Rotor of an asynchronous machine

Abstract

A rotor of an asynchronous machine with a cage rotor includes a laminated core formed from a plurality of partial laminated cores. The laminated core has substantially axially extending conductors arranged in slots in the laminated core. The conductors include at least two materials of different electrical conductivities, such that a material with a higher electrical conductivity surrounds a material with a lower electrical conductivity by at least 65% in a circumferential direction.

Claims

1. A method for producing a rotor of an asynchronous machine with a cage rotor, said method comprising: punching and stacking laminations to form a laminated core composed of a plurality of partial laminated cores having slots and spaced-apart from one another by a predetermined spacing; axially aligning the slots of the partial laminated cores; inserting a hollow pipe of a first electrical conductivity in the aligned slots of the partial laminated cores along a length of the laminated core in an axial direction; filling the hollow pipe by high-pressure die-casting with a material of a second electrical conductivity which is less than the first electrical conductivity and simultaneously expanding the hollow pipe due to the high pressure along its entire length perpendicular to the axial direction to establish a positive contact between an outer wall of the hollow pipe and a side wall of the slots, and simultaneously during the high-pressure die-casting forming end rings on an end face of the laminated core, with at least 65% of the material of the second electrical conductivity being surrounded by a material of the first electrical conductivity in a circumferential direction.

2. The method of claim 1, wherein the hollow pipe is made of copper.

3. The method of claim 1, wherein the material filling the hollow pipe is aluminum.

4. The method of claim 1, wherein the predetermined spacing between the partial laminated cores comprises a cooling gap.

5. The method of claim 1, wherein the hollow pipe has different wall thicknesses in the circumferential direction.

6. The method of claim 1, wherein some of the slots in the laminated core are partially open in sections at a radially outer edge.

7. The method of claim 1, wherein an inner contour of the slots is different from an outer contour of the inserted hollow pipe before expansion of the hollow pipe.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention and further advantageous embodiments of the invention are described in more detail with reference to several exemplary embodiments. Herein, the drawings show:

(2) FIG. 1 a basic longitudinal section of an asynchronous machine,

(3) FIG. 2 the basic design of a rotor in longitudinal section,

(4) FIG. 3 a basic longitudinal section of a rotor with partial laminated cores,

(5) FIGS. 4 and 5 detail sections of an end ring,

(6) FIGS. 6 to 10 production method,

(7) FIGS. 11 to 13 a further production method,

(8) FIG. 14 a detail view of a slot,

(9) FIGS. 15 and 16 perspective views in each case of a hollow rod.

(10) FIG. 17 a detail view of a partially open slot.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(11) FIG. 1 is a basic longitudinal section showing a dynamoelectric machine 1 embodied as an asynchronous machine with a cage rotor and the substantial active electrical and magnetic parts of this dynamoelectric machine 1. Hence, it does not show bearings, housings, fans etc., which also belong to the fittings of a functional dynamoelectric machine 1.

(12) A rotor 7 or rotating part that is axially rotatable about a shaft 22 is arranged non-rotatably on a shaft 6. In the axial direction, the rotor 7 has a laminated core 8 comprising axially stacked laminations with slots 14 extending substantially in the axial direction. The laminated core of the rotor 7 and/or stator 23 also contains substantially axially extending cooling ducts, but these are only partially shown in this depiction.

(13) The air flow through the cooling ducts in the stator 23 and/or rotor 7 through their axially extending cooling ducts 5 is generated internally or externally by correspondingly mounted fans. The slots 14 in the rotor 7 contain electrical conductors connected to one another in an electrically conductive manner via end rings 13 on the respective end faces of the rotor 7. In slots 4 in the stator 23, the stator 23 has a winding system 2 that forms winding heads 3 on the end faces of the stator 23. This winding system 2 generates magnetic fields that interact electromagnetically with the rotor 7 and the cage winding thereof through an air gap 21. The electromagnetic interaction during the operation of the dynamoelectric machine 1, in particular the stator 23, through the air gap 21 to the rotor 7 causes rotation about the axis 22 to take place in the rotor 7.

(14) FIG. 2 shows a rotor 7 with its cage winding and its non-rotating connection on its shaft 6. Conductor bars 15 made of at least two materials of different electrical conductivities protrude axially from the end faces of the rotor 7 or from the laminated core 8 in the rotor 7. A first material with a first electrical conductivity and a material with a second electrical conductivity, wherein the material with the first electrical conductivity is the material with the better electrical conductivity.

(15) In one specific embodiment, the material with a first electrical conductivity is copper, while the material with comparatively poorer electrical conductivity is aluminum.

(16) The conductor bars 15 protruding from the laminated core 8 in the rotor 7 are cast in a material 16i.e. aluminum for examplewith a second electrical conductivity and hence form an end ring 13. The conductor bars 15 are substantiallyfirstembodied as hollow and are then, both in the end ring 13 and in the conductor bars 15, filled with the material with second electrical conductivity. Herein, the material with the second electrical conductivity is aluminum, while the conductor bar 15 is embodied as a copper hollow profile.

(17) Hence, a conductor bar 15 with a closed circumference (i.e. without a slit 24 as shown in FIG. 15) and a uniform wall thickness (unlike the case in FIG. 16) at its radial outer circumference has higher electrical conductivity than the aluminum with comparatively low electrical conductivity in the interior of the conductor bar 15.

(18) FIG. 4 is a detailed representation of the axial projection 20 of the conductor bar 15 into the end ring 13.

(19) FIG. 5 also shows an axial projection 20 of a conductor bar 15 into the end ring 13, wherein, in this exemplary embodiment, in the region of the end rings 13, the conductor bar 15 has special surface-area-enlarged structures 19 on its end and/or within its axial projection 20 in order to obtain correspondingly improved adherence within the end ring 13. FIG. 5 also shows a cooling duct 17 of the rotor 7 with a substantially axial extension.

(20) FIG. 3 shows in a further embodiment a rotor 7 formed by four partial laminated cores 9, 10, 11 and 12. The end rings 13 are also located on the end faces of the rotor 7. Between the partial laminated cores 9, 10, 11 and 12, there are located radial cooling slits 18 separating the partial laminated cores 9, 10, 11 and 12 from one another. During the production of such a rotor 7, the punch-laminated partial laminated cores 9, 10, 11 and 12 are now, optionally now or after filling, non-rotatably connected to the shaft 6. The hollow conductor bars 15 with comparatively high electrical conductivityi.e. in particular copper hollow profilesare inserted into the more or less axially aligned slots 14 in the rotor 7. For the filling with a material with comparatively lower electrical conductivity, according to the invention, the conductor bar 15 now simultaneously functions as a seal in the region of the cooling slits 18 for this cast-in material with reduced conductivity. Here again, the copper hollow profiles are expanded either separately or by the aluminum diecasting method and structured such that the lining, i.e. the walls of the hollow profile of the conductor bar 15, nestles in a positive-fitting manner on the side walls of the respective slot 14.

(21) FIG. 6 to FIG. 9 are basic representations of a production method with reference to one single slot 14, wherein the method can be used both for rotors 7 as shown in FIG. 2 and for rotors 7 as shown in FIG. 3, 4, 5 and in principle for stators.

(22) FIG. 6 shows a laminated core 8 with axially extending slots 14 in which now a hollow section as shown in FIG. 7, in particular a hollow rod made of copper, is inserted into the laminated core 8 as shown in FIG. 8. This hollow section is expanded by means of a high-pressure assembly process and designed such that the lining, i.e. the walls of the hollow profile of the rod 15, now nestles in a positive-fitting manner on the side walls of the slot 14.

(23) Filling the remaining hollow space within the hollow profile, in particular the conductor bar 15, and simultaneously casting the end rings 13 onto the end face of the rotor 7 is a simple way of producing a cage rotor, as shown in a partially perspective representation in FIG. 10. This cage rotor now has conductor bars 15 with a comparatively good electrically conductive material on their outer edge in the slot 14, while the rest of the slot 14 contains comparatively poorly conductive material.

(24) To simplify representation, FIG. 10 does not show any hollow profiles protruding out of the slot 14. For elucidation, FIG. 10 further indicates cross-sectional surfaces of the end ring 13 that are not intended to represent cut surfaces of the end ring 13.

(25) As shown in FIG. 10 or also as shown in FIG. 4 or FIG. 5, the end ring 13 is arranged directly on the end face of the laminated core in the rotor 7. It is also possible to arrange the end ring 13 extending axially from the end face of the laminated core. Herein, the hollow profiles 15 protrude from the slot 14 and only enter the end ring 13 after a predetermined axial distance.

(26) FIG. 11 to FIG. 13 show the use of the invention with other slot shapes that are developed such that now a special starting cage is formed, wherein, for a normal operating mode, the conductive copper is still provided on the radially outer edge of the slot 14. Here again, there is a laminated core 8 with axially extending slots 14 into which now a hollow sectioni.e. the conductor bar 15in particular a hollow rod made of copper is inserted. This hollow section is formed and expanded by means of a high-pressure assembly process such that the lining of the hollow profile of the conductor bar 15 now nestles in a positive-fitting manner on the side walls of the slot 14, in this case the lower part of the double slot in the rotor 7. The upper part separated from the lower part of the slot 14 is also filled with aluminum.

(27) In FIG. 14, a hollow conductor bar 15 with an axially extending slit 24 as shown in FIG. 15 has been inserted. Unlike the case in FIG. 13, hence, the cast-in material in the lower and upper part of the slot 14 is in contact and can in particular be produced in one casting process.

(28) When considered in the circumferential direction, a hollow conductor bar 15 as shown in FIG. 16 has different wall thicknesses 25, which inter alia ultimately permits the optimization of the start-up behavior of an asynchronous machine.

(29) Also conceivable are combinations of the embodiments of the hollow profiles relating to wall thicknesses, cross section, materials, slit widths etc. within a rotor 7 or within a slot 14, for example within a slot that is partially open at a radially outer edge, as shown in FIG. 17.

(30) The slot shapes shown here should not be interpreted as being restrictive; instead, the invention can also be used in laminated cores of rotors with other slot shapes such as tapered-bar slots, double slots, double-bar slots, drop-bar slots and high-bar slots.

(31) In principle, the inventive concept is also applicable to stators in asynchronous machines or synchronous machines.

(32) Due to the advantageous overload and start-up behavior, including with respect to load torques, asynchronous motors with such rotors, are in particular used in e-cars, traction drives and also in cranes, elevators, conveyors or centrifuges.