Method for operating an electric powertrain, powertrain and motor vehicle

Abstract

The invention relates to a method for operating an electric drive train (1) in the event of a failure, wherein the electric drive train (1) comprises at least one electric motor (3) connected to a drive axle (2) in a torque-transmitting manner, a battery (4) for storing electrical energy (5), an inverter (6) for transferring the energy (5) from the battery (4) to the electric motor (3) and from the electric motor (3) to the battery (4), and a control unit (7) that is designed to carry out the method; wherein, within the framework of the method, a failure is detected, a temperature (8) of a component (9) of the inverter (6) is measured, a rotational speed (10) of the motor (3) or a voltage (11) induced by the rotational speed (10) in the inverter (6) is monitored and measured.

Description

[0001] The invention relates to a method for operating an electric drive train, a drive train and a motor vehicle.

[0002] An electric drive train comprises at least one electric motor (also called traction drive) connected to a drive axle in a torque-transmitting manner, a battery (also called secondary battery) for storing electrical energy, and an inverter for transferring the energy from the battery to the electric motor and from the electric motor to the battery.

[0003] The battery is usually connected to the inverter via electrical connecting cables. The inverter is usually connected to the motor via connecting cables. Signal cables may also be provided to connect the components to each other or to a control unit.

[0004] In drive train or motor vehicle applications, the connecting cables between the battery and the inverter are subjected to high voltages, usually higher than 100 volts, especially more than 200 volts and even more than 380 volts, or between 100 and 900 volts.

[0005] In the event of an accident (damage event), these high-voltage connecting cables between the battery and the inverter or power converter can be damaged and possibly exposed.

[0006] In this case of damage, the inverter usually switches to the safety state of a so-called "active short circuit" (ASC) and discharges all of the electrical energy present in the inverter via corresponding components (particularly resistors) inside the inverter within the shortest possible time. In particular, the electrical energy present in the inverter is converted into heat.

[0007] If the motor vehicle or even just the drive train is set in motion, e.g. by towing the vehicle, the electric motor, which is set in rotation via the drive axle, induces electrical energy into the inverter. This leads to heating of the inverter components, which continue to be in the described safety state. If the temperature in the inverter or at least one component exceeds a critical threshold or a predetermined limit, the inverter changes from the "active short circuit" (ASC) safety state to the "open circuit" (OC) state and diverts the electrical energy to the battery. This is intended to lower the temperature in the inverter or at the components and thus prevent the inverter from being destroyed or a fire in the vehicle.

[0008] However, if the connecting cables between the inverter and the battery are damaged or not covered, a person touching them or the metal parts that come into contact with them may receive a life-threatening electric shock.

[0009] A vehicle control device is known from DE 11 2018 000 264 T5.

[0010] CN 1 14 435 137 A relates to a method for active short-circuit control.

[0011] From DE 10 2021 208 438 A1 a method for controlling the operation of an electrical machine of a motor vehicle is known.

[0012] DE 10 2010 031 583 A1 is directed to a method and a device for operating an electric drive device.

[0013] A drive system for a vehicle is known from DE 10 2018 209 243 A1.

[0014] The object of the present invention is to at least partially solve the problems cited with reference to the prior art. In particular, a method for operating an electric drive train is proposed that minimizes the risk to persons in the event of a failure.

[0015] A method having the features according to claim 1 contributes to solving these problems. Advantageous further developments are the subject of the dependent claims. The features listed individually in the claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and / or details from the figures, whereby further embodiments of the invention are shown.

[0016] A method for operating an electric drive train in the event of a failure is proposed. The electric drive train comprises at least one electric motor connected to a drive axle in a torque-transmitting manner, a battery for storing electrical energy, an inverter for transmitting energy from the battery to the electric motor and from the electric motor to the battery, and a control unit. The control unit is suitably designed to carry out the method or has means for carrying out the steps of the method and / or has means that are suitably equipped, configured, or programmed to carry out the steps of the method or that carry out the method.

[0017] The procedure includes at least the following steps: a) Determination of a drive train failure; b) measuring a temperature of at least one component of the inverter; c) Monitoring and measuring at least one speed of the electric motor or an electrical voltage induced by the speed in the inverter.

[0018] The above (non-exhaustive) division of the procedural steps into a) to c) is primarily intended to serve as a distinction and does not enforce any order and / or dependency. The frequency of the procedural steps, e.g. during or after the occurrence of the damage event, can also vary. It is also possible that procedural steps overlap one another at least partially. With particular preference, procedural steps b) and c) take place before step a), i.e. before a damage event occurs. However, steps b) and c) can also be conditional and may only be carried out if a damage event or a specific damage event is identified in step a). In particular, steps a) to c) are carried out in the specified order.

[0019] The electric drive train comprises, in particular, only one electric motor connected to a drive axle in a torque-transmitting manner, or possibly also several motors connected to a drive axle (possibly assigned to individual wheels) or to different drive axles in a torque-transmitting manner. In particular, the drive train comprises one or more batteries (also referred to as a secondary battery) for storing (releasing and reabsorbing) electrical energy. The drive train further comprises an inverter for transmitting energy from the at least one battery to the at least one electric motor and from the at least one electric motor to the at least one battery. Several inverters can also be provided.

[0020] The battery is connected to the inverter via electrical connecting cables. The inverter is connected to the motor via connecting cables. Signal cables can also be provided to connect the components to each other or to the control unit. These signal cables can be used to transmit measured values ​​such as temperature, voltage, and speed to the control unit.

[0021] In the event of an accident (damage event), the live connecting cables between the battery and the inverter or power converter, which are designed to transmit electrical energy, may be damaged and possibly exposed.

[0022] It is known that in certain accidents (e.g., depending on the severity of the accident, such as negative or positive acceleration or the failure of certain components of a motor vehicle), error signals are stored in the control system of a motor vehicle or in the control unit. If this error signal is stored in the control system of the motor vehicle or in the control unit of the powertrain, the damage can be determined through step a) of the method.

[0023] It is known that in this event of damage, the inverter enters the previously described safety state of the so-called "active short circuit" (ASC), discharging all of the electrical energy present in the inverter via corresponding components (especially resistors) inside the inverter within the shortest possible time. In particular, the electrical energy present in the inverter is converted into heat.

[0024] In this state of the motor vehicle or the drive train, i.e. with a discharged inverter and components or the engine at a standstill, there is no danger to a person from electric shock, e.g., from contact with damaged connecting cables.

[0025] If the temperature in the inverter or at least one component exceeds a critical threshold or a predetermined first limit, the inverter transitions from the "active short circuit" (ASC) safety state to the "open circuit" (OC) state and diverts the electrical energy to the battery. This is intended to reduce the temperature in the inverter or its components, thus preventing the inverter from being destroyed or a fire in the vehicle.

[0026] For these known steps, only monitoring or measuring the temperature according to step b) was required.

[0027] However, if the vehicle or even just the drivetrain is set in motion (i.e., after the damage has been detected or occurred), e.g., by towing the vehicle, the electric motor, which is set in rotation via the drive axle, induces electrical energy into the inverter. This leads to (further) heating of the inverter components, which then remains in one of the described safety states, ASC or OC.

[0028] If the connecting cables between the inverter and the battery are damaged or not covered, a person touching them or the metal parts that come into contact with them can suffer a life-threatening electric shock if, for example, the drive train is in the OC safety state.

[0029] It is therefore proposed that, in addition to the temperature of the inverter or a component of the inverter (see step b)), a speed of the motor (or a component of the drive train connected to it) and / or an electrical voltage induced in the inverter by the speed is also monitored and measured.

[0030] The procedure checks whether the (directly or indirectly) measured speed and / or the (directly or indirectly) measured voltage corresponds to, falls below, or exceeds a second limit value.

[0031] The speed and / or voltage can also be determined indirectly based on other parameters. For example, the current or rotor position can be monitored or measured to determine the speed.

[0032] The second limit value can be set individually for each specific drivetrain. In particular, it remains constant for each drivetrain.

[0033] In particular, this check is only performed if the temperature measured in step b) exceeds the first limit. Alternatively, this check can also be performed continuously, particularly after the damage event has occurred and been detected. In particular, this check can be performed when the measured temperature approaches the first limit.

[0034] By monitoring and / or measuring the speed and / or voltage (directly or indirectly) it is possible to decide whether the OC safety state can be maintained or should be terminated.

[0035] In particular, it is proposed that, if the temperature measured in step b) exceeds a first limit value and the speed or voltage measured in step c) corresponds at most to a second limit value, in a step d1), the energy induced by the motor in the inverter is directed to the battery (and thus the safety state OC is initiated or maintained).

[0036] The second limit value is selected in particular in such a way that the voltage induced in the inverter or then possibly present on the connecting lines is set to a value at which there is no danger to persons in particular with regard to electric shock.

[0037] The relationship between the speed of the motor and the voltage then present in the inverter (or its course and its final value) is known in particular from the characteristics of the components used (in particular the inverter).

[0038] It is further proposed in particular (additionally or alternatively) that if the temperature measured in step b) exceeds a first limit value and the speed or voltage measured in step c) exceeds a second limit value, in a step d2) the electrical energy induced by the motor in the inverter is converted into heat exclusively in the inverter (and thus the safety state OC is not initiated or terminated).

[0039] Here too, the (non-exhaustive) division of the procedural steps into a) to d1) or d2) primarily serves to distinguish them and does not enforce any order and / or dependency. The frequency of the procedural steps, e.g. during or after the occurrence of the damage event, can also vary. It is also possible that procedural steps overlap one another at least partially. Most preferably, procedural steps b) and c) take place at least temporarily during the respective step d1) and d2). Steps b) to d1) or d2) can be conditional and may only be carried out if a damage event or a specific damage event is identified in step a).

[0040] In particular, it is possible to switch back and forth between steps d1) and d2), in particular depending on the parameters monitored and / or measured in steps b) and / or c).

[0041] In particular, step d2) is carried out if at least one of steps b) and c), in particular if (only) step c) can no longer be carried out or does not provide any reliable measured values.

[0042] In particular, steps a) to d1) or d2) are carried out in the order listed.

[0043] In particular, step d2) is maintained until at least the inverter is destroyed (e.g., destroyed by fire). This is intended to ensure, in particular, that the drive train cannot independently return to the OC safety state or to the state according to step d1) of the method. This is intended to at least prevent any risk of electric shock to persons.

[0044] In particular, with (the initiation or execution of) step d2), a previously performed step d1), in which the energy induced by the motor in the inverter is directed to the battery, is terminated. In particular, step d1) can therefore be performed before step d2). In particular, during step d2), the energy induced in the inverter is then no longer directed to the battery, but is converted exclusively into heat in the inverter.

[0045] In particular, step d2), in which the electrical energy induced by the motor in the inverter is converted into heat exclusively in the inverter, is terminated and step d1) is initiated (if necessary again) when the currently measured speed or voltage (again) falls to a value that corresponds at most to the second limit value.

[0046] This can, for example, prevent a fire or fire damage to the inverter and direct the energy (at least partially) to the battery.

[0047] In particular, it is not taken into account (i.e. when step d2) is terminated and step d1) is initiated) whether the temperature reaches or exceeds the first limit value, but the energy is dissipated to the battery in any case (i.e. only taking the second limit value into account).

[0048] In particular, the damage case involves damage to at least one electrical connection line between the battery and the inverter. This does not necessarily have to be present. In step a), a decision is only made (e.g., depending on error messages in the vehicle's control system or the powertrain control unit) that this damage case (possibly) exists.

[0049] In particular, immediately after step a) (i.e., once the damage has been determined), the control unit, in step a1), converts the electrical energy present in the inverter as quickly as possible and converts it into heat. This step a1) corresponds to the creation of the "active short circuit" (ASC) safety state described above.

[0050] A drive train for a motor vehicle is further proposed. The electric drive train comprises, in particular, only one electric motor that can be connected or is connected to a drive axle in a torque-transmitting manner, or possibly also a plurality of motors that can be connected or are connected to a drive axle (possibly assigned to individual wheels) or to different drive axles in a torque-transmitting manner. In particular, the drive train comprises one or more batteries (also referred to as a secondary battery) for storing (releasing and reabsorbing) electrical energy. The drive train further comprises an inverter for transmitting the energy from the at least one battery to the at least one electric motor and from the at least one electric motor to the at least one battery. Multiple inverters can also be provided. The drive train also comprises a control unit.

[0051] The control unit is designed to be suitable for carrying out the described method or has means for carrying out the steps of the method and / or has means that are suitably equipped, configured or programmed to carry out the steps of the method or that carry out the method.

[0052] In particular, the control unit is connected via signal lines to the drivetrain components, e.g., the inverter, the connecting cables, the battery, the motor, the drive axle, etc., or to the sensors located there. Measured values ​​of the aforementioned parameters (e.g., temperature, speed, voltage) can be transmitted to the control unit via the signal lines. In particular, measured values ​​can also be actively queried from the control unit, so that they are only recorded by the sensors upon request.

[0053] A motor vehicle is further proposed, comprising at least the described drive train and a drive axle connected to the engine in a torque-transmitting manner. As stated, the motor vehicle can also have multiple drive axles (driven by one engine or by other engines).

[0054] In particular, the control unit is provided as a data processing system having means that are suitably equipped, configured or programmed to carry out the method or that carry out the method.

[0055] The means include, for example, a processor and a memory in which instructions to be executed by the processor are stored, as well as data or signal lines or transmission devices that enable the transmission of instructions, measured values, data or the like between the elements mentioned.

[0056] The “means” may in particular comprise one or more of the following components: controller(s), microcontroller, data memory, data connection, display devices (such as a display), counter or timer, at least one further sensor, an energy source, etc.

[0057] A computer program is further proposed, comprising instructions which, when the computer program is executed by a computer, cause the computer to carry out the described method or the steps of the described method.

[0058] Furthermore, a computer-readable storage medium is proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the described method or the steps of the described method.

[0059] The statements regarding the method are particularly transferable to the drive train, the motor vehicle, the control unit or the data processing system and / or the computer-implemented method (i.e. the computer program and the computer-readable storage medium) and vice versa.

[0060] In addition to monitoring the inverter temperature, once the damage has been detected, the motor speed or the voltage induced in the inverter is also monitored or measured. If the motor or drive axle begins rotating again after the inverter has been discharged (e.g., during the initiation of ASC), the control unit, in particular, evaluates the critical temperature of at least one component of the inverter and whether the speed (on the connecting cables) is generating or induced a dangerous voltage in the inverter.

[0061] If the temperature on or in the inverter exceeds the first limit, the drive train only goes into a safe open circuit (OC) state if the rotation or the existing speed only generates a safe voltage.

[0062] If the speed is so high that a dangerous voltage is generated, the active short circuit (ASC) safety state is maintained to protect people from electric shock, even if the inverter components may then overheat or burn out.

[0063] The use of indefinite articles ("a," "an," "one," and "another"), particularly in the patent claims and the description reproducing them, is to be understood as such and not as a numeral. Terms or components introduced accordingly are therefore to be understood as appearing at least once and, in particular, as being able to appear multiple times.

[0064] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily prescribe any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be necessary, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment. To the extent that a component can occur multiple times ("at least one"), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

[0065] The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments cited. In particular, it should be noted that the figures, and in particular the proportions shown, are only schematic. They show: Fig. 1: a motor vehicle with a drive train; Fig. 2: the drive train Fig. 1 after a damage event has occurred; Fig. 3: a diagram showing step a1); Fig. 4: the drive train Fig. 1 and Fig. 2 in the state ASC; Fig. 5: the drive train Fig. 4 in the state OC; Fig. 6: a flow of the method for establishing the state OC; Fig. 7: a flow of a procedure with a diagram; and Fig. 8: the drive train to Fig. 5 in the state according to step d2).

[0066] The Fig. 1 shows a motor vehicle 14 with a drive train 1 and a drive axle 2 connected to the engine 3 in a torque-transmitting manner. Fig. 2 shows the drive train 1 after Fig. 1 after a damage event has occurred. Fig. 3 shows a diagram illustrating step a1). Fig. 1 to 3 are described together below.

[0067] Furthermore, the drive train 1 comprises an inverter 6 for transmitting the energy 5 from the battery 4 to the electric motor 3 and from the electric motor 3 to the battery 4. In addition, the drive train 1 comprises a control unit 7.

[0068] The battery 4 is connected to the inverter 6 via electrical connecting lines 13. The inverter 6 is connected to the motor 3 via electrical connecting lines 13. Additionally, signal lines 15 are provided, via which the components are connected to each other and to the control unit 7. Measured values ​​of temperature 8, voltage 11, and speed 10 recorded by sensors 16 can be transmitted to the control unit 7 via the signal lines 15.

[0069] In the event of an accident (damage, see Fig. 2) the connecting lines 13 between the battery 4 and the inverter 6, which are energized 11 and intended for the transmission of electrical energy 5, may be damaged and possibly exposed (and then become damaged connecting lines 22, see Fig. 2).

[0070] In certain accidents, error signals are stored in the control system 14 of a motor vehicle or in the control unit 7. If this error signal is stored in the control system of the motor vehicle 14 or in the control unit 7 of the drive train 1, the damage event can be determined by step a) of the method.

[0071] It is known that in this case of damage, the inverter 6 is transferred to the above-described safety state of the so-called “active short circuit” (ASC) and in the process discharges the entire electrical energy 5 present in the inverter 6 via corresponding components (in particular resistors 18) inside the inverter 6 within the shortest possible time 17 (see Fig. 3). The electrical energy 5 present in the inverter 6 is converted into heat.

[0072] In Fig. 3, the voltage 11 in the inverter 6 is plotted on the vertical axis, and time 17 is plotted on the horizontal axis. The first curve 19 shows the increase in voltage 11 during operation of the motor vehicle 14. In the event of damage, this is determined in step a), and immediately after step a) (i.e., when it has been determined that the damage has occurred), the control unit 7, in step a1), converts the electrical energy 5 present in the inverter 6 as quickly as possible and converts it into heat in the inverter 6. This step a1) corresponds to the creation of the "active short circuit" (ASC) safety state described above.

[0073] In this ASC state of the motor vehicle 14 or the drive train 1, i.e. with the inverter 6 discharged and the components or engine 3 stationary, there is no danger to a person with regard to an electric shock, e.g., by contacting damaged connecting lines 22.

[0074] If the temperature 8 in the inverter 6 or at least one component 9 exceeds a critical threshold or a predetermined first limit value 20, the inverter 6 goes from the safety state “active short circuit” (ASC; see Fig. 2) into the “open circuit” state (OC, see e.g. Fig. 5) and transfers the electrical energy 5 to or toward the battery 4, i.e., toward the connecting lines 13. This is intended to lower the temperature 8 in the inverter 6 or at the components 9, thus preventing the destruction of the inverter 6 or a fire in the motor vehicle 14.

[0075] For these known steps, only monitoring or measuring the temperature 8 according to step b) was required.

[0076] Fig. 4 shows the drive train 1 after Fig. 1 and Fig. 2 in the state ASC. Fig. 5 shows the drive train 1 after Fig. 4 in the OC state. Fig. 6 shows a flow of the method for establishing the state OC. Fig. 4 to 6 are described together below. The explanations for the Fig. Reference is made to paragraphs 1 to 3.

[0077] However, if after the detection or occurrence of the damage according to step a) the motor vehicle 14 or just the drive train 1 is set in motion, e.g. by towing the motor vehicle 14, the electric motor 3, which is set in rotation via the drive axle 2, induces electrical energy 5 into the inverter 6 (see Fig. 4). This leads to a (further) heating of the components 9 of the inverter 6, which continues to be in one of the described safety states ASC (see Fig. 4) or OC (see Fig. 5).

[0078] If the connecting lines 13 between the inverter 6 and the battery 4 are damaged or not covered, a person who touches them or the metal parts that come into contact with them may suffer a life-threatening electric shock if the drive train 1 is, for example, in the OC safety state (see Fig. 5).

[0079] In Fig. 6 shows a sequence of the method for establishing the OC state. The Fig. The steps explained in section 6 serve only to explain the process and do not represent separate steps of the procedure.

[0080] In a first step 21, the damage is determined. Damaged connecting lines 22 are present. After the first step 21, the drive train 1 is transferred to the ASC state in a second step 23. For this purpose, the inverter 6 is discharged in a third step 24. In a fourth step 25, it is determined that the motor 3 is rotating (e.g., by towing the damaged motor vehicle 14). As a result of the speed 10 generated at the motor 3, the inverter 6 is charged with a voltage 11 or a voltage 11 is induced in a fifth step 26. In a sixth step 27, a check is carried out to determine whether a temperature 8 on or in the inverter 6 exceeds a first limit value 20. If the temperature 8 is lower than the first limit value 20, the drive train 1 remains in the ASC state according to the seventh step 28.If the temperature 8 exceeds the first limit value 20, the drive train 1 is transferred to the OC state in an eighth step 29.

[0081] There is therefore a voltage potential on the damaged connecting lines 22, which are potentially dangerous for a person 30.

[0082] In order to avoid endangering a person 30 by electric shock, it is therefore proposed that, in addition to the temperature 8 of the inverter 6 or a component 9 of the inverter 6 (according to step b) of the method), a rotational speed 10 of the motor 3 (or a component of the drive train 1 connected thereto, e.g. a rotational speed of the drive axle 2) and / or an electrical voltage 11 induced by the rotational speed 10 in the inverter 6 is monitored and measured.

[0083] As part of the procedure, it is checked whether the (directly or indirectly) measured speed 10 and / or the (directly or indirectly) measured voltage 11 corresponds to a second limit value 12 or falls below or exceeds it.

[0084] In Fig. Figure 7 shows a procedure flow together with a diagram in which the second limit value 12 is taken into account.

[0085] In the diagram, the voltage 11 induced at the inverter 6 is plotted on the vertical axis and the time 17 is plotted on the horizontal axis.

[0086] The Fig. The process shown in Figure 7 differs from the process according to Fig. 6 in the further procedure after the sixth step 27. If the temperature 8 is lower than the first limit value 20, the drive train 1 remains in the state ASC according to the seventh step 28 (as in Fig. 6). However, if the temperature 8 exceeds the first limit value 20, the drive train 1 is further analyzed in a ninth step 31.

[0087] In the ninth step 31 (step c) of the method), a rotational speed 10 of the motor 3 (or a component of the drive train 1 connected thereto, e.g. a rotational speed of the drive axle 2) and / or an electrical voltage 11 induced by the rotational speed 10 in the inverter 6 is additionally monitored and measured.

[0088] In the ninth step 31, it is determined whether the speed 10 or voltage 11 measured in step c) of the method corresponds to or exceeds a second limit value 12. If the speed 10 or voltage 11 is lower than the second limit value 12, in the tenth step 32, i.e., within the scope of a step d1) of the method, the energy 5 induced by the motor 3 in the inverter 6 is directed to the battery 4, thus initiating or maintaining the safety state OC.

[0089] The second limit value 12 is selected or set such that the voltage 11 induced in the inverter 6 or then possibly present on the connecting lines 13 or damaged connecting lines 22 is set to a value at which there is no danger to persons 30 with regard to an electric shock.

[0090] If the speed 10 or voltage 11 measured in the ninth step 31 is greater than the second limit value 12, in the eleventh step 33, i.e. within the scope of a step d2) of the method, the electrical energy 5 induced by the motor 3 in the inverter 6 is converted into heat exclusively in the inverter 6 (ASC state) and thus the safety state OC is not initiated or ended.

[0091] These steps 31, 32, 33 are shown in the diagram of Fig. 7. The diagram shows the curves 35 of the induced voltage 11 as a function of the respective (constant) speed 10 over time 17. For the curves 35 that would exceed the second limit value 12 over time 17, step d2) of the method is now carried out, ie the electrical energy 5 induced by the motor 3 in the inverter 6 is converted exclusively into heat in the inverter 6 (ASC state).

[0092] For the curves 35 which would not exceed the second limit value 12 over time 17, step d1) of the method is carried out, ie the energy 5 induced by the motor 3 in the inverter 6 is directed to the battery 4 and thus the safety state OC is initiated or maintained.

[0093] Step d2) of the method is maintained until at least the inverter 6 is destroyed, e.g., destroyed by fire damage, represented here by the twelfth step 34.

[0094] Fig. 8 shows the drive train 1 after Fig.5 in the state according to step d2) of the method. The electrical energy 5 induced by the rotating motor 3 in the inverter 6 is converted into heat exclusively in the inverter 6 (ASC state), and thus the OC safety state is neither initiated nor terminated. Step d2) of the method is maintained until at least the inverter 6 is destroyed, e.g., destroyed by fire. List of reference symbols 1 drivetrain 2 drive axle 3 Engine 4 Battery 5 Energy 6 inverters 7 Control unit 8 Temperature 9 Component 10 speed 11 Tension 12 second limit 13 connecting line 14 Motor vehicle 15 Signal line 16 Sensor 17 Time 18 Resistance 19 first course 20 first limit 21 first step 22 damaged connecting line 23 second step 24 third step 25 fourth step 26 fifth step 27 sixth step 28 seventh step 29 eighth step 30 people 31 ninth step 32 tenth step 33 eleventh step 34 twelfth step 35 History

Claims

[1] Method for operating an electric drive train (1) in the event of a failure, wherein the electric drive train (1) has at least one electric motor (3) connected to a drive axle (2) in a torque-transmitting manner, a battery (4) for storing electrical energy (5), an inverter (6) for transmitting the energy (5) from the battery (4) to the electric motor (3) and from the electric motor (3) to the battery (4), and a control unit (7) which is designed to carry out the method; wherein the method comprises at least the following steps: a) Determination of damage to the drive train (1); b) measuring a temperature (8) of at least one component (9) of the inverter (6); c) monitoring and measuring at least one rotational speed (10) of the electric motor (3) or an electrical voltage (11) induced by the rotational speed (10) in the inverter (6); wherein, if the temperature (8) measured in step b) exceeds a first limit value (20) and the rotational speed (10) or voltage (11) measured in step c) exceeds a second limit value (12), in a step d2), the electrical energy (5) induced by the motor (3) in the inverter (6) is converted into heat exclusively in the inverter (6), wherein step d2) is maintained until at least the inverter (6) is destroyed. [2] Method according to claim 1, wherein, if the temperature (8) measured in step b) exceeds a first limit value (20) and the speed (10) or voltage (11) measured in step c) corresponds at most to a second limit value (12), in a step d1) the energy (5) induced by the motor (3) in the inverter (6) is directed to the battery (4). [3] Method according to one of the preceding claims, wherein step d2) terminates a previously performed step d1), in which the energy (5) induced by the motor (3) in the inverter (6) is conducted to the battery (4). [4] Method according to one of the preceding claims, wherein step d2), in which the electrical energy (5) induced by the motor (3) in the inverter (6) is converted into heat exclusively in the inverter (6), is terminated and step d1), in which the energy (5) induced by the motor (3) in the inverter (6) is conducted to the battery (4), is initiated when the currently measured speed (10) or voltage (11) falls to a value which corresponds at most to the second limit value (12). [5] Method according to one of the preceding claims, wherein the damage case comprises damage to at least one electrical connecting line (13) between the battery (4) and the inverter (6). [6] Method according to one of the preceding claims, wherein immediately after step a) the electrical energy (5) present in the inverter (6) is converted as quickly as possible by the control unit (7) in a step a1) and converted into heat in the inverter (6). [7] Drive train (1) for a motor vehicle (14), at least comprising an electric motor (3) which can be connected to a drive axle (2) in a torque-transmitting manner, a battery (4) for storing electrical energy (5), an inverter (6) for transmitting the energy (5) from the battery (4) to the electric motor (3) and from the electric motor (3) to the battery (4), and a control unit (7) which is designed to carry out the method according to one of the preceding claims. [8] Motor vehicle (14), at least comprising a drive train (1) according to claim 7 and a drive axle (2) connected to the engine (3) in a torque-transmitting manner.

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