DE102021205919B4 - Laminated core for a rotor or a stator of an electrical machine and corresponding electrical machine - Google Patents

Abstract

The present invention relates to a laminated core (10) for a rotor or a stator of an electrical machine, with a plurality of laminations (12) and welds (14) of the laminations (12) on the periphery (18, 22) of the laminated core (10), which Weld pattern (20) of corresponding weld points on the peripheral surface of the laminated core (10). It is provided that when the weld pattern (20) is approximated as a binary image in a grid ( 24) in which in each individual grid field (26) there is either no welding point, which corresponds to a state 0 of the corresponding grid field (26), or a welding point is present, which corresponds to a state 1 of the corresponding grid field (26), a through Fourier transformation of this binary image in the angular / spatial range yielding function, ie the Fourier transform of the binary image, a flat Ver running in the axial direction and/or in the circumferential direction, in particular a flat course both in the axial direction and in the circumferential direction.The invention further relates to an electrical machine with a rotor and a stator, in which the rotor or the stator is such a Laminated core (10).

Description

The present invention relates to a laminated core for a rotor or a stator of an electrical machine, with a plurality of laminations and welds of the laminations on the periphery of the laminated core, which result in a weld pattern of corresponding welds on the peripheral surface of the laminated core.

The present invention also relates to an electrical machine with a rotor and a stator, the rotor or the stator having a corresponding laminated core.

Stamped stacked laminated cores for rotors or stators of electrical machines are usually welded in a straight line at several positions around the circumference on the outer circumferential surface (shell surface) after packing.

During operation of the electrical machine, the laminated cores are excited to vibrate via the electromagnetic tooth forces. These vibrations form both over the circumference and over the axial length. Ultimately, these vibrations are transmitted to the housing and the air and perceived as noise, which is usually perceived as annoying.

Possible solutions for influencing the transmission behavior of the electromagnetically induced vibrations have already been worked out in the past. If the straight weld seams, which are evenly distributed over the circumference, are executed in such a way that they change the deflection shapes in the axial direction in terms of frequency and amplitude, a changed acoustic behavior can be expected, in which disturbing noise components are reduced.

From the DE 100 12 849 A1 a stator core according to the preamble of patent claim 1 is known.

the EP 2 605 370 A1 describes a method and an arrangement for determining a circumferential order of stator segments.

The pamphlet DE 35 17 330 A1 describes a laminated core for a stator of an electrical machine designed as a three-phase generator, with several laminations and welds of the laminations on the periphery of the laminated core, which result in a weld pattern of corresponding welds on the peripheral surface of the laminated core, which is more complex than the pattern that results from welds, which are aligned only in the circumferential direction or only perpendicular to the circumferential direction. The weld pattern results from diagonal welds running symmetrically in opposite directions, which are applied "truss-like and crossing each other on the inner and/or outer circumference". A recognizable reduction in noise during operation of the electrical machine is achieved via such a welding point pattern.

However, there remains a need to further reduce such noises/noise components that are perceived as disturbing.

It is therefore the object of the present invention to provide measures that enable a further noise reduction of such noises or noise components during the operation of an electrical machine.

The present invention is achieved by a laminated core with the features of claim 1 and an electrical machine with the features of claim 7. Preferred embodiments of the invention are described in the subclaims, in the description or in the figures, with others in the subclaims or in The features described or shown in the description or the figures, individually or in any combination, may represent an object of the invention if the context does not clearly indicate the opposite.

In the case of the laminated core according to the invention for a rotor or a stator of an electrical machine, with a plurality of laminations and welds of the laminations on the periphery of the laminated core, which result in a weld pattern of corresponding welds on the peripheral surface of the laminated core, it is provided that when the weld pattern is approximated as a binary image in a grid resulting from a corresponding segmentation of the circumferential surface both in the axial direction and in the circumferential direction, in which there is either no weld point in each individual grid field, was one Corresponds to state 0 of the corresponding grid field, or a weld is present, which corresponds to a state 1 of the corresponding grid field, a function resulting from Fourier transformation of this binary image in the angular/local area, i.e. the Fourier transform of the binary image, a flat profile in the axial direction and/or in the circumferential direction, in particular a flat course both in the axial direction and in the circumferential direction. This design of the welding point pattern serves to reduce the transmission behavior of electromagnetically induced vibrations and thus to reduce the resulting acoustic radiation. In this way, the noise or noise components occurring due to autocorrelation are suppressed.

der Funktion x(t) im Zeitbereich (und ein entsprechendes Spektrum) sowie die fouriertransformierte Funktion $$F\left(x\left(\phi \right)\right)=C\ast {\displaystyle {\int }_0^{2pi}X\left(\phi \right)e^{-i\omega \phi }d\phi }$$

der Funktion x(φ) im Winkel- bzw. Ortsbereich (und ein entsprechendes Spektrum).With the binary image of the weld pattern as a function of the circumference, binary sequences now result with different "0" and "1" states over the angle 360° (or 2π). This function over the angle/location (the 360°) can now be Fourier-transformed and the Fourier-transformed function results $$f\left(x\left(t\right)\right)=\frac{1}{\sqrt{2pi}}{\displaystyle {\int }_0^{T}X\left(t\right)e^{-i\omega t}\mathrm{i.e}t}$$

the function x(t) in the time domain (and a corresponding spectrum) and the Fourier transformed function $$f\left(x\left(\phi \right)\right)=C\ast {\displaystyle {\int }_0^{2pi}X\left(\phi \right)e^{-i\omega \phi }\mathrm{i.e}\phi }$$

of the function x(φ) in the angular or spatial domain (and a corresponding spectrum).

The binary image approximation of the weld pattern is optimal when a “spectrum” that is as flat as possible is achieved after a Fourier transformation according to the location or angle (equation (2)). This applies to the circumferential and axial direction of the laminated core.

The definition of the flat course of the function resulting from Fourier transformation of the binary image in the angular/spatial domain is then defined, for example, by a maximum permissible level difference between a minimum and a maximum function value of this function. This level difference can then be set at 6 dB, for example.

The laminated core usually has the shape of a hollow cylinder, which is characterized by an axial length/height, an inner radius and an outer radius. Accordingly, such a laminated core has an outer circumference and an inner circumference. Said welds can be placed on each of these perimeters.

According to a preferred embodiment of the invention, it is provided that the binary image at least in the circumferential direction, but preferably both in the axial direction and in the circumferential direction, for each individual row/column of the grid as a binary code sequence according to a binary code with low autocorrelation with the two states 0 and 1 is approachable. When the individual rows or columns are read out, a binary code sequence then results in each case according to the binary code with low autocorrelation.

It is provided in particular that the respective binary code with low autocorrelation is a Barker code or a Willard code. In most cases, the Barker code is the best choice. In contrast to the code sequences of the Barker code, the alternative Williard code has a higher autocorrelation.

According to a further preferred embodiment of the invention, the segmentation of the circumferential surface in the axial direction is a segmentation into 4, 5, 7, 11 or 13 uniform segments and the segmentation of the circumferential surface in the circumferential direction is a segmentation into 4, 5, 7, 11 or 13 uniform segments . The number of segments corresponds to the length of the code sequence. A code sequence length of less than four is possible, but makes less sense for the present application. A length of the code sequence greater than 13 is not known for the Barker code.

According to yet another preferred embodiment of the invention, it is provided that the flat progression of the function resulting from Fourier transformation of the binary image in the angular/spatial domain is given by a maximum permissible level difference between a minimum and a maximum function value of this function of 3 dB. which corresponds to a factor of 1/SQRT(2).

Finally, with regard to the laminated core, it is advantageously provided that the grid fields are of rectangular design, with a circumferentially running first side of the respective grid field being significantly longer than the axially running second side of the respective grid field. Accordingly, the welds are usually carried out as weld seams. However, individual spot welds can also be added, or the entire spot weld pattern can be made up of such spot welds.

In the electrical machine according to the invention with a rotor and a stator, it is provided that the rotor or the stator has a laminated core as mentioned above. This stack of laminations then has welds of the laminations on the circumference of the stack of laminations, which result in a corresponding pattern of welds.

According to a preferred embodiment of the electric machine according to the invention, it is provided that this is designed as an electric motor and/or as an electric generator, ie as an electric motor, as a generator or as a so-called motor generator.

According to a further preferred embodiment of the electric machine according to the invention, it is provided that this is designed as a synchronous machine. A synchronous machine is a rotating electrical machine in which the rotor runs synchronously with the rotating field of the stator. Synchronous machines are often designed as three-phase machines, ie as three-phase synchronous machines. In principle, any synchronous machine can be operated as an electric motor and/or electric generator.

According to yet another preferred embodiment of the electrical machine according to the invention, it is provided that this is designed as an asynchronous machine. An asynchronous machine, often also called a three-phase asynchronous machine or three-phase induction machine, is a three-phase machine in which the rotor either leads or lags the rotating field of the stator.

With regard to further advantages and technical features of the laminated core and the electrical machine, reference is made to the description, to the figures and to the description of the figures.

The invention is explained in more detail below with reference to the figure, wherein one or more features of the figure can be a feature of the invention, either alone or in combination. Furthermore, figure and example are only to be seen as examples but in no way restrictive.

• 1 in einer schematischen Darstellung ein Blechpaket für einen Stator einer elektrischen Maschine.

It shows:

• 1 in a schematic representation of a laminated core for a stator of an electrical machine.

the 1 shows schematically a laminated core 10 for a (not shown here) stator of an electrical machine. The laminated core 10 comprises a plurality of laminations 12 , not shown in detail here, which are stacked along an axis 14 . Each of the sheets 12 has roughly the shape of an annular disk, similar to a washer. The core 10 further includes welds 16 of the laminations 12 on the outer periphery 18 of the core 10 which result in a weld pattern 20 of corresponding welds on the peripheral surface of said perimeter 18 of the core 10 . The laminated core 10 itself roughly has the shape of a hollow cylinder, which is characterized by an axial length/height, an inner radius and an outer radius. Accordingly, such a laminated core 10 has an inner circumference 22 in addition to the outer circumference 18. In principle, the said welds 16 can be arranged on each of these circumferences 18, 22. Here in the case of the laminated core 10 for the stator, the welds 16 are on the outer circumference 18 while teeth (not shown here) are arranged circumferentially on the inner circumference 22 and are provided with corresponding windings (also not shown here).

Stamped laminated cores 10 for rotors and/or stators of electrical machines are segmented both in the circumferential and longitudinal direction for the purpose of applicability of the procedure described here. When approximating the weld spot pattern 20 as a binary image in a grid (dashed lines) 24, which results from the corresponding segmentation of the peripheral surface both in the axial direction and in the circumferential direction, in which there is either no weld spot in each individual grid field 26 (which corresponds to a state 0 of the corresponding grid field 26) or a welding spot is present (which corresponds to a state 1 of the corresponding grid field 26) a function resulting from Fourier transformation of this binary image in the angular/spatial area, i.e. the Fourier transform of the binary image, has a flat profile both in has axial direction as well as in the circumferential direction.

This configuration of the welding point pattern 20 serves to reduce the transmission behavior of electromagnetically induced vibrations and thus to reduce the acoustic radiation. In this case, the number of circumferential segments can differ from those in the longitudinal direction, with the respective direction-related segments having to be designed to be equidistant. Based on the respective number of segments, ie the number of grid fields 26 per row or column, the Barker code with the length n=number of segments is selected for welding the segments here in the example.

• N_axial = 11: Anzahl der Segmente in Längsrichtung
• N_umfänglich = 7: Anzahl der Segmente in Umfangsrichtung

In this example, the result is an N _axial x N _{circumferential} grid with:

• N _axial = 11: number of segments in the longitudinal direction
• N _{circumferential} = 7: number of segments in the circumferential direction

$${\text{A}}_{\text{umf}\ddot{\text{a}}\text{ñglich}}=\left[\begin{array}{ccccccc}1& 1& 1& 0& 0& 1& 0\end{array}\right]$$

According to the Barker Code, the following code sequences result: $${\text{A}}_{\text{axial}}=\left[\begin{array}{ccccccccccc}1& 1& 1& 0& 0& 0& 1& 0& 0& 1& 0\end{array}\right]$$

$${\text{A}}_{\text{comp}\ddot{\text{a}}\text{possible}}=\left[\begin{array}{ccccccc}1& 1& 1& 0& 0& 1& 0\end{array}\right]$$

Negations or inversions of the code sequences are possible.

A parameter value of 1 indicates that the sheets 12 in the corresponding grid 26 are to be welded, while a parameter value of 0 indicates that the corresponding grid 26 is to remain free of welds.

So it turns out that in 1 at least partially shown grid 24, in which either no welding point is present in each individual grid field 26, which corresponds to a state 0 of the corresponding grid field 26, or a welding point is present, which corresponds to a state 1 of the corresponding grid field 26.

In matrix notation, a welding specification results from the binary image:

As an alternative to using the Barker code, the Willard code or any other binary code with low autocorrelation can also be used.

Claims (10)

Laminated core (10) for a rotor or a stator of an electrical machine, with a plurality of laminations (12) and welds (14) of the laminations (12) on the periphery (18, 22) of the laminated core (10), which have a weld pattern (20) corresponding Welds on the circumferential surface of the laminated core (10), characterized in that when the weld pattern (20) is approximated as a binary image in a grid (24) resulting from appropriate segmentation of the circumferential surface both in the axial direction and in the circumferential direction, in the case of the in each individual grid field (26) either no welding point is present, which corresponds to a state 0 of the corresponding grid field (26), or a welding point is present, which corresponds to a state 1 of the corresponding grid field (26), a Fourier transformation of this binary image in angular /Local area resulting function, ie the Fourier transform of the binary image, a flat profile in the axial direction and / or r in the circumferential direction, in particular a flat profile both in the axial direction and in the circumferential direction. laminated core after claim 1 , characterized in that the binary image can be approached both in the axial direction and in the circumferential direction for each individual row/column of the grid (24) as a binary code sequence according to a binary code with low autocorrelation with the two states 0 and 1. laminated core after claim 2 , characterized in that the respective binary code with low autocorrelation is a Barker code or a Willard code. Sheet metal package according to one of Claims 1 until 3 , characterized in that the segmentation of the circumferential surface in the axial direction is a segmentation into 4, 5, 7, 11 or 13 uniform segments and the segmentation of the circumferential surface in the circumferential direction is a segmentation into 4, 5, 7, 11 or 13 uniform segments. Sheet metal package according to one of Claims 1 until 4 , characterized in that the flat progression of the function resulting from Fourier transformation of the binary image in the angular/local range is defined by a maximum permissible level difference between a minimum and a maximum function value of this function of 3 dB. Sheet metal package according to one of Claims 1 until 5 , characterized in that the grid fields (26) are rectangular, a circumferential first side of the respective grid field (26) being significantly longer than the axially running second side of the respective grid field (26). Electrical machine with a rotor and a stator, characterized in that the rotor or the stator is a laminated core (10) according to one of Claims 1 until 6 having. Electric machine after claim 7 , designed as an electric motor and / or as a generator. Electric machine after claim 7 or 8th , designed as a synchronous machine. Electric machine according to one of Claims 7 or 8th , designed as an asynchronous machine.

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