 are full in this example.

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 notches 4 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 the insertion, the presence of the bosses 5 facilitates the advancement of the bars 10 within the pack 2 of plates 1. Then, the 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

I. Rotating electric machine rotor, comprising:

a package (2) of magnetic sheets (113) defining notches,

bars (10) of a first electrically conductive material received in the notches,

a second material (20) electrically conductive, different from the first, injected into the notches,

- pins (70) or rivets inserted in the notches in contact with the bars

(10).

2. Rotor according to claim 1, the pins or rivets (70) being inserted between the bottom of the slots and the bars.

3. Rotor according to claim 1 or 2, at least one short-circuit ring (120, 130) being overmolded on the pins or rivets.

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

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

6. Rotor according to any one of the preceding claims, comprising pins or rivets (70) at only one end of the rotor.

7. Rotor according to any one of claims 1 to 5, having pins or rivets (70) at each end of the rotor.

8. Rotor according to any one of the preceding claims, the pins (70) being full.

9. Rotor according to any one of claims 1 to 7, the pins (70) being hollow.

10. Rotor according to any one of claims 1 to 7, the pins (70) being slit.

I. The rotor according to any one of claims 1 to 7, the pins (70) having a diameter (D) which decreases when approaching their end.

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

A method of manufacturing a rotor according to any one of claims 1 to 11, comprising the steps of: manufacturing by punching or lasering magnetic laminations (113) of the rotor, forming the rotor laminations by superimposing the laminations, inserting bars (10) of the first material into the notches of the bundle inserting the pins or rivets (70 ) in the notches (4) to block the bars injecting the second material (20) into the notches (4).