DE102018122674B4 - Method of controlling an electric motor - Google Patents

Abstract

Method for controlling an electric motor (10) in the form of a reluctance motor in order to provide a desired torque (Msoll) of the electric motor (10), which is generated by two current desired values (Idsoll, Iqsoll) in field coordinates (d, q), wherein the desired current values (Idsoll, Iqsoll) are determined by a motor-side control unit (11) with the aid of operating-point-dependent characteristic diagrams (Mmax(VDC, ωactual), Idmax(VDC, ωactual), Iqmax(VDC, ωactual)), which calculate a maximum torque ( Mmax) of the electric motor (10) and/or two corresponding current values (Idmax, Iqmax) as a function of an applied intermediate circuit voltage (VDC) and/or a speed (ωactual) of the electric motor (10), and wherein when determining the current setpoints (Idsoll, Iqsoll) at least one mapping function (F1, F2) for the current setpoints (Idsoll, Iqsoll) is taken into account, which maps a ratio between the maximum torque (Mmax) and the desired torque (Msoll) of the electric motor (10), dad characterized in that the operating-point-dependent characteristic fields (Mmax(VDC, ωactual), Idmax(VDC, ωactual), Iqmax(VDC, ωactual)) are modeled at an optimal operating temperature (T1) of the electric motor (10), that when determining the current setpoints (Idsoll, Iqsoll), at least one correction map (Mmax(VDC, ωactual), Idmax(VDC, ωactual), Iqmax(VDC, ωactual)) is taken into account, and that the at least one correction map (Mmax(VDC, ωactual), Idmax( VDC, ωist), Iqmax(VDC, ωist)) at an optional operating temperature (T2, T3) of the electric motor (10) is modeled.

Description

The invention relates to a method for controlling an electric motor, in particular a reluctance motor, according to the preamble of the independent method claim. Furthermore, the invention relates to an electric motor according to the preamble of the independent device claim. In addition, the invention relates to a system for controlling an electric motor, in particular a reluctance motor, according to the preamble of the independent system claim.

In the drive of an electric car, a permanent-magnet synchronous machine is usually used as an electric motor. A disadvantage of the permanent-magnet synchronous machine is the higher cost due to the use of rare earths. The use of a reluctance motor as an electric motor represents a cost-reduced alternative. For optimal utilization of the intermediate circuit voltage, control of an electric motor is often used, which uses the D component of the current as a manipulated variable. However, such a regulation of the intermediate circuit voltage can become unstable when the controlled system parameters are changed. A conservative design of the controller can in turn show an insufficient control speed.

Further prior art is from the generic document DE 10 2010 050 344 A1 known.

The object of the invention is therefore to partially overcome at least one disadvantage known from the prior art when controlling electric motors. In particular, the object of the invention is to provide a method for controlling an electric motor, in particular a reluctance motor, which can be carried out easily and quickly and which enables reliable, stable and safe control of an electric motor.

The object of the invention is achieved by a method for controlling an electric motor, in particular a reluctance motor, with the features of the independent method claim, in particular from the characterizing part, by a corresponding electric motor with the features of the independent device claim and by a system for controlling an electric motor, in particular a reluctance motor, with the features of the independent system claim, in particular from the characterizing part. Preferred developments of the invention are listed in the dependent claims. Features that are disclosed for the individual aspects of the invention can be combined with one another in such a way that reference is or can always be made to one another with regard to the disclosure of the aspects of the invention.

The invention provides a method of controlling an electric motor in the form of a reluctance motor to provide a desired electric motor torque produced by two current command values in field coordinates. For this purpose, it is provided according to the invention that the current setpoints are determined by a motor-side control unit using operating-point-dependent characteristic diagrams, which map a maximum torque of the electric motor and/or two corresponding current values as a function of an applied intermediate circuit voltage and/or a speed of the electric motor.

In the context of the invention, characteristic diagrams can be understood to mean functions that map the variables (a maximum torque of the electric motor and/or two corresponding current values) as a function of an applied intermediate circuit voltage and/or a speed of the electric motor. At least one characteristic diagram, advantageously a plurality of characteristic diagrams, can be provided for each variable. The large number of maps for each size can be created at different operating temperatures of the electric motor. The two current values corresponding to the maximum torque can be used as manipulated variables. Dependent on the operating point means in the context of the invention that the variables are mapped as functions of different, for example two, operating parameters of the electric motor. An intermediate circuit voltage and/or a speed and/or the temperature of the electric motor can serve as the operating parameter. The operating parameters are known and/or measurable during operation of the electric motor, so that the operating point of the electric motor can be determined from the sum of the operating parameters. Consequently, for each operating point, the desired current values that are to be set in order to obtain a desired torque of the electric motor can be easily read from the characteristic diagrams without high computational effort using small-sized and inexpensive control units.

One idea of the invention is that the electric motor is not regulated, which is associated with complex measurements of torques during operation of the electric motor and high computing requirements, but is controlled in the classic sense. The proposed method of determining setpoint values uses the pre-calculated characteristic diagrams for the control of the electric motor.

The electric motor is modeled beforehand, knowing its topology, in order to create the characteristic diagrams as defined above. The creation of characteristic maps can be done completely independently of the electric motor. The electric motor does not need to be operated when creating the maps. All engine-side control units can remain offline when creating the maps. Finally, when the electric motor is in operation, the modeled, operating-point-dependent maps are used to control the electric motor. The characteristic maps can be stored in a memory of a motor-side control unit, which can now be designed with small dimensions and cost-effectively because it has to muster a significantly reduced computing power than when controlling the electric motor. According to the invention, a calculation of the desired current values of a reluctance motor that is optimal in terms of efficiency and saves CPU resources is thus provided.

Furthermore, as part of a method for controlling an electric motor, the invention can provide for the operating-point-dependent characteristic maps to be modeled by an external control unit before the current setpoints are determined by a motor-side control unit while the motor-side control unit is offline. Advantageously, the computing power upstream of the engine-side control unit can thus be outsourced to the external control unit.

Furthermore, as part of a method for controlling an electric motor, the invention can provide for the operating point-dependent characteristic diagrams to be stored in a memory of the motor-side control unit before the current setpoint values are determined by a motor-side control unit. Thus, a simple control of the electric motor can be made possible. The determined current setpoints in field coordinates are used as manipulated variables. The torque of the electric motor that can be controlled in this way is not measured and therefore does not affect the manipulated variables. Thus, a simple, stable, and reliable control method for the electric motor can be provided.

Furthermore, within the scope of a method for controlling an electric motor, the invention can provide for the operating-point-dependent characteristic diagrams to be provided in the form of artificial neural networks. An intelligent controller or an intelligent network can thus be provided which is capable of learning. In other words, the maps can be not only static, but also verifiable, trainable and updatable. In addition, artificial neural networks can act with foresight, e.g. reduce the torque in anticipation of a red light and/or a traffic jam. Data from a navigation system can be used for this. Engine aging can also be taken into account in advance and the torque can be adjusted accordingly. Furthermore, it is advantageous that artificial neural networks can complete incomplete data. It is conceivable here to complete missing areas in the characteristic diagrams or even to interpolate between the characteristic diagrams in order to generate new characteristic diagrams, for example for (not yet) modeled operating temperatures of the electric motor.

In addition, as part of a method for controlling an electric motor, the invention provides that when determining the current setpoints, at least one mapping function for the current setpoints is taken into account, which maps a relationship between the maximum torque and the desired torque of the electric motor. The maximum torque that can be achieved in order to optimally utilize the intermediate circuit voltage corresponds to the maximum efficiency and can therefore be modeled with high accuracy. The ratio between the maximum torque and the desired torque of the electric motor can be easily calculated and taken as a measure of how much the current setpoints, which are read from the characteristic springs at the given operating point of the electric motor, must be reduced in order to achieve the desired To achieve torque of the electric motor.

In addition, the invention can provide that the mapping function is modeled as a function of a topology of the electric motor. In this way, the exact structure or geometry (i.e. topology) of the motor can be reliably taken into account when controlling the motor. To a certain approximation, or in an optimal case, the mapping function for a reluctance motor can be a simple linear function.

Within the scope of the invention, the characteristic diagrams that depend on the operating point are modeled at an optimal operating temperature, for example 80° C., of the electric motor. In this way, values can be modeled that match the optimal operating temperature of the electric motor. Basically, it is conceivable that such maps come closest to the normal operation of the engine.

Furthermore, the invention provides that at least one correction characteristics map is taken into account when determining the desired current values. The current temperature of the engine can also flow into the control via the at least one correction characteristic map. Between a correction map and the map dern in the sense of claim 1 can advantageously be interpolated further characteristics.

The invention provides that the at least one (advantageously two) correction characteristics map(s) is (are) modeled by an external control unit. This means that the computing power can also be outsourced here.

It is also conceivable that at least one correction characteristic map is modeled at an optional operating temperature, in particular of 120° C. or 90° C., of the electric motor. In this way, the typical range of temperatures that occurs during ongoing operation of the electric motor can be covered.

Furthermore, within the framework of a method for controlling an electric motor, the invention can provide that the maximum torque of the electric motor is modeled below a permissible upper limit for reasons of component protection. Thus, the components of the electric motor and the adjacent components can be protected from damage.

Furthermore, within the scope of a method for controlling an electric motor, the invention can provide that the operating-point-dependent characteristic diagrams are provided and/or verified and/or corrected by measuring the electric motor. Measuring the electric motor to create the characteristic diagrams is also conceivable (e.g. on a test stand). The measured values can basically be used to check the modeled values, i. H. to verify. In addition, the measured values can be used to correct the modeled values. Thus, within the scope of the invention, the method can be improved to provide more accurate results for the current setpoints.

In addition, as part of a method for controlling an electric motor, the invention can provide for the operating-point-dependent characteristic diagrams to be made available in the form of updates from an external control unit to the motor-side control unit. It can thus be ensured that the version of the characteristic diagrams can be updated.

In addition, the invention can provide, as part of a method for controlling an electric motor, that if the torque of the electric motor, which is generated by the two determined current setpoints, deviates from the desired torque of the electric motor, which is expected according to the characteristic diagrams, the motor-side control unit sends an error message to an external control unit and/or a request for an update. The characteristic diagrams can thus be checked, which ensures safe and reliable control of the electric motor. It is conceivable that the torque is randomly measured, for example at regular intervals, in order to check the characteristic diagrams.

Furthermore, the object according to the invention is achieved by an electric motor, in particular a reluctance motor, having a motor-side control unit in order to provide a desired torque of the electric motor, which is generated by two current setpoints in field coordinates. For this purpose, a memory is provided according to the invention, in which operating-point-dependent characteristic maps are stored, which map a maximum torque of the electric motor and/or two corresponding current values as a function of an applied intermediate circuit voltage and/or a speed of the electric motor, and that the motor-side control unit has control electronics, to determine the current setpoints using operating-point-dependent maps. It is conceivable within the scope of the invention that the method described above for controlling the electric motor is used. The electric motor according to the invention achieves the same advantages as described above in connection with the method according to the invention. Reference is made in full to these advantages here.

Furthermore, the invention can provide for an electric motor that the motor-side control unit has an interface via which a communication link can be set up with an external control unit that is designed to model the operating-point-dependent characteristic diagrams. Information can thus be exchanged between the engine-side control unit and the external control unit. A contactless communication link, for example a radio link, or a contact-based communication link, for example a USB connection, a bus connection or the like is conceivable as a possible communication connection.

In addition, it is conceivable that the engine-side control unit can have an internet connection. The engine-side control unit can thus call up information from the Internet and, if necessary, post error messages and/or requests for an update on the Internet.

In terms of the invention, it is conceivable that the memory can be integrated within the engine-side control unit. It is also conceivable within the scope of the invention that the memory can be provided by an external data memory, for example a cloud. Thus, within the framework of the electric motor, not only computing capacities but also storage capacities can be outsourced.

Furthermore, the object according to the invention is achieved by a system for controlling an electric motor, in particular a reluctance motor, in order to provide a desired torque of the electric motor, which is generated by two current setpoints in field coordinates. For this purpose, according to the invention, a motor-side control unit is provided in order to determine the current setpoints using operating-point-dependent characteristic diagrams, which map a maximum torque of the electric motor and/or two corresponding current values as a function of an applied intermediate circuit voltage and/or a speed of the electric motor. Furthermore, an external control unit is provided in order to model the operating-point-dependent maps. It is conceivable within the scope of the invention that the method described above is carried out with the aid of the system. The system according to the invention achieves the same advantages as described above in connection with the method according to the invention and/or the electric motor according to the invention. Reference is made in full to these advantages here.

In addition, the invention can provide a memory in a system in which operating-point-dependent characteristic maps are stored, the memory being integrated within the engine-side control unit, or the memory being provided by an external data memory, in particular a cloud. It is also conceivable that the external control unit can be provided by an external data service, in particular a cloud. Thus, within the framework of the system, not only computing capacities but also storage capacities can be outsourced.

• 1 eine schematische Darstellung eines Systems zum Steuern eines Elektromotors, insbesondere eines Reluktanzmotors.

Further measures improving the invention are presented in more detail below with the description of the preferred exemplary embodiments of the invention with reference to the figure. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. It should be noted that the figure has only a descriptive character and is not intended to limit the invention in any way. It shows:

• 1 a schematic representation of a system for controlling an electric motor, in particular a reluctance motor.

the 1 shows a system 100 for controlling an electric motor 10, which can be designed in particular in the form of a reluctance motor. The system 100 serves to provide a desired torque Msoll of the electric motor 10, which is generated by two desired current values Idsoll, Iqsoll in field coordinates d, q. For this purpose, it is provided according to the invention that the current setpoint values Idsoll, Iqsoll are determined by a motor-side control unit 11 with the aid of operating-point-dependent characteristic diagrams Mmax(V _{DC ,} ωactual), Idmax(V _{DC ,} ωactual), Iqmax(V _{DC ,} ωactual). which depict a maximum torque _Mmax of electric motor 10 and/or two corresponding current values Idmax, Iqmax as a function of an applied intermediate circuit voltage V _DC and/or a speed ω actual of electric motor 10 .

In order to generate the desired torque Msoll or a desired torque of the electric motor 10, two desired current values Idsoll, Iqsoll are determined in field coordinates Id, Iq within the scope of the invention. These desired current values Idsoll, Iqsoll serve as input values for two current controllers 15, 16 within the framework of control electronics 14, 15, 16 of the motor-side control unit 11. Iqsoll provided.

In the 1 shows the structure of the setpoint calculation. The desired torque Msoll of the electric motor 10 can be limited to Lim [%] for reasons of component protection, for example.

Depending on the operating point (T, V _DC , ω _act ), the following variables are determined: a maximum convertible torque Mmax and two currents Idmax and Iqmax that match this maximum torque Mmax in field coordinates d, q.

Three measured operating parameters T, V _DC , ω _actual of the electric motor 10 are used as input variables for modeling the characteristic diagrams Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _{DC ,} ω actual ) : the current intermediate circuit voltage V _DC , the _speed ω and the temperature T of the electric motor 10.

The characteristic diagrams Mmax(V _DC , ω actual ) _, Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual ) are modeled in an external control unit 12.

The map calculation can be performed while the engine-side control unit 11 is offline.

Three maps Mmax(V _{DC ,} ω actual ), Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual ) for two input variables or two operating parameters (the intermediate circuit voltage V _DC and/or the speed ω _actual ) of the electric motor 10 is precalculated. The characteristic diagrams Mmax(V _DC ,ω actual ) _, Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual ) are determined for an optimum operating temperature T1 (for example 80° C.) of electric motor 10 .

Furthermore, for example two, correction maps Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _{DC ,} ω actual ) per modeled variable Mmax, Idmax and Iqmax for an optional operating temperature T2, T3 ( for example 0°C and/or 120°C) in order to take into account the influence of temperature, advantageously to compensate. The correction maps Mmax(V _DC , ω actual ) _, Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual ) represent a percentage correction factor. This representation reduces the memory requirement.

The maps Mmax(V _{DC ,} ω actual ), Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual ) and, if applicable, the correction maps Mmax(V _DC , ω actual ) _, Idmax(V _{DC ,} ω actual ) , Iqmax(V _DC , ω _ist ) can be stored in a memory 13 .

The system 100 according to the invention achieves optimum efficiency and maximum utilization of the intermediate circuit voltage V _DC at a maximum torque Mmax of the electric motor 10. For a smaller desired torque Msoll of the electric motor 10, the current values Idmax and Iqmax read from the tables are dependent on the ratio between the desired Torque Msoll and the maximum torque Mmax of the electric motor 10 is reduced. Two mapping functions F1 and F2 are provided for this. In the simplest case, these mapping functions F1, F2 can represent a proportional reduction in both current values Idmax and Iqmax. This is referred to as linear characteristics. However, it is also conceivable that the mapping functions F1 and F2 can be implemented as non-linear characteristic curves, which can correspond to a specific topology of the electric motor 10 . In this case, better control of electric motor 10 can be achieved for smaller setpoint torques Msoll.

The engine-side control unit 11 can have an interface 17 for communication with the external control unit 12 . In addition, it is conceivable that the engine-side control unit 11 can have an internet connection 18 .

Within the scope of the invention, it is conceivable that the memory 13 can be (structurally) integrated within the engine-side control unit 11, or that the memory 13 can be provided by an external data memory, in particular a cloud.

It is also conceivable within the scope of the invention that the external control unit 12 can also be provided by an external data service, in particular a cloud.

The above description of the figures describes the present invention exclusively within the framework of examples. It goes without saying that individual features of the embodiments can be freely combined with one another, insofar as this makes technical sense, without departing from the scope of the invention.

Reference List

10

electric motor

11

engine-side control unit

12

external control unit

13

Storage

14

control electronics

15

Control electronics, current controller

16

Control electronics, current controller

17

interface

18

Internet connection

100

system

i.e

field coordinate

q

field coordinate

Msoll

torque

max

torque

Idsol

electricity

Iqset

electricity

Idmax

electricity

Iqmax

electricity

vdc

intermediate circuit voltage

ωis

rotational speed

T

temperature

T1

optimal operating temperature

T2

optional operating temperature

T3

optional operating temperature

Mmax(VDC, ωactual)

Map, correction map

Idmax(VDC, ωactual)

Map, correction map

Iqmax(VDC, ωactual))

Map, correction map

F1

mapping function

F2

mapping function

Claims (15)

Method for controlling an electric motor (10) in the form of a reluctance motor in order to provide a desired torque (Msoll) of the electric motor (10), which is generated by two current desired values (Idsoll, Iqsoll) in field coordinates (d, q), wherein the current setpoint values (Idsoll, Iqsoll) are determined by a motor-side control unit (11) using operating-point-dependent characteristic diagrams (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )). , which depict a maximum torque (Mmax) of the electric motor (10) and/or two corresponding current values (Idmax, Iqmax) as a function of an applied intermediate circuit voltage (V _DC ) and/or a speed (ω _ist ) of the electric motor (10), and wherein when determining the current setpoints (Idsoll, Iqsoll), at least one mapping function (F1, F2) for the current setpoints (Idsoll, Iqsoll) is taken into account, which is a ratio between the maximum torque (Mmax) and the desired torque (Msoll ) of the electric motor (10), characterized in that the operating point-dependent maps (Mmax(V _DC , ω actual ) _, Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual )) at an optimum operating temperature (T1) of the electric motor ( 10) must be modeled so that at least one correction map (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _DC , ω actual )) _is taken into account when determining the current setpoints (Idsoll, Iqsoll). , and that the at least one correction map (Mmax(V _DC , ω _is ), Idmax(V _DC , ω _is ), Iqmax(V _DC , ω _is )) at an optional operating temperature (T2, T3) of the electric motor (10) modeled becomes. Method according to the preceding claim, characterized in that before the current setpoint values (Idsoll, Iqsoll) are determined by a motor-side control unit (11), the operating-point-dependent characteristic diagrams (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ) , Iqmax(V _DC , ω _ist )) can be modeled by an external control unit (12) while the motor-side control unit (11) is offline. Method according to one of the preceding claims, characterized in that before the current setpoint values (Idsoll, Iqsoll) are determined by a motor-side control unit (11), the operating-point-dependent characteristic diagrams (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual) _. ), Iqmax(V _DC , ω _ist )) in a memory (13) of the engine-side control unit (11). Method according to one of the preceding claims, characterized in that the operating point-dependent maps (Mmax (V _DC , ω _is ), Idmax (V _DC , ω _is ), Iqmax (V _DC , ω _is )) are provided in the form of artificial neural networks . Method according to one of the preceding claims, characterized in that the mapping function (F1, F2) is modeled as a function of a topology of the electric motor (10) and/or that a linear mapping function (F1, F2) is used. Method according to one of the preceding claims, characterized in that the at least one correction map (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _{DC ,} ω actual )) by an external control unit (12) is modeled. Method according to one of the preceding claims, characterized in that the maximum torque (Mmax) of the electric motor (10) is modeled below a permissible upper limit for reasons of component protection. Method according to one of the preceding claims, characterized in that the operating point-dependent maps (Mmax (V _DC , ω _is ), Idmax (V _DC , ω _is ), Iqmax (V _DC , ω _is )) by measuring the electric motor (10) provided and/or verified and/or corrected. Method according to one of the preceding claims, characterized in that the operating point-dependent maps (Mmax (V _DC , ω _is ), Idmax (V _DC , ω _is ), Iqmax (V _DC , ω _is )) in the form of updates from an external control unit (12) are provided to the motor-side control unit (11). Method according to one of the preceding claims, characterized in that when a torque (Msoll*) of the electric motor (10), which is generated by the two determined desired current values (Idsoll, Iqsoll), deviates from the desired torque (Msoll) of the electric motor (10), which is expected according to the characteristic diagrams (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )), the engine-side control unit (11) sends an error message to an external Control unit (12) and / or sends a query for an update. Electric motor (10) in the form of a reluctance motor, comprising: a motor-side control unit (11) in order to provide a desired torque (Msoll) of the electric motor (10), which is determined by two current desired values ((Idsoll, Iqsoll) in field coordinates (d, q) is generated, characterized in that a memory (13) is provided in which operating-point-dependent characteristics (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )) are stored, which a maximum torque (Mmax) of the electric motor (10) and/or two corresponding current values (Idmax, Iqmax) as a function from an applied intermediate circuit voltage (V _DC ) and/or a rotational speed (ω _ist ) of the electric motor (10), and that the control unit (11) on the motor side has control electronics (14, 15, 16) in order to calculate the desired current values (( Idsoll, Iqsoll) with the help of operating point-dependent maps (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )), whereby when determining the current setpoints (Idsoll, Iqsoll ) at least one mapping function (F1, F2) for the current setpoints (Idsoll, Iqsoll) is taken into account, which maps a relationship between the maximum torque (Mmax) and the desired torque (Msoll) of the electric motor (10), and that the operating point-dependent Maps (Mmax(V _DC , ω actual ) _, Idmax(V _{DC ,} ω actual ), Iqmax(V _{DC ,} ω actual )) with one o optimal operating temperature (T1) of the electric motor (10) are modeled so that when determining the current setpoints (Idsoll, Iqsoll) at least one correction map (Mmax(V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω actual )) _is taken into account, and that the at least one correction map (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _{DC ,} ω actual )) at an optional operating temperature (T2, T3) of the electric motor (10) is modeled. Electric motor (10) according to the preceding claim, characterized in that the motor-side control unit (11) has an interface (17) via which a communication link can be set up with an external control unit (12) which is designed to display the operating point-dependent characteristic diagrams (Mmax (V _DC , ω _ist ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )) and/or that the motor-side control unit (11) has an internet connection (18). Electric motor (10) according to any one of the preceding Claims 11 or 12 , characterized in that the memory (13) is integrated within the engine-side control unit (11), or that the memory (13) is provided by an external data memory, in particular a cloud. System (100) for controlling an electric motor (10) in the form of a reluctance motor to provide a desired torque (Msetpoint) of the electric motor (10) generated by two current setpoints (Idsetpoint, Iqsetpoint) in field coordinates (d,q). is provided, characterized in that a motor-side control unit (11) is provided in order to calculate the desired current values (Id, Iq) with the aid of operating-point-dependent characteristic diagrams (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax( V _DC , ω _ist )) to determine which maximum torque (Mmax) of the electric motor (10) and/or two corresponding current values (Idmax, Iqmax) as a function of an applied intermediate circuit voltage (V _DC ) and/or a speed (ω _actual ) of the electric motor (10) and that an external control unit (12) is provided to map the operating-point-dependent characteristic diagrams (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _DC , ω actual ) _. )), whereby when determining the current setpoints (Idsoll, Iqsoll) at least one A mapping function (F1, F2) for the current setpoint values (Idsoll, Iqsoll) is taken into account, which maps a relationship between the maximum torque (Mmax) and the desired torque (Msoll) of the electric motor (10) so that the operating-point-dependent characteristic diagrams (Mmax( V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _{DC ,} ω actual )) at an optimum operating temperature (T1) of the electric motor (10) are modeled such that when the current setpoint values (Idsoll, Iqsoll) at least one correction map (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _DC , ω actual )) _is taken into account, and that the at least one correction map (Mmax(V _{DC ,} ω actual ) ), Idmax(V _DC , ω _ist ), Iqmax(V _DC , ω _ist )) at an optional operating temperature (T2, T3) of the electric motor (10) is modeled. System (100) according to the preceding claim, characterized in that a memory (13) is provided, in which operating point-dependent characteristic fields (Mmax(V _DC , ω actual ) _, Idmax(V _DC , ω actual ) _, Iqmax(V _DC , ω _is )) are stored, the memory (13) being integrated within the engine-side control unit (11), or the memory (13) being provided by an external data memory, in particular a cloud, and/or the external control unit (12) is provided by an external data service, in particular cloud.

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