METHOD AND ARRANGEMENT FOR MONITORING A PERMANENTLY EXCITED SYNCHRONOUS MACHINE

Abstract

The present disclosure provides a method for monitoring a rotor position sensor of a PSM machine having at least three phases operated by a field oriented control, where the electrical angle of the PSM machine may corresponds with a rotor position. A first calculation of the electrical angle of the PSM machine may be based on a measured mechanical rotor position and the pole-pair number of the PSM machine. A second calculation of the electrical angle of the PSM machine may be based on the phase of a phase current indicator and regulated target currents in the d,q-coordinate system. The method may include a comparison of the values of the respective electrical angles of the PSM machine determined by the first calculation and the second calculation.

Claims

1. A method for monitoring a rotor position sensor of a PSM machine having at least three phases operated by a field oriented control, wherein the electrical angle (Θel) of the PSM machine corresponds with a rotor position, the method comprising: a first calculation of the electrical angle (Θ.sub.el1) of the PSM machine, wherein the first calculation is based on a measured mechanical rotor position and the pole-pair number of the PSM machine; a second calculation of the electrical angle (Θ.sub.el2) of the PSM machine, wherein the second calculation is based on the phase of a phase current indicator and regulated target currents in the d,q-coordinate system; and a comparison of the values of the respective electrical angles (Θ.sub.el1, Θ.sub.el2) of the PSM machine determined by the first calculation and the second calculation.

2. The method according to claim 1, wherein the electrical angle (Θ.sub.el1) is calculated with the first calculation as follows:
θ.sub.el=Z.sub.p.Math.θ.sub.mech, wherein Z.sub.P is the pole-pair number of the PSM machine and Θ.sub.mech is the measured mechanical rotor position, and wherein the electrical angle (Θ.sub.el2) is calculated with the second calculation is calculated as follows:
θ.sub.el2=θ.sub.Is−θ.sub.Last, wherein Θ.sub.Last is the load angle of the regulated target currents in the d,q-coordinate system, and Θ.sub.Is is the phase of the phase current indicator of the PSM machine.

3. The method according to claim 2, wherein the load angle Θ.sub.Last is calculated as follows: ${\theta }_{\mathrm{Last}}=\arctan \left(\frac{I_{\mathrm{sdRefF}}}{I_{\mathrm{sdRefF}}}\right),$ wherein I.sub.sdRefF and I.sub.sqRefF are delayed target values of the d,q-currents, and the phase of the current indicator Θ.sub.Is is calculated as follows:
I.sub.sw=−I.sub.su−I.sub.sv, wherein I.sub.sw, I.sub.su, and I.sub.sv are phase currents of the at least three phases, and the current components I.sub.sα and I.sub.sβ are in a α,β-coordinate system and are obtained from the transformation of the phase currents of the PSM machine follows: $\left(\begin{array}{c}{I}_{s.Math..Math.\alpha }\\ I_{s.Math..Math.\beta }\end{array}\right)=\left(\begin{array}{ccc}\frac{2}{3}& -\frac{1}{3}& -\frac{1}{3}\\ 0& \frac{1}{\sqrt{3}}& -\frac{1}{\sqrt{3}}\end{array}\right).Math.\left(\begin{array}{c}{I}_{\mathrm{su}}\\ I_{\mathrm{sv}}\\ I_{\mathrm{sw}}\end{array}\right),$ and wherein the phase of the current indicator Θ.sub.Is is determined therefrom as follows: ${\theta }_{\mathrm{Is}}=\arctan \left(\begin{array}{c}{I}_{s.Math..Math.\alpha }\\ I_{s.Math..Math.\beta }\end{array}\right).$

4. The method according to claim 1, wherein a pre-defined minimum current (I.sub.sAmplMin) is applied to the machine in order to determine a load angle Θ.sub.Last and a phase Θ.sub.Is of the phase current indicator, wherein the minimum current (I.sub.sAmplMin) is calculated on the basis of a current amplitude (I.sub.sAmpl) of the PSM machine and the target currents (I.sub.sdRef, I.sub.sqRef) in the q,t-coordinate system as follows:
I.sub.sAmpl=√{square root over (I.sub.sdRef.sup.2+I.sub.sqRef.sup.2)}  (Eq. 9), wherein, when I.sub.sAmpl<I.sub.sAmplMin, a new I.sub.sd-target current is defined:
I.sub.sAmpl<I.sub.sAmplMinI.sub.sdRefNeu=−√{square root over (I.sub.sAmplMin.sup.2−I.sub.sqRef.sup.2)}  (Eq. 10), wherein, when I.sub.sAmpl≧I.sub.sAmplMin, the new I.sub.sd-target current is defined as follows:
I.sub.sAmpl≧I.sub.sAmplMinI.sub.sdRefNeu=I.sub.sdRef  (Eq. 11), wherein I.sub.sdRef is the originally required d-target current and I.sub.sdRefNeu is the re-calculated d-target current for maintaining the minimum current I.sub.sAmplMin in the machine.

5. The method according to claim 1, wherein the comparison of the two determined electrical angles (Θ.sub.el1, Θ.sub.el2) occurs through taking the difference of the values for the electrical angle (Θ.sub.el1, Θ.sub.el2) determined with the first and second calculations.

6. The method according to claim 1, wherein, when it has been detected that a deviation between the determined electrical angles (Θ.sub.el1, Θ.sub.el2) exists, an evaluation of the deviation occurs to determine an error.

7. The method according to claim 6, wherein, if an error is detected, at least one of the following measures is taken: transmission of an error signal, shutting off the machine, and modifying the machine parameters.

8. An assembly for monitoring a PSM machine having at least three phases operated by a field oriented control, the assembly comprising: at least one position sensor configured to determine the rotor position (Θ.sub.mech) of the PSM machine; a sampling device for sampling the phase current of at least one of the phases; an execution device for performing at least a first calculation and a second calculation, wherein the first calculation and the second calculation independently determine the rotor position of the PSM machine; and a monitoring device, the monitoring device configured to evaluate errors when a deviation is detected between the determined rotor position as respectively determined by the first calculation and the second calculation.

9. The assembly according to claim 8, wherein the execution device comprises: a first device for performing the first calculation, a second device for performing the second calculation; and a comparison device configured to compare the respective electrical angles calculated with the first and second calculations.

10. The assembly according to claim 9, wherein the execution device includes the monitoring device.

11. The assembly according to claim 8, wherein the first calculation is based on a measured mechanical rotor position and the pole-pair number of the PSM machine

12. The assembly according to claim 11, wherein the second calculation is based on the phase of a phase current indicator and regulated target currents in the d,q-coordinate system.

13. The assembly according to claim 12, wherein a first electrical angle (Θ.sub.el1) is calculated with the first calculation as follows:
θ.sub.el=Z.sub.p.Math.θ.sub.mech, wherein Z.sub.P is the pole-pair number of the PSM machine and Θ.sub.mech is the measured mechanical rotor position.

14. The assembly according to claim 13, where a second electrical angle (Θ.sub.el2) is calculated with the second calculation is calculated as follows:
θ.sub.el2=θ.sub.Is−θ.sub.Last, wherein Θ.sub.Last is the load angle of the regulated target currents in the d,q-coordinate system, and Θ.sub.Is is the phase of the phase current indicator of the PSM machine.

15. The assembly according to claim 8, wherein detecting the deviation includes taking the difference of the values for the electrical angle determined with the first and second calculations.

16. The assembly according to claim 14, wherein the load angle Θ.sub.Last is calculated as follows: ${\theta }_{\mathrm{Last}}=\arctan \left(\frac{I_{\mathrm{sdRefF}}}{I_{\mathrm{sdRefF}}}\right),$ wherein I.sub.sdRefF and I.sub.sqRefF are delayed target values of the d,q-currents, and the phase of the current indicator Θ.sub.Is is calculated as follows:
I.sub.sw=−I.sub.su−I.sub.sv, wherein I.sub.sw, I.sub.su, and I.sub.sv are phase currents of the at least three phases, and the current components I.sub.sα and I.sub.sβ are in a α,β-coordinate system and are obtained from the transformation of the phase currents of the PSM machine follows: $\left(\begin{array}{c}{I}_{s.Math..Math.\alpha }\\ I_{s.Math..Math.\beta }\end{array}\right)=\left(\begin{array}{ccc}\frac{2}{3}& -\frac{1}{3}& -\frac{1}{3}\\ 0& \frac{1}{\sqrt{3}}& -\frac{1}{\sqrt{3}}\end{array}\right).Math.\left(\begin{array}{c}{I}_{\mathrm{su}}\\ I_{\mathrm{sv}}\\ I_{\mathrm{sw}}\end{array}\right),$ and wherein the phase of the current indicator Θ.sub.Is is determined therefrom as follows: ${\theta }_{\mathrm{Is}}=\arctan \left(\begin{array}{c}{I}_{s.Math..Math.\alpha }\\ I_{s.Math..Math.\beta }\end{array}\right).$

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Certain embodiments shall be explained below in greater detail, based on the attached drawings.

[0028] FIG. 1 shows a depiction of different coordinate systems for a PSM.

[0029] FIG. 2 shows a block diagram of a FOR of a PSM with decoupling.

[0030] FIG. 3 shows a depiction of different angles in the course of the current vector I.sub.s of the PSM.

[0031] FIG. 4 shows a block diagram of a FOR of a PSM with a monitoring of the rotor position according to at least one embodiment of the present disclosure.

[0032] FIG. 5 shows curves of a simulation at the control of FIG. 4, without errors, according to at least one embodiment of the present disclosure.

[0033] FIG. 6 shows curves of a simulation at the control of FIG. 4, with an offset error of 180° in the electrical angle, according to at least one embodiment of the present disclosure.

[0034] FIG. 7 shows curves of a simulation at the control of FIG. 4, with an error in the inverter, according to at least one embodiment of the present disclosure.

[0035] In the following description of the Figures, identical elements and functions are provided with the same reference symbols.

DETAILED DESCRIPTION

[0036] FIG. 3 shows a depiction of different angles in the course of the current vector {right arrow over (I)}.sub.s of the PSM, wherein θ.sub.el is the angle of the electrical angle of the machine, θ.sub.Last is the load angle of the filtered d and q-target currents, and θ.sub.Is is the phase of the current indicator of the machine. The relationship between the load angle θ.sub.Last, the electrical angle θ.sub.el and the phase (or the angle) θ.sub.Is of the phase current indicator Is can be derived from FIG. 3:

θ.sub.Is=θ.sub.el+θ.sub.Last  (Eq. 2).

Thus, the estimated electrical angle {circumflex over (θ)}.sub.el can be determined as a function of the two angles, which are calculated over the current:

{circumflex over (θ)}.sub.el=θ.sub.Is−θ.sub.Last  (Eq. 3).

[0037] The load angle θ.sub.Last is determined from the filtered target currents in the d and q axes. The FOR has a selected dynamic, i.e. the required d, q-currents are first set after a certain time, wherein the delay of the d, q-current can be reproduced, for example, with a low pass filter 250 (or another suitable filter). The time constant of the low pass filter 250 for each current (d or q) should be selected such that the dynamic of the FOR is reproduced in the respective axis (d or q). This means that the d (or q) target current filtered with the low pass filter 250 should have the same curve as the transformed d (or q) current from the measured phase currents of the machine. The reproduced phase currents of the machine, transformed into the d, q-coordinate system, are obtained through the delayed target values of the d, q-currents I.sub.sdRefF and I.sub.sqRefF. The expected load angle can be calculated from the two currents I.sub.sdRefF and I.sub.sqRefF:

[00004]$\begin{array}{cc}{\theta }_{\mathrm{Last}}=\arctan \left(\frac{I_{\mathrm{sdRefF}}}{I_{\mathrm{sdRefF}}}\right).& \left(\mathrm{Eq}..Math.4\right)\end{array}$

For the calculation of the phase of the current indicator of the machine, two phase currents (e.g. Isu and Isv) are sufficient. The third phase (e.g. Isw) can be determined from the two known phase currents, e.g.:

I.sub.sw=−I.sub.su−I.sub.sv  (Eq. 5).

Through a transformation of the phase currents of the machine using Eq. 6, Isα and Isβ, thus the currents in the α, β-coordinate system, can be determined:

[00005]$\begin{array}{cc}\left(\begin{array}{c}{I}_{\mathrm{s\alpha }}\\ I_{\mathrm{s\beta }}\end{array}\right)=\left(\begin{array}{ccc}\frac{2}{3}& -\frac{1}{3}& -\frac{1}{3}\\ 0& \frac{1}{\sqrt{3}}& -\frac{1}{\sqrt{3}}\end{array}\right).Math.\left(\begin{array}{c}{I}_{\mathrm{su}}\\ I_{\mathrm{sv}}\\ I_{\mathrm{sw}}\end{array}\right).& \left(\mathrm{Eq}..Math.6\right)\end{array}$

From this, the phase (or angle) θ.sub.Is of the phase current indicator (or current vector) of the machine can be determined:

[00006]$\begin{array}{cc}{\theta }_{\mathrm{Is}}=\arctan \left(\begin{array}{c}{I}_{s.Math..Math.\alpha }\\ I_{s.Math..Math.\beta }\end{array}\right).& \left(\mathrm{Eq}..Math.7\right)\end{array}$

It should be noted that with Equation 4 and Equation 7, the denominator can equal zero, such that in these cases, the arctangent can also be determined, depending on the sign of the counter, without division.

[0038] Thus, the electrical angle θ.sub.el2 can be calculated by a second method, and independently of the mechanical angle θ.sub.mech of the rotor, and compared with the calculated electrical angle θ.sub.el1 from Equation 1. By comparing the two electrical angles θ.sub.el and θ.sub.el2 from Equation 1 and Equation 3, the behavior of the machine, in particular the rotor position sensor, can be monitored. If the two electrical angles θ.sub.el1 and θ.sub.el2 are equal, or deviate only slightly, then the position sensor is functioning correctly. If deviations can be observed, i.e. that a predefined threshold value has been exceeded, for example, these deviations can be evaluated by monitoring levels. There are different methods for evaluating deviations, e.g. taking an average, integration of the deviations over time, etc., for detecting malfunctions. The selected method depends on the application, and is determined by a person skilled in the art.

[0039] Furthermore, with the determination of the load angle θ.sub.Last of the filtered d and q-target currents and the phase of the phase current indicator θ.sub.Is, it should be noted that a sufficiently high phase current should be present. For this reason, the current of the machine should be increased such that, on one hand, the torque does not change, and on the other hand, sufficient phase current flows in the machine. This is achieved by implanting a blind current I.sub.sd. Because the blind current I.sub.sd is not, or is only negligibly, involved in the generation of the torque, its increase can lead to an increase in the phase current I.sub.sd of the machine. Depending on signal measurement noises of the current sensors, the correct resolution of the machine current can first occur at a minimum phase current I.sub.sAmplMin, such that this minimum current can always been maintained, or ensured, such that the effects of noise on the determination of the current indicator phase θ.sub.Is and the expected load angle θ.sub.Last can be kept low. This can take place in that a current specification can be calculated as a function of the current amplitude I.sub.SAmpl, in order to ensure that, on one hand, the current amplitude is large enough, and on the other hand, that the torque does not change. The calculation of the electrical torque T.sub.el is carried out via Equation 8:

[00007]$\begin{array}{cc}{T}_{\mathrm{el}}=\frac{3}{2}.Math.\mathrm{Zp}.Math.{\Psi }_{\mathrm{PM}}.Math.I_{\mathrm{sq}}+\frac{3}{2}.Math.\mathrm{Zp}.Math.\left(L_{\mathrm{sd}}-L_{\mathrm{sq}}\right).Math.I_{\mathrm{sd}}.Math.I_{\mathrm{sq}}.& \left(\mathrm{Eq}..Math.8\right)\end{array}$

Because the linked flux is Ψ.sub.PM>>(L.sub.sd−L.sub.sq)*I.sub.sd, and for small currents, is I.sub.sd, (L.sub.sd−L.sub.sq).Math.I.sub.sd≈0, the electrical torque of the machine depends only on I.sub.sq, and the reluctance term [3/2*Z.sub.p*(L.sub.sd−Lsq)*I.sub.sd*I.sub.sq] of the torque can be ignored.

[0040] When a machine fulfills the condition L.sub.sd=L.sub.sq, there is actually no reluctance term for the torque. The torque cannot be compromised. When the machine has a reluctance part (Lsd≠Lsq), in Equation 8, the desired torque can be selected via the two currents, such that the minimum current value is obtained. This is only necessary with very small torques. Starting at a torque target value, the current Isq is large enough from the start to maintain the minimum value of the phase current amplitude.

[0041] The phase current amplitude I.sub.sAmpl can be calculated as follows:

I.sub.sAmpl=√{square root over (I.sub.sdRef.sup.2+I.sub.sqRef.sup.2)}  (Eq. 9).

In order to ensure a minimum current I.sub.sAmplMin in the machine, the Isd-target value I.sub.sdRefNeu can be redefined based on the following equation:

I.sub.sAmpl<I.sub.sAmplMinI.sub.sdRefNeu=−√{square root over (I.sub.sAmplMin.sup.2−I.sub.sqRef.sup.2)}  (Eq. 10),

I.sub.sAmpl≧I.sub.sAmplMinI.sub.sdRefNeu=I.sub.sdRef  (Eq. 11),

wherein I.sub.sdRef is the d-target current originally required by the FOR.

[0042] FIG. 4 shows the FOR shown in FIG. 2 with the expanded monitoring of the rotor position sensor and the behavior of the drive via the comparison of the electrical angle of the machine in a low rotational rate range, as well as at a standstill. Using Equation 1, the electrical angle θ.sub.el1 of the machine is calculated directly thereby, via a first method, via the measured mechanical rotor position θ.sub.mech and the pole-pair number Z.sub.p of the PSM machine 100.

[0043] The electrical angle θ.sub.el2 of the machine is calculated by a second method based on the phase currents I.sub.su, I.sub.sv, I.sub.sw and the current target values I.sub.sdRefF, I.sub.sqRefF filtered by means of the filter 250, or the new target current value I.sub.sdRefNeu corrected via the Equations 9 to 11, Eq. 9, Eq. 10, Eq. 11, instead of the target current value I.sub.sdRefF of the machine in the d, q-coordinate system via Eq. 4, Eq. 6, and Eq. 7. Because the FOR always has sufficient voltage in reserve in the low rotational rate range and at a standstill, the required d, q-target currents are adjusted with a set desired dynamic. In order to not use data regarding the mechanical angle θ.sub.mech in the second calculation of the electrical angle θ.sub.el, the reproduced d,q-currents I.sub.sdRefF, I.sub.sqRefF are used. The reproduction of the d, q-currents is obtained via at least one filter 250, which depict(s) the same dynamic of the regulator in the respective axis (d, q). The expected d, q-currents, and thus the expected load angle, can be determined with the filtered d, q-target currents I.sub.sdRefF, I.sub.sqRefF (see Equation 4). The angle (or phase) of the phase current indicator θ.sub.Is is determined by means of the measured phase currents, using the Equations 5 to 7. The estimated electrical angle θ.sub.el2 of the machine is obtained by means of Equation 3, Eq. 3, which is compared 260 with the electrical angle θ.sub.el1 calculated directly from Equation 1, Eq. 1. If the two angles are identical, or have only very slight deviations, i.e. are within defined tolerance limits, then the rotor position sensor 240 is functioning correctly, and the regulation of the machine 100 is functioning without error.

[0044] If larger deviations are observed, i.e. a pre-defined threshold value has been exceeded, for example, this deviation can be evaluated through a monitoring level 300. There are different methods for evaluating the deviations, e.g. taking an average, integration of the deviations over time, etc., for detecting malfunctions, and there are also different reactions to the respective detected deviation, or error. When a malfunction has been discovered, the drive can be shut off, in order to avoid causing an uncontrolled state, or a re-adjustment can occur. The measures taken are dependent on the application and are determined by a person skilled in the art.

[0045] FIG. 5 shows curves of a simulation on the control from FIG. 4 without error according to at least one embodiment of the present disclosure. The unit of the X-axis is seconds in FIGS. 5-7. It can be seen in FIG. 5 that the d, q-currents from the machine (second and third image) follow the target value, and conform to the filtered d, q-currents. The d-current target value is increased over time in order to maintain the minimum value of the phase current amplitude. The two electrical angles from Eq. 1 and Eq. 2 are identical, and have only very slight deviations (fourth and fifth image). The same applies for the estimated rotational rate and for the rotational rate calculated directly from the position sensor (sixth image). The deviations are negligible.

[0046] FIG. 6 shows curves of a simulation on the control from FIG. 4, with an offset error of 180° in the electrical angle according to at least one embodiment of the present disclosure. The sequence of the images of the measurement corresponds to that in FIG. 5. The simulation was run under the same conditions as in FIG. 5, wherein, in addition, an error in the rotor position sensor at the point in time t=0.1 s is reproduced in the simulation runtime. Such an offset in the angle can occur through the slipping of the sensor on the shaft of the machine. In this case, the extreme case is depicted, and an offset of 180° in the electrical angle is simulated, corresponding to an offset of 36° of the mechanical rotor position with a pole-pair number of Zp=5. It can be seen that the d, q-actual currents of the machine starting at t=0.1 s run in the opposite direction, compared to the d, q-target currents, although the filtered target currents have the same direction as the target currents. This can lead to a dangerous state, i.e. that, e.g., instead of an acceleration, a braking occurs, i.e. the machine runs in the wrong direction. It can further be seen that the estimated electrical angle has a difference of ±180°, which is conveyed to the monitoring level, such that a quick reaction of the monitoring level to this state is enabled, and a suitable measure can be taken in a timely manner.

[0047] FIG. 7 shows curves of a simulation on the control from FIG. 4, with an error in the inverter according to at least one embodiment of the present disclosure. The simulation was run under the same conditions as in FIG. 5, wherein, additionally, an error in the inverter at the point in time t=0.2 s in the simulation runtime has been reproduced. The sequence of the images of the measurement corresponds to that in FIG. 5 and FIG. 6. In this case, the upper MOSFET is permanently short-circuited in phase U at the point in time t=0.2 s. It can be seen that the d, q-actual currents of the machine starting at t=0.2 s attain an uncontrolled state, and they no longer follow the d, q-target currents. This can lead to a dangerous state, e.g. that the machine runs in the wrong direction. The phase currents increase, which can lead to damage to the inverter. Furthermore, the machine can suffer permanent damage due to partial or entire demagnetization of the rotor. The estimated electrical angle exhibits a large difference, which is conveyed to the monitoring level, by means of which a quick reaction of the monitoring level to this state is enabled, such that a quicker protection of the drive is enabled.

[0048] As can be seen from the exemplary simulations, the concept for monitoring the electrical angle of the machine that has been developed can detect errors not only in the rotor position, but also in the inverter (e.g. MOSFET short circuit, MOSFET malfunctions, etc.) or the machine (e.g. phase interruptions, short circuits in the windings, etc.), such that corresponding measures for protecting the drive can also be taken in a timely manner.

[0049] Diagnosis possibilities for monitoring the overall drive are important for the safety of the product, as well as for fulfilling certain standards for the certification. With the present concept, the electrical angle of the machine (and thus the rotor position sensor) can also be monitored when the motor is at a standstill, or running in a low rotational rate range, which could not be done with the methods known so far in a simple and unimpeded manner. As a result of the present concept, an implanting of high-frequency signals (acoustic problem) is no longer necessary, unlike with injection methods. As a result, costs for expensive current sensors, quick and expensive A/D converters, and microcontrollers, etc., for example, are eliminated. Through the monitoring of the electrical angle of the machine in the entire rotational rate range, i.e. even at low rotational rates and at a standstill, a safer and improved monitoring is achieved in relation to conventional EMF-based methods. In addition, the functionality of the rotor position sensor can be monitored well, and errors can be detected in a timely manner, such that suitable measures can be taken quickly, in order to avoid uncontrolled and dangerous states due to errors that occur, or through a malfunction of the rotor position sensor.

REFERENCE SYMBOLS

[0050] 100 induction machine [0051] 101 rotor [0052] 102 rotational axis [0053] 103 permanent magnet [0054] {right arrow over (I)}.sub.s current indicator or current vector U, V, W phases [0055] Ψ.sub.PM flux of the permanent magnet [0056] Θ.sub.el1 Dell electrical angle of the machine, calculated via Eq. 1 [0057] Θ.sub.el2 electrical angle of the machine, calculated via Eq. 2 [0058] Θ.sub.mech mechanical angle of the machine, calculated via Eq. 4-7 [0059] 205 control component [0060] 210 converter [0061] 215 vector modulator [0062] 220 pulse inverter [0063] 225 sampling device/current sensors [0064] 230 position sensor [0065] 240 decoupling device [0066] 250 filter [0067] 260 comparison device [0068] 300 monitoring level [0069] Z.sub.P pole-pair number of the machine [0070] Eq. 1 calculation of Θ.sub.el1 based on Θ.sub.mech and the pole-pair number Z.sub.P [0071] Eq. 3-7 calculation of Θ.sub.el2 based on the phase current and regulated target currents in the d, q-coordinate system [0072] Eq. 9-11 calculation of the new Isd target value I.sub.sdRefNeu based on the minimum current I.sub.sAmplMin in the machine.

TABLE-US-00001 APPENDIX GLOSSARY FOR THE DRAWINGS GL. Eq. (Equation) Phasenstroeme Phase currents Strom current Sollwert target value Istwert actual value gefilteter Sollwert filtered target value Elektrischer Winkel electrical angle Soll und geschaetzter target and estimated (Grad) (degree) Abweichung zwischen Soll und Deviation between target and geschaetzten elektrischen Winkel estimated electrical angle Soll und geschaetzte Drehzahl Target and estimated der Maschine rotational rate of the machine