WO2023222152A1

WO2023222152A1 - Method for operating an electric machine, computer program product, control unit, electric machine, hybrid module

Info

Publication number: WO2023222152A1
Application number: PCT/DE2023/100280
Authority: WO
Inventors: Erhard Hodrus; Alexander Rösch
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2022-05-20
Filing date: 2023-04-20
Publication date: 2023-11-23
Also published as: DE102022112712A1

Abstract

The invention relates to a method for operating an electric machine (1), comprising a stator (2) and a rotor (3), which is rotatable relative to said stator with variation of a rotation position at a rotor rotational speed n, wherein the electric machine (1), in a first operating state (4), is operated with electrical open-loop control as a function of a rotation angle position of the rotor (3) that is measured by a rotation angle sensor (5), and, in a temporally succeeding second operating state (6), is operated with electrical closed-loop control as a function of a rotation angle position of the rotor (3) that is calculated without the measured rotation angle position of the rotation angle sensor (5), wherein between the first operating state (4) and the second operating state (6) a time interval (7) is defined in which the rotation angle position of the rotor (3) that is measured at the beginning of the time interval (7) and the calculated rotation angle position of the rotor (3) that is expected at the end of the time interval (7) are interpolated by means of a mathematical function and/or a mathematical method, such that the measured rotation angle position transitions toward the calculated rotation angle position of the rotor (3) during the operation of the electric machine (1) within the time interval (7).

Description

Method for operating an electrical machine, computer program product, control unit, electrical machine, hybrid module

The present invention relates to a method for operating an electrical machine, comprising a stator and a rotor that can be rotated relative to it while changing a rotational position with a rotor speed n, wherein the electrical machine is electrically in a first operating state depending on a rotation angle position of the rotor measured by a rotation angle sensor is operated in a controlled manner and is operated in an electrically controlled manner in a temporally subsequent second operating state depending on a rotation angle position of the rotor which is calculated without the measured rotation angle position of the rotation angle sensor. The invention further relates to a computer program product, a control unit, an electrical machine and a hybrid module.

A growing need for individual mobility, an increasing number of cars and increasing car dimensions require measures to improve the parking situation in urban areas. In addition to aspects such as urban densification and increasing vehicle numbers, constantly increasing vehicle dimensions lead to a shortage of parking spaces and complicated parking procedures. One way to overcome this challenge is to implement new vehicle and transport concepts that aim to replace conventional cars. Alternative vehicle structures and new steering technologies are able to meet specific parking and important customer requirements simultaneously.

For this reason, such cars are increasingly being equipped with rear-axle steering, which significantly improves the maneuverability of these vehicles and, in particular, also supports automatic parking of the car. Electrically and/or hydraulically actuated actuators are usually used to actuate the rear axle steering. For obvious safety-relevant reasons, it is important to detect the exact position of the actuator or the rear axle steering safely and as accurately as possible. From DE 10 2018 130 228 A1 an actuator for a rear axle steering of a motor vehicle is known, comprising a push rod which is longitudinally displaceable within a housing and has an anti-rotation device. A sensor unit is integrated into the housing of the rear axle steering actuator.

In addition to various actuator functions, such as the steering actuator system mentioned, electric machines, in particular permanently excited synchronous motors, are also increasingly being used for driving motor vehicles in order to create alternatives to internal combustion engines that require fossil fuels. Significant efforts have already been made to improve the suitability of electric drives for everyday use and to offer users the usual driving comfort.

With permanently excited synchronous motors, it is also very important how the parts through which the magnetic field flows are positioned relative to one another. This also applies to the exact knowledge of the angular position of the rotating parts, because the constantly changing position of the magnets integrated in the rotating rotor (angular position) in the rotating motor must always be known exactly relative to the windings integrated in the stator in order to control the electric motor to be able to navigate correctly. The changing angular position of the rotor must be known exactly at any time in order to align the rotor components (e.g. the rotor magnets, which are usually designed as permanent magnets) relative to the stator components (e.g. the stator magnets, which are usually designed as electromagnets / stator windings) and to be able to adjust the motor control accordingly.

The control of such an electric motor is achieved by imposing a rotating field in the windings of the motor. Depending on the rotor position angle, the rotating field must be adjusted via a control system. As a rule, the position of the rotor is measured using a rotor position sensor and the determined rotor position angle is sent to the control of the Electric motor handed over.

In order to save costs and installation space, encoderless controls have already become known, which do not require a physical rotor position sensor. In this case, only the current sensors, which are indispensable for field-oriented control, are used. This control concept, which is particularly widespread in 3-phase permanently excited synchronous machines, is based on a transformation of the 3-phase alternating variables into a two-axis coordinate system, which rotates synchronously with the rotor flux of the machine. In such a coordinate system, usually referred to as a d/q coordinate system, for example the three phase currents of the stator winding i_u, i_v, i_w are represented by a 2-dimensional current vector with the components i_q and i_d. With an ideally sinusoidal rotor flux and ideally sinusoidal phase currents, the original alternating variables i_u, i_v, i_w are mapped to equal sizes i_q, i_d as a result of the coordinate system rotating synchronously with the rotor flux.

In field-oriented current control, the voltage values or current values of the phases of the stator of the synchronous machine are transformed in a known manner to a two-dimensional coordinate system, the mutually perpendicular axes of which are usually designated d (“direct”) and q (“quadrature”). This coordinate system rotates relative to the stator of the synchronous machine and rests relative to the rotor of the synchronous machine. The transformation itself is called the park transformation, the two-dimensional coordinate system to which the transformation is carried out is called the park coordinate system. The park transformation can take place via the intermediate step of a, also known, Clarke transformation, which transforms the voltage values or current values of the phases of the stator of the synchronous machine to a two-dimensional, orthogonal coordinate system that is at rest relative to the stator.

When operating an electric motor without sensors - as already mentioned above - the rotor position sensor, which is usually used to determine the current angle of the rotor, is dispensed with. For example, current sensor signals and measured or estimated phase voltages are used to use a model to determine the rotor position and the Close the speed of the motor. Below a speed threshold of absolute speed, it is necessary to feed in so-called injection signals, which support the identification of the rotor position and the speed in this speed range.

WO 2020 001 681 A1 describes an electric motor with a stator and a rotor that can be rotated relative to it, and a control system that can output a current pulse to the electric motor, the current pulse causing a rotational movement of the rotor in a first direction of rotation and by a first angle of rotation and thereby causes an induced voltage that is received by the control system and through which the control system determines the direction of rotation and / or the rotational position of the rotor with respect to the stator.

DE 102018 120 421 A1 discloses a method for sensorless control of permanent magnet, synchronous electric motors, in which a description of a system is carried out in a stationary aß coordinate system of an electric motor. The system includes an electromagnetic model and a mechanical model of an electric motor and drive train. For the model, differential inductances, which depend on the currents of the electric motor, are stored in the form of look-up tables. The look-up tables can be called up for the calculation. Based on the electromagnetic and mechanical model, the speed and angle of the electric motor are estimated through a Kalman filter, which is mainly done via the mechanical model. The electrical model can be used to supply an internal torque for the torque equation in order to determine a change in speed or angle.

Sensorless operation of electrical machines has not yet become established in electric vehicles. The reason for this is that sensorless operation has been proven to work well and stably at higher speeds. For speeds close to zero, operation is only possible with the addition of injection signals. However, choosing suitable injection signals represents a very big challenge, as the effects of injection signals are not always positive on the system. On the one hand, it can happen because of the injection signals disturbing noise developments occur, and on the other hand it is difficult to find a stable and robust combination when choosing the injection signals in terms of frequency and amplitude.

However, the use of a safety-certified rotation angle sensor for the rotation angle position of the rotor also fundamentally helps when discussing safety-critical scenarios in functional safety. For example, for pump drives, compressors or fans, sensorless operation of corresponding electrical machines is already part of the state of the art. A popular procedure for starting the engine is to switch from a purely controlled start-up of the electric motor by specifying a rotating field to a sensorless controlled electric motor. This approach avoids the use of injection signals for speeds close to zero.

Switching from controlled operation to sensorless-controlled operation inevitably results in strong impulses in the current or

Voltage signals, since the angle signal required for the control of the electric motor usually has a discontinuity between the controlled operation and the regulated operation. During startup, the current angle signal is assigned to a specific angular position in the rotor-fixed coordinate system, e.g. d-direction. The angular position that occurs in sensorless controlled operation differs from this, since q-direction components are then added to the d-direction components.

The object of the invention is to avoid or at least reduce the disadvantages known from the prior art and to provide an improved method for operating an electrical machine. Furthermore, it is the object of the invention to realize an improved computer program product, an optimized control unit, an improved electrical machine and an improved hybrid module.

This task is solved by a method for operating an electrical

Machine, having a stator and a stator opposite this

Changing a rotational position with a rotor speed n rotatable rotor, where the electric machine is operated in an electrically controlled manner in a first operating state depending on an angle of rotation position of the rotor measured by a rotation angle sensor and is operated in an electrically controlled manner in a second operating state that follows, depending on a rotation angle position of the rotor calculated without the measured angle of rotation position of the angle of rotation sensor, between which First operating state and the second operating state, a time interval is defined in which the rotation angle position of the rotor measured at the beginning of the time interval and the calculated rotation angle position of the rotor expected at the end of the time interval are interpolated by means of a mathematical function and / or a mathematical method, so that during operation of the electrical machine within the time interval a fade of the measured rotation angle position to the calculated rotation angle position of the rotor takes place.

According to the invention, it is therefore proposed to fade the controlled operation into the regulated operation in a defined time interval.

This has the advantage that the signals necessary for operating the engine continue to flow smoothly and vibrations in the overall system can be avoided.

Sensorless operation is understood to mean operation without taking into account a rotational position measured with a sensor, for example a rotation angle sensor.

First, the individual elements of the claimed subject matter of the invention are explained in the order in which they are mentioned in the claim sentence and particularly preferred embodiments of the subject matter of the invention are described below.

For the purposes of this application, motor vehicles are land vehicles that are moved by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (passenger cars), trucks (lorries), mopeds, light vehicles, motorcycles, motor buses (KOM) or tractors. A hybrid electric vehicle, also known as a Hybrid Electric Vehicle (HEV), is an electric vehicle that is powered by at least one electric motor and another energy converter and draws energy from both its electrical storage (battery) and additional fuel.

For the purposes of this application, the drive train of a motor vehicle is understood to mean all components that generate the power in the motor vehicle to drive the motor vehicle and transmit it to the road via the vehicle wheels.

An electrical machine is used to convert electrical energy into mechanical energy and/or vice versa. In connection with the invention, the electrical machine can be designed as a radial or axial flux machine. An electrical machine usually includes a stationary part called a stator, stand or armature and a part called a rotor or rotor which is arranged to be movable relative to the stationary part. An electrical machine can be designed to run dry or wet.

According to an advantageous embodiment of the invention, it can be provided that the electrical machine is designed as a permanently excited synchronous machine.

The electric machine is intended in particular for use within an electrically operable drive train of a motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. The electric motor particularly preferably has a power greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, most preferably greater than 12,500 rpm.

The angle of rotation sensor is preferably designed as an absolute angle of rotation sensor for an electrical machine. The rotation angle sensor preferably sets the Sensor signal representing rotor angular position is available. Most preferably, the sensor signal is sent to a control device for controlling the electrical machine.

An electrical machine can also have a control device. A control device, as can be used in the present invention, is used in particular for the electronic control and/or regulation of one or more technical systems of the electrical machine.

A control device has in particular a wired or wireless signal input for receiving, in particular, electrical signals, such as sensor signals. Furthermore, a control device also preferably has a wired or wireless signal output for transmitting, in particular, electrical signals.

Control operations and/or regulation operations can be carried out within the control device. It is particularly preferred that the control device comprises hardware that is designed to execute software. The control device preferably comprises at least one, preferably two, electronic processors for executing program sequences defined in software. The two processors can also be structurally integrated into a processor as computer cores, with the corresponding computer cores then each representing a processor in the sense of the invention.

The control device can also have one or more electronic memories in which the data contained in the signals transmitted to the control device can be stored and read out again. Furthermore, the control device can have one or more electronic memories in which data can be stored in a changeable and/or unchangeable manner.

A control device can comprise a plurality of control devices, which are arranged in particular spatially separated from one another in the motor vehicle. Control units are also known as Electronic Control Units (ECU) or Electronic Control Modules (ECM) and preferably have electronic microcontrollers Carrying out arithmetic operations to process data, particularly preferably using software. The control devices can preferably be networked with one another, so that wired and/or wireless data exchange between control devices is possible. In particular, it is also possible to network the control devices with one another via bus systems present in the motor vehicle, such as CAN bus or LIN bus.

Very particularly preferably, the control device has at least one processor and at least one memory, which in particular contains a computer program code, the memory and the computer program code being configured with the processor to cause the control device to execute the computer program code.

The control unit can particularly preferably include power electronics for energizing the stator or rotor. Power electronics is preferably a combination of various components that control or regulate a current to the electrical machine, preferably including the peripheral components required for this, such as cooling elements or power supplies. In particular, the power electronics or one or more power electronics components contain which are set up to control or regulate a current. This is particularly preferably one or more circuit breakers, e.g.

Power transistors. Particularly preferably, the power electronics has more than two, particularly preferably three, phases or current paths that are separate from one another, each with at least one separate power electronics component. The power electronics are preferably designed to control or regulate a power per phase with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W.

Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically sensible manner and can define further embodiments of the invention. In addition, the features specified in the claims are in the Description is more precise and explained, with further preferred embodiments of the invention being presented.

According to an advantageous embodiment of the invention, it can be provided that the mathematical function is a linear function. The advantage of this design is that a linear function can be implemented with little effort.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the blending between the rotation angle position of the rotor measured at the beginning of the time interval and the calculated rotation angle position of the rotor expected at the end of the time interval is carried out by changing the weighting of the two rotation angle positions at any time within the time interval, the sum of the two weighted rotation angle positions corresponds to the value, whereby at the beginning of the time interval the measured rotation angle position of the rotor has the weighted value and the expected calculated rotation angle position of the rotor has the weighted value and at the end of the time interval the measured rotation angle position of the rotor the weighted value and the expected calculated rotation angle position of the rotor has the weighted value. The advantageous effect of this embodiment is that a continuous angle signal is achieved by weighting with continuously running functions.

According to a further particularly preferred embodiment of the invention, it can be provided that the time interval has a period of time between 0.001-0.1 see. having. This makes it possible, in particular, to achieve the effect that the linear interpolation has a different slope. The maximum excitation in the signal curve can be influenced in this way and can be determined via simulations and tests.

Furthermore, the invention can also be further developed in such a way that the method is used when the rotor starts up. The advantage of this configuration is that the use of injection signals can be dispensed with. The object of the invention is further achieved by a computer program product which is stored on a machine-readable carrier, or computer data signal, embodied by an electromagnetic wave, with program code which is suitable for carrying out the method according to claims 1-5.

The object of the invention can also be achieved by a control unit for controlling and powering an electrical machine, in particular an electrical synchronous machine, comprising a processor and a memory which contains a computer program code, the memory and the computer program code being configured with the processor To cause the control unit to carry out a method according to claims 1-5.

The object of the invention can further be achieved by an electric machine, in particular for a drive train of an electrically operated motor vehicle, comprising a control unit according to claim 7.

Finally, the object of the invention can also be achieved by a hybrid module for a drive train of a motor vehicle, comprising an electric machine according to claim 8.

The invention will be explained in more detail below using figures without restricting the general idea of the invention.

It shows:

Figure 1 is a rotor angular position-time diagram,

Figure 2 shows a measurement for blending the measured angle of rotation position to the calculated angle of rotation position of the rotor,

Figure 3 shows the timing of the startup without fading on the same

Test setup like the one used for Figure 2, Figure 4 shows the timing of the start-up without fading on the same

Test setup like that used for Figures 2-3,

Figure 5 shows an electrical machine in a schematic axial sectional representation,

Figure 6 Hybrid module in a drive train of a motor vehicle in a schematic block diagram.

The method according to the invention for operating an electrical machine 1 is first explained in more detail with reference to FIG. 1 and FIG. 5.

The electric machine 1 has a stator 2 and a rotor 3 which can be rotated relative to it by changing a rotational position with a rotor speed n, which can be clearly seen from FIG. The electric machine 1 is configured for a drive train 21 of an electrically operable motor vehicle 22 and has a control unit 13 for controlling and energizing the electric machine 1. In the exemplary embodiment shown, the electric machine 1 is designed as a synchronous machine. The control unit 13 comprises a processor 14 and a memory 15 which contains a computer program code, the memory 15 and the computer program code being configured with the processor 14 to cause the control unit 13 to carry out a method for operating an electrical machine 1, which follows is explained in more detail.

The electric machine 1 is operated in an electrically controlled manner in a first operating state 4 depending on an angle of rotation position of the rotor 3 measured by a rotation angle sensor 5 and in a second operating state 6 which follows in time, it is operated electrically depending on a rotation angle position of the rotor 3 calculated without the measured angle of rotation position of the angle of rotation sensor 5 is operated in a controlled manner. 1, a time interval 7 is defined between the first operating state 4 and the second operating state 6, in which the rotation angle position of the rotor 3 measured at the beginning of the time interval 7 is determined by means of a mathematical function and/or a mathematical method and the calculated angle of rotation position of the rotor 3 expected at the end of the time interval 7 are interpolated, so that during operation of the electrical machine 1 within the time interval 7, a fade of the measured angle of rotation position to the calculated angle of rotation position of the rotor 3 takes place.

The resulting rotation angle is shown as a highlighted line. Before the time interval 7, which can also be referred to as the fade interval, this corresponds to the controlled rotation angle position, while after the time interval 7 it corresponds to the estimated value of the rotation angle position. From Figure 1 it can also be seen that the mathematical function, which interpolates the measured rotation angle position of the rotor 3 and the calculated rotation angle position of the rotor 3 expected at the end of the time interval 7, is a linear function.

The blending between the rotation angle position of the rotor 3 measured at the beginning of the time interval 7 and the calculated rotation angle position of the rotor 3 expected at the end of the time interval 7 can be carried out, for example, by changing the weighting of the two rotation angle positions by adding the sum at each time within the time interval 7 of the two weighted rotation angle positions corresponds to the value 1, whereby at the beginning of the time interval 7 the measured rotation angle position of the rotor 3 has the weighted value 1 and the expected calculated rotation angle position of the rotor 3 has the weighted value 0 and at the end of the time interval 7 the measured rotation angle position of the rotor 3 has the weighted value 0 and the expected calculated rotation angle position of the rotor 3 has the weighted value 1.

The method described can be used in particular when the rotor 3 is running up. 2 shows a measurement with a total of five diagrams arranged one below the other for blending. The X-axis is a time axis. The crossfade area is marked by two vertical dashed lines. The angle of rotation is shown in the first diagram. You can first see the angle curve 8, which results from the rotation angle sensor 5. Of course, this will no longer be available later in encoderless operation. The angle profile 9 shows the estimated angle from the corresponding angle estimation algorithm. The angle curve 10 shows the angle from the controlled run-up; this angle is used to start at the time of the fade. By the end of the fade, this portion is then reduced to zero and the portion of the estimated angle is increased, starting from zero, to the full value. The value valid at the time can be determined, for example, by linear interpolation from the respective start and end values. The angle course 11, the interpolated value within the time interval 7 can be clearly seen.

The speeds are shown in the second diagram. By changing from controlled to sensorless control, a slight drop in speed can be observed.

The phase voltages are shown in the third diagram. The target current is shown in the fourth of the five diagrams. Since the controlled startup is carried out with pure d current, the q current is zero. From the speed, a desired target current in the d and q directions can be determined for the time after the crossfade within the time interval 7. At the time the crossfade starts, the controlled i-q current pair is calculated to the value after the crossfade by linear interpolation. The phase currents are shown in the fifth diagram.

In Figure 3, the timing of the startup is shown without fading (time interval 7 is missing) using the same test setup as that used for Figure 2. At the time of switching (vertical dashed line), the motor stops more or less abruptly and only manages to return to the desired speed after a small delay to keep turning.

In Figure 4, the timing of the startup without fading (time interval 7 is missing) is shown using the same test setup as that used for Figures 2 and 3. You can clearly see that there are strong fluctuations in the signals, but compared to Figure 3, the engine continues to run better. Without the crossfade, an unpredictable influence can occur. The difference is between the system response in Figure 3 and Figure 4 is the time at which the switchover occurs. This switchover can take place without major influences on the speed, as shown in FIG. 4, or can lead to the engine stalling, as in FIG. 3. Therefore, fading, as shown in Figures 1-2, is very suitable for ensuring safe operation of the electrical machine 1, since it cannot then show the undesirable system behavior of Figures 3-4.

When you look at Figure 2 together with Figures 3-4, you can clearly see how effective the blending of the signals is. This can ensure a smooth and, above all, reproducible transition from controlled startup to encoderless operation.

Finally, Figure 6 shows a possible use of the electrical machine 1, as known from Figure 5, in a hybrid module 20 for a drive train 21 of a motor vehicle 22. In principle, it is of course also conceivable to use the electrical machine 1 from Figure 5 suitable uses, for example as an actuator within a steering system of a motor vehicle or as a drive machine in an axle drive train of a motor vehicle.

The invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be viewed as limiting but rather as illustrative. The following patent claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description are 'first' and If you define a 'second' characteristic, this designation serves to distinguish two similar characteristics without specifying a ranking.

Reference character list

1 electric machine

2 stators

3 rotor

4 Operating status

5 rotation angle sensor

6 Operating status

7 time interval

8 angle progression

9 Angle course

10 angle progression

11 Angle course

13 control unit

14 processor

15 memories

20 hybrid module

21 Drivetrain

22 motor vehicle

Claims

Claims Method for operating an electrical machine (1), comprising a stator (2) and a rotor (3) which can be rotated relative to it by changing a rotational position at a rotor speed n, the electrical machine (1) being in a first operating state (4). Dependence on a rotation angle position of the rotor (3) measured by a rotation angle sensor (5) is operated electrically controlled and in a temporally subsequent second operating state (6) depending on a rotation angle position of the rotor (3) calculated without the measured rotation angle position of the rotation angle sensor (5). is operated in a controlled manner, characterized in that a time interval (7) is defined between the first operating state (4) and the second operating state (6), in which, by means of a mathematical function and / or a mathematical method, the time interval at the beginning of the time interval (7) measured rotation angle position of the rotor (3) and the calculated rotation angle position of the rotor (3) expected at the end of the time interval (7) are interpolated, so that during operation of the electrical machine (1) within the time interval (7) a fade of the measured rotation angle position to the calculated rotation angle position of the rotor (3). Method according to claim 1, characterized in that the mathematical function is a linear function. Method according to one of the preceding claims, characterized in that the blending between the rotation angle position of the rotor (3) measured at the beginning of the time interval (7) and that at the end of the time interval (7) The expected calculated rotation angle position of the rotor (3) is carried out by changing the weighting of the two rotation angle positions, in that at every point in time within the time interval (7) the sum of the two weighted rotation angle positions corresponds to the value 1, with the measured one at the beginning of the time interval (7). Angle of rotation position of the rotor (3) has the weighted value 1 and the expected calculated angle of rotation position of the rotor (3) has the weighted value 0 and at the end of the time interval (7) the measured angle of rotation position of the rotor (3) has the weighted value 0 and the expected calculated angle of rotation position of the rotor (3) has the weighted value 1. Method according to one of the preceding claims, characterized in that the time interval (7) has a period of time between 0.001-0.1 see. having. Method according to one of the preceding claims, characterized in that the method is used when the rotor (3) starts up. Computer program product stored on a machine-readable medium, or computer data signal embodied by an electromagnetic wave, with program code suitable for carrying out the method according to claims 1-5. Control unit (13) for controlling and powering an electrical machine (1), in particular an electrical synchronous machine, comprising a processor (14) and a memory (15) which contains a computer program code, the memory and the computer program code being configured with the processor (14) to cause the control unit (13) to carry out a method according to claims 1-5. Electric machine (1), in particular for a drive train (21) of an electrically operated motor vehicle (22), comprising a control unit (13) according to claim 7. Hybrid module (20) for a drive train (21) of a motor vehicle (22) comprising an electric machine ( 1) according to claim 8.