Method and apparatus for operating an electric machine and electric machine

Abstract

The electric machine comprises a rotor and a torque sensor with a sensing element (6). The sensing element (6) is arranged on the rotor. Furthermore, the electric machine includes a field-oriented control system, or the field-oriented control system is assigned to the electric machine. The electric machine has a module, or the module is assigned to the electric machine. The module comprises a predefined machine model and / or an additional sensor and is configured to acquire and / or determine an input variable for the field-oriented control system and to provide this input variable for the field-oriented control system. A characteristic value representative of the rotor's output torque is acquired and / or determined by means of the torque sensor, and a parameter of the machine model and / or a measurement error of the additional sensor is adapted depending on the characteristic value.

Description

[0001] The invention relates to a method and a corresponding device for operating an electrical machine and the electrical machine.

[0002] Electric machines are increasingly being used as drive motors in motor vehicles. For efficient operation of the controlled electric machine, precise determination of reference variables as well as precise acquisition or determination of feedback variables for control are advantageous.

[0003] The documents DE 10 2008 062 515 A1, DE 101 08 173 A1 and US 2013 / 0 181 642 A1 relate to methods and devices for operating electric motors.

[0004] The object underlying the invention is to provide a method and a corresponding device for operating an electrical machine which enable precise control of the electrical machine and / or more efficient operation of the electrical machine.

[0005] The problem is solved by the features of the independent patent claims.

[0006] According to a first and second aspect, the invention is characterized by a method and a corresponding device for operating an electrical machine. The electrical machine comprises a rotor and a torque sensor with a sensor element. The sensor element is arranged on the rotor, for example on a rotor shaft or a rotor core of the rotor. Furthermore, the electrical machine comprises a field-oriented control system or the field-oriented control system is assigned to the electrical machine. The electrical machine has a module or the module is assigned to the electrical machine. The module comprises a predetermined machine model and / or a further sensor and is designed to detect and / or determine an input variable for the field-oriented control system and to provide this input variable for the field-oriented control system.A parameter is recorded and / or determined by means of the torque sensor, which is representative of the torque output of the rotor, and a parameter of the machine model and / or a detection error of the further sensor is adapted depending on the parameter.

[0007] Through direct torque measurement, the machine model and / or correction values ​​for the additional sensor can be adapted to achieve the highest possible efficiency of the electric machine over the lifetime of the electric machine. This enables optimal or at least improved utilization of a drive that includes the electric machine, regardless of tolerances, for example manufacturing tolerances and / or sensor tolerances. The adaptation improves the feedforward control of the field-oriented control, which leads to a further increase in the efficiency of the drive and thus, for example, improves the range of a vehicle that features the electric machine. In addition, tolerances due to aging of mechanical components of the machine as well as electrical components such as inverters, half-bridges and / or sensors can be adapted over the lifetime of the machine.

[0008] Furthermore, this provides a further degree of freedom in the design of electrical machines. Tolerances can be relaxed and cheaper materials can be used. This makes it possible to reduce the cost of the electrical machine.

[0009] In an advantageous embodiment according to the first and second aspects, the module has the machine model and is configured to determine, depending on a predetermined torque for the rotor and the predetermined machine model, target components of a stator current of the electric machine, which are fed to the field-oriented control as input variables. The machine model comprises a predetermined characteristic map for determining the target components of a stator current for optimized operation of the electric machine with respect to an efficiency and / or a degree of effectiveness of the electric machine, and adapting the parameter of the machine model comprises adapting the characteristic map.

[0010] The specified characteristic map is typically determined for a reference machine and then used for identical or similar machines. The characteristic map is used to design and calibrate the torque of the electric machine. Due to tolerances of the electric machine and its control system, the set torque differs when both machines are operated under the same operating conditions. Adapting the characteristic map for the electric machine allows the optimal target components of the stator current to be determined quickly and easily for all operating points using the adapted characteristic map.

[0011] In a further advantageous embodiment according to the first and second aspects, adapting the characteristic map comprises determining a control torque for the electric machine depending on a requested torque of the electric machine and the characteristic variable. Furthermore, for the determined control torque, the components of the stator current are optimized with respect to a minimum length of a resulting current vector of the components of the stator current depending on predetermined modulation degrees of a space-vector modulation of the field-oriented control. When an operating point is reached at which a predetermined optimization criterion is met, the characteristic map for this operating point is adapted with respect to the components of the stator current to be adjusted and / or the modulation degree and / or the torque.

[0012] In a further advantageous embodiment according to the first and second aspects, the module has, as the further sensor, an angular position detection sensor, which is designed to detect and / or determine an angular position of the rotor. In this case, the at least one input variable comprises the detected angular position of the rotor, and adapting the detection error of the further sensor comprises adapting a rotation angle error of the angular position detection sensor.

[0013] Due to the direct torque measurement, the angular position detection sensor can be adapted over the lifetime of the electric machine.

[0014] In a further advantageous embodiment according to the first and second aspects, in order to adapt the angle of rotation error, the electric machine is operated at a stationary operating point for which a target torque of the rotor is specified. During operation, in a step (a), a current angular position of the rotor is detected, and in a step (b), a corrected angular position is determined depending on a specified adaptation rule. In a step (c), the corrected angular position is provided as the input variable for the field-oriented control. Steps (a) to (c) are repeated until the difference between the measured characteristic and the specified target torque is minimal.

[0015] In a further advantageous embodiment according to the first and second aspects, the electric machine is operated in field-weakening mode, preferably in field-weakening mode without voltage limitation. This has the advantage that a torque deviation in the case of angle errors is larger and less dependent on other error variables. The error source can thus be better isolated.

[0016] In a further advantageous embodiment according to the first and second aspects, the electric machine, in the steady-state operating state, has a speed above a predetermined limit speed. It is advantageous if the machine is operated at the highest possible speed, so that possible cross-influences due to tolerances in the magnetic flux, current sensors, rotor temperature, and stator inductances play a subordinate role.

[0017] In a further advantageous embodiment according to the first and second aspects, the sensor element comprises at least one strain gauge. The strain gauge is preferably designed as a piezoresistive strain gauge. In particular, the sensor element can have four strain gauges.

[0018] In a further advantageous embodiment according to the first and second aspects, the rotor has a rotor shaft and the sensor element is arranged on an end face of the rotor shaft of the rotor.

[0019] In a further advantageous embodiment according to the first and second aspects, the rotor comprises a rotor shaft and a rotor core. The rotor core has at least two first recesses separated by a web. The sensor element is arranged on one of the webs, which is formed between two adjacent recesses. Alternatively, the rotor can have multiple sensor elements, and the respective sensor elements can each be arranged on one of the webs.

[0020] In a further advantageous embodiment according to the first and second aspects, the at least two first recesses extend along a longitudinal axis of the rotor core.

[0021] In a further advantageous embodiment according to the first and second aspects, the at least two first recesses are arranged symmetrically around the rotor shaft in the circumferential direction of the rotor core. This advantageously prevents or at least minimizes imbalance in the electric machine. By arranging the at least one sensor element directly on the rotor, the rotor can be balanced after the at least one sensor element has been applied, so that any imbalance caused by the at least one sensor element can be minimized.

[0022] In a further advantageous embodiment according to the first and second aspects, the rotor core has second recesses for arranging permanent magnets or windings, and the first recesses are arranged radially between the first recesses and the rotor shaft. The integration of the magnets has the advantage that the rotor diameter can be reduced. Furthermore, the concentration of the magnetic field can increase the magnetic flux density of the air gap, which enables less magnetic control of the electric machine.

[0023] According to a third aspect, the invention is characterized by an electric machine comprising a device according to the second aspect, a rotor, and a torque sensor with a sensor element. The sensor element is arranged on the rotor, and the device is signal-coupled to the sensor element.

[0024] Advantageous embodiments according to the second aspect are also valid for the third aspect.

[0025] Embodiments of the invention are explained below with reference to the schematic drawings.

[0026] They show: Fig. 1a a perspective view of an embodiment of a rotor of an electric machine, Fig. 1b is a frontal view of a further embodiment of a rotor of an electrical machine, Fig. 2 an exemplary arrangement of a sensor element on a rotor shaft, Fig. 3 an exemplary model for a field-oriented control of an electrical machine, Fig. 4 an exemplary isoline diagram for a torque of an electrical machine, Fig. 5 an example torque characteristic of an electric machine, Fig. 6 a flow chart for a program for operating the electrical machine and Fig. 7 an exemplary model for an extended field-oriented control of the electrical machine.

[0027] Elements of the same construction or function are provided with the same reference symbols throughout the figures.

[0028] Fig. 1a shows a perspective view of an embodiment of a rotor of an electric machine.

[0029] The electrical machine, for example, is a permanent magnet synchronous machine.

[0030] How Fig. As shown in Figure 1, the rotor comprises a rotor core 1 and a rotor shaft 2, with the rotor shaft 2 being disposed within the rotor core 1; in particular, the rotor shaft 2 is fixedly disposed within a shaft hole in the rotor core 1 to allow the rotor core 1 to rotate the rotor shaft 2 together with the rotor core 1. The material of the rotor core 1 includes, for example, silicon steel.

[0031] As in Fig. 1a, at least two first recesses 4 are arranged in the rotor core 1, which are separated by a web 5. In the Fig. In the embodiment shown in Figure 1, the rotor core 1 has four first recesses 4. The first recesses 4 extend along an axial longitudinal direction of the rotor shaft 2. The first recesses 4 serve, in particular, to reduce a rotational mass of the rotor.

[0032] The first recesses 4 are arranged, for example, symmetrically around the rotor shaft 2 in the circumferential direction of the rotor core 1.

[0033] Preferably, the respective first recesses 4 are identical or at least very similar in their design. However, the first recesses 4 can be designed differently from rotor to rotor.

[0034] The rotor core 1 has, for example, second recesses 3 for arranging permanent magnets or windings. The first recesses 4 are preferably arranged in the radial direction between the second recesses 3 and the rotor shaft 2.

[0035] The rotor comprises a torque sensor with at least one sensor element 6, which is designed to detect and / or determine a measured variable that is representative of a torque of the rotor.

[0036] The at least one sensor element 6 is arranged on the rotor. For example, the sensor element 6 is arranged on the rotor core 1.

[0037] The sensor element 6 is arranged on the rotor, for example on one of the webs 5, which is formed between two adjacent first recesses 4.

[0038] The sensor element 6 can be clamped, glued, or screwed to the rotor, for example. The sensor element 6 can be arranged on the rotor by means of a detachable connection or a permanent connection.

[0039] A torque transmitted through the rotor leads to torsion of the rotor, which occurs in the form of compressive and tensile stresses at a 45° angle to the rotor's axial direction. The rotor torsion leads to a change in the resistance of the strain gauges, which is evaluated, for example, by a suitable voltage measurement on the strain gauges.

[0040] Fig. Figure 1b shows a front view of another embodiment of a rotor of an electric machine. The rotor comprises a rotor core 1, a rotor shaft 2, first recesses 4, and second recesses 3. The rotor shaft 2 is designed, for example, as a hollow shaft. In contrast to the embodiment shown in Fig. 1a are shown in the embodiment shown in Fig. 1b, the second recesses 3 are shaped differently. Furthermore, the rotor in Fig. 1b has four sensor elements 6, which are arranged, for example, symmetrically around the rotor shaft 2 in order to minimize possible imbalances.

[0041] The Fig. 1a and Fig. The sensor elements 6 shown in Fig. 1b comprise, for example, at least one piezoresistive strain gauge.

[0042] The torque sensor has a Fig. 1a and Fig. 1b, which is electrically coupled to the sensor element(s) 6 for receiving sensor signals from the sensor element(s) 6. The first evaluation electronics is arranged, for example, in a bearing shell of the rotor. The first evaluation electronics is, for example, wirelessly coupled to a computing unit, which can also be referred to as a device for operating the electric machine.

[0043] Alternatively, the sensor element 6 can be arranged on the rotor shaft 2 of the rotor.

[0044] Fig. Figure 2 shows an exemplary arrangement of the sensor element 6 on a front side of the rotor shaft 2. The torque transmitted via the shaft leads to torsion of the rotor, which occurs in the form of compressive and tensile stresses at a 45° angle along a longitudinal axis of the rotor shaft 2. The sensor element 6 is therefore preferably arranged at an angle of 45° with respect to the longitudinal axis of the rotor.

[0045] The sensor element has at least one strain gauge. The strain gauge is preferably a piezoresistive strain gauge.

[0046] The at least one strain gauge is arranged, for example, on a silicon chip. The at least one strain gauge is, for example, glass-coated onto the silicon chip. The strain gauges are designed, for example, as a microelectromechanical system (MEMS) chip.

[0047] Alternatively, the sensor element comprises a plurality of strain gauges forming a resistance network, in particular an ohmic resistance network. For example, sensor element 5 comprises four piezoresistive strain gauges. The strain gauges are electrically coupled to form a measuring bridge.

[0048] Fig. 3 shows an exemplary model for a field-oriented control of an electrical machine.

[0049] The control system is designed, for example, as field-oriented control. Field-oriented control (Field Oriented Control or Vector Control) is a control method for three-phase machines. The goal of this control method for asynchronous or synchronous machines is to achieve decoupled control of magnetic flux and torque in order to simulate the behavior of a DC shunt machine.

[0050] The Fig. The model shown in Figure 3 applies to a permanent magnet synchronous machine.

[0051] In the forward direction, the model comprises, for example, a PI current controller 20, a first unit 22 configured to perform an inverse Clarke transformation and a space vector pulse width modulation, and, for example, a B6 inverter 24. A second unit 26 configured to perform a Clarke-Parks transformation is arranged in a feedback loop. Furthermore, a first module 28 is connected upstream of the field-oriented control loop. The first module 28 is configured to determine target components Id_s, Iq_s of a stator current of the electric machine, which are fed to the control loop, depending on input variables such as speed, magnetic flux, and requested torque Treq, and a predefined characteristic map.

[0052] The torque of a permanent magnet synchronous machine can be described using Equation 1: Tq=3 / 2*(Zp*[Ψ*id+(Ld+Lq)*Id*Iq] Here, the following are used: Tq internal torque (electromagnetic torque without mechanical torque losses) Iq, Id components of the stator current in the field-oriented d / q coordinate system Ψ rotor flux in the field-oriented d / q coordinate system Ld, Lq components of the stator inductances in the field-oriented d / q coordinate system Zp number of pole pairs

[0053] The quantities Ψ, Ld, and Lq are not precisely known due to manufacturing tolerances and aging of the electric machine. Furthermore, the determination of the actual components Iq_i, Id_i of the stator current is subject to tolerances due to the measurement accuracy of shunt or Hall sensors, as well as the tolerance in the rotor position.

[0054] The output torque is therefore subject to tolerances, which have a negative impact on control accuracy, particularly in hybrid drives, and on the efficiency of the electric machine.

[0055] The target components Id_s, Iq_s of the stator current are determined, for example, using a characteristic map. The characteristic map represents the inverse of equation (1) above and uses a requested torque, a speed, a magnetic flux, and a temperature as input variables. Since tolerances for the actual machine are not taken into account in the characteristic map, efficient operation of the machine is often not guaranteed. Furthermore, there is no guarantee that the requested torque will actually be achieved. Deviations of approximately 10% between the requested and actual torque are possible.

[0056] Currently, the tolerances of the electrical machine are minimized by using expensive, high-quality materials, for example for the permanent magnets, as well as tight manufacturing tolerances.

[0057] Optimum operating parameters for electrical machines are currently determined primarily based on a selected electrical machine. The optimal operating parameters are stored in the form of characteristic maps. The characteristic maps are then used, for example, for identical electrical machines for pre-control, as in Fig. 3 shown, used.

[0058] Fig. Figure 4 shows an example diagram with isolines for the torque. The operating range of the electric machine is limited by a maximum current, which, for example, an inverter tuned to the machine can deliver, as well as a maximum modulation level of the space-vector pulse-width modulation. The optimal operating point is reached when a resulting vector from the components Iq and Id of the stator current reaches a minimum length. Fig. 4, the bold line represents the optimal components Iq and Id of the stator for steady-state operating points.

[0059] Since the machines are never exactly identical in design and additional differences can occur between the machines due to their lifetime and / or service life, an adaptation of the characteristic map used by the electric machine, which is used for pre-control of the torque to be delivered by the electric machine in conjunction with the field-oriented control, is desirable.

[0060] Fig. Figure 5 shows an example torque characteristic of an electric motor as a function of speed or rpm. The electric motor delivers the highest torque at low speeds, but this torque decreases continuously after reaching peak power.

[0061] In a first operating area, which is Fig. 5 is marked with the number 1 and where the output torque is highest, tolerances of the magnetic flux, the accuracy of a phase current sensor and an inaccuracy of a rotor temperature model lead to torque deviations. In a second operating range, which is Fig. 5 is marked with the number 2, tolerances of the magnetic flux, the accuracy of a phase current sensor, an inaccuracy of a rotor temperature model, and further tolerances of a rotor position sensor also lead to torque deviations. In a third operating range, which is Fig. 5 is marked with the number 3 and is characterized by low torque output at high speed, tolerances of a rotor position sensor in particular lead to torque deviations.

[0062] The output torque is therefore subject to tolerances. It has been shown that tolerances with respect to a detected and / or determined angular position of the rotor lead to torque errors, especially at higher speeds.

[0063] The direct measurement of the torque delivered to the rotor enables improved torque feedforward control and / or increased control accuracy.

[0064] Fig. 6 shows a flow chart for a program for operating the electrical machine, which enables an adaptation of the control, or more precisely an adaptation of the feedforward control and a feedback loop of the control.

[0065] The electric machine includes a field-oriented control system. Alternatively, the field-oriented control system can be assigned to the electric machine. The electric machine has a module that includes a predefined machine model and / or another sensor and is configured to detect and / or determine an input variable for the field-oriented control system and to provide this input variable for the field-oriented control system. Alternatively, the electric machine does not have the module itself; instead, the module is assigned to the electric machine.

[0066] The program is executed, for example, by the computing unit. The electrical machine, for example, includes the computing unit. Alternatively, the computing unit can be assigned to the electrical machine. The computing unit can also be referred to as a device for operating an electrical machine.

[0067] The program is started in a step S1.

[0068] In a step S3, a characteristic value that is representative of an output torque of the rotor, which is detected and / or determined by means of a torque sensor, is read in.

[0069] In a step S5, a parameter of the machine model and / or a detection error of the further sensor is adapted depending on the characteristic.

[0070] In a step S7, for example, the adapted machine model and / or an adaptation map for the further sensor for the field-oriented control of a predetermined interface is provided.

[0071] In step S9, the program is terminated. Preferably, however, continuous adaptation occurs, so that the program is repeatedly executed at predetermined intervals.

[0072] The module has, for example, the machine model and is designed to determine, depending on a predetermined torque for the rotor and the predetermined machine model, target components Id_s, Iq_s of a stator current of the electrical machine, which are fed to the field-oriented control as input variables, wherein the machine model comprises a predetermined characteristic map for determining the target components Id_s, Iq_s of a stator current for optimized operation of the electrical machine with respect to an efficiency and / or an efficiency of the electrical machine.

[0073] Adapting the machine model parameter involves adapting the characteristic map. In this case, the module corresponds, for example, to the Fig. 3 and Fig. 7 shown first module 28.

[0074] In this case, for example, in step S5 for adapting the characteristic map, a control torque for the electric machine is determined depending on a requested torque of the electric machine and the characteristic variable.

[0075] For example, as in Fig. 7 can be seen, which in Fig. The field-oriented control shown in Figure 3 is initially extended by a torque control loop.

[0076] For example, the output torque of the electric machine is determined based on a mechanical model 32 for a rotor bearing of the electric machine and the detected or determined rotor torque. The difference between the determined output torque and the requested torque is fed to a PI controller 29.

[0077] The torque control loop makes it possible to set an actually requested torque.

[0078] In a next step, the components of the stator current are optimized for the control torque with respect to a minimum length of a resulting current vector of the components of the stator current depending on given modulation degrees of a space-vector modulation of the field-oriented control.

[0079] For this purpose, the stator current components are optimized using an optimization method, such as a gradient method, a parameter estimation method, Kalman filtering, and / or model predictive control, for a given modulation level of a space-vector modulation of the field-oriented control, such that the resulting current vector of the stator current components has a minimal length. The operating limits of maximum current and maximum voltage / modulation level are maintained. In a subsequent step, it is checked whether a further reduction in power can be achieved with a lower modulation level. To this end, the previous steps are repeated at a lower modulation level.

[0080] When an operating point is reached where a specified optimization criterion is met, the characteristic map for this operating point is adjusted with respect to the stator current components to be adjusted and / or the modulation level and / or the torque. For example, if the product of current and modulation level (voltage) is minimal, the characteristic map is adapted for the operating point.

[0081] This means that the correct pre-control value(s) is already available for the next change to this operating point. For example, the target components Id_s, Iq_s of the electric machine's stator current are stored in the characteristic map as a function of the requested torque, speed, and magnetic flux. The target components Id_s, Iq_s of the stator current are adapted as a function of the torque, speed, and magnetic flux, with the magnetic flux depending on the degree of modulation and the rotor temperature.

[0082] Alternatively, the module comprises an angular position detection sensor configured to detect and / or determine an angular position of the rotor. The at least one input variable comprises the detected angular position of the rotor, and adapting the detection error of the further sensor comprises adapting a rotation angle error of the angular position detection sensor.

[0083] In this case, for example, in step S5 for adapting the rotation angle error, the electric machine is operated at a stationary operating point for which a target torque of the rotor is specified.

[0084] The electric machine is preferably operated in field-weakening mode at the highest possible speed. The current angular position of the rotor is recorded, and a corrected angular position is determined based on a predefined adaptation rule. The corrected angular position is used as the input variable for the field-oriented control. This adaptation of the angular position is repeated until the requested torque, measured on the shaft by the torque sensor, is achieved.

[0085] For example, the rotor position is adapted step by step with an angular offset.

[0086] Without adaptation of the detected angular position, deviations in the range of 0° to ± 2° can occur. Adapting the detected angular position of the angular position detection sensor allows for improved detection accuracy. This eliminates the need for more precise, and therefore more expensive, angular position sensors. List of reference symbols 1 rotor core 2 rotor shaft 3 second recess 4 first recess 5 bridge 6 Sensor element 20 PI current controllers 22 first unit 24 B6 inverters 26 second unit 28 first module 29 PI torque controller 32 Mechanical model Iq_i, Id_i actual components of the stator current Iq_s, Id_s Target components of the stator current S1 to S9 program steps

Claims

[1] Method for operating an electrical machine, in which - the electric machine has a rotor and a torque sensor with a sensor element (6), wherein the sensor element (6) is arranged on the rotor, - the electrical machine includes a field-oriented control or the field-oriented control is assigned to the electrical machine, - the electrical machine has a module or the module is assigned to the electrical machine, wherein the module comprises a predetermined machine model and / or a further sensor and is designed to detect and / or determine an input variable for the field-oriented control and to provide this for the field-oriented control, and the method comprises the following steps: - Providing a characteristic value which is representative of an output torque of the rotor, which is detected and / or determined by the sensor element (6) and - Adapting a parameter of the machine model and / or a detection error of the other sensor depending on the parameter, - the module has the machine model and is designed to determine, depending on a predetermined torque for the rotor and the predetermined machine model, target components (Id_s, Iq_s) of a stator current of the electrical machine, which are fed to the field-oriented control as input variables, wherein the machine model comprises a predetermined characteristic map for determining the target components (Id_s, Iq_s) of a stator current for optimized operation of the electrical machine with respect to an efficiency and / or an efficiency of the electrical machine, - adapting the parameter of the machine model comprises adapting the characteristic map, wherein adapting the characteristic map comprises the steps: - Determination of a control torque for the electrical machine depending on a requested torque of the electrical machine and the characteristic, - Optimizing the components of the stator current with respect to a minimum length of a resulting current vector of the components of the stator current depending on given modulation levels of a space-vector modulation of the field-oriented control for the control torque, - when an operating point is reached at which a specified optimization criterion is met, the characteristic map for this operating point is adapted with regard to the components of the stator current to be adjusted and / or the degree of modulation and / or the torque, - the module comprises an angular position detection sensor which is designed to detect and / or determine an angular position of the rotor, - the at least one input variable comprises the detected angular position of the rotor, and - adapting the detection error of the further sensor comprises adapting a rotation angle error of the angular position detection sensor, wherein the sensor element (6) comprises at least one strain gauge and where adapting the angle error comprises the steps: - Operating the electrical machine at a stationary operating point for which a target torque of the rotor is specified, and during operation (a) Detecting a current angular position of the rotor, (b) Determining a corrected angular position depending on a given adaptation rule, (c) Providing the corrected angular position as the input for the field-oriented control, (d) Repeat steps (a) to (c) until the difference between the measured characteristic and the specified target torque is minimal. [2] Device for operating an electrical machine which is designed to carry out the method according to claim 1. [3] An electrical machine comprising a device according to claim 2 and a rotor and a torque sensor with a sensor element (6), wherein the sensor element (6) is arranged on the rotor and comprises at least one strain gauge, and the device is signal-coupled to the torque sensor.

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