Rotor of an electric asynchronous machine and method for determining the rotational position of the rotor

Abstract

Rotor (10) of an electric asynchronous machine (100), comprising - a rotor shaft (11) which extends along an axis of rotation (DA), - a rotor lamination stack (12) which is directly or indirectly connected to the rotor shaft (11), wherein the rotor lamination stack (12) comprises a plurality of individual laminations, each of which is oriented perpendicular to the axis of rotation (DA) and lies parallel to each other in the direction of the axis of rotation (DA), - a plurality of rotor bars (13, 13a, 13b, 13c) extending in the direction of the axis of rotation (DA) and arranged circumferentially around the axis of rotation (DA), in particular regularly, wherein each rotor bar (13, 13a, 13b, 13c) is arranged in a rotor groove (14) which penetrates the rotor lamination stack (12) in the direction of the axis of rotation (DA), - at least one short-circuit ring which electrically connects all rotor bars (13, 13a, 13b, 13c) to each other, wherein the plurality of rotor bars (13, 13a, 13b, 13c) comprises at least three different rotor bars (13a, 13b, 13c), namely at least one first rotor bar (13a) with a first width, at least one second rotor bar (13b) with a second width and at least one third rotor bar (13c) with a third width, wherein the width is defined as the maximum extent of the respective rotor bar (13a, 13b, 13c) in the circumferential direction around the axis of rotation (DA), wherein the first width, the second width and the third width are each different from each other.

Description

[0001] The invention relates to a rotor of an electric asynchronous machine, comprising a rotor shaft extending along an axis of rotation, a rotor lamination stack directly or indirectly connected to the rotor shaft, a plurality of rotor bars extending in the direction of the axis of rotation and arranged circumferentially around the axis of rotation, and at least one short-circuit ring electrically connecting all rotor bars to one another. The plurality of rotor bars comprises at least three different rotor bars, each differing in width. The invention further relates to an electric asynchronous machine with a rotor and a method for determining the rotational position of the rotor.

[0002] In asynchronous electric machines, windings in a stator are energized with alternating current, which generates a magnetic field that in turn induces a voltage in the rotor. The current flow through the short-circuit ring in the rotor, in turn, generates a magnetic field which, together with the magnetic field of the stator, causes a torque and thus rotation of the rotor. Such electric machines can also be called induction machines. To determine the rotational position of the rotor in the stator, a rotor position sensor is usually mounted on the rotor of asynchronous machines. A sensor is provided on the stator which, after a learning process, detects the position of the rotor position sensor as it rotates with the rotor. The rotational positions of the rotor can then be deduced from the sensor signals. The inclusion of the rotor position sensor and the sensor increases the complexity of the electric machine and requires additional effort for the learning process.

[0003] DE 694 32 226 T2 describes a method and a device for the sensorless determination of the position and speed of a rotor of an AC motor. In this method, the rotational position of the rotor relative to the stator is determined by measuring the impedance of the rotor during operation.

[0004] US 2014 / 0246940A1 describes an electric motor and a motor system. The motor's rotor has several permanent magnets whose magnetic properties change circumferentially around the rotor shaft. These varying magnetic properties are used to determine the rotor's rotational positions.

[0005] US 2003 / 0102762A1 describes permanent magnet synchronous machines and methods for their manufacture. The rotor of such a synchronous machine can have slots arranged at varying distances from the rotor's axis of rotation.

[0006] US Patent 3,597,646 A describes dynamoelectric machines. These machines comprise a rotor that is divided into several segments circumferentially. Within each of these segments, rotor bars are arranged such that the cumulative cross-sectional area of ​​the rotor bars is greatest in a central region of each segment and decreases circumferentially towards the edges of each segment.

[0007] The object of the invention is to propose solutions with which the rotational position of the rotor of an electric asynchronous machine can be determined simply and at the same time precisely.

[0008] The object of the invention is solved by a rotor of an electric asynchronous machine comprising - a rotor shaft extending along an axis of rotation, - a rotor lamination stack which is directly or indirectly connected to the rotor shaft, wherein the rotor lamination stack comprises a plurality of individual laminations which are each oriented perpendicular to the axis of rotation and lie parallel to each other in the direction of the axis of rotation, - a plurality of rotor bars extending in the direction of the axis of rotation and arranged circumferentially around the axis of rotation, in particular regularly, wherein each rotor bar is arranged in a rotor groove which penetrates the rotor lamination stack in the direction of the axis of rotation, - at least one short-circuit ring which electrically connects all rotor bars to each other, wherein the plurality of rotor bars comprises at least three different rotor bars, namely at least one first rotor bar with a first width, at least one second rotor bar with a second width and at least one third rotor bar with a third width, wherein the width is defined as the maximum extent of the respective rotor bar in the circumferential direction around the axis of rotation, wherein the first width, the second width and the third width each differ from each other.

[0009] The rotor according to the invention is intended for use in an electric asynchronous machine. The inductive properties of the rotor are asymmetrically distributed around its axis of rotation. Due to these asymmetrically distributed inductive properties, the rotational position of the rotor can be easily determined by the method described below.

[0010] The rotor according to the invention comprises a rotor shaft extending along an axis of rotation. This axis of rotation is the axis around which the rotor rotates during operation. The rotor further comprises a lamination stack, which is composed of a plurality of laminations that are directly or indirectly connected to the rotor shaft. The laminations are arranged parallel to one another and are electrically insulated from each other, for example, by applying a coating to the respective surface of the laminations. The rotor also comprises a plurality of rotor bars that penetrate the lamination stack and are arranged within it. During operation of the rotor, a current is generated in the rotor bars by a magnetic field produced by the stator. The rotor bars can, for example, comprise copper or aluminum. Each rotor bar is arranged in a rotor slot.A rotor groove is a recess in the rotor lamination stack into which the respective rotor bar is inserted. The rotor bars are preferably arranged regularly in the circumferential direction, that is, at constant intervals from one another. The multitude of rotor bars together forms a cage. The rotor also includes at least one short-circuit ring, which electrically connects all rotor bars circumferentially around the axis of rotation. Preferably, two such short-circuit rings are provided, each arranged at one end face of the rotor bars.

[0011] According to the invention, the rotor bars differ from one another in their geometry. The plurality of rotor bars comprises at least three types of rotor bars, which are dimensioned differently. In the following, "rotor bar" is to be understood as also referring to a type of rotor bar. For example, a "first rotor bar" is to be understood as also referring to a first type of rotor bar. There may be only one or several rotor bars of the same type provided for the first rotor bar. A first rotor bar has a first width, a second rotor bar has a second width, and a third rotor bar has a third width. "Width" is defined here as the maximum circumferential extent of the respective rotor bar around the axis of rotation. The first width, the second width, and the third width each differ from one another, which is why the first, second, and third rotor bars have different dimensions.Due to their different geometric dimensions, the inductive properties of these rotor bars also differ. Their impedance under the influence of a magnetic field generated by the stator varies. These different inductive properties of the first, second, and third rotor bars can be used to easily determine the rotor's rotational position using the method according to the invention. Because of their different widths, the rotor bars exhibit different scattering structures. If different rotor bars are arranged at different positions circumferentially around the axis of rotation, the rotor exhibits anisotropic inductive behavior. This anisotropic inductive behavior is sufficient to determine the rotor's rotational position without the need for an additional rotor position sensor or other sensor.This reduces the number of components in the rotor or in an electric asynchronous machine to which the rotor belongs. Furthermore, the rotor according to the invention saves the effort and time required for sensor calibration. Another advantage of the rotor according to the invention is that no signal lines are needed to transmit the sensor signals between the electric asynchronous machine and its associated power electronics. Eliminating such signal lines improves the electromagnetic compatibility (EMC) of the electric machine and its control electronics. Moreover, the rotor according to the invention enables a very precise determination of its rotational position relative to the stator.

[0012] In one embodiment, at least three different rotor bars are arranged adjacent to each other circumferentially around the axis of rotation. Specifically, at least three different rotor bars of varying widths are arranged directly adjacent to each other circumferentially. The width of the rotor bars differs from one to the next. These differing widths of adjacent rotor bars create an asymmetrical sinusoidal impedance pole of the rotor at this point. This sinusoidal pole can be particularly well utilized in the method to determine the rotational position of the rotor.

[0013] In a further embodiment, a first rotor bar is arranged circumferentially around the axis of rotation between two second rotor bars, and these two second rotor bars are arranged circumferentially around the axis of rotation between two third rotor bars. In this embodiment, a total of at least five rotor bars of different widths are arranged directly adjacent to one another. A single first rotor bar is circumferentially surrounded by a pair of second rotor bars, which in turn are surrounded by a pair of third rotor bars. This arrangement is particularly effective at generating a sinusoidal impedance pole. Naturally, it is also possible to arrange an even larger number of rotor bars of different widths side by side or adjacent to one another circumferentially.Preferably, the first width of the first, centrally located rotor bar is smaller than the second width of the adjacent rotor bars, which in turn is smaller than the width of the adjacent third rotor bars. However, a reverse arrangement is also possible, in which the first width of the centrally located first rotor bar is larger than the second width of the second rotor bars, which in turn is larger than the third width of the outermost third rotor bars.

[0014] In one embodiment, the at least three different rotor bars have an equal cross-sectional area in a plane perpendicular to the axis of rotation, and in particular, all rotor bars have an equal cross-sectional area in a plane perpendicular to the axis of rotation. It is provided that at least all different rotor bars with different widths have an equal cross-sectional area in a plane perpendicular to the axis of rotation. This equal cross-sectional area ensures that the current-carrying capacity of all rotor bars is the same. This prevents uneven heating of the rotor during operation. Furthermore, each rotor bar generates the same torque during operation, resulting in favorable concentricity characteristics of the rotor or the electric asynchronous machine.Since the different rotor bars have different widths, to produce a cross-sectional area of ​​the same size, another dimension of the different rotor bars must be changed inversely proportionally. Such an embodiment is described below.

[0015] In one embodiment, the at least one first rotor bar has a first thickness, the at least one second rotor bar has a second thickness, and the at least one third rotor bar has a third thickness, wherein the thickness is defined as the maximum radial extent of the respective rotor bar to the axis of rotation, and the first, second, and third thicknesses differ from one another. In this embodiment, the different rotor bars differ not only in width but also in thickness. The widths are inversely proportional to the thicknesses. This means that if a first rotor bar has a first width that is greater than the second width of a second rotor bar, the first thickness of the first rotor bar is correspondingly smaller than the second thickness of the second rotor bar. The same applies, of course, conversely, if the first width is smaller than the second width.In this case, the first thickness is greater than the second thickness. By selecting the thickness and width dimensions in this way, it can be easily ensured that all rotor bars have the same cross-sectional area in a plane perpendicular to the axis of rotation.

[0016] The object of the invention is further solved by an electric asynchronous machine comprising - a rotor according to one of the embodiments described above, - and a stator comprising a stator lamination stack, wherein the stator lamination stack comprises a plurality of individual laminations, each oriented perpendicular to the axis of rotation and parallel to each other in the direction of the axis of rotation, and wherein the stator comprises a plurality of stator windings, which are arranged at least partially in the stator lamination stack, wherein the rotor is rotatably mounted in the stator about the axis of rotation, - a power electronics unit which is electrically connected to the stator windings and is configured to supply the stator windings with alternating voltages as required, wherein when the stator windings are supplied with alternating voltages by the power electronics, a current flow is established in the rotor, in particular in the rotor bars, according to an impedance which is asymmetrically distributed in the circumferential direction around the axis of rotation, wherein the impedance of the rotor at a circumferential position around the axis of rotation, where the at least three different rotor bars are arranged, differs from the impedance of the rotor at a circumferential position around the axis of rotation where none of the at least three different rotor bars are arranged.

[0017] The electric asynchronous machine according to the invention comprises a rotor according to one of the previously described embodiments, which has at least three different rotor bars with different widths. The electric asynchronous machine according to the invention further comprises a stator, which includes a stator lamination stack with a plurality of individual laminations. Within the stator lamination stack, a plurality of stator windings are arranged, which can be supplied with an alternating current. The rotor is rotatably mounted about the axis of rotation in the stator. Furthermore, power electronics are provided, which are electrically connected to the stator windings and supply the stator windings with an alternating current during operation.The power electronics are connected to a control unit, which transmits control signals to the power electronics to generate a three-phase alternating voltage system, dependent on the operating point. This system applies alternating voltages to the stator windings. The control system is responsible for adjusting the speed and torque of the asynchronous electric machine. When alternating voltages are applied to the stator windings, a current flows in the windings, generating a time-varying magnetic field. This field induces voltages in the rotor, particularly in its rotor bars, resulting in a current flow in these bars. The rotor's impedance is asymmetrically distributed around the axis of rotation because the rotor bars have different widths.In the area of ​​these different rotor bars with varying widths, the rotor exhibits an impedance that differs from other circumferential positions around the axis of rotation where no different rotor bars are arranged. This difference in impedance or the magnetic behavior of the rotor in the circumferential direction around the axis of rotation can be used to determine the rotor's rotational position within the stator without additional electrical components, such as sensors. The induction-based electric asynchronous machine thus has a reduced number of components compared to known solutions and is therefore simple in design. At the same time, it enables the precise determination of the rotor's rotational position.

[0018] In one embodiment of the electric asynchronous machine, at least one signal generation unit and at least one measuring unit are provided. The signal generation unit is configured to generate a measurement signal for determining the rotor's rotational position and transmit it to the stator windings. The measuring unit is configured to detect a response signal from the stator windings and to determine the rotor's rotational position from the measurement signal and the response signal. In this embodiment, the electric asynchronous machine includes a signal generation unit configured to transmit a high-frequency measurement signal to the power electronics or to the stator windings. This measurement signal is superimposed on the alternating voltages required for operation, which are applied to the stator windings by the power electronics.Furthermore, a measuring unit is provided which is configured to detect a response signal from the stator windings. The response signal is superimposed on the alternating current transmitted between the power electronics and the stator. The measuring unit is further configured to determine the rotational position of the rotor in the stator from the response signal and the measurement signal. This determination of the rotational position is preferably carried out according to the method according to the invention.

[0019] The object of the invention is finally achieved by a method for determining the rotational position of the rotor of an electric asynchronous machine according to one of the embodiments described herein, comprising the method steps A) Generation of a measurement signal by the signal generation unit and transmission of the measurement signal to the stator windings, wherein the measurement signal is formed by a voltage signal, B) Transmission of a response signal from the stator windings to the measuring unit, wherein the response signal is formed by a current signal, C) Determination of the rotor's rotational position by the measuring unit from the response signal.

[0020] The method according to the invention is designed to determine the rotational position of the rotor in the stator simply and precisely. An induction motor according to the invention is used to carry out the method. The method according to the invention is preferably carried out in the sequence of process steps A) to C).

[0021] In a first process step A), a measurement signal is generated by the signal generation unit. This measurement signal is transmitted from the signal generation unit, in particular via the power electronics, to the stator windings. The measurement signal is a voltage signal that preferably has a significantly higher frequency than the frequency at which the power electronics transmit alternating current to the stator windings. The measurement signal induces a current in the rotor. The resulting induced current in the rotor, in turn, causes a high-frequency current response in the stator, which is a response signal to the measurement signal.

[0022] In a second process step B), the response signal, which is inductively generated based on the previously transmitted measurement signal, is transmitted to the measuring unit. The response signal is formed by a high-frequency current signal, which is detected by the measuring unit.

[0023] In a third process step C), the measuring unit determines the rotational position of the rotor within the stator. This determination is based on the response signal transmitted in process step B). This evaluation, which can be performed using a demodulation algorithm, allows the geometric rotational position of the rotor to be deduced.

[0024] No additional components, such as sensors or rotor position encoders, are required to carry out the method according to the invention. Therefore, it is also unnecessary to train one or more sensors in a complex learning process to determine the rotational position. The method according to the invention thus allows the rotational position of the rotor to be determined simply and precisely.

[0025] In one embodiment of the method, the measurement signal is formed by a square wave or a sine wave and / or lies within a range of 1 kHz to 10 kHz. In this embodiment, the measurement signal is a voltage signal which, viewed over time, is either a square wave or a sine wave. Corresponding to the shape of the measurement signal, a corresponding response signal of the same shape is generated in the rotor and stator of the asynchronous electric machine. If the measurement signal is a square wave, the response signal is also a square wave. The same applies if the measurement signal is a sine wave; in this case, the response signal is also a sine wave. The frequency of the measurement signal lies between 1 kHz and 10 kHz. In this way, the measurement signal is easily distinguishable from other signals during the operation of the asynchronous electric machine.The specified frequency range is below the switching frequency of an inverter, which is approximately between 10 and 20 kHz. Furthermore, the specified frequency range is above the frequency used by the controller to operate the power electronics. This frequency is a maximum of 1 kHz.

[0026] In one embodiment, it is provided that in process step C) the determination of the rotational position is carried out as a function of time, in particular whereby the process is carried out continuously during the operation of the asynchronous machine. By determining the rotational position over time, the current rotational position of the rotor can always be inferred. Furthermore, it is possible to predict future rotational positions of the rotor. Preferably, the entire process is carried out continuously during the operation of the electric asynchronous machine. In this way, the current rotational position of the rotor in the stator is always known.

[0027] Features, effects, and advantages disclosed in connection with the rotor and the electric asynchronous machine are also deemed disclosed in connection with the method. Conversely, features, effects, and advantages disclosed in connection with the method are also deemed disclosed in connection with the rotor and the electric asynchronous machine.

[0028] The invention is schematically illustrated with reference to embodiments in the drawings and is further described with reference to the drawings. The drawings show: Fig. 1 in a schematic, cutaway side view a partial area of ​​an electric asynchronous machine according to an embodiment of the invention, Fig. 2 in a schematic view an electric asynchronous machine according to an embodiment of the invention.

[0029] The figures are described in a coherent and comprehensive manner. The same reference symbols are assigned to the same components.

[0030] Fig. Figure 1 shows a schematic, cutaway side view of a partial area of ​​an electric asynchronous machine 100 according to an embodiment of the invention. Fig. Figure 1 shows an exemplary section of the electric asynchronous machine 100. On the right side, a section of the stator 20 is shown, which has a stator lamination stack 21 formed by a multitude of individual laminations. A plurality of stator windings 22 are also visible, arranged within the stator lamination stack 21. On the left side, a section of the rotor 10 is shown.

[0031] An air gap exists between the rotor 10 and the stator 20. The rotor 10 is rotatably mounted in the stator 20 about the axis of rotation DA by its rotor shaft 11. The rotor 10 comprises a lamination stack 12, which in turn comprises a plurality of individual laminations. These laminations are oriented perpendicular to the axis of rotation DA and lie parallel to one another in the direction of the axis of rotation DA. Several rotor slots 14 are arranged at regular intervals in the circumferential direction of the lamination stack 12. These rotor slots 14 penetrate the lamination stack 12 in the direction of the axis of rotation DA. A rotor bar 13, 13a, 13b, 13c is arranged in each rotor slot 14. In the illustrated embodiment, each rotor bar 13, 13a, 13b, 13c completely fills a rotor slot 14. A first rotor bar 13a with a first width in the circumferential direction around the axis of rotation DA can be seen in the middle of the depicted sector of the rotor 10.This first rotor bar 13a is arranged circumferentially around the axis of rotation DA between two second rotor bars 13b, each of which has a second width. In the illustrated embodiment, the first width is smaller than the second width. The two second rotor bars 13b are arranged circumferentially around the axis of rotation DA between two third rotor bars 13c, each of which has a third width. In the illustrated embodiment, the third width is larger than the second width. The two third rotor bars 13c are arranged between further rotor bars 13, which have a width greater than the width of the third rotor bars 13c. Thus, in the illustrated sector, the width of the adjacent rotor bars 13, 13a, 13b, 13c decreases circumferentially, starting from rotor bar 13 and proceeding to the first rotor bar 13a.Moving circumferentially around the axis of rotation DA, the width increases again from the first rotor bar 13a up to rotor bar 13. In this way, an anisotropic inductive behavior of the rotor 10 is created in the sector shown. In the illustrated embodiment, all other rotor bars 13, which are not shown, are of the same type as the rotor bars 13 shown at the outer edge. The different widths in the sector shown, and the resulting different distances between adjacent rotor bars 13, 13a, 13b, 13c, cause the anisotropic inductive behavior of the rotor in the magnetic field of the stator 20, which can be used with the method according to the invention to determine the rotational position DP of the rotor 10.In the illustrated embodiment, the continuously changing widths of the rotor bars 13, 13a, 13b, 13c inductively form a sinusoidal pole, which is particularly suitable for an accurate determination of the rotational position DP of the rotor 10 in the method according to the invention.

[0032] All rotor bars 13, 13a, 13b, 13c have the same cross-sectional area in the depicted section plane perpendicular to the axis of rotation DA. This ensures that the current-carrying capacity of all rotor bars 13, 13a, 13b, 13c is equal, thus preventing uneven heat distribution during operation. The thickness of the rotor bars 13, 13a, 13b, 13c is defined radially to the axis of rotation DA. To achieve the same cross-sectional area for all rotor bars 13, 13a, 13b, 13c, this thickness is inversely proportional to the previously described width in the circumferential direction around the axis of rotation. It is clearly visible that the first rotor bar 13a, with the smallest width, has the greatest thickness. Accordingly, the rotor bars 13, 13a, 13b, 13c with different widths also have different thicknesses.The rotor slots 14, in which the respective rotor bars 13, 13a, 13b, 13c are arranged, have a width and thickness which corresponds to the width and thickness of the respective rotor bars 13, 13a, 13b, 13c arranged therein.

[0033] Fig. Figure 2 shows a schematic view of an electric asynchronous machine 100 according to an embodiment of the invention. Fig. Figure 2 is a schematic embodiment of the electric asynchronous machine 100, but in a different manner than in Figure 2. Fig. 1 shown. Fig. 2 enables a description of the electrical and electronic components of the electric asynchronous machine 100, whereas Fig. Figure 1 primarily shows their geometric structure. The stator 20 and the rotor 10 are in Fig. Figure 2 on the right is symbolic. The stator 20, or rather its stator windings 22, is electrically connected to a power electronics unit LE. During operation of the electric asynchronous machine 100, the power electronics unit LE applies alternating voltages to the stator windings 22, resulting in an alternating current in the windings of the stator 22. This alternating current in the stator 20, in turn, leads to a time-varying magnetic field, which induces voltages in the rotor 10. These voltages, in turn, result in a current flow in the rotor bars 13, 13a, 13b, 13c. This current, in turn, creates a magnetic field in the rotor 10, which, in combination with the magnetic field of the stator 20, generates a torque in the rotor 10, thus setting it in motion. The rotational speed is controlled by the controller R, which is shown on the far left.The controller R transmits control signals to the power electronics LE for generating the alternating voltages, which in turn supply the stator 20, and in particular its windings 22, with corresponding alternating voltages. A signal generation unit 101 is provided to determine the rotational position DP of the rotor 10, which generates a high-frequency measurement signal. This measurement signal is superimposed on the signal from the controller R and transmitted to the power electronics LE. The measurement signal is thus also transmitted to the stator 20 and the rotor 10. (See figure below.) Fig.Figure 2 shows a measuring unit 102, which measures and analyzes the electrical currents flowing between the power electronics LE and the stator 20. The measuring unit 102 is configured to detect and extract the response signal from the stator 20 and rotor 10 to the measurement signal generated by the signal generation unit 101 within the analyzed electrical currents. Furthermore, the measuring unit 102 is configured to determine the rotational position DP of the rotor 10 by comparing the measurement signal and the response signal and to output this position to other electrical or electronic components not shown. REFERENCE MARK LIST: 10 Rotor 11 Rotor shaft 12 Rotor lamination package 13, 13a, 13b, 13c Rotor rod 14 Rotor slot 20 Stator 21 Stator lamination package 22 Stator winding 100 electric asynchronous machines 101 Signal generation unit 102 Unit of measurement DA axis of rotation DP rotation position R regulator

Claims

[1] Rotor (10) of an electric asynchronous machine (100), comprising - a rotor shaft (11) which extends along an axis of rotation (DA), - a rotor lamination stack (12) which is directly or indirectly connected to the rotor shaft (11), wherein the rotor lamination stack (12) comprises a plurality of individual laminations, each of which is oriented perpendicular to the axis of rotation (DA) and lies parallel to each other in the direction of the axis of rotation (DA), - a plurality of rotor bars (13, 13a, 13b, 13c) extending in the direction of the axis of rotation (DA) and arranged circumferentially around the axis of rotation (DA), in particular regularly, wherein each rotor bar (13, 13a, 13b, 13c) is arranged in a rotor groove (14) which penetrates the rotor lamination stack (12) in the direction of the axis of rotation (DA), - at least one short-circuit ring which electrically connects all rotor bars (13, 13a, 13b, 13c) to each other, wherein the plurality of rotor bars (13, 13a, 13b, 13c) comprises at least three different rotor bars (13a, 13b, 13c), namely at least one first rotor bar (13a) with a first width, at least one second rotor bar (13b) with a second width and at least one third rotor bar (13c) with a third width, wherein the width is defined as the maximum extent of the respective rotor bar (13a, 13b, 13c) in the circumferential direction around the axis of rotation (DA), wherein the first width, the second width and the third width are each different from each other. [2] Rotor (10) according to claim 1, in which at least three different rotor bars (13a, 13b, 13c) are arranged adjacent to each other in the circumferential direction around the axis of rotation (DA). [3] Rotor (10) according to any one of the preceding claims 1 to 2, wherein a first rotor bar (13a) is arranged circumferentially around the axis of rotation (DA) between two second rotor bars (13b) and these two second rotor bars (13b) are arranged circumferentially around the axis of rotation (DA) between two third rotor bars (13c). [4] Rotor (10) according to any one of the preceding claims 1 to 3, wherein the at least three different rotor bars (13a, 13b, 13c) have an equal cross-sectional area in a section plane perpendicular to the axis of rotation (DA), in particular wherein all rotor bars (13, 13a, 13b, 13c) have an equal cross-sectional area in a section plane perpendicular to the axis of rotation (DA). [5] Rotor (10) according to any one of the preceding claims 1 to 4, wherein the at least one first rotor bar (13a) has a first thickness, the at least one second rotor bar (13b) has a second thickness and the at least one third rotor bar (13c) has a third thickness, wherein the thickness is defined as the maximum extent of the respective rotor bar (13a, 13b, 13c) radially to the axis of rotation (DA), wherein the first thickness, the second thickness and the third thickness are each different from each other. [6] Electric asynchronous machine (100), comprising - a rotor (10) according to any of the preceding claims, - a stator (20) comprising a stator lamination stack (21), wherein the stator lamination stack (21) comprises a plurality of individual laminations, each oriented perpendicular to the axis of rotation (DA) and abutting each other parallel to each other in the direction of the axis of rotation (DA), and wherein the stator (20) comprises a plurality of stator windings (22) which are arranged at least partially in the stator lamination stack (21), wherein the rotor (10) is rotatably mounted about the axis of rotation (DA) in the stator (20), - a power electronics unit (LE) which is electrically connected to the stator windings (22) and is configured to supply the stator windings (22) with alternating voltages as required, wherein when the stator windings (22) are supplied with alternating voltages by the power electronics unit (LE), a current flow is established in the rotor (10), in particular in the rotor bars (13, 13a, 13b, 13c), according to an impedance which is asymmetrically distributed in the circumferential direction around the axis of rotation (DA), wherein the impedance of the rotor (10) at a circumferential position around the axis of rotation (DA), where the at least three different rotor bars (13a, 13b, 13c) are arranged, differs from the impedance of the rotor (10) at a circumferential position of the axis of rotation (DA), where none of the at least three different rotor bars (13a, 13b, 13c) are arranged. [7] Electric asynchronous machine (100) according to claim 6, wherein at least one signal generation unit (101) and at least one measuring unit (102) are provided, wherein the signal generation unit (101) is configured to generate a measurement signal for determining the rotational position of the rotor (10) and to transmit it to the stator windings (22), and the measuring unit (102) is configured to detect a response signal from the stator windings (22), wherein the measuring unit (102) is configured to determine the rotational position (DP) of the rotor (10) from the measurement signal and the response signal. [8] Method for determining the rotational position (DP) of the rotor (10) of an electric asynchronous machine (100) according to one of the preceding claims, comprising the method steps A) Generation of a measurement signal by the signal generation unit (101) and transmission of the measurement signal to the stator windings (22), wherein the measurement signal is formed by a voltage signal, B) Transmission of a response signal from the stator windings (22) to the measuring unit (102), wherein the response signal is formed by a current signal, C) Determination of the rotational position (DP) of the rotor (10) by the measuring unit (102) from the response signal. [9] Method according to the preceding claim 8, wherein the measurement signal is formed by a square wave signal or a sine wave signal and / or the measurement signal is in a range between 1 kHz and 10 kHz. [10] Method according to one of the preceding claims 8 or 9, wherein in method step C) the determination of the rotational position (DP) is carried out as a function of time, in particular wherein the method is carried out continuously during the operation of the asynchronous machine (100).

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