Method for regulating an electric rotary current machine, and rotary current machine system for such a method

Abstract

A rotary current machine system and method for controlling an electric rotary current machine, in particular an induction machine, having a rotor, a stator and at least two phase windings is disclosed. At least one electrical signal, in particular a voltage signal, is applied to at least one phase winding, preferably all phase windings, of the rotary current machine, and the current waveform in the at least one phase winding is measured. An intermodulation signal component, induced in the rotary current machine by slotting effects and magnetic saturation effects, which is determined from the current waveform measured in the at least one phase winding, is used for controlling the rotary current machine.

Claims

1. A method for controlling an electric rotary current machine, with a rotor, a stator and at least two phase windings, wherein at least one electrical signal is applied to at least one phase winding of the rotary current machine and an electrical signal waveform in the at least one phase winding is measured or determined, wherein an intermodulation signal component caused by slotting effects and magnetic saturation effects in the rotary current machine, which intermodulation signal component is determined from the signal waveform determined or measured in the at least one phase winding, is used for controlling the rotary current machine, wherein a mechanical angular position and/or a rotation speed of the rotor is determined from the intermodulation signal component and the angular position and/or the rotation speed is used to control the rotary current machine.

2. The method according to claim 1, wherein the intermodulation signal component is determined from a rate of change of the signal waveform.

3. The method according to claim 1, wherein in at least two phase windings of the rotary current machine, current waveforms are determined and the current waveforms are combined by a mathematical equation to form a combined signal and the intermodulation signal component is determined from the combined signal.

4. The method according to claim 3, wherein the mathematical equation is an equation for calculating a tensor.

5. The method according to claim 1, wherein the intermodulation signal component is extracted by elimination of saturation signal components due to magnetic saturation effects in the rotary current machine and/or slot signal components due to slotting effects.

6. The method according to claim 5, wherein from an angle of the intermodulation signal component a slotting angle is determined by combining the angle of the intermodulation signal component with an angle of a saturation signal component contained in at least one signal waveform, using the calculation rule
θ.sub.slot(t)=±θ.sub.sat(t)−θ.sub.inter(t).

7. The method according to claim 6, wherein a mechanical angular position of the rotor is determined by dividing the slotting angle by the number of slots of the rotor.

8. The method according to claim 6, wherein the angle of the intermodulation signal component is corrected by an intermodulation correction value as a function of the rotation speed of the rotor and/or the load on the rotary current machine.

9. The method according to claim 6, wherein the angle of the saturation signal component is corrected by a saturation correction value as a function of the rotation speed of the rotor and/or the loading on the rotary current machine.

10. The method according to claim 1, wherein the electrical signal comprises an excitation signal, which is essentially independent of the generation of a fundamental wave of the rotary current machine and the fundamental frequency of which is at least five times as great as a temporal frequency of the fundamental wave of the voltages in a phase winding for generating the fundamental wave of the rotary current machine.

11. The method according to claim 1, wherein the electrical signal is a current signal and the response of the rotary current machine to the current signal is evaluated to determine the intermodulation signal component.

12. A rotary current machine system, comprising: a rotary current machine having a rotor, a stator and at least two phase windings; a converter which is electrically connected to the rotary current machine, wherein the converter is configured to apply electrical signals to at least one phase winding of the rotary current machine; at least one measuring device which is configured to measure or determine at least one electrical signal waveform in the at least one phase winding; wherein: a control unit is provided that is configured to control the rotary current machine on the basis of an intermodulation signal component caused by slotting effects and magnetic saturation effects in the rotary current machine, which intermodulation signal component is contained in the at least one electrial signal waveform, wherein a mechanical angular position and/or a rotation speed of the rotor is determined from the intermodulation signal component and the angular position and/or the rotation speed is used to control the rotary current machine.

13. The System according to claim 12, wherein the control unit is integrated into the converter.

14. The system according to claim 12, wherein the intermodulation signal component is determined from a rate of change of the at least one electrical signal waveform.

15. The system according to claim 12, wherein in at least two phase windings of the rotary current machine, current waveforms are determined and the current waveforms are combined by a mathematical equation to form a combined signal and the intermodulation signal component is determined from the combined signal.

16. The system according to claim 12, wherein the intermodulation signal component is extracted by elimination of saturation signal components due to magnetic saturation effects in the rotary current machine and/or slot signal components due to slotting effects.

17. The system according to claim 16, wherein from an angle of the intermodulation signal component a slotting angle is determined by combining the angle of the intermodulation signal component with an angle of a saturation signal component contained in at least one signal waveform, using the calculation rule
θ.sub.slot(t)=±θ.sub.sat(t)−θ.sub.inter(t).

18. The system according to claim 17, wherein a mechanical angular position of the rotor is determined by dividing the slotting angle by the number of slots of the rotor.

19. The system according to claim 12, wherein the electrical signals comprise an excitation signal, which is essentially independent of the generation of a fundamental wave of the rotary current machine and the fundamental frequency of which is at least five times as great as a temporal frequency of the fundamental wave of the voltages in a phase winding for generating the fundamental wave of the rotary current machine.

20. The system according to claim 12, wherein the electrical signals comprise a current signal and the response of the rotary current machine to the current signal is evaluated to determine the intermodulation signal component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the present teaching is described by reference to the figures, but is not intended to be limited thereby.

(2) FIG. 1 shows a schematic view of a rotary current machine system with a converter and a rotary current machine;

(3) FIG. 2 shows an induction machine in cross-section;

(4) FIG. 3A shows a schematic view of an exemplary excitation signal;

(5) FIG. 3B shows schematic current waveforms in response to the excitation signal according to FIG. 3A (at different rotor positions);

(6) FIG. 4A shows a combined signal in the time domain, which was generated from a combination of current waveforms of all phase windings of the rotary current machine;

(7) FIG. 4B shows the combined signal of FIG. 4A in the frequency domain;

(8) FIG. 5 shows a real component of the combined signal;

(9) FIG. 6 shows a real component of an intermodulation signal component;

(10) FIGS. 7A-7D show different signal waveforms of the rotary current machine in different operating states of the rotary current machine;

(11) FIGS. 8A-8C each show waveforms of correction values;

(12) FIG. 9 shows a block circuit diagram as an example implementation of the present teaching; and

(13) FIGS. 10A-10C illustrate excitation signals and resulting current waveforms.

DETAILED DESCRIPTION

(14) In the following the method according to the present teaching is explained in further detail based on an application to an induction machine.

(15) FIG. 1 shows a schematic view of a rotary current machine system 1 with a rotary current machine 3 designed as an induction machine 2 driven by a converter 4, which has a multiplicity of electronic switches (not shown), for example semiconductor switches. The converter 4 is configured to output voltages with predefined frequencies, amplitudes and (zero) phase angles at an output 6 by means of appropriate switching operations. The output 6 of the converter 4 is connected to the phase windings U, V, W of the induction machine 2. Due to the generated voltages of the converter 4, a rotating magnetic field is generated in an air gap of the induction machine 2 between rotor 21 and stator 20 (see FIG. 2), which induces voltages in the rotor 21 of the induction machine 2 and sets the rotor into rotation due to the resulting rotor currents.

(16) The induction machine 2 is shown schematically in FIG. 1 as a circuit diagram. The induction machine 2 has three phase windings U, V, W with a phase winding resistance R.sub.U, R.sub.V, R.sub.W and a phase winding inductance L.sub.U, L.sub.V, L.sub.W respectively. The voltages E.sub.U, E.sub.V, E.sub.W denote the voltages (back EMF) induced in the stator 20 of the induction machine 2. The currents I.sub.U, I.sub.V, I.sub.W flowing in the phase windings U, V, W can be measured or determined using current measuring sensors 7a and/or 7b of a measuring device 8a or 8b respectively. Phase currents can also be determined using the current measuring sensors 7b, for example on the basis of a current flowing into the converter 4. It may be the case that a current measuring sensor 7a is provided in each phase winding U, V, W. The current measuring sensors 7a or 7b can be integrated into the converter 4 or can be independent elements. With the aid of current measuring sensors 7a and/or 7b, the time-domain current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t) of the currents I.sub.U, I.sub.V, I.sub.W in the phase windings U, V, W can be determined.

(17) FIG. 2 shows schematically an induction machine 2 without windings in cross-section with a stator 20, a rotor 21 and a slot 23, on each of the rotor 21 and stator 20. For illustration, an angular position θ.sub.mech(t) of the rotor 21 is indicated.

(18) As mentioned above, the induction machine 2 shows asymmetries which can vary according to time and location, thus allowing information to be obtained on the angular position θ.sub.mech(t) and/or the rotation speed of the rotor 21. An example of such an asymmetry is the slotting 23 of rotor 21 and/or stator 20. Another example of an asymmetry is the saturation of the magnetic flux paths in the induction machine 2. Both asymmetries cause temporal and spatial inductance changes in the operation of the induction machine 2, which can be determined by evaluating the current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t). For example, in a greatly simplified model to illustrate an asymmetry, it can be assumed, for example, that the three phase winding inductances L.sub.U, L.sub.V, L.sub.W in the phase windings U, V, W each have a mean value Lo and, as a function of a mechanical angular position θ.sub.mech(t) of the rotor 21, deviate from this mean value Lo sinusoidally (with an amplitude Lim):

(19) $\begin{array}{cc}{L}_U\left({\theta }_{mech}\left(t\right)\right)=L_{U,0}+L_{U,M}\sin \left({\theta }_{mech}\left(t\right)\right)& \left(6A\right)\end{array}$$\begin{array}{cc}{L}_V\left({\theta }_{mech}\left(t\right)\right)=L_{V,0}+L_{V,M}\sin \left({\theta }_{mech}\left(t\right)+\frac{2\pi }{3}\right)& \left(6B\right)\end{array}$$\begin{array}{cc}{L}_W\left({\theta }_{mech}\left(t\right)\right)=L_{W,0}+L_{W,M}\sin \left({\theta }_{mech}\left(t\right)+\frac{4\pi }{3}\right).& \left(6C\right)\end{array}$

(20) The change in the angular position θ.sub.mech(t) of the rotor 21 therefore also changes the inductances L.sub.U, L.sub.V, L.sub.W. The variable inductance components can therefore also be referred to as modulated inductances. The changes in inductances L.sub.U, L.sub.V, L.sub.W can be caused, for example, by the slot 23 of the rotor 21 or stator 20 and/or the magnetic saturation of magnetic iron paths in the rotary current machine 3.

(21) The determination of the angular position θ.sub.mech(t) of the rotor 21 for induction machines 2 has up to now presented a major challenge, since induction machines 2, particularly in comparison to most synchronous machines, have significantly smaller asymmetries and thus significantly smaller inductance fluctuations in operation.

(22) To determine inductance changes, electrical signals, preferably voltage signals U.sub.U(t), U.sub.V(t), U.sub.W(t), are applied to the phase windings U, V, W of the induction machine 2 and the resulting current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t) are measured using the current measuring sensors 7. The voltages or voltage pulses applied by the converter 4 to operate the induction machine 2 can be used as voltage signals U.sub.U(t), U.sub.V(t), U.sub.W(t). The electrical signals can contain excitation signals 9 to determine the operating state of the rotary current machine 3. The excitation signals 9 can be essentially independent of the generation of a rotating field of the rotary current machine 3. Here, excitation signals 9 can be used which are applied between the voltage (pulses) generated by the converter 4 for generating the rotating field, or superimposed on them. It is also possible to use voltage waveforms with frequencies higher than that used to generate the fundamental component of the rotating field.

(23) In FIG. 10A to FIG. 100, the application of an example excitation signal 9 and the resultant current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t) in the phase windings U, V, W of a rotary current machine 3 are illustrated. Any ohmic resistances can be ignored here. FIGS. 10A-10C show two switch positions of the converter 4, with which a rectangular excitation signal 9 with a positive voltage +U and a negative voltage −U can be generated (amplitude V.sub.DC). If such an excitation signal 9, which is shown against time tin the upper partial image of FIG. 10A, is applied, as shown in FIG. 10B, corresponding current increases di.sub.U/dt, di.sub.V/dt, di.sub.W/dt are obtained in the current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t). In FIG. 10B, current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t) and current slopes di.sub.U/dt, di.sub.V/dt, di.sub.W/dt of each phase winding U, V, W are shown. Electrical equivalent circuit diagrams of the induction machine 2 with applied voltages +U and −U of the excitation signal 9 are shown in the lower two images of FIG. 10A. If the excitation signal 9 is applied, with a positive voltage +U (with the electrical sign convention according to FIG. 1) a positive current slope di.sub.U/dt initially occurs in phase winding U (and thus a positive voltage drop across the phase winding inductance L.sub.U) and a negative current slope di.sub.V/dt or di.sub.W/dt in each of the phase windings V and W (and thus a negative voltage drop across the phase winding inductances L.sub.V and L.sub.W). With a negative voltage −U of the excitation signal 9, the case is reversed.

(24) On account of different phase winding inductances L.sub.U, L.sub.V, L.sub.W due to asymmetries in the rotary current machine 3, an additional deviation of the current slopes di.sub.U/dt, di.sub.V/dt, di.sub.W/dt is obtained. This additional deviation is not shown in FIG. 10B, but can be seen in FIG. 3B.

(25) In one embodiment, rectangular excitation signals 9, such as those shown in FIG. 3A, are applied to the phase windings U, V, W of the induction machine 2 for the determination of inductance. FIG. 3A shows the excitation signal 9 in normalized form. As a result of such an excitation signal 9, which can be applied, for example, between the voltage pulses applied to generate the rotating field in the induction machine 2, a current slope of di.sub.U/dt, di.sub.V/dt, di.sub.W/dt occurs in the phase windings U, V, W due to the relationship illustrated in equation (2). Any ohmic resistance can usually be ignored here.

(26) In FIG. 3B, as an example, three different current slopes di.sub.U/dt of the phase current I.sub.U in phase winding U are shown at different times and thus for different phase winding inductances L.sub.U due to the asymmetries of the rotary current machine 3 (cf. equation 6A-6C). Similar illustrations also apply to the remaining phase windings V and W. The illustrations shown in the figures have been simplified and are intended to illustrate schematically the principle of the inductance determination. The variation in the current waveforms i.sub.U(t), i.sub.V(t), i.sub.W(t) over time allows information to be obtained about the change in the inductances L.sub.U, L.sub.V, L.sub.W.

(27) The current slopes di.sub.U/dt, di.sub.V/dt, di.sub.W/dt in the phase windings U, V and W, determined preferably at regular intervals, can then be combined using a mathematical equation into a combined signal ϑ.sub.Saliency. However, in particular in the case of sinusoidal excitation signals 9, the current values, i.e., the amplitudes, or RMS values, or instantaneous values, of the currents I.sub.U, I.sub.V, I.sub.W can also be used and combined. Preferably, a mathematical equation for calculating a space vector is used to combine the current waveforms, for example:

(28) $\begin{array}{cc}{\vartheta }_{\mathrm{saliency}}=\frac{{\mathrm{di}}_U\left(t\right)}{\mathrm{dt}}+\frac{{\mathrm{di}}_V\left(t\right)}{\mathrm{dt}}{e}^{j2\frac{\pi }{3}}+\frac{{\mathrm{di}}_W\left(t\right)}{\mathrm{dt}}{e}^{j4\frac{\pi }{3}}.& \left(4b\right)\end{array}$

(29) The combined signal ϑ.sub.Saliency can also be called a “saliency signal”. When the signal ϑ.sub.Saliency is calculated as a space vector, ϑ.sub.Saliency represents a tensor.

(30) FIG. 4A shows the trace of the tensor ϑ.sub.Saliency, where both the abscissa and the ordinate represent an amplitude in amperes/second. The abscissa represents the real part and the ordinate the imaginary part of the signal ϑ.sub.Saliency.

(31) FIG. 4B illustrates the signal ϑ.sub.Saliency shown in FIG. 4A in the frequency domain, where the abscissa plots the harmonics N.sub.harmonisch of the signal. As can be seen in FIG. 4B, ϑ.sub.Saliency contains three distinct signal components. A first prominent signal component is formed by a slot signal component ϑ.sub.slot, which is attributable to the slots 23 of the rotor 21 and of the stator 20 of the rotary current machine 3. A second prominent signal component is formed by a saturation signal component ϑ.sub.sat, which is attributable to the saturation of magnetic flux paths in the rotary current machine 3. A third significant signal component is formed by an intermodulation signal component ϑ.sub.inter, which is attributable to a physical interlinking of the slot signal component ϑ.sub.slot and the saturation signal component ϑ.sub.sat. The slot signal component ϑ.sub.slot, the saturation signal component ϑ.sub.sat and the intermodulation signal component ϑ.sub.inter each having different fundamental frequencies.

(32) In the prior art, in sensorless control using the slot information, the intermodulation signal component ϑ.sub.inter and the saturation signal component ϑ.sub.sat were previously eliminated as interference signals and the slot signal component ϑ.sub.slot was used to determine an angular position and/or a rotation speed of the rotor. However, as can be seen in FIG. 4B, in the present case the slot signal component ϑ.sub.slot is relatively small compared to other signal components. It can therefore be difficult to identify and extract the slot signal component ϑ.sub.slot, particularly at higher loads of the rotary current machine 3. In FIG. 4B, the slot signal component ϑ.sub.slot already has approximately the same order of magnitude of higher harmonics as the saturation signal component ϑ.sub.sat.

(33) According to the present teaching, it is therefore provided not to use the slot signal component ϑ.sub.slot directly for controlling the rotary current machine 3, but to use the intermodulation signal component ϑ.sub.inter and its indirectly included slot or rotor angle information for controlling the electric rotary current machine 2. The method according to the present teaching can be implemented in a control unit 12 (see FIG. 1). The intermodulation signal component ϑ.sub.inter is a dominant signal component in the ϑ.sub.Saliency signal over a wide rotation speed range and can therefore be easily identified. The present teaching is based on the finding that there is a relation between the fundamental frequency of the intermodulation signal component ϑ.sub.inter and the fundamental frequency of the slot signal component ϑ.sub.slot, which allows information to be obtained about the angular position and/or rotation speed of the rotor 21. The relation can be described by equation (1):
ω.sub.inter=±ω.sub.sat−ω.sub.slot,  (1)

(34) where ω.sub.inter denotes the fundamental frequency of the intermodulation signal component ϑ.sub.inter, ω.sub.sat the fundamental frequency of the saturation signal component ϑ.sub.sat, and ω.sub.slot the fundamental frequency of the slot signal component ϑ.sub.slot. The sign of ω.sub.sat depends on the design and construction of the rotary current machine 3.

(35) In order to determine the angular position of the rotor, which can be used for controlling the rotary current machine 2, the intermodulation signal component ϑ.sub.inter is separated from other signal components, i.e., essentially isolated, for example by filtering or estimating the unwanted signal components and subtraction. An angle θ.sub.inter(t) is determined from the signal ϑ.sub.inter, in particular from its fundamental frequency. The angle can be a phase angle that changes over time. This can be carried out using a PLL (phase-locked loop), for example. In addition, an angle, in particular a phase angle, θ.sub.sat(t) of the saturation signal component ϑ.sub.sat is determined, in particular from its fundamental frequency. The two angles θ.sub.sat(t) and θ.sub.inter(t) are combined, for example, using the equation:
θ.sub.slot(t)=−θ.sub.inter(t)±θ.sub.sat(t),  (5)

(36) to obtain a calculated angle θ.sub.slot(t) of a slot angle. In this disclosure, θ is used to designate angles, while ϑ represents signals or signal components. The slot angle θ.sub.slot(t) determined by equation (5) is essentially a calculated angle of the slot signal component ϑ.sub.slot. By dividing the slot angle θ.sub.slot(t) by the number N of slots of the rotor, a mechanical angular position θ.sub.mech(t) of the rotor 21 can be determined from θ.sub.slot(t). θ.sub.mech(t) can subsequently be used, for example, for controlling the rotary current machine 3. For example, θ.sub.mech(t) can be used to represent electrical variables in a rotor-referenced coordinate system, or to control the angular position (angular position control) and/or the rotation speed (speed control) of the rotor.

(37) FIG. 5 shows a temporal waveform of the real component of the combined current signal ϑ.sub.Saliency in seconds. This signal contains the slot signal component ϑ.sub.slot, the saturation signal component ϑ.sub.sat and the intermodulation signal component ϑ.sub.inter.

(38) FIG. 6 shows a temporal waveform of the real part of the intermodulation signal component ϑ.sub.inter, in seconds, wherein the slot signal component ϑ.sub.slot and the saturation signal component ϑ.sub.sat have been eliminated. However, the signal shown still contains its own harmonics and those of other signal components.

(39) FIG. 7A-7D show signal waveforms for different operating states of the induction machine 2 at different times. The time tin seconds is plotted on the abscissa in all of the figures FIG. 7A-7D. FIG. 7A shows the real part 10 and the imaginary part 11 of the intermodulation signal component ϑ.sub.inter. FIG. 7B shows the mechanical rotation speed ω.sub.mech of the rotor 21 in revolutions per minute (rpm) against time. FIG. 7C shows the torque generated by the rotary current machine 3 in relation to a nominal torque against time. FIG. 7D shows an angular deviation θ.sub.dev between the mechanical angular position θ.sub.mech(t) of the rotor, determined by means of the method according to the present teaching, and a mechanical angular position in degrees determined using a rotary encoder. In FIG. 7D it is apparent that the method according to the present teaching can be used to determine mechanical angular positions θ.sub.mech(t) of the rotor which show a deviation from the actual (measured) mechanical angular position of less than 1°.

(40) Experiments have shown that the accuracy of the method according to the present teaching can be further increased by taking into account the dependencies of the angle θ.sub.inter(t) of the intermodulation signal component ϑ.sub.inter and the angle θ.sub.sat(t) of the saturation signal component ϑ.sub.sat on the rotation speed and/or load of the rotary current machine 3. It has been shown that the angle θ.sub.inter(t) of the intermodulation signal component ϑ.sub.inter and the angle θ.sub.sat(t) of the saturation signal component ϑ.sub.sat may show deviations as a function of the load, in particular of the torque M of the rotary current machine 3. In one embodiment, it can therefore be provided that the angle θ.sub.inter(t) of the intermodulation signal component ϑ.sub.inter is corrected as a function of the load of the rotary current machine 3, in particular the torque M, by means of an intermodulation correction value θ.sub.inter_corr. The dependency of θ.sub.inter_corr on the torque M (in % relative to the rated torque) of the rotary current machine 3 is shown in FIG. 8A.

(41) It can also be provided that the angle θ.sub.sat(t) of the saturation signal component ϑ.sub.sat is corrected as a function of the load and the rotation speed of the rotary current machine 3, in particular the torque M, by means of a saturation correction value θ.sub.sat_corr. The dependency of θ.sub.sat_corr on the torque M (in % relative to the rated torque) of the rotary current machine 3 is shown in FIG. 8B.

(42) The angle θ.sub.inter of the intermodulation signal component ϑ.sub.inter may also be dependent on the rotation speed of the rotary current machine 3 (see FIG. 8C). This dependency can also be taken into account by means of the intermodulation correction value θ.sub.inter_corr, in addition to or as an alternative to the torque dependency.

(43) FIG. 9 shows a schematic representation of a possible implementation of the method according to the present teaching. In the exemplary embodiment shown, the input variables used are the intermodulation signal component ϑ.sub.inter, an electrical angle θ.sub.ele(t), a torque M and a mechanical angular velocity ω.sub.mech. θ.sub.ele(t) represents the angle of the fundamental component of the stator current and can be determined from the measured phase currents I.sub.U, I.sub.V, I.sub.W, for example as space vectors. ω.sub.mech can be determined from the intermodulation signal component ϑ.sub.inter. By multiplying the electrical angle θ.sub.ele(t), preferably by a factor of 2, the angle θ.sub.sat(t) of the saturation signal component ϑ.sub.sat can be obtained, which can be corrected by means of a previously determined saturation correction value θ.sub.sat_corr. By means of a phase-locked-loop signal processing unit (PLL), the angle θ.sub.inter(t) of the intermodulation signal component ϑ.sub.inter can be obtained from the intermodulation signal component ϑ.sub.inter and corrected by means of an intermodulation correction value θ.sub.inter_corr. By combining the two angles θ.sub.inter(t) and θ.sub.sat(t), in particular using the equation (5), a slot angle θ.sub.slot(t) can be calculated. The slot angle θ.sub.slot(t) is calculated in an UNWRAP block to give a coherent angular path (unwrapped phase) and then divided by the number of slots N of the rotor to obtain a mechanical angular position θ.sub.mech(t) of the rotor. The mechanical angular position can then be converted back again in a WRAP block so that θ.sub.mech(t) is represented in an angular interval, in particular between [−180°;180°] or [0°;360°] (wrapped phase). θ.sub.mech(t) can then be used for controlling the rotary current machine 3.