DE102022200117A1 - Method for operating an electrical machine - Google Patents

Abstract

The invention relates to a method for operating an electrical machine (2), having an electric motor (4) with a stator with a rotating field winding (19) with at least three phases (U, V, W) and with a rotor rotatably mounted inside the stator Permanent magnets, whereby the phases (U, V, W) form a number of magnetic poles (66, 68, 70, 72) or pairs of magnetic poles of the rotary field winding (19) when energized with phase currents (lu, Iv, Iw), in which a calibration for each magnetic pole (66, 68, 70, 72) or each pair of magnetic poles of the rotating field winding (19): a predetermined voltage vector is applied to the rotating field winding (19), a resulting position signal (64) for the rotor position is determined, an electrical and /or mechanical offset value is determined as the difference between the voltage vector and the position signal (64), the determined offset value is stored, and in which the stored offset values are used for a calculation and closed-loop control of the phase currents (lu, Iv, Iw) are used to energize the rotating field winding (19).

Description

The invention relates to a method for operating an electrical machine which has an electric motor with a stator with a rotary field winding and with a rotor rotatably mounted within the stator, the phases forming a number of magnetic poles or magnetic pole pairs when phase currents are applied. The invention also relates to an electrical machine and software for carrying out the method.

Adjustment systems powered or operated by electric motors as motor vehicle components, such as window lifters, seat adjusters, door and sunroof drives or radiator fan drives, as well as pumps and interior fans, typically have an electric drive with a controlled electric motor. Furthermore, electrical machines are used, for example, as drives in the form of hub motors in electrically driven or drivable vehicles, such as in particular an electrically driven or drivable two-wheeler, for example a standing vehicle or e-scooter or an e-bike or pedelec.

So-called brushless electric motors (brushless DC motors, BLDC motors) are increasingly being used for such electromotive drives, in which the wear-prone brush elements of a rigid (mechanical) commutator are replaced by electronic commutation of the motor current.

Electromotive drives for motor vehicles are usually fed by a (high-voltage) battery as an on-board energy store, from which the electric motor is supplied with electrical energy in the form of a direct current (direct current). In order to convert the direct current into the motor current, a power converter (inverter) is suitably connected between the battery and the electric motor. The power converter has a bridge circuit, which is supplied with the direct current or direct voltage of the energy store via an electrical intermediate circuit. The motor current is generated as a multi-phase output current by a pulse width modulated (PWM) control or regulation of semiconductor switches of the bridge circuit. The semiconductor switches are switched between a conducting and a blocking state in a clocked manner by the pulses of the PWM signals.

During operation, the bridge circuit feeds phase currents assigned to the phases (motor current, three-phase current) into the stator coils of the electric motor, which subsequently generate a rotating magnetic field with respect to the stator. In this case, the rotor of the electric motor suitably has a number of permanent magnets, the interaction of the permanent magnets with the rotary field producing a resulting torque which causes the rotor to rotate.

The phases of the generated three-phase current and the associated rotating field are referred to as (motor) phases. In a figurative sense, this also includes the stator coils (phase winding) assigned to such a phase with the associated connecting lines (phase end). In this case, the phases are connected to one another, for example, in a star point of a star connection.

For efficient operation, it is necessary that the phases are supplied with power at the right time. Vector control, also known as field-oriented control (FOC), is possible for this purpose. The FOC is particularly suitable for permanent magnet synchronous machines (PMSM) because it has a high dynamic torque behavior. However, FOC requires information about the orientation of the rotor flux, which is typically obtained using a position sensor mounted on the rotor or a motor shaft. The relative displacement between the position sensor and the zero point of the rotor is an important calibration required to correctly align the rotating field generated by the stator with respect to the rotor magnetic field.

In a FOC, the three-phase (phase) currents are identified as two orthogonal components that can be visualized with a current space vector. One component (direct component) defines the magnetic flux of the motor, the other the torque (quadrature current). The field-oriented regulation regulates the three-phase current in a d/q coordinate system (reference system, reference system) of the electric motor. In the ideal case, the current space vector is fixed in terms of amount and direction (quadrature) in relation to the rotor, i.e. independent of the rotation. Since the current space vector is static in the d/q reference system, the current is controlled using direct current signals. This isolates the regulators from the time varying winding currents and voltages and therefore eliminates the limitation of regulator frequency response and phase shift on motor torque and speed.

In this case, the electric motor has an associated motor controller, which calculates the corresponding current component setpoint values from the flux and torque setpoints, which are specified by a speed controller.

In order to specify the electronic commutation of the electric motor at the correct time and to be able to implement an effective FOC, a sufficiently precise knowledge of the rotor position with regard to the rotating field winding is necessary so that the required coordinate transformations into the d/q coordinate system can be reliably carried out. When determining the rotor position, an offset (offset angle) must also be taken into account, which in particular indicates a deviation of an actual zero position from a detected rotor position. In this case, a mechanical offset relates to an absolute deviation from the mechanical position of the rotor, with an electrical offset in particular specifying the position deviation relevant for the commutation of the phase currents.

A mechanical offset can arise, for example, if a Hall magnet is attached to the motor shaft in a substantially random alignment, so that there is an angular deviation between the rotor position detected by a Hall sensor and the actual rotor position. An electrical offset occurs, for example, when a magnetic center of a pair of magnetic poles is shifted. This occurs, for example, in the case of stators with stamped-packaged laminated cores if variances and deviations arise due to tolerances during the stamping of the stator sheet metal layers and/or due to tolerances in insulation between the stator sheet metal layers.

As a rule, only a mechanical offset with regard to the alignment with regard to a position or location sensor is calibrated and stored using an alignment process. Offsets between the magnetic poles or pairs of magnetic poles within the rotating field winding are typically not taken into account. The consequence is a periodic disturbance, which can lead to errors in determining the position and/or the determination of the rotational speed, and thus makes it difficult to regulate the operation of the motor. This can, for example, have an adverse effect on the efficiency, the acoustics, or the stability of the electrical machine or the electric motor.

The invention is based on the object of specifying a particularly suitable method for operating an electrical machine. In particular, the aim is to calibrate mechanical and/or electrical offsets as precisely as possible. The invention is also based on the object of specifying a particularly suitable electrical machine and particularly suitable software.

With regard to the method, the object is achieved with the features of claim 1 and with regard to the electrical machine with the features of claim 8 and with regard to the software with the features of claim 10 according to the invention. Advantageous refinements and developments are the subject of the dependent claims.

The method according to the invention is provided for the operation of an electrical machine and is suitable and set up for this. The electrical machine is designed, for example, as an electric motor drive or traction machine for a motor vehicle, for example an electrically driven or drivable motor vehicle, such as in particular an electrically driven or drivable two-wheeler. The associated electric motor is designed in particular as a permanent magnet synchronous motor or as a permanent magnet synchronous machine and has a stator with a rotary field winding with at least three phases and a rotor with permanent magnets rotatably mounted within the stator. When energized with phase currents, the phases of the rotary field winding form a number of magnetic poles or pairs of magnetic poles to generate the rotary magnetic field, which, through the interaction with the permanent magnets, causes a torque that causes the rotor to rotate.

According to the invention, an (offset) calibration is carried out for each magnetic pole or each magnetic pole pair of the rotary field winding.

An alignment process is carried out for each magnetic pole or each pair of magnetic poles, in which a predetermined current or voltage vector is applied to the rotary field winding. In other words, a magnetic field with a predetermined orientation is generated by means of the rotary field winding. For example, the respective magnetic pole or the respective pair of magnetic poles is energized. The resulting torque moves or rotates the rotor so that it aligns with the magnetic field of the stator. Alternatively, a rotating current or voltage vector with a constant amplitude can also be specified for alignment.

The rotor position is then determined using a resulting position signal. In this case, the position signal can be detected or measured, for example, by means of a position sensor (eg Hall sensor, resolver, rotary encoder). The position signal is a measure of the (angular) position or setting of the rotor with respect to the stator and indicates, for example, a mechanical position or an electrical position of the rotor. the mechanic The mechanical position (mechanical angle) describes in particular the absolute mechanical position of the rotor in relation to the stator, with the electrical position (electrical angle) describing in particular the position value that is decisive for the commutation of the motor current.

An electrical and/or mechanical offset value, ie a deviation from the electrical and/or mechanical position, for example due to electrical and/or mechanical (angle) jitter, is determined from the determined rotor position and the known orientation of the voltage vector. An electrical and/or mechanical offset value is also to be understood here as meaning a mechanical-to-electrical offset or an electrical-to-mechanical offset. The offset value is determined as a difference, in particular as an angle difference, between the voltage vector and the position signal.

The conjunction “and/or” is to be understood here and in the following in such a way that the features linked by means of this conjunction can be designed both together and as alternatives to one another.

The offset value is stored for each magnetic pole or each pair of magnetic poles, for example in a (look-up) table. As a result, a number of offset values corresponding to the number of magnetic poles or the number of magnetic pole pairs are stored. According to the method, the stored offset values are used for a calculation and closed-loop control of the phase currents, ie the three-phase or motor current, for energizing the rotary field winding. In this case, the phase currents are preferably regulated by means of a field-oriented regulation. A particularly suitable method for operating an electrical machine is thereby implemented.

The method determines the electrical and/or mechanical offsets for each magnetic pole or each magnetic pole pair of the electric motor, so that the calibration according to the invention improves the quality of the phase current control and, as a result, reduces the misalignment of the rotor during motor operation. This improves the quality and consistency of the torque generated, reducing torque ripple and improving engine acoustics.

In an advantageous embodiment, the offset values are interpolated, with the phase currents being calculated and closed-loop controlled using the stored and interpolated offset values. For example, it is conceivable that the offset values are interpolated segment by segment for the mechanical rotation of the rotor. This further improves the current regulation of the phase currents.

In a preferred embodiment, the rotary field winding has at least six phases, which are divided into a number of three-phase subsystems in terms of control technology. In this case, the rotary field winding has, in particular, 3×n phases, where n>1. In this case, the calibration is carried out for each of the subsystems. This improves current control in multi-phase electric motors (multi-phase drives).

The calibration of the subsystems is preferably carried out one after the other. In this case, in particular, an offset value for the electrical and/or mechanical offset between the subsystems is determined and stored on the basis of the calibrations. In this case, the subsystems can have different behaviors, for example due to a winding offset. By determining the offset between the subsystems, a simple and reliable determination of the mechanical and/or electrical winding offset can be implemented, as a result of which particularly effective current regulation is ensured in multi-phase electric motors.

In a conceivable embodiment, the calibration is carried out in the course of manufacturing the electric motor. In particular, the calibration is performed as an end-of-line calibration. It is conceivable here, for example, for the electric motor or the electric machine to be sensorless, that is to say without a dedicated position sensor for the rotor, so that the position signal is determined by means of a position sensor external to the motor or machine. This ensures a particularly cost-effective electric motor.

Alternatively, the electrical machine or the electric motor has a position sensor for the rotor. In this case, the method or the calibration can be carried out, for example, when the device is put into operation for the first time or before each start-up. For example, it is also possible for the calibration to be repeated regularly, for example after a certain period of time or after a certain number of start-up processes. It is also possible, for example, for the calibration to be triggered by a user.

The electric machine according to the invention is intended for a motor vehicle and is suitable and set up for it. The electric machine is, for example, as a hub drive for an electrically powered or drivable vehicle, such as in particular an electrically driven or drivable two-wheeler, for example an e-scooter. The advantages and configurations given with regard to the method can also be transferred to the electrical machine and vice versa.

The electrical machine has a brushless electric motor, in particular a permanent magnet synchronous motor. The electric motor has a stator with a rotating field winding with at least three phases and a rotatably mounted rotor with permanent magnets within the stator, the phases forming a number of magnetic poles or magnetic pole pairs of the rotating field winding when phase currents are applied.

To energize the rotary field winding, the electric motor is connected to an energy store (vehicle battery) by means of an inverter, for example. The inverter has electronics which are preferably coupled to a controller (ie a control unit). The controller has, for example, a current regulator for, in particular, field-oriented regulation of the motor operation or the phase currents (the motor current).

In this case, the controller is generally set up—in terms of program and/or circuitry—to carry out the method according to the invention described above. The controller is thus specifically set up to calibrate the mechanical and/or electrical offsets for each magnetic pole or each magnetic pole pair of the rotary field winding and to implement a particularly field-oriented regulation of the phase currents using the offset values determined.

In a preferred embodiment, the controller is formed, at least in its core, by a microcontroller with a processor and a data memory, in which the functionality for carrying out the method according to the invention is implemented programmatically in the form of operating software (firmware), so that the method - optionally in interaction with a machine user - is carried out automatically when the operating software is executed in the microcontroller. Alternatively, within the scope of the invention, the controller can also be formed by a non-programmable electronic component, such as an application-specific integrated circuit (ASIC), in which the functionality for carrying out the method according to the invention is implemented with circuitry means.

In an advantageous development, the rotor is joined to a motor shaft so that it is fixed to the shaft, with a position sensor for detecting the position signal being arranged on the motor shaft, in particular on a front side or a shaft end. The position sensor is used here in particular for detecting the position or position of the rotor at low speeds and in the course of calibration. At higher speeds, at which an induced counter-EMF is sufficiently high, a sensorless position determination of the rotor position preferably takes place.

In this case, the controller is suitably designed as a self-adaptive controller. This means that the controller is designed and arranged to recalibrate the offset values over the lifetime of the electric motor. In other words, the offset values are updated by the controller during engine operation. The updating or recalibration takes place here, for example, regularly or preferably continuously, that is to say essentially without interruption.

An additional or further aspect of the invention provides software on a medium or data carrier for carrying out or executing the method described above. This means that the software is stored on a data medium and is provided for executing the method described above, and is suitable and designed for this when the software runs on a computer or a computer. As a result, particularly suitable software for the operation of an electrical machine is implemented, with which the functionality for carrying out the method according to the invention is implemented in terms of programming. The software is thus in particular operating software (firmware), with the data carrier being, for example, a data memory of the controller, and with the computer being in particular a processor of the controller. The explanations in connection with the method and/or the electrical machine also apply to the software and vice versa.

• 1 eine elektrische Maschine mit einer Stromquelle und mit einem Elektromotor sowie mit einem dazwischen verschalteten Stromrichter,
• 2 drei Phasenwicklungen eines dreiphasigen Elektromotors der Maschine in Sternschaltung,
• 3 ein Brückenmodul einer Brückenschaltung des Stromrichters zur Ansteuerung einer Phasenwicklung des Elektromotors,
• 4 ein Ersatzschaltbild für die Stromquelle,
• 5 bis 7 in vereinfachten Polardarstellungen die Phasen einer elektrischen Maschine mit zwei 5-poligen Teilsystemen ohne mechanischen und/oder elektrischen Offset,
• 8 bis 10 in vereinfachten Polardarstellungen die Phasen einer elektrischen Maschine mit zwei 5-poligen Teilsystemen konstanten Offset zueinander, und
• 11 bis 13 in vereinfachten Polardarstellungen die Phasen einer elektrischen Maschine mit zwei 5-poligen Teilsystemen, wobei jedes Teilsystem zufällige Offsets zwischen den Magnetpolen aufweist.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 an electrical machine with a power source and with an electric motor and with a power converter connected in between,
• 2 three phase windings of a three-phase machine electric motor in star connection,
• 3 a bridge module of a bridge circuit of the power converter for controlling a phase winding of the electric motor,
• 4 an equivalent circuit for the current source,
• 5 until 7 in simplified polar representations, the phases of an electrical machine with two 5-pole subsystems without mechanical and/or electrical offset,
• 8th until 10 in simplified polar representations, the phases of an electrical machine with two 5-pole subsystems with a constant offset to one another, and
• 11 until 13 in simplified polar representations, the phases of an electrical machine with two 5-pole subsystems, each subsystem having random offsets between the magnetic poles.

Corresponding parts and sizes are always provided with the same reference symbols in all figures.

The 1 shows an electric machine 2 for an electric motor drive of a motor vehicle, not shown, for example a hub drive for an electrically driven or drivable motor vehicle, such as in particular an electrically driven or drivable two-wheeler, for example an e-scooter. For this purpose, the electrical machine 2 comprises a three-phase brushless electric motor 4 which is connected to a power source (voltage supply) 8 by means of a power converter (converter, inverter) 6 . In this exemplary embodiment, the power source 8 comprises a vehicle-internal energy store in the form of a (vehicle) battery 10 and a (DC voltage) intermediate circuit 12 connected thereto, which extends at least partially into the power converter 6 .

The intermediate circuit 12 is essentially formed by a forward line 12a and a return line 12b, by means of which the power converter 6 is connected to the battery 10. The lines 12a and 12b are at least partially routed into the power converter 6, in which an intermediate circuit capacitor 14 and a bridge circuit 16 are connected between them.

During operation of the electrical machine 2 , an input current I _E supplied to the bridge circuit 16 is converted into a three-phase output current (motor current, three-phase current) Iu, Iv, Iw for the three phases U, V, W of the electric motor 4 . The output currents lu, Iv, Iw, also referred to below as phase currents, are fed to the corresponding phase (windings) U, V, W ( 2 ) out of a stator, not shown. The electric motor 4 is in this case designed as a permanent magnet synchronous motor and has a rotor which is provided with permanent magnets and which is arranged so as to be rotatable or rotatable relative to the stator.

In the 2 a star connection 18 of the three phase windings U, V, W is shown. The phases or phase windings U, V, W here form a rotary field winding 19 of the stator. The phase windings U, V and W are each connected to a (phase) end 22, 24, 26 to a respective bridge module 20 ( 3 ) of the bridge circuit 16 out, and connected to each other with the respective opposite end in a star point 28 as a common connection terminal. In the representation of 2 the phase windings U, V and W are each shown by means of an equivalent circuit diagram in the form of an inductance 30 and an ohmic resistance 32 and a respective voltage drop 34, 36, 38. The respectively across the phase winding U, V, W dropping voltage 34, 36, 38 is represented schematically by arrows and results from the sum of the voltage drops across the inductance 30 and the ohmic resistance 32 and the induced voltage 40. The movement of a Rotor of the electric motor 4 induced voltage 40 (electromagnetic force, EMF, EMF) is in the 2 represented by a circle.

The star circuit 18 is controlled by means of the bridge circuit 16. The bridge circuit 16 is designed with the bridge modules 20 in particular as a B6 circuit. In this embodiment, during operation, each of the phase windings U, V, W is switched at a high switching frequency between a high (DC) voltage level of the supply line 12a and a low voltage level of the return line 12b. In this case, the high voltage level is in particular an intermediate circuit voltage U _ZK of the intermediate circuit 12, the low voltage level preferably being a ground potential UG. This clocked control is available as a - in 1 PWM control, illustrated by arrows, is carried out by a controller 42, with which control and/or regulation of the speed, the power and the direction of rotation of the electric motor 4 is possible.

The bridge modules 20 each include two semiconductor switches 44 and 46, which in the 2 are shown only schematically and as an example for the W phase. The bridge module 20 is connected on the one hand with a potential connection 48 to the supply line 12a and thus to the intermediate circuit voltage U _ZK . On the other hand, the bridge module 20 is contacted with a second potential connection 50 to the return line 12b and thus to the ground potential U _G . The respective phase end 22, 24, 26 of phase U, V, W can be connected via the semiconductor switches 44, 46 either to the intermediate circuit voltage U _ZK or to the ground potential U _G . If the semiconductor switch 44 is closed (conducting) and the semiconductor switch 46 is open (non-conducting, blocking), then the phase end 22, 24, 26 is connected to the potential of the intermediate circuit voltage U _ZK . Correspondingly, when the semiconductor switch 44 opens and the semiconductor switch 46 closes, the phase U, V, W is in contact with the ground potential U _G . This makes it possible to apply two different voltage levels to each phase winding U, V, W using PWM control.

In the 3 a single bridge module 20 is shown in simplified form. In this exemplary embodiment, the semiconductor switches 44 and 46 are implemented as MOSFETs (metal-oxide semiconductor field-effect transistors), which each switch clocked by means of PWM control between an on state and an off state. For this purpose, the respective gate connections are routed to corresponding control voltage inputs 52, 54, by means of which the signals of the PWM control of the controller 42 are transmitted.

The 4 shows an equivalent circuit diagram for the current source 8. During operation, the battery 10 generates a battery power P _Bat ( 5 ), A battery voltage U _Bat and a corresponding battery current I _Bat for operating the power converter 6. In the 4 the internal resistance of the battery 10 is shown as an ohmic resistance 56 and an inherent inductance of the battery 10 as an inductance 58 . A shunt resistor 60, across which the intermediate circuit voltage U _ZK drops, is connected in the return line 12b.

Depending on the switching states of the (power) semiconductor switches 44, 46, the phase current Iu, Iv, Iw flows through the shunt resistor 60. The voltage drop across the shunt resistor 60 is amplified and evaluated. The phase currents Iu, Iv, Iw are reconstructed by the controller 42 using measurements and the state of knowledge of the switching states of the semiconductor switches 44, 46. Other measurement methods can also be used to determine the motor currents (e.g. direct phase current measurement). The phase voltages Uu, Uv, Uw and the phase currents Iu, Iv, Iw are available to the controller 42 together with the measured and/or calculated phase voltages (Uu, Uv, Uw).

The electrical machine 2 also has a position sensor 62 , for example a resolver or Hall sensor, for detecting a rotor position 64 . For example, a two-pole Hall magnet is arranged on a shaft end face or a shaft end, the magnetic field of which is detected by means of a Hall sensor.

The controller 42 is provided for, in particular, field-oriented regulation (FOC) of the phase currents Iu, Iv, Iw and is suitable and set up for this. In this case, the phase voltages Uu, Uv, Uw and/or the phase currents Iu, Iv, Iw are converted using the position signal 64 into a rotor-fixed d/q coordinate system.

In the 5 until 13 shows the phase angles of an electrical machine 2 with an electric motor 4 with two 5-pole subsystems for different electrical and/or mechanical offsets. The 5 , 8th and 11 each show a polar representation of the phase positions, with the 6 , 9 and 12 an unrolled linear representation phase positions and the 7 , 10 and 13 show the first and second pairs of magnetic poles of the first subsystem enlarged in each case, with the angular position being plotted horizontally, ie along the abscissa axis (X-axis).

In this case, the first subsystem has, for example, five positive magnetic poles 66 and five negative magnetic poles 68, which together form five pairs of magnetic poles. Correspondingly, the second subsystem has five positive magnetic poles 70 and five negative magnetic poles 72, which together form five pairs of magnetic poles. The magnetic poles 66, 68, 70, 72 or pairs of magnetic poles are formed here by the coil windings of the rotating field winding 19 which are supplied with current.

In the representations of 5 until 7 the phase position of the magnetic poles 66, 68, 70, 72 is shown without mechanical and electrical offset, the subsystems having an electrical phase offset of 180° relative to one another. The five magnetic poles 66, 68, 70, 72 in each case are arranged in a uniformly distributed manner, ie each have an angular offset of 72° with respect to one another. The magnetic poles 66 and 68 or 70 and 72 of the pairs of magnetic poles are in this case arranged opposite one another.

In the representations of 8th until 10 is the phase position of the second subsystem by an offset 74 compared to the position in FIGS 5 until 6 relocate The offset 74 is shown schematically as an arrow in the figures. The offset 74 is a mechanical offset of +4° or an electrical offset of +20°. Correspondingly, the magnetic poles 70, 72 of the second subsystem are opposite to those in FIGS 4 until 6 shifted by offset 74.

In the representations of 11 until 13 is the phasing of subsystems with a random offset jitter. In other words, the phase position for each magnetic pole 66, 68, 70, 72 with a random offset 74 between ±3° for the mechanical offset and between ±15° for the electrical offset. In the 11 until 13 the offset 74 is only shown as an example for the first two pairs of magnetic poles.

The following is particularly based on the 7 until 12 a method for operating the electric machine 2 is explained in more detail.

According to the method, an (offset) calibration for each magnetic pole 66, 68, 70, 72 or each pair of magnetic poles of the rotary field winding 19 is carried out. An alignment process is carried out for each magnetic pole 66, 68, 70, 72 or each pair of magnetic poles, in which a predetermined voltage vector (composed of the phase voltages Uu, Uv, Uw) is applied to the rotary field winding 19. In other words, the rotary field winding 19 is energized in a specific way for each magnetic pole 66, 68, 70, 72 or each pair of magnetic poles, so that the rotary field winding 19 generates a magnetic field with a predetermined orientation. The resulting torque moves or rotates the rotor so that it aligns with the magnetic field of the stator. The rotor position is then detected with the position sensor 62 and determined using the position signal 64 . From the determined rotor position and the known orientation of the voltage vector, an electrical and/or mechanical offset value for the offsets 74 is determined by subtraction. The offset values are stored and are then available to the field-oriented control as correction values in order to enable a particularly effective and error-reduced calculation and control of the phase currents I _U , I _V , I _W .

The calibration is preferably carried out separately for each of the subsystems. The calibration of the subsystems is carried out one after the other, for example. In this case, in particular, an offset value for the electrical and/or mechanical offset between the subsystems is determined and stored on the basis of the calibrations.

In one possible embodiment, the offset values are interpolated, with the phase currents Iu, Iv, Iw being calculated and closed-loop controlled using the stored and interpolated offset values.

The controller 42 is suitably implemented as a self-adaptive controller. This means that the controller 42 is provided and set up to recalibrate the offset values during the lifetime of the electric motor 4 .

The claimed invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived from this by the person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all of the individual features described in connection with the various exemplary embodiments can also be combined in other ways within the scope of the disclosed claims, without departing from the subject matter of the claimed invention.

Reference List

2

electrical machine

4

electric motor

6

power converter

8th

power source

10

battery

12

intermediate circuit

12a

direction

12b

return line

14

intermediate circuit capacitor

16

bridge circuit

18

star connection

19

rotating field winding

20

bridge module

22,24,26

phase end

28

star point

30

inductance

32

Resistance

34, 36, 38

voltage drop

40

Tension

42

controllers

44, 46

semiconductor switch

48, 50

potential connection

52, 54

control voltage input

56

Resistance

58

inductance

60

shunt resistance

62

position sensor

64

position signal

66, 68, 70, 72

magnetic pole

74

offset

AND MANY MORE

phase/phase winding

lu, Iv, Iw

phase current/output current

Uu, Uv, Uw

phase voltage

ie

input current

UCC

intermediate circuit voltage

UG

earth potential

IBat

battery power

UBat

battery voltage

PBat

battery power

Claims (10)

Method for operating an electrical machine (2), having an electric motor (4) with a stator with a rotary field winding (19) with at least three phases (U, V, W) and with a rotor with permanent magnets that is rotatably mounted inside the stator, the Phases (U, V, W) form a number of magnetic poles (66, 68, 70, 72) or magnetic pole pairs of the rotating field winding (19) when energized with phase currents (lu, Iv, Iw), - in which in the course of a calibration for each magnetic pole (66, 68, 70, 72) or each pair of magnetic poles of the rotating field winding (19): a) a predetermined voltage vector is applied to the rotary field winding (19), b) a resultant position signal (64) for the rotor position is determined, c) an electrical and/or mechanical offset value is determined as the difference between the voltage vector and the position signal (64), d) the determined offset value is stored, and - In which the stored offset values are used for a calculation and closed-loop control of the phase currents (lu, Iv, Iw) for energizing the rotary field winding (19). procedure after claim 1 , characterized in that the offset values are interpolated, the phase currents (lu, Iv, Iw) being calculated and closed-loop controlled using the stored and interpolated offset values. procedure after claim 1 or 2 , characterized in that the rotary field winding (19) has at least six phases, which are divided into a number of three-phase subsystems in terms of control technology, the calibration being carried out for each subsystem. procedure after claim 3 , characterized in that the calibration of the subsystems is carried out one after the other. procedure after claim 3 or 4 , characterized in that an offset value for the electrical and/or mechanical offset between the subsystems is determined and stored on the basis of the calibrations. Procedure according to one of Claims 1 until 5 , characterized in that the calibration is carried out during the manufacture of the electric motor (4). procedure after claim 6 , characterized in that the position signal (64) is determined by means of a motor-external position sensor. Electrical machine (2) for a motor vehicle, having an electric motor (4) with a stator with a rotary field winding (19) with at least three phases (U, V, W) and with a rotor with permanent magnets that is rotatably mounted inside the stator, the phases (U, V, W) form a number of magnetic poles (66, 68, 70, 72) or magnetic pole pairs of the rotary field winding (19) when energized with phase currents (lu, Iv, Iw), and a controller (42) for carrying out a Procedure according to one of Claims 1 until 7 . Electrical machine (2) after claim 8 , characterized in that the rotor is shaft-fixed to a motor shaft, on which a position sensor (62) for detecting the position signal (64) is arranged. Software on a data carrier for carrying out a method according to one of Claims 1 until 7 , if the software runs on a computer.

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