Method and device for operating an electric machine with an electrically generated excitation magnetic field
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-11-14
- Publication Date
- 2026-06-04
Smart Images
Figure EP2025083004_04062026_PF_FP_ABST
Abstract
Description
[0001] R. 410820
[0002] - 1 -
[0003] Description
[0004] title
[0005] Method and apparatus for operating an electric machine with an electrically generated excitation magnetic field
[0006] Technical field
[0007] The invention relates to electrically excited synchronous machines and in particular to methods for the contactless transmission of electrical energy into a rotor of an electric machine with an excitation winding.
[0008] Technical background
[0009] A stator of an electrically excited synchronous machine is already known from JP H04 347566 A, comprising a multiphase stator winding with several phase strands and a primary part of an inductive transformer system for transferring electrical energy into an excitation winding of a rotor of the synchronous machine, wherein the primary part of the inductive transformer system has a primary transformer winding, the primary transformer winding being formed by several hybrid phase strands of the stator winding, each serving both to generate a rotating field of a three-phase system for driving the rotor and to generate a transformer field of the transformer system, and into each of which both a phase current of the three-phase system and a primary transformer current of the transformer system can be fed.
[0010] The transformer system of the JP H04 347566 A exhibits comparatively high ohmic losses because a resistor network R. 410820 is used to supply the excitation current.
[0011] - 2 - is provided. As a result, a portion of the three-phase current from the three-phase system flows through the resistors of the resistor network with high ohmic losses, and this portion of the three-phase current cannot contribute to torque generation. The excitation current of the transformer system also flows through the resistors of the resistor network, resulting in a significant loss of the input power in the resistors of the resistor network. The requirements of the three-phase system and the transformer system are contradictory because high conductivity of the resistors improves the efficiency of the excitation current injection but reduces the efficiency of the three-phase current injection. An excitation current source is galvanically isolated from the three-phase system, which entails considerable effort. In JP H04 347566 A, the excitation current is injected into the neutral point of the stator winding.The excitation current then flows through the hybrid phase strands and, via corresponding nodes, through the resistor network back to the excitation current source. The number of poles in the rotating field (2-pole) is less than the number of poles in the transformer field (6-pole). This can lead to a higher leakage inductance in the transformer system. From the perspective of the transformer current, the hybrid phase strands are connected in parallel.
[0012] Furthermore, an electrically excited synchronous machine is known from US Patent 2005 / 0218740 A1, comprising a stator with a multiphase stator winding having multiple phase strands and a primary part of an inductive transformer system for transferring electrical energy to an excitation winding of a rotor of the synchronous machine. The primary part of the inductive transformer system comprises a primary transformer winding.Furthermore, the electrically excited synchronous machine of US 2005 / 0218740 A1 comprises a rotor having an excitation winding for generating a rotor field to excite the synchronous machine and a secondary part of an inductive transformer system for transferring electrical energy to the excitation winding of the rotor, wherein the secondary part of the inductive transformer system comprises at least one secondary transformer winding for providing a transformer AC voltage and at least one rectifier circuit acting as a rectifier for rectifying the transformer AC voltage into a secondary DC voltage for the excitation winding. R. 410820.
[0013] - 3 -
[0014] A disadvantage is that the primary and secondary parts of the inductive transformer system are arranged as a transformer unit within a cavity of the rotor. This transformer unit requires a comparatively large installation space and, as an additional component, generates additional costs. The transformer unit comprises an excitation stator and an excitation rotor, which interact inductively as a transformer. In power transmission with a transformer as an additional component, the transformer must be as small as possible to reduce costs and installation space. This generally leads to an increase in the electrical frequency, reduces efficiency, and increases system complexity.
[0015] The object of the present invention is to provide an improved transmission of electrical energy into the excitation winding of a rotor of an electric machine, avoiding the disadvantages of the prior art and enabling a simple and robust implementation.
[0016] Technical background
[0017] This problem is solved by the method for operating an electric machine with a transfer of electrical energy into an excitation winding of a rotor according to claim 1, as well as a corresponding device and a motor system according to the dependent claims.
[0018] Further details are specified in the dependent claims.
[0019] According to a first aspect, a method for operating a multiphase electrical machine is provided, wherein a stator arrangement is provided whose regular phase strands are each formed from several stator coils connected in parallel, wherein the stator coils of the regular phase strands can be driven with a common phase voltage, wherein the stator arrangement provides a hybrid phase from several hybrid phase strands, each with one or more stator coils, wherein the hybrid phase strands can be driven separately with a respective phase voltage, wherein in operation a regular phase voltage is assigned to the respective regular phase strands and the hybrid phase strands, which is derived from a predetermined R. 410820
[0020] - 4 -
[0021] Driving torque and a predetermined commutation scheme result, wherein all phase strands are connected in a star connection, wherein the electric machine has a rotor with a secondary coil into which an excitation current can be provided by transformer coupling with the stator coils of the hybrid phase, wherein the electric machine is operated by the following steps:
[0022] Determining the phase voltages for the regular phases and the hybrid phase according to a voltage vector to be provided for controlling the stator arrangement for the operation of the electric machine;
[0023] Determining the excitation alternating voltage to be set depending on the currents through the stator coils of the hybrid phase;
[0024] Applying an excitation alternating voltage to the phase voltages for the hybrid phase strands, so that the average of the two phase voltages for the hybrid phase strands corresponds to the regular phase voltage for the hybrid phase strands.
[0025] The above method applies to multiphase electrical machines with multiple phase strands in the stator. If each phase is assigned several stator coils connected in parallel, these can be distributed around the stator, thus forming several controllable sub-machines. The phase strands are connected in a star configuration, so that when a phase voltage is applied to one phase strand, all stator coils of the entire phase strand are energized accordingly.
[0026] In contrast to the conventional design of an electric synchronous machine, at least one phase is now designed as a hybrid phase with several hybrid phase strands that can be energized separately or supplied with separate phase voltages. As a result, the stator coils of the hybrid phase strands together form, firstly, a regular phase strand of the electric machine by jointly providing a corresponding portion or component of the stator magnetic field, and secondly, a transformer winding that enables the transformer-based transfer of electrical energy to a secondary winding on the rotor of the electric machine.
[0027] The stator coils of the hybrid phase strands thus make it possible to use both the R. 410820
[0028] - 5 -
[0029] The drive system for the electric machine is designed to also generate the excitation magnetic field, eliminating the need for an additional winding in the stator to generate the excitation current. This avoids the need for additional components to provide a transformer winding, thereby reducing the manufacturing complexity of the electric machine.
[0030] The stator coils of the hybrid phase strands are assigned to different sub-machines. Thus, the stator coils of the hybrid phase strands, the hybrid strand coils, are arranged in the stator offset from each other by a first offset angle, specifically by 180° in the case of six stator poles. In this way, each hybrid phase strand can generate a stator magnetic field component from the DC current component of two in-phase hybrid sub-strands and a transmission magnetic field for generating the excitation current from the current difference of the in-phase driven hybrid phase strands.
[0031] Due to the two separately controllable hybrid phase strands, the control of a three-phase electric machine must be implemented with four phases, or more generally, with the regular phase count of the electric machine increased by one. When the two phase terminals of the hybrid phase strands are short-circuited, the electric machine behaves like a conventional synchronous machine with a number of phases corresponding to the phase count of the electric machine.
[0032] The separate controllability of the hybrid phase strands allows an excitation AC voltage to be superimposed on the regular phase voltage (for generating the stator magnetic field component) of the hybrid phase strands, thus transferring an excitation current into a secondary coil in the rotor. This is achieved by electrically controlling the half-bridge, which applies the required phase voltages to the hybrid phase strands.
[0033] For control, the above method involves operating the electric machine like a conventional synchronous machine, for example using a predefined commutation scheme, such as a block commutation method. The two hybrid phase strands are controlled with a respective voltage, which is derived from the commutation method used to generate the R. 410820.
[0034] - 6 -
[0035] stator magnetic field and the torque specification of a drive torque in a manner known per se.
[0036] To transfer electrical energy into the secondary coil, an excitation alternating voltage uU is applied to the regular phase voltage uU of the hybrid phase strands. Di ff superimposed, resulting in the following: uU Di ff = uU1— uU2 = uU Di ff Amp SquareWave(2nFrq Exc t + <p Exc ) where the average of the two resulting phase voltages uU1, uU2 for the hybrid phase strands (hybrid phase voltages) corresponds to a phase voltage uU that results from the commutation method and the target torque of the electric machine. The difference between the two hybrid phase voltages uU1, uU2 for the hybrid phase strands corresponds to the excitation AC voltage uU. Di ff with a predetermined excitation amplitude uU Di ff Amp , an assigned transmission frequency Frq Exc and the specified phase shift <p Exc The rotating field frequency Frq Funda and the phase shift <p FundaThese correspond to the electrical frequency of the rotating field in the stator, which depends on the rotational speed of the electric machine. A square wave corresponds to a rectangular waveform. This induces a corresponding voltage in the secondary coil of the transmission device in the rotor, which is then rectified, so that an excitation current is available in the rotor.
[0037] The actual excitation current can be derived as a current difference by measuring the currents in the hybrid phase strands. A controller (e.g., a PI or PID controller) can be provided to regulate the excitation current, controlling the actual excitation current to a predefined target excitation current, as per R. 410820.
[0038] - 7 -
[0039] Excitation alternating voltage uU Diff The manipulated variable corresponds to the effective value of the differential current from the two hybrid phase strands. This can be calculated as... where MA nwhich corresponds to the moving average with n sampling points. The transmission frequency Frq Exc The voltage used to transfer the excitation AC voltage to the secondary coil of the excitation arrangement can be lower than the modulation frequency for pulse-width modulated control to generate the phase voltages. SV-PWM modulation of the multiphase system can be used to control the phase strings, and the control of the hybrid phase strings can be modulated with the desired voltages, as if there were two independent three-phase systems ulH, uV, uW and ull2, uV, uW.
[0040] It is therefore assumed that the electric machine is made up of two or more than two sub-machines which are operated to provide a common torque, whereby the phase voltages of the hybrid phase strands are superimposed on the opposite-phase excitation alternating voltage to generate the excitation current in the rotor.
[0041] However, since the phase voltages have a common neutral point due to the star connection, a different neutral voltage of the star point and thus of the effective phase voltage results depending on the switching combination of the phase voltages during commutation.
[0042] A control method is designed to achieve better voltage utilization. The desired voltage vector for control is then represented by a 3D vector uS = [ua, uß, ulldiff]. The duty cycles for providing the phase voltages uU1, uU2, uV, uW are then determined by decomposing uS into six basic vectors. The six basic vectors are uU, uV, -uW, Zb, Za, Za' with the corresponding duty cycles D1 to D6 and the R. 410820
[0043] - 8 -
[0044] Vectors, according to the following table.
[0045] S_U1 , S_U2, S_V, S_W represent the switch positions for the half-bridge circuits of the power driver.
[0046] These six basic vectors correspond to different control patterns. The values for ua, uß, and uZ are normalized to the maximum voltage of a phase strand. ua and uß are the standard 2D (Cartesian) space vector representations. This is achieved through the Park transformation 3(UVW)To2(aß) or as a complex vector = uaß = 2 / 3*(ull + uV*exp(j*2*pi / 3) + uW*exp(j*4*pi / 3)). uZ here represents the differential voltage, which corresponds to the desired voltage for the excitation AC and is symmetrically superimposed on the phase voltage of the hybrid phase strands. To obtain a differential voltage, the switches in S_U1 and S_U2 must be switched against each other, i.e., 0-1 or 1-0. Depending on the combinations, a Z-component R is then generated. 410820
[0047] - 9 - generates the differential voltage required for excitation. Pointers A and B are used to set the conventional stator voltage, and Z is for excitation. The basic vectors are marked in the table as those to which a duty cycle is assigned. A 3D vector can be completely represented using the symmetry principle.
[0048] The calculation is only considered in the first octant (+ua + uß + uZ) of the 3D vector. For the other octants, the analysis can be converted according to the symmetric principle, in particular as (+ua + uß - uZ), (-ua + uß + uZ), (+ua - uß + uZ), (-ua - uß + uZ), (-ua - uß - uZ), (-ua + uß - uZ), (+ua - uß - uZ).
[0049] A pyramid can be defined using three adjacent (closest to each other) basic vectors, so that a total of four pyramids Pymdl , Pymd2, Pymd3, Pymd4 are formed from the six basic vectors as a space region determined by the basic vectors, which together completely overlap the first octant.
[0050] The determination of the control pattern is carried out as follows:
[0051] A desired 3D voltage vector is provided according to the above procedure of superimposing the generation of the rotating field and the generation of the excitation alternating voltage by the corresponding control;
[0052] The 3D stress vector is then assigned to a corresponding pyramid in such a way that it falls within the spatial region of the corresponding pyramid;
[0053] After selecting the pyramid, the duty cycles for the basic vectors that define the pyramid in question are calculated.
[0054] Brief description of the drawings
[0055] The embodiments are explained in more detail below with reference to the accompanying drawings. These show:
[0056] Figure 1 shows a schematic representation of an electric machine with contactless transmission of an excitation current in R. 410820
[0057] - 10 - a rotor; and
[0058] Figure 2 shows an equivalent circuit diagram for controlling the phase strands of the electric machine of Figure 1 using half-bridge circuits; and
[0059] Figure 3 shows a representation of the pyramids for choosing combinations of the basic vectors.
[0060] Description of embodiments
[0061] Figure 1 schematically shows an electric machine 1 with a stator 2 and a rotor 3. The stator 2 has a stator assembly 21 with six stator teeth 22, each wound with a stator coil 23. The stator coils 23 are each assigned to a phase II, V, W and form two sub-machines, such that the stator coils 23 assigned to the same phase are opposite each other and electrically connected in parallel with respect to a neutral point N. The stator coils 23 of the phase strands V, W themselves are connected in parallel between the neutral point N and a corresponding phase terminal V, W. Hybrid phase strands U1, U2 each have a stator coil 23 that is connected to the neutral point N but can be separately controlled via a phase terminal U1, U2 with a corresponding hybrid phase voltage.
[0062] An equivalent circuit diagram for controlling the phase strands of the electric machine is shown in Figure 2. The separate bridge circuits 4 for generating the respective phase voltages λH, λI12, λV, λW for each of the stator coils 23 of the hybrid phase strand and the two remaining phase strands of the electric machine 1 can be seen. The bridge circuits 4 each have a high-side switch 41 and a low-side switch 42, which are arranged in series.
[0063] The stator assembly 21 is coupled to a rotor 3, which is located inside the cylindrical stator assembly 21 and is mounted for rotation. The rotor 3 has at least one secondary coil 32 to generate an excitation current by inductive or transformer coupling with the hybrid strand coils of the R. 410820.
[0064] - 11 -
[0065] Hybrid phase strands are provided. These serve to couple to the hybrid phase via a transformer in order to provide electrical energy for energizing an excitation winding 31. The secondary coil 32 is electrically connected to the excitation winding 31 via a rectifier 33 to generate a static excitation magnetic field (not an alternating magnetic field).
[0066] A control unit 5 is provided for controlling the bridge circuits 4, which determines the phase voltages.
[0067] To transfer electrical energy to the secondary coil in the rotor, different voltages are impressed onto the phase strands of the regular phases V, W and the hybrid phase U1, U2, as follows: uU Di ff = uU1— uU2 = uU Di ff Amp SquareWave(2nFrq Exc t + <p Exc ) The average of the two resulting hybrid phase voltages uU1, uU2 corresponds to a phase voltage uU, which is determined by the commutation process and the target torque of the electric machine. This results in a phase voltage to be applied to the hybrid phase strands, calculated using the resulting hybrid phase voltages uUH, uUIL2. The phase voltage of phase strand U, together with the phase voltages uV, uW, is to be applied to the regular phase strands according to the commutation process to drive the electric machine. The difference between the two hybrid phase voltages uU1, uU2 for the hybrid strand coils corresponds to the excitation AC voltage uU. D tff with a predetermined excitation amplitude uU Di ff Amp , an assigned transmission frequency Frq Exc and the specified phase shift <p Exc The rotating field frequency Frq Funda and the phase shift <p Funda correspond to R. 410820
[0068] - 12 - electrical frequency of the rotating field in the stator, which depends on the rotational speed of the electric machine. Square wave corresponds to a rectangular waveform. This induces a corresponding voltage in the secondary coil of the transmission device in the rotor, which is then rectified, so that an excitation current is available in the rotor.
[0069] Since the excitation current in rotor 3 cannot be measured directly, a measured quantity llldiff is determined, which can be described by a characteristic curve or a mathematical function of the excitation current, llldiff = F(lexc).
[0070] A controller then regulates the measurable effective differential current between the phase strands U1 and U2 of the hybrid phase, which corresponds to the desired excitation current. For this purpose, the currents through the hybrid phase strands are measured separately using current sensors 6.
[0071] The effective value of the differential current iU DiffEffcan now be calculated as a moving average. U Differential Ef where MA n the moving average with n points, where the number n of points for the moving average is chosen such that n = kx (Frq Sampie / Frq Exc ), where k is an integer, Frq Sampie the sampling frequency of the current sampling and Frq Exc corresponds to the transmission frequency for the secondary coil. The combination of k, Frq Sampie and Frq Exc are chosen such that n becomes an integer. That is, Frq Sampie and Frq Exc are tuned so that n becomes an integer, or Fr q S at P ie = 10 kHz, Frq Exc = 1,500 Hz, k = 3, n = 20. The sampling rate Frq Sampie It must also be large enough to satisfy sampling theory. Frq Sampie < 2 x Frq Exc .
[0072] If a transmission frequency Frq is set Excfixed, optimized for the designed R. 410820
[0073] - 13 -
[0074] Given the impedance of the transmission system to the secondary coil 32, only the amplitude of the differential voltage uU needs to be determined. Diff The desired effective differential current iU is set between the phase strands U1 and U2 of the hybrid strand. Diff The system is set and the excitation current lexc is activated.
[0075] Since the electric machine is driven by a four-phase inverter, i.e., four half-bridge circuits, a suitable modulation method must be used to provide the phase voltages. The transmission frequency Frq is... Exc below the range of the modulation frequency of a pulse width modulation to be applied.
[0076] The simplest method is to use SV-PWM modulation for a three-phase system and to modulate the hybrid phase strands U1 and U2 with the desired phase voltages ulH and ull2, so that two independent three-phase systems U1, V, W and U2, V, W are operated.
[0077] The differential voltage ulldiff in the phase strands of the hybrid phase causes a deviation in the voltages at the neutral point, which affects the effective applied phase voltage, i.e., the voltage present at the respective phase strand. For control purposes, a desired voltage vector is then assumed to be a 3D vector uS = [ua, uß, ulldiff], where ua and uß represent components of a vector in the stator-fixed coordinate system, and uLldiff represents the differential voltage of the hybrid phase strand voltages uU1 and uU2.
[0078] The duty cycles for the individual regular phases and the hybrid phase are then determined by decomposing the 3D vector uS into six basic vectors. These six basic vectors are defined as the switching vectors with which all vectors in the first octant can be described and correspond to uU, uV, -uW, Zb, Za, Za' with the corresponding duty cycles D1 to D6, as can be seen in the table above.
[0079] The switching combinations of the corresponding basic vectors are listed in the following table. The calculation is only considered in the first octant +ua, +uß, +uZ; for the other octants, the analysis can be carried out according to R. 410820.
[0080] - 14 - can be converted using the symmetrical principle. uZ here represents the differential voltage, which corresponds to the desired voltage for the excitation alternating current. To obtain a differential voltage, the switches in S_U1 and S_U2 must be switched against each other, i.e., 0-1 or 1-0. Depending on the combinations, a Z component is then generated for the differential voltage required for excitation. The phasors ua and uß are for setting the conventional stator voltage, and Z is for excitation. The basic vectors are marked in the table as those to which a duty cycle is assigned. A 3D vector can be completely represented using the symmetry principle.
[0081] With three adjacent basic vectors, a pyramid can be defined as a region of space between the adjacent basic vectors. In total, the six basic vectors uaNrm, ußNrm, uZNrm (Nrm: "normalized") form four pyramids: Pymdl, Pymd2, Pymd3, Pymd4, which together overlap the first octant and are shown graphically in Figure 3.
[0082] Based on the instantaneous value for the generation of the rotating magnetic field and the excitation alternating voltage, a voltage phasor with the voltage values ua, uß is determined, and the differential voltage uUdiff results from the current control for the excitation current.
[0083] The resulting 3D stress vector is then assigned to a corresponding pyramid by finding the 3D stress vector that lies in the spatial region of the corresponding pyramid.
[0084] For the selected pyramid, the duty cycles for providing the basic vectors are calculated. R. 410820
[0085] - 15 -
[0086] The duty cycles dCyc for the individual phase strands are determined from the duty cycles D1 - D6. R. 410820
[0087] - 16 -
[0088] The phase strands are then energized with a commutation pattern derived from the respective duty cycle (R. 410820).
[0089] - 17 -
[0090] This results in the switching times of the phase strands.
Claims
1. R. 410820 - 18 - Claims 1. Method for operating a multiphase electric machine (1), wherein a stator arrangement (21) is provided, the regular phase strands (V, W) of which are each formed from several stator coils (23) connected in parallel, wherein the stator coils (23) of the regular phase strands (V, W) can be controlled with phase voltages, wherein the stator arrangement (21) provides a hybrid phase consisting of several hybrid phase strands (U1, U2) each with one or more stator coils (23), wherein the hybrid phase strands (U1, U2) can be controlled separately with a respective phase voltage, wherein in operation a regular phase voltage is assigned to each of the respective regular phase strands (V, W) and the hybrid phase strands (U1, U2), which result from a predetermined drive torque and a predetermined commutation scheme, wherein all phase strands (U1, U2, V, W) are connected in a star connection,wherein the electric machine (1) has a rotor (3) with a secondary coil (32) into which an excitation current can be supplied by transformer coupling with the stator coils (23) of the hybrid phase, wherein the electric machine (1) is operated with the following steps:, Determining the phase voltages for the regular phase strands (V, W) and the hybrid phase according to a voltage vector to be provided for controlling the stator arrangement (21) for the operation of the electric machine (1); Determining the excitation alternating voltage to be set depending on the currents through the stator coils of the hybrid phase; Applying an excitation alternating voltage to the phase voltages for the hybrid phase strands (I11 , U2) so that the mean value of the two phase voltages (ulH , ull2) for the hybrid phase strands (U1 , U2) corresponds to the regular phase voltage (ull) for the hybrid phase strands (U1, U2). R. 410820 - 19 - 2. Method according to claim 1, wherein the excitation alternating voltage is obtained from a desired excitation current in the rotor (3) of the electric machine (1) and the current flows through the hybrid phase strands (U1, U2) of the hybrid phase by means of a current control which provides the excitation alternating voltage as a control variable.
3. Method according to claim 1 or 2, wherein the transmission frequency (FrqExc) with which the excitation alternating voltage is transmitted into the secondary coil (32) of the rotor (3) is smaller than the modulation frequency for a pulse width modulated control for generating the phase voltages.
4. Method according to one of claims 1 to 3, wherein duty cycles for the phases are used to determine the phase voltages to be set by means of SV-PWM modulation.
5. Method according to one of claims 1 to 4, wherein the excitation alternating voltage to be set is determined by means of a control system depending on currents through the stator coils of the hybrid phase.
6. Method according to any one of claims 1 to 5, wherein a voltage vector is generated in a stator-fixed coordinate system for control purposes.
7. Method according to claim 6, wherein, for applying an excitation alternating voltage to the phase voltages for the hybrid phase strands (U1 , U2), a desired 3D voltage vector is provided by superimposing a generation of a rotating field and a generation of the excitation alternating voltage.
8. Method according to claim 7, wherein the 3D voltage vector is assigned to those basic vectors (ua, uß, uZ) of a control of the phase strands and the hybrid phase strands that enclose the 3D voltage vector.
9. Method according to claim 8, wherein, after the assignment of the basic vectors (ua, uß, uZ), the duty cycles for the control by the basic vectors (ua, uß, uZ) are determined. R. 410820 - 20 - 10. Device for operating a multiphase electric machine (1), wherein a stator arrangement (21) is provided for the electric machine, the regular phase strands (V, W) of which are each formed from several stator coils (23) connected in parallel, wherein the stator coils (23) of the regular phase strands (V, W) can be controlled with phase voltages, wherein the stator arrangement (21) provides a hybrid phase consisting of several hybrid phase strands (U1, U2) each with one or more stator coils (23), wherein the hybrid phase strands (U1, U2) can be controlled separately with a respective phase voltage, wherein in operation a regular phase voltage is assigned to each of the respective regular phase strands (V, W) and the hybrid phase strands (U1, U2), which result from a predetermined drive torque and a predetermined commutation scheme, wherein all phase strands (U1, U2, V, W) are connected in a star connection,wherein the electric machine (1) has a rotor (3) with a secondary coil (32) into which an excitation current can be supplied by transformer coupling with the stator coils (23) of the hybrid phase, wherein the device is configured to:, Assigning a regular phase voltage to the respective regular phase strands and hybrid phase strands, wherein the regular phase voltages result from a predetermined drive torque and a predetermined commutation scheme, Determining the phase voltages for the regular phase strands (V, W) and the hybrid phase according to a voltage vector to be provided for controlling the stator arrangement (21) for the operation of the electric machine (1); Determining the excitation alternating voltage to be set depending on the currents through the stator coils of the hybrid phase; Applying an excitation alternating voltage to the phase voltages for the hybrid phase strands (I11 , U2) so that the mean value of the two phase voltages (ulH , ull2) for the hybrid phase strands (U1 , U2) corresponds to the regular phase voltage (ull) for the hybrid phase strands (U1, U2).