Method for operating an electric drive train

Abstract

The invention relates to a method for operating an electric drive train (1) comprising at least one electric machine (2) for driving a motor vehicle (3) as well as further electrical components (4, 5, 6) for controlling and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for temperature control of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6); wherein the method comprises operating the drive train (1) in certain operating states such that electrical losses are deliberately generated in at least one of the electrical components (2, 4, 5, 6).

Description

[0001] The invention relates to a method for operating an electric drive train. The drive train comprises at least one electric motor for driving the motor vehicle, as well as further electrical components for controlling and operating the electric motor, a traction battery, and a cooling circuit for controlling the temperature of the traction battery, the electric motor, and the electrical components.

[0002] Motor vehicles have at least one cooling circuit in which a cooling fluid is pumped through the cooling circuit by one or more pumps (each). The cooling fluid absorbs heat energy from the components integrated in the respective cooling circuit, in particular an electric motor, a pulse-changing rectifier, a charger, a voltage converter, and a battery. This heat energy is then released into the environment (air) via an ambient heat exchanger (a cooling device).

[0003] Increasing the range of BEVs (exclusively electric vehicles), for example, is a constant challenge. This paper proposes a method that allows the energy that cannot be stored in the vehicle's traction battery due to thermal recuperation limits to be used to heat the traction battery.

[0004] At low temperatures, the traction battery can only be charged with a low current due to the limitations of chemical processes within the traction battery. Therefore, during braking, the full potential for recovering braking energy cannot be utilized. Any braking energy that cannot be stored in the traction battery must then be dissipated, for example, via the braking system. The faster the temperature of the traction battery is increased, the sooner the full potential of recuperation can be utilized. At a higher temperature of the traction battery, more electrical energy can be recovered and the use of the braking system is reduced. For example, it is known to increase the temperature of the traction battery using an electric auxiliary heater or a heat pump.However, both the heat pump and the electric auxiliary heater require valuable electrical energy from the traction battery, which has adverse effects on the vehicle's range.

[0005] Further environmental pollution is the emission of particulate matter from braking systems and tire wear. Reducing the load on the mechanical braking system leads to a reduction in particulate matter pollution due to reduced brake wear. On long downhill journeys with a fully charged traction battery, regenerative braking is necessary to prevent thermal overload of the braking system. However, recuperation in the traditional sense is only possible if the electrical energy generated can be stored in the traction battery or consumed directly in the vehicle. If the braking system is at its limit and the traction battery cannot absorb any more electrical energy, the electrical energy generated by the regenerative braking process must be consumed directly.Under these operating conditions, it is known that powerful consumers, primarily the interior climate control heating elements, the air conditioning system in AC mode, the traction battery heater, the seat heater, and other available consumers, are activated. This leads to significant thermal and acoustic impairments and, over a longer period, also impairs the vehicle user's ability to concentrate. The user has no way of intervening in or deactivating this process.

[0006] DE 10 2020 126 659 A1 discloses a system for controlling regenerative braking for an electric motor-driven vehicle. It proposes an electrical resistor for converting excess electrical energy into thermal energy.

[0007] The KR 101526430 B1 is directed to a regenerative braking device for a motor vehicle.

[0008] 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 is to be provided by which a drive train of an electrically powered motor vehicle, and in particular a traction battery, can be operated in an energy-efficient manner.

[0009] A method having the features according to claim 1 contributes to achieving these objectives. 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 demonstrated.

[0010] A method for operating an electric drive train of a motor vehicle is proposed. The drive train comprises at least one electric motor for driving the motor vehicle, as well as further electrical components for controlling and operating the electric motor, a traction battery, and a cooling circuit for controlling the temperature of the traction battery, the electric motor, and the electrical components. The method comprises operating the drive train in certain operating states in such a way that electrical losses are deliberately generated in at least one of the electrical components.

[0011] Electrical components are considered to include, in particular, an electric motor (or possibly another one) for driving the motor vehicle, a charger, a pulse-controlled inverter, a voltage converter (in particular a DC / DC converter), and an inverter. These electrical components are generally known in terms of their functionality.

[0012] The method deliberately generates electrical losses in existing drivetrain components. In particular, the electrical losses are generated exclusively in electrical components intended for controlling or operating the at least one electric machine (except for the traction battery). This specifically does not include a separate heating resistor.

[0013] In particular, the targeted generation of electrical losses is carried out in at least one of the following operating states of the drive train or the motor vehicle: i. first operating state in which the traction battery has a temperature that limits a charging current during recuperation to a value that is below a maximum possible charging current; ii. second operating state in which the traction battery cannot absorb any further electrical energy; and iii. third operating state, in which the traction battery can no longer absorb any further electrical energy and can be heated to a higher temperature (without being damaged).

[0014] In particular, in the first operating state, the thermal energy generated by the electrical losses is used at least to heat the traction battery (first operating mode of the drive train). In particular, as little of the thermal energy as possible is dissipated, e.g., to the environment, but rather as much thermal energy as possible is transferred to the traction battery. A cooling device of the cooling circuit is bypassed, in particular, via a suitable bypass.

[0015] In particular, in the second operating state, the thermal energy generated by the electrical losses is dissipated to an environment of the motor vehicle at least via a cooling device of the cooling circuit (second operating mode of the drive train).

[0016] In particular, it is possible to implement the method in such a way that the thermal energy generated by the electrical losses is used at least temporarily to heat the traction battery and is temporarily dissipated (in parallel and / or staggered temporally) to the environment of the motor vehicle via a cooling device of the cooling circuit. In particular, the method can alternate between these two operating modes (first and second operating modes alternating) (third operating mode of the drive train).

[0017] In particular, in the third operating mode, the thermal energy generated by the electrical losses is used to further heat the traction battery (fourth operating mode of the powertrain). The traction battery should only be heated to the extent that it is not damaged. It is particularly irrelevant whether the further heating allows the charging current during recuperation to be further increased or whether it decreases as a result of the heating. If necessary, the cooling fluid can also be routed through a cooling device in the cooling circuit.

[0018] In particular, you can switch between the different operating modes at any time.

[0019] In particular, the electrical losses are generated at least by an intervention in a field-oriented control of the electrical machine or by a change in switching times or a switching frequency of a power electronics system intended as an electrical component. In particular, these interventions are not aimed at the otherwise usual efficient operation of the electrical components or at the operation considered optimal for the respective operating point of the drive train, but on the contrary at an otherwise inefficient, energy-wasting operation of the drive train. The electrical energy is therefore deliberately generated only to generate as much heat as possible in the electrical components, without being geared towards meeting the requirements of the motor vehicle's drive system, as is otherwise usual.

[0020] With the proposed method, in particular, the energy that cannot be stored in the traction battery due to thermally induced recuperation limits (e.g., if the traction battery is too cold and therefore the charging current must be limited) can be used to heat the traction battery (e.g., in the first operating mode). The method generates additional thermal losses in the electrical components through targeted control interventions in the control of these electrical components, so that the traction battery can be heated via the cooling circuit using excess potential and kinetic energy (e.g., first operating mode). For example, this is achieved through control interventions in the field-oriented control of the electric machine and / or by changing the switching times or the switching frequency of the power electronics.

[0021] With the proposed method, it is no longer necessary, at least in most cases, to switch on the aforementioned consumers (high-performance consumers, primarily the heating elements of the interior climate control, the air conditioning in AC mode, the heating of the traction battery, the seat heating and other available consumers) in the aforementioned operating states. The disadvantages mentioned can thus also be reduced, for example, during long downhill journeys with a fully charged traction battery. The potential energy of the vehicle is then converted into heat (thermal energy) in the electrical components within the framework of the proposed method, dissipated from the electrical components in particular by the cooling circuit and released into the environment of the vehicle (i.e. into the ambient air) via a cooling device in the cooling circuit (e.g. a basically known low-temperature cooler) (second operating state orSecond operating mode). Regenerative braking, thus relieving the load on the braking system, can be achieved without compromising comfort for the user. Particulate matter pollution from the brake wear that would otherwise be present is reduced.

[0022] The conversion of kinetic energy into thermal energy can be achieved, for example, by adjusting the field-oriented control of the electrical machine and / or by changing the switching times or the switching frequency of the power electronics (one or more of the following components: charger, pulse-controlled inverter, voltage converter, inverter).

[0023] At low temperatures, the traction battery may have more recuperation energy available than can be charged into the traction battery, especially in certain driving or operating conditions. To prevent damage to the cell chemistry of the traction battery, the charging current of the traction battery must be limited at low temperatures.

[0024] It is known that recuperation can be limited by the maximum permissible charging current of the traction battery. During braking operations outside the recuperation limits, the braking system is activated, and the energy is not used to temper the traction battery. In this case, an increase in the recuperation limits by increasing the temperature of the traction battery does not occur. The frequency of use of the braking system is also not reduced.

[0025] With the proposed method, recuperation is controlled in such a way that the maximum permissible charging current of the traction battery is maintained. The excess recuperation energy is converted into thermal energy, among other things, by deliberately generating additional electrical losses in the electrical components. This thermal energy is then used to regulate the temperature of the traction battery.

[0026] This allows, in particular, the frequency of use of the braking system to be reduced. As a result of the temperature increase in the traction battery, more braking energy can be absorbed than electrical energy by the traction battery, because the maximum possible charging current can be further increased. As the temperature of the traction battery increases, the internal losses of the traction battery decrease. The improved recovery of braking energy and the lower internal resistance of the traction battery increase the energy efficiency of the vehicle.

[0027] When a traction battery is fully charged, little braking energy can be stored in the traction battery. In this context, it is common practice to apply only the brake system, for example, during a long downhill ride. If the braking system is at its thermal limit, the load must be relieved by regenerative braking. However, since the (fully charged) traction battery cannot absorb any more energy, the excess electrical energy must be dissipated by connecting powerful electrical consumers. This results in a corresponding reduction in comfort in the vehicle's interior.

[0028] With the proposed method, additional thermal losses are deliberately generated during regenerative braking and dissipated to a cooling device via the cooling circuit. This reduces the load on the braking system, preventing any impairment of driving comfort in many areas of vehicle operation. Reduced use of the braking system also reduces particulate matter pollution from brake wear (e.g., in the second, third, or fourth operating mode).

[0029] If the traction battery can be heated further (without being damaged as a result), the excess recuperation energy can be stored (exclusively) as thermal energy in the traction battery or (exclusively or additionally) dissipated to the environment via a cooling device.

[0030] The proposed method can achieve the following advantages in particular: • Increasing the efficiency of the drive train operation and in particular the operation of the traction battery through targeted thermal losses; • Reduction of comfort losses when the braking system is subjected to high thermal loads; • lower environmental impact due to reduced brake wear; • Increasing the range of the vehicle.

[0031] In particular, the different operating modes can also be specifically selected for other reasons (not only based on the current operating conditions). For example, the first operating mode can be preferred with a view to increasing range and efficiency. With regard to environmental pollution from particulate matter and future legislation in this context, as well as interior comfort when the braking system is subject to high loads, the second, third and fourth operating modes are to be preferred.

[0032] In particular, the cooling circuit has at least one first bypass for bypassing the traction battery. With the first bypass, the cooling fluid flowing through the cooling circuit can be guided past the traction battery, in particular, so that further heating of the traction battery due to the thermal energy of the cooling fluid can be prevented. In particular, a plurality of first bypasses are provided. In a first bypass, the cooling fluid can be guided, for example, via a so-called chiller, through which the cooling fluid is connected to a refrigerant circuit of an air conditioning system of the motor vehicle. The cooling fluid can be cooled via the chiller. In another first bypass, the cooling fluid can also be guided past the chiller. The first bypass is used in particular in the second and third operating modes.

[0033] In particular, the cooling circuit (in addition to or as an alternative to the first bypass) has at least one second bypass for bypassing a cooling device, wherein heat can be dissipated to the environment of the motor vehicle via the cooling device. This bypass is used in particular in the first operating mode.

[0034] As a cooling device, in particular a basically known low-temperature cooler is provided, in which the cooling fluid can be cooled in the ambient air.

[0035] In particular, the cooling circuit can have a return line, in addition to or as an alternative to the bypasses (or the individual bypasses), through which the cooling fluid immediately downstream of the traction battery can be at least partially returned to a connection point immediately upstream of the traction battery. In this case, a heating heat exchanger and / or a high-voltage heater can be provided in this return line.

[0036] A high-voltage heater can be used to quickly heat the cooling fluid, although this consumes electrical energy from the traction battery. This high-voltage heater can be used particularly in the first operating mode.

[0037] Heat can be transferred between the interior and the cooling circuit via the heater core. In particular, the heater core and high-voltage heater can be arranged in a single return circuit (or, if necessary, in a separately operable part of a return circuit).

[0038] In particular, an expansion tank is connected to the cooling circuit. The expansion tank ensures that sufficient cooling fluid is present in the cooling circuit. Furthermore, the expansion tank can compensate for any expansion of the cooling fluid via an air reservoir.

[0039] A motor vehicle is further proposed, at least comprising an electric drive train, which includes at least one electric motor for driving the motor vehicle and further electrical components for controlling and operating the electric motor, a traction battery, a cooling circuit for controlling the temperature of the traction battery, the electric motor, and the electrical components, as well as a control unit. The control unit has means for executing the described method and / or has means that are suitably equipped, configured, or programmed for executing the described method or that execute the method.

[0040] 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 lines or transmission devices that enable the transmission of instructions, measured values, data or the like between the elements mentioned.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The statements regarding the method are particularly transferable to the motor vehicle and / or the computer-implemented method (i.e. the computer program and the computer-readable storage medium) and vice versa.

[0045] 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.

[0046] As a precaution, it should also 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.

[0047] 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, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description. 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 and a first embodiment of a cooling circuit operated in a first operating mode; Fig. 2: a motor vehicle with a drive train and a second embodiment of a cooling circuit operated in a first operating mode; Fig. 3: the motor vehicle after Fig. 1, wherein the cooling circuit is operated in a second operating mode; Fig. 4: the motor vehicle after Fig. 2, wherein the cooling circuit is operated in a second operating mode; Fig. 5: the motor vehicle after Fig. 1 and Fig. 3, wherein the cooling circuit is operated in a fourth operating mode; and Fig. 6: the motor vehicle after Fig. 2 and Fig. 4, whereby the cooling circuit is operated in a fourth operating mode.

[0048] The Fig. 1 shows a motor vehicle 3 with a drive train 1 and a first embodiment of a cooling circuit 8, which is operated in a first operating mode. The motor vehicle 3 has an electric drive train 1, which has two electric motors 2 for driving the motor vehicle 3, as well as further electrical components 4, 5 for controlling and operating the electric motors 2, a traction battery 7, a cooling circuit 8 for controlling the temperature of the traction battery 7, the electric motors 2, and the electrical components 4, 5, as well as a control unit 13.

[0049] The electrical components 4, 5, and 6 are considered to be an electric machine 2 for driving the motor vehicle 3 as the third electrical component 6, a charger or voltage converter as the first electrical component 4, and a pulse-controlled inverter as the second electrical component 5. These electrical components are generally known with regard to their functionality and serve to control and operate the electric machines 2.

[0050] The electric motors 2 can be provided to drive individual wheels or individual axles of the motor vehicle. In particular, at least one electric motor 2 is permanently provided as a traction drive, with the other electric motor 2 only being switched on (e.g., to provide higher drive power or to drive another axle).

[0051] A cooling fluid 15 flows through the cooling circuit 8. Two pumps 14 are provided in the cooling circuit 8, by means of which a volume flow of the cooling fluid 15 can be regulated. Furthermore, control valves 16 are provided, via which the flow through certain sections of the cooling circuit 8 (in particular also with regard to the respective volume flow) can be regulated.

[0052] An expansion tank 17 is connected to the cooling circuit 8. The expansion tank 8 ensures that sufficient cooling fluid 15 is present in the cooling circuit 8. Furthermore, the expansion tank 17 can compensate for any expansion of the cooling fluid 15 via an air reservoir.

[0053] The cooling circuit 8 has a first bypass 11 for bypassing the traction battery 7. With the first bypass 11, the cooling fluid 15 flowing through the cooling circuit 8 can optionally be guided past the traction battery 7, so that further heating of the traction battery 7 due to the thermal energy of the cooling fluid 15 can be prevented. In the present case, two first bypasses 11 are provided. In a (lower) first bypass 11, the cooling fluid 15 can be guided over a so-called chiller 19, through which the cooling fluid 15 is connected to a refrigerant circuit of an air conditioning system of the motor vehicle 3. The cooling fluid 15 can be cooled via the chiller 19. In another (upper) first bypass 11, the cooling fluid 15 can also be guided past the chiller 19.

[0054] In addition to the first bypass 11, the cooling circuit 8 has a second bypass 12 for bypassing a cooling device 9, wherein heat can be dissipated to an environment 10 of the motor vehicle 3 via the cooling device 9. The cooling device 9 is designed as a generally known low-temperature cooler in which the cooling fluid 15 can be cooled by the ambient air.

[0055] In addition to the bypasses 11, 12, the cooling circuit 8 has a return line 22, via which the cooling fluid 15 immediately downstream of the traction battery 7 can be at least partially returned to a connection point immediately upstream of the traction battery 7. A high-voltage heater 20 is provided in this return line 22, via which the cooling fluid 15 can be quickly heated, although this consumes electrical energy from the traction battery 7.

[0056] In the cooling circuit 8, some sensors 18 are provided for determining the temperature of the cooling fluid 15.

[0057] In this case, the drive train 1 is operated in a first operating mode. The thermal energy generated by the electrical losses is used at least to heat the traction battery 7. For example, a first operating state of the drive train 1 or the motor vehicle 3 exists in which the traction battery 7 has a temperature that limits the charging current during recuperation to a value that is below the maximum possible charging current.

[0058] The deliberately generated electrical losses are intended to generate thermal energy, which is then used via the cooling fluid 15 to heat the traction battery 7 as quickly as possible. In the first operating mode, the cooling fluid 15 is deliberately directed via the second bypass (and thus bypasses the cooling device 9) and exclusively via the traction battery 7 (and not via one of the first bypasses 11 or the return line 22) and back to the electrical components 2, 4, 5, 6.

[0059] The Fig. 2 shows a motor vehicle 3 with a drive train 1 and a second embodiment of a cooling circuit 8, which is operated in a first operating mode. Reference is made to the explanations for Fig. 1 is referred to.

[0060] In the second embodiment of the cooling circuit 8, only one electric motor 2 is provided. Furthermore, the cooling device 9 and the second bypass are arranged downstream of the traction battery 7 and thus between the traction battery 7 and the electrical components 2, 4, 5.

[0061] In addition, the cooling circuit 8 has a return line 22, via which the cooling fluid 15 immediately downstream of the traction battery 7 can be at least partially returned to a connection point immediately upstream of the traction battery 7, wherein a heating heat exchanger 21 and a high-voltage heater 20 are provided in this return line 22.

[0062] Heat can be transferred between the interior of the motor vehicle 3 and the cooling circuit 8 via the heater core 21. The heater core 21 and the high-voltage heater 20 are arranged in a separately operable part of the return line 22. A separate pump 14 is arranged in this part of the return line 22, so that the cooling fluid 15 can be pumped in this outwardly closed part of the return line 22.

[0063] In the first operating mode, the cooling fluid 15 is directed specifically via the second bypass 12 (and thus past the cooling device 9) and exclusively via the traction battery 7 (and not via one of the first bypasses 11 or the return line 22) and back to the electrical components 2, 4, 5.

[0064] Fig. 3 shows the motor vehicle after Fig. 1, wherein the cooling circuit 8 is operated in a second operating mode. Fig. 4 shows the motor vehicle 3 after Fig. 2, wherein the cooling circuit 8 is operated in a second operating mode. The explanations regarding the Fig. 1 and Fig. 2 is referred to. The Fig. 3 and Fig. 4 are described together below.

[0065] In this case, the drive train 1 is operated in a second operating mode. The thermal energy generated by the electrical losses is dissipated to an environment 10 of the motor vehicle 3, at least via the cooling device 9 of the cooling circuit 8. This may involve, for example, a second operating state of the drive train 1 or the motor vehicle 3 in which the traction battery 7 cannot absorb any further electrical energy (and possibly no thermal energy).

[0066] Thus, for example, during long downhill rides with a fully charged traction battery 7, the potential energy of the motor vehicle 3 can be converted into heat (thermal energy) in the electrical components 2, 4, 5, 6 within the framework of the proposed method. This heat can be dissipated from the electrical components 2, 4, 5, 6 through the cooling circuit 8, and released into the environment 10 of the motor vehicle 3 (i.e., into the ambient air) via the cooling device 9 of the cooling circuit 8. Regenerative braking, and thus the relief of the braking system, can thus be achieved without any loss of comfort for the user. The particulate matter pollution caused by the brake wear that would otherwise be present is reduced.

[0067] Fig. 5 shows the motor vehicle 3 after Fig. 1 and Fig. 3, wherein the cooling circuit 8 is operated in a fourth operating mode. Fig. 6 shows the motor vehicle 3 after Fig. 2 and Fig. 4, wherein the cooling circuit 8 is operated in a fourth operating mode. The explanations regarding the Fig. 1 to 4 is referred to. The Fig. 5 and Fig. 6 are described together below.

[0068] In the present case, the drive train 1 is operated in a fourth operating mode. The thermal energy generated by the electrical losses is, on the one hand, dissipated via the cooling device 9 of the cooling circuit 8 to an environment 10 of the motor vehicle 3 and, on the other hand, used to further heat the traction battery 7. This can, for example, result in a third operating state of the drive train 1 or the motor vehicle 3 in which the traction battery 7 cannot absorb any further electrical energy but can be further heated. The traction battery 7 should only be further heated to the extent that the traction battery 7 is not damaged. In this case, it is particularly irrelevant whether the further heating allows the charging current during recuperation to be further increased or whether it decreases as a result of the heating. List of reference symbols 1 drivetrain 2 electric machine 3 Motor vehicle 4 first electrical component 5 second electrical component 6 third electrical component 7 Traction battery 8 Cooling circuit 9 Cooling device 10 Surroundings 11 first bypass 12 second bypass 13 Control unit 14 Pump 15 Cooling fluid 16 Control valve 17 Expansion tank 18 Sensor 19 chillers 20 high-voltage heaters 21 heating heat exchangers 22 Repatriation QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 126 659 A1

[0006] KR 101526430 B1

[0007]

Claims

[1] Method for operating an electric drive train (1) which has at least one electric machine (2) for driving a motor vehicle (3) and further electrical components (4, 5, 6) for controlling and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for controlling the temperature of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6); wherein the method comprises operating the drive train (1) in certain operating states in such a way that electrical losses are deliberately generated in at least one of the electrical components (2, 4, 5, 6). [2] Method according to claim 1, wherein the targeted generation of electrical losses is carried out in at least one of the following operating states of the drive train (1): i. first operating state in which the traction battery (7) has a temperature that limits a charging current during recuperation to a value that is below a maximum possible charging current; ii. second operating state in which the traction battery (7) cannot absorb any further electrical energy; and iii. third operating state, in which the traction battery (7) can no longer absorb any further electrical energy and can be heated to a higher temperature. [3] Method according to claim 2, wherein in the first operating state the thermal energy generated by the electrical losses is used at least for heating the traction battery (7). [4] Method according to claim 2, wherein in the second operating state the thermal energy generated by the electrical losses is dissipated to an environment (10) of the motor vehicle (3) at least via a cooling device (9) of the cooling circuit (8). [5] Method according to one of the preceding claims, wherein the electrical losses are generated at least by an intervention in a field-oriented control of the electrical machine (2) or by a change in switching times or a switching frequency of a power electronics provided as an electrical component (4, 5, 6). [6] Method according to one of the preceding claims, wherein the cooling circuit (8) has at least one first bypass (11) for bypassing the traction battery (7). [7] Method according to one of the preceding claims, wherein the cooling circuit (8) has at least one second bypass (12) for bypassing a cooling device (9) arranged in the cooling circuit (8), wherein heat can be dissipated to an environment (10) of the motor vehicle (3) via the cooling device (9). [8] Motor vehicle (3), at least comprising an electric drive train (1) which has at least one electric machine (2) for driving the motor vehicle (3) and further electrical components (4, 5, 6) for regulating and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for controlling the temperature of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6) and a control unit (13) which has means for carrying out the method according to one of the preceding claims.

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