Measuring and evaluating magnetic fluxes of a permanent magnet synchronous motor

Abstract

The invention relates to a method for measuring magnetic fluxes (ψd, ψq) of a permanent magnet synchronous motor, the motor voltages of which are generated by a rectifier, depending on motor currents (id, iq) of the synchronous motor. Multiple individual measurements (E1 to E4) are carried out. In each individual measurment (E1 to E4), a motor voltage is generated as a voltage pulse with initially insignificant motor current. A d-portion (ψd) of the magnetic flux is determined from a d-portion (Ud) of the motor voltage via integration over the pulse duration of the voltage pulse, a q-portion (ψq) of the magnetic flux is determined from a q-portion (Uq) of the motor voltage via integration over the pulse duration of the voltage pulse, and a measurement value for a d-portion (id) and a measurement value for a q-portion (iq) of the motor current are detected. The invention also relates to a measuring and evaluation system (3) for measuring and evaluating magnetic fluxes (ψd, ψq) of a permanent magnet synchronous motor.

Description

[0001] Description

[0002] Measurement and evaluation of magnetic fluxes of a permanent magnet synchronous motor

[0003] The invention relates to a method for measuring magnetic fluxes of a permanent-magnet synchronous motor, whose motor voltages are generated by a power converter, as a function of motor currents of the synchronous motor. Furthermore, the invention relates to a measuring and evaluation system for measuring and evaluating magnetic fluxes of such a synchronous motor.

[0004] With permanent magnet synchronous motors there is a trend towards smaller motors with greater overload capacity which means that the non-linear behavior of these motors is more pronounced and the motor control models have to be expanded to take these effects into account. This requires measured data that describe this non-linearity. Magnetic fluxes as a function of the motor current have proven to be a very useful description, in particular the d-component of the magnetic flux and the q-component of the magnetic flux as a function of the d-component and the q-component of the motor current in a rotor-fixed d / q coordinate system. The d-component of a quantity such as a motor current, a magnetic flux or a motor voltage is often referred to as the d-component of the quantity in the d / q coordinate system or as the component of the quantity in the d-direction of the d / q coordinate system. The same applies to the q-component of a quantity.

[0005] To date, for example, differential inductances in the d-direction and q-direction have been measured within the framework of motor data identification. The measurement is carried out using a current offset and a superimposed sinusoidal measuring current. The measurement in the d-direction can be carried out when the rotor of the synchronous motor is stationary, but the measurement in the q-direction leads to strong movement and acceleration of the motor rotor. In some cases, the measurement cannot be completed due to the movement, as otherwise the maximum speed of the motor would be exceeded. With such a measurement, the magnetic flux can be calculated by integrating the inductance, although this then gives the flux as a function of only one variable. A measurement of this type with two changing variables is relatively time-consuming.

[0006] US 2017 / 0179859 A1 discloses a method for diagnosing the condition of the permanent magnets of a permanent magnet-excited motor. For example, a q-axis current, a d-axis current, a q-axis voltage, and / or a d-axis voltage of the motor are determined based on sensed current and voltage information of the motor. This information is used to determine flux information about magnetic fluxes of the motor. The flux information is used to evaluate condition conditions of the permanent magnets of the motor. The evaluations can be used to identify deterioration or damage to permanent magnets that may occur as a result of elevated temperatures, physical, or chemical deterioration.

[0007] US 2022 / 196741 A1 discloses a method and system for determining electrical characteristics of an electric motor. The system includes a signal modulation circuit, a signal demodulation circuit, and a resistance and inductance estimation circuit. The signal modulation circuit is configured to control an AC reference voltage based on a requested maximum AC current and an estimated maximum AC current, and to control a DC reference voltage based on a requested DC current and an estimated DC current. The signal demodulation circuit is configured to generate the estimated maximum AC current and the estimated DC current for the signal modulation circuit. The resistance and inductance estimation circuit is configured to determine an inductance of the electrical load based on the estimated maximum AC current and a phase shift.

[0008] The invention is based on the object of providing an improved method for measuring magnetic fluxes of a permanent-magnet synchronous motor, whose motor voltages are generated by a power converter, as a function of the motor currents of the synchronous motor. Furthermore, the invention is based on the object of providing an improved measuring and evaluation system for measuring and evaluating magnetic fluxes of a permanent-magnet synchronous motor.

[0009] The object is achieved according to the invention by a method having the features of claim 1 and a measuring and evaluation system having the features of claim 15.

[0010] Advantageous embodiments of the invention are the subject of the dependent claims.

[0011] In the method according to the invention for measuring magnetic fluxes of a permanent magnet synchronous motor, whose motor voltages are generated by a power converter, as a function of motor currents of the synchronous motor, several individual measurements are carried out, with each individual measurement

[0012] - a motor voltage is generated as a voltage pulse with initially vanishing motor current,

[0013] - a d-component of the magnetic flux is determined from a d-component of the motor voltage by integration over the pulse duration of the voltage pulse,

[0014] - a q-component of the magnetic flux is determined from a q-component of the motor voltage by integration over the pulse duration of the voltage pulse and

[0015] - a measured value for a d-component and a measured value for a q-component of the motor current are recorded.

[0016] A voltage pulse is defined as a voltage that assumes values ​​other than zero with a specific amplitude only during a short pulse duration. The voltage can assume the value zero several times during the pulse duration, meaning it can consist of several individual pulses. For example, a voltage pulse is generated by a PDM signal (pulse width modulation signal).

[0017] In other words, the method according to the invention carries out a large number of individual measurements in which, when the motor current initially disappears, a d-component and a q-component of the magnetic flux are determined and a d-component and a q-component of the motor current are measured. The d-component and the q-component of the magnetic flux are each determined by integrating the corresponding component of the motor voltage over the pulse duration of the voltage pulse used to generate the motor voltage in the individual measurement. By suitably selecting voltage pulses for the individual measurements, the d-component and the q-component of the magnetic flux can each be determined as a function of the d-component and the q-component of the motor current.Since the motor current disappears at the beginning of each individual measurement and the voltage pulses are relatively short, the individual measurements can be carried out when the rotor of the synchronous motor is virtually at a standstill, so that the above-mentioned problems resulting from a strong movement of the rotor can be avoided.

[0018] In one embodiment of the invention, the d-component of the motor voltage, by the integration of which the d-component of the magnetic flux is determined, is the difference between a d-component of a measured output voltage of the power converter and an ohmic component of a voltage drop across a stator winding of the synchronous motor, and the q-component of the motor voltage, by the integration of which the q-component of the magnetic flux is determined, is the difference between a q-component of the measured output voltage of the power converter and the ohmic component of the voltage drop across the stator winding of the synchronous motor. The aforementioned embodiment of the invention therefore uses measured values ​​for the motor-side output voltage of the power converter, which is applied to terminals of the synchronous motor, and takes into account the ohmic component of a voltage drop across the stator winding of the synchronous motor.

[0019] In an alternative embodiment of the invention to the aforementioned embodiment, the d-component of the motor voltage, by the integration of which the d-component of the magnetic flux is determined, is the difference between a setpoint value for a d-component of an output voltage of the power converter and an ohmic component of a voltage drop at a stator winding of the synchronous motor and a modeled voltage mapping error for the d-component of the output voltage of the power converter, and the q-component of the motor voltage, by the integration of which the q-component of the magnetic flux is determined, is the difference between a setpoint value for a q-component of the output voltage of the power converter and the ohmic component of the voltage drop at the stator winding of the synchronous motor and a modeled voltage mapping error for the q-component of the output voltage of the power converter.The voltage mapping error for a portion of the converter output voltage is understood to be the difference between the setpoint value for this portion of the converter output voltage and the actual value of this portion of the converter output voltage.

[0020] The aforementioned embodiment of the invention therefore uses setpoint values ​​instead of measured values ​​for the converter's output voltage to determine the magnetic fluxes. Due to the unknown voltage mapping errors, it is somewhat less accurate than determining the magnetic fluxes based on measured values ​​for the converter's output voltages. However, it has the advantage that the converter's output voltages do not have to be measured.

[0021] In both of the aforementioned embodiments of the invention, the ohmic voltage drop across the stator winding of the synchronous motor is calculated, for example, from an ohmic resistance of the stator winding and the motor current.

[0022] Preferably, the measured value for the d-component of the motor current recorded during an individual measurement is a value for which an amount of the d-component of the motor current is maximum, and the measured value for the q-component of the motor current recorded during an individual measurement is a value for which an amount of the q-component of the motor current is maximum. This embodiment of the invention takes into account that the motor current increases from zero to a maximum value during an individual measurement, which maximum value is used for the measured values ​​for the d-component and the q-component of the motor current. If, for example, only mean values ​​of the motor currents are measured over one clock period of a pulse duration modulation during the current measurement, a vanishing motor voltage is generated for one clock period after the voltage pulse generated during an individual measurement, and the motor current is measured for this clock period because it then still approximately has its maximum value.

[0023] In a further embodiment of the invention, measurement sequences of four consecutive individual measurements are carried out, with each measurement sequence

[0024] - in the individual measurements, at least approximately the same d-component of the motor voltage and at least approximately the same amount of the q-component of the motor voltage are generated,

[0025] - in a second individual measurement following a first individual measurement and in a third individual measurement following the second individual measurement, the sign of the q-component of the motor voltage is inverted compared to the first individual measurement and

[0026] - in a fourth individual measurement following the third individual measurement, a q-component of the motor voltage is generated with the same sign as in the first individual measurement. The aforementioned embodiment of the invention aims at minimizing movements and changes in position of the rotor of the synchronous motor during the measurements. This is achieved on the one hand by inverting the sign of the q-component of the motor voltage in the second individual measurement of a measurement sequence compared to the first individual measurement in order to stop the movement of the rotor caused by the first individual measurement. In the third individual measurement of the measurement sequence, the rotor is then moved in the opposite direction to the first individual measurement in order to reverse the change in position of the rotor caused by the first individual measurement.During the fourth measurement of a measurement sequence, the sign of the q-component of the motor voltage is inverted compared to the third measurement to stop the rotor movement caused by the third measurement. Therefore, after a measurement sequence, the motor is at least approximately in the same state as before the measurement sequence.

[0027] In a further embodiment of the invention, for each measurement sequence, an average value of the d-components of the magnetic flux determined in the individual measurements and an average value of the measured values ​​for the d-component of the motor current recorded in the individual measurements are formed.

[0028] In a further embodiment of the invention, for each measurement sequence, an average value of the q-components of the magnetic flux determined in the first individual measurement and the fourth individual measurement and an average value of the measured values ​​for the q-component of the motor current recorded in the first individual measurement and the fourth individual measurement are formed.

[0029] In a further embodiment of the invention, for each measurement sequence, an average value of the q-components of the magnetic flux determined in the second individual measurement and the third individual measurement and an average value of the measured values ​​for the q-component of the motor current recorded in the second individual measurement and the third individual measurement are calculated. The three aforementioned embodiments of the invention summarize the individual measurements of a measurement sequence by averaging the values ​​of corresponding components of the magnetic flux and the motor current determined in the individual measurements. This compensates for differences between individual measurements and measurement inaccuracies caused by movements and changes in the position of the rotor.

[0030] In a further embodiment of the invention, each measurement sequence is carried out with the rotor initially moving at a vanishing point, or more precisely, with the relative movement of the rotor and the stator of the synchronous motor initially vanishing point. For example, after each measurement sequence, a relative movement of the rotor and the stator is stopped by a voltage pulse that counteracts the relative movement.

[0031] The above-mentioned embodiment of the invention also aims to carry out the measurements with the smallest possible movement of the rotor.

[0032] In a further embodiment of the invention, value pairs are specified, each consisting of a target value for the d-component and a target value for the q-component of the motor current, and a measurement sequence is carried out for each value pair, the measured values ​​of which for the d-component and for the q-component of the motor current correspond to the corresponding target values ​​of the value pair with a predetermined minimum accuracy. For example, to carry out a measurement sequence corresponding to a value pair, an iteration is carried out over several measurement sequences.

[0033] The aforementioned embodiment of the invention aims to distribute measured values ​​for the d-component and for the q-component of the motor current across a measuring range in a manner predetermined by value pairs in order to cover the measuring range as completely as possible. For example, value pairs are selected that evenly space the measuring range. In order to determine a measuring point characterized by a value pair, an iteration is carried out over several measuring sequences until the measured values ​​for the d-component and for the q-component of the motor current agree with the target values ​​of the value pair with the required minimum accuracy.

[0034] In a further embodiment of the invention, the d-component of the magnetic flux and the q-component of the magnetic flux are each approximated by a parameterized function of the d-component and the q-component of the motor current, and the parameters of these functions are determined from the d-components and q-components of the magnetic flux determined during the measurements and the associated d-components and q-components of the motor current.

[0035] The functions determined in this way can be advantageously used for various quantitative calculations of the synchronous motor's characteristics, for example, to calculate so-called MTPA operating points (MTPA = Maximum Torque Per Ampere). These are operating points at which a desired torque is achieved with the lowest required motor current.

[0036] A measuring and evaluation system according to the invention for measuring and evaluating magnetic fluxes of a permanent magnet synchronous motor, whose motor voltages are generated by a power converter, comprises

[0037] - a measuring unit which is designed to measure magnetic fluxes of the synchronous motor as a function of motor currents of the synchronous motor according to the method according to the invention, and

[0038] - an evaluation unit which is set up to calculate inductances of the synchronous motor and / or a torque of the synchronous motor and / or a torque-current ratio and / or a reluctance torque constant of the synchronous motor from the measurement results of the measuring unit as a function of the motor currents of the synchronous motor.

[0039] The measuring and evaluation system according to the invention exploits the fact that the inventive measurement of magnetic fluxes as a function of the motor currents of the synchronous motor makes it possible to calculate various operationally relevant parameters of the synchronous motor, such as inductances, a torque, a torque-current ratio, and a reluctance torque constant, as a function of the motor currents of the synchronous motor. Specific formulas for calculating these parameters are given below in the description of the figures.

[0040] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings.

[0041] FIG 1 Time courses of various quantities of a permanent magnet synchronous motor during a measurement of magnetic fluxes as a function of motor currents,

[0042] FIG 2 an inductance as a function of motor currents of a permanent magnet synchronous motor,

[0043] FIG 3 shows a characteristic curve of a permanent magnet synchronous motor calculated using measurements carried out according to the method according to the invention and a characteristic curve measured with the rotor of the synchronous motor rotating,

[0044] FIG 4 shows a calculated optimal load angle as a function of a torque of a permanent magnet synchronous motor,

[0045] FIG 5 calculated optimal d and q components as well as the calculated optimal amount of the motor current as a function of the torque of a permanent magnet synchronous motor,

[0046] FIG. 6 shows a block diagram of an exemplary embodiment of a measuring and evaluation system for measuring and evaluating magnetic fluxes as a function of motor currents in a permanent-magnet synchronous motor. Corresponding parts are provided with the same reference numerals in the figures.

[0047] Figure 1 ( FIG 1 ) illustrates an embodiment of the method according to the invention for measuring magnetic fluxes of a permanent magnet synchronous motor as a function of motor currents of the synchronous motor using curves of various variables i d , i q , U d , U q , n and a of the synchronous motor as a function of time t . Where i d a d-component of a motor current, i q a q-component of the motor current, U d a d-component of a motor voltage, U qa q-component of the motor voltage, n a speed, and a a rotor position angle of the synchronous motor. The motor voltages are generated by a converter, for example, pulse-width modulated by PWM signals from the converter.

[0048] For example, the d-component U d the motor voltage, the difference between a d-component of a measured output voltage of the converter and an ohmic component of a voltage drop at a stator winding of the synchronous motor, and the q-component U q The motor voltage is the difference between a q-component of the measured output voltage of the converter and the resistive component of the voltage drop across the stator winding of the synchronous motor. Alternatively, the d-component U dthe motor voltage, the difference between a setpoint value for the d-component of the output voltage of the converter and the resistive component of the voltage drop at the stator winding of the synchronous motor and a modeled voltage mapping error for the d-component of the output voltage of the converter, and the q-component U qof the motor voltage is the difference between a setpoint for the q-component of the output voltage of the converter and the ohmic component of the voltage drop at the stator winding of the synchronous motor and a modeled voltage mapping error for the q-component of the output voltage of the converter. The ohmic component of the voltage drop at the stator winding of the synchronous motor is calculated from an ohmic resistance of the stator winding and the motor current. In the method, measurement sequences S of four consecutive individual measurements El to E4 are carried out. For each individual measurement El to E4, a motor voltage is generated as a voltage pulse with an initially vanishing motor current. From the d-component Ud of the motor voltage, a d-component of the magnetic flux is determined by integration over the pulse duration of the voltage pulse. From the q-component U qThe motor voltage is used to determine a q-component of the magnetic flux by integrating it over the pulse duration of the voltage pulse.

[0049] Furthermore, for each individual measurement El to E4, a measured value for the d-component id and a measured value for the q-component i q of the motor current. For example, the measured value for the d-component id of the motor current is a value for which an amount of the d-component id of the motor current is maximum, and the measured value for the q-component i q of the motor current is a value for which an amount of the q-component i q of the motor current is maximum.

[0050] In each measurement sequence S, the individual measurements El to E4 each measure at least approximately the same d-component Ud of the motor voltage and at least approximately the same amount of the q-component U qof the motor voltage. In a second individual measurement E2 following a first individual measurement E1 and in a third individual measurement E3 following the second individual measurement E2, the sign of the q-component U q of the motor voltage is inverted compared to the first individual measurement El. In a fourth individual measurement E4 following the third individual measurement E3, a q-component U q the motor voltage with the same sign as in the first individual measurement El .

[0051] For each measurement sequence S, an average value of the d-components of the magnetic flux determined during the individual measurements and an average value of the measured values ​​for the d-component id of the motor current recorded during the individual measurements El to E4 are calculated. Furthermore, for each measurement sequence S, an average value of the q-components of the magnetic flux determined during the first individual measurement El and the fourth individual measurement E4 and an average value of the measured values ​​for the q-component i recorded during the first individual measurement El and the fourth individual measurement E4 are calculated. q of the motor current. Accordingly, for each measurement sequence S, an average value of the q-components of the magnetic flux determined in the second individual measurement E2 and the third individual measurement E3 and an average value of the measured values ​​for the q-component i recorded in the second individual measurement E2 and the third individual measurement E3 are calculated. q of the motor current.

[0052] Each measurement sequence S is performed with the relative motion of a rotor and a stator of the synchronous motor initially vanishing. For this purpose, after each measurement sequence S, a relative motion of the rotor and the stator is stopped by a voltage stop pulse H that counteracts the relative motion and has only a d-component.

[0053] Preferably, pairs of values ​​( i ds , i qs ), each consisting of a target value i ds for the d-part i d and a target value i qs for the q-part i q of the motor current. For each pair of values, a measurement sequence S is carried out, the measured values ​​for the d-component and for the q-component of the motor current are compared with the corresponding target values ​​i ds and i qsof the value pair with a specified minimum accuracy. The value pairs are specified, for example, in such a way that they contain ranges for the d-part i d and the q-part i q the motor current is evenly rasterized.

[0054] To perform a function on a pair of values ​​( i ds , i qs ) corresponding measurement sequence S , for example, an iteration of several measurement sequences S is carried out, where motor voltages U d and U q be corrected separately in order to achieve the target values ​​i ds and i qs with the required minimum accuracy. For example, motor voltages U d and U q for the first step of the iteration. After that, the actual measured values ​​for i d and i qthese specifications are corrected and the measurement is repeated until the target values ​​i ds and i qs with the required minimum accuracy. If several measurements have already been performed, the differential inductances of measurements near the respective measuring point can be used to speed up the convergence of the iteration.

[0055] Figure 1 shows an example of an increase in the target values ​​i ds and i q s at times ti and t2. After each of these times, two measurement sequences S are carried out and the target values ​​ids and iqs are achieved with the required minimum accuracy in the second measurement sequence S.

[0056] However, contrary to Figure 1, in practice one would not necessarily use both target values ​​i ds and i qs change simultaneously. For example, you start with small target values ​​i dsand iqs and then successively increases the target value i according to a fixed grid qs until you reach the desired range for i q Then you change the target value i ds and for the changed target value you move again the grid of target values ​​i qs For the d-component id, target values ​​i ds must always be specified for both signs of the current. For example, one can start with small current values ​​and first process the positive target values ​​i ds and then, similarly starting with small current values, process the negative target values ​​i ds. This is necessary because a permanent magnet synchronous motor with respect to i d is not point-symmetric or axially symmetric. In a measurement sequence S, q-components i q with different signs on . For the q-part i q There is usually an axial symmetry, so that the specification of target values ​​i qsis sufficient for a sign . However , measurements have shown that this symmetry does not exist for all motors , so that the symmetry cannot always be used and target values ​​i qs must also be used for both signs. The measurements also take into account the maximum current of the synchronous motor or the converter, so that no target values ​​are specified that would result in the maximum current being exceeded. A great deal of information can be derived from the measurement of the d-component and the q-component of the magnetic flux. On the one hand, the inductances L dd (i d ,i q ) and L qq (i d ,i q ) can be calculated by differentiating a portion of the magnetic flux with the corresponding portion of the motor current. In addition, the transverse inductances L dq (i d ,i q ) and L qd (i d ,i q) , if one differentiates one part of the magnetic flux according to the other part of the motor current:

[0057] Here, ji d the d-component of the magnetic flux and ji q denotes the q-component of the magnetic flux.

[0058] The flux measurement in d-direction is still missing the offset of the permanent magnet flux W dPM , which cannot be measured when the synchronous motor is at a standstill. The missing value can be calculated using a voltage constant k E calculate according to bE

[0059] 'b'dPM — A / 6 ■ Tl ■ Zp

[0060] This is e.g. p the number of pole pairs and the voltage constant k E is the line-to-line effective voltage at no load divided by the speed of the synchronous motor. The value of U dPM must be added to a measured d-component of the magnetic flux in order to ¥ d to obtain .

[0061] Alternatively, U dPMbe measured by measuring the motor voltage when the synchronous motor is running idle at a suitable speed (from this one could also k E determine) .

[0062] Figure 2 ( FIG 2 ) shows an example of a result of a determination of the inductance L dd depending on i d and i q .

[0063] The measurement of the magnetic fluxes , that is the d-part and q-part of the magnetic flux , as a function of i d and i q In principle, it also functions position-dependently, i.e., depending on the rotor position angle a of the synchronous motor, with the uncertainty of the movement. Synchronous motors with single-tooth windings often also have a position-dependent magnetic flux, so that the magnetic flux can also be measured depending on the rotor position.

[0064] The magnetic fluxes can also be used to calculate the torque of the synchronous motor according to

[0065] The cogging torques were neglected or the cogging torques must be considered separately.

[0066] The torque calculated from the measured magnetic fluxes takes the saturation dependence into account. For example, the torque can be used to calculate a k T -Characteristic curve k T ( i q ) for a torque-current ratio k T , which shows the relationship between the torque and the q-component i q of the motor current, calculate according to or the reluctance moment constant k TRei ( id, iq) for all working points according to

[0067] Figure 3 ( FIG 3 ) shows an example of such a calculated k T - Characteristic curve 1 compared to a k measured with the rotor of a synchronous motor rotating T -Characteristic curve 2 . The good agreement between the two results is clearly visible.

[0068] Another possibility is to model the magnetic fluxes with a suitable parameterized function of i d and iq and thus calculate optimal operating points. Such functions are, for example,

[0069] Here are kao to ka bo to kb kco to kc d and kdo to kd d Parameters that are determined from the d-components and q-components of the magnetic flux determined during the measurements and the corresponding d-components and q-components of the motor current.

[0070] The magnetic fluxes parameterized in this way are used, for example, to calculate MTPA operating points.

[0071] Figure 4 ( FIG 4 ) and Figure 5 ( FIG 5 ) show examples of MTPA operating points calculated in this way for a synchronous motor.

[0072] Figure 4 shows a calculated optimal load angle p as a function of the torque Mi and Figure 5 shows calculated optimal d and q current components ido and i qo and the calculated optimal current amount | i o I of the motor current as a function of the torque M d .

[0073] Figure 6 ( FIG 6 ) shows a block diagram of an embodiment of a measuring and evaluation system 3 for the measurement and evaluation of magnetic fluxes i|i d , ^g of a permanent magnet synchronous motor , whose motor voltages are generated by a converter, as a function of motor currents i d , i q of the synchronous motor. The measuring and evaluation system 3 comprises a measuring unit 4 which is set up to measure magnetic fluxes i|i according to the inventive method described above. d , ^g of the synchronous motor depending on motor currents i d , i q of the synchronous motor. Furthermore, the measuring and evaluation system 3 comprises an evaluation unit 5, which is set up to calculate inductances L from the measurement results of the measuring unit 3. dd , Lqq , L dq , L qd of the synchronous motor, a torque M d of the synchronous motor, a torque-current ratio k T and a reluctance moment constant k TRei of the synchronous motor depending on the motor currents i d , i q of the synchronous motor. The evaluation unit 5 is designed, for example, as a computer program that is executed on a processor and calculates the above-mentioned variables L dd , L qq , L dq , L qd , M d , k T and k TRei of the synchronous motor according to the formulas given above.

[0074] Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1 . Method for measuring magnetic fluxes ( ji d , ji q ) of a permanent magnet synchronous motor , whose motor voltages are generated by a converter, as a function of motor currents ( i d , i q ) of the synchronous motor, whereby several individual measurements (El to E4) are carried out and for each individual measurement (El to E4) - a motor voltage is generated as a voltage pulse with initially vanishing motor current, - from a d-component (U d ) of the motor voltage by integration over the pulse duration of the voltage pulse a d-component ( ji d ) of the magnetic flux is determined, - from a q-component (U q ) of the motor voltage by integration over the pulse duration of the voltage pulse a q-component ( ji q ) of the magnetic flux is determined and - a measured value for a d-component ( i d) and a measured value for a q-component ( i q ) of the motor current can be recorded. 2 . Method according to claim 1 , wherein the d-component (U d ) of the motor voltage is the difference between a d-component of a measured output voltage of the converter and an ohmic component of a voltage drop at a stator winding of the synchronous motor and the q-component (U q ) of the motor voltage is the difference between a q-component of the measured output voltage of the converter and the ohmic component of the voltage drop at the stator winding of the synchronous motor. 3 . Method according to claim 1 , wherein the d-component (U d) of the motor voltage is the difference between a setpoint value for a d-component of an output voltage of the power converter and an ohmic component of a voltage drop at a stator winding of the synchronous motor and a modeled voltage mapping error for the d-component of the output voltage of the power converter and the q-component (U q ) of the motor voltage, the difference of a setpoint for a q-component of the output voltage of the converter and the ohmic component of the voltage drop at the stator winding of the synchronous motor and a modelled voltage mapping error for the q-component of the converter's output voltage.

4. The method according to claim 2 or 3, wherein the ohmic voltage drop across the stator winding of the synchronous motor is calculated from an ohmic resistance of the stator winding and the motor current.

5. Method according to one of the preceding claims, wherein the measured value for the d-component (id) of the motor current recorded in an individual measurement (El to E4) is a value for which an amount of the d-component (id) of the motor current is maximum, and the measured value for the q-component (i q ) of the motor current is a value for which an amount of the q-component (i q ) of the motor current is maximum.

6. Method according to one of the preceding claims, wherein measurement sequences (S) of four consecutive individual measurements (El to E4) are carried out, wherein for each measurement sequence (S) - in the individual measurements (El to E4) at least approximately the same d-component (Ud) of the motor voltage and at least approximately the same amount of the q-component (U q ) of the motor voltage, - in the case of a second individual measurement (E2) following a first individual measurement (El) and in the case of a third individual measurement (E3) following the second individual measurement (E2), the sign of the q-component (U q ) of the motor voltage is inverted compared to the first individual measurement (El) and - in a fourth individual measurement (E4) following the third individual measurement (E3), a q-component (U q ) of the motor voltage with the same sign as in the first individual measurement (El).

7. The method according to claim 6, wherein for each measurement sequence (S) an average value of the d-components (ji d ) of the magnetic flux and an average value the measured values ​​recorded during the individual measurements (El to E4) for the d-component (id) of the motor current.

8. The method according to claim 6 or 7, wherein for each measurement sequence (S) an average value of the q-components (ji q ) of the magnetic flux and an average value of the measured values ​​for the q-component (i q ) of the motor current.

9. Method according to one of claims 6 to 8, wherein for each measurement sequence (S) an average value of the q-components (ji q ) of the magnetic flux and an average of the measured values ​​for the q-component (i q ) of the motor current.

10. Method according to one of claims 6 to 9, wherein each measurement sequence (S) is carried out with initially vanishing relative movement of a rotor and a stator of the synchronous motor.

11. Method according to one of claims 6 to 10, wherein after each measuring sequence (S) a relative movement of the rotor and the stator is stopped by a voltage stop pulse (H) counteracting the relative movement.

12. Method according to one of claims 6 to 11, wherein pairs of values ​​each consisting of a target value (ids) for the d- Share (id) and a target value (i qs ) for the q-part (i q ) of the motor current, and for each pair of values ​​a measurement sequence (S) is carried out, the measured values ​​of which for the d-component (id) and for the q-component (i q ) of the motor current match the corresponding target values ​​(ids, iqs) of the value pair with a specified minimum accuracy.

13. The method according to claim 12, wherein an iteration over several measurement sequences (S) is carried out to carry out a measurement sequence (S) corresponding to a pair of values.

14. Method according to one of the preceding claims, wherein the d-component (ji d ) of the magnetic flux and the q-component (ji q ) of the magnetic flux by a parameterized function of the d-component (id) and the q-component (i q ) of the motor current and the parameters of these functions are calculated from the d-components (ji d ) and q-components (ji q ) of the magnetic flux and the associated d-components (i d ) and q-parts (i q ) of the motor current.

15. Measuring and evaluation system (3) for the measurement and evaluation of magnetic fluxes (ji d , ji q) of a permanent magnet synchronous motor, whose motor voltages are generated by a converter, as a function of motor currents (i d , i q ) of the synchronous motor, the measuring and evaluation system (3) comprising - a measuring unit (4) which is arranged according to one of the preceding claims to measure magnetic fluxes (ji d , ji q ) of the synchronous motor depending on motor currents (i d , i q ) of the synchronous motor, and - an evaluation unit (5) which is set up to calculate inductances (L dd , L qq , L dq , L qd ) of the synchronous motor and / or a torque (M d ) of the synchronous motor and / or a torque-current ratio (k T ) and / or a reluctance moment constant (k TRe i) of the synchronous motor depending on the motor currents (i d , i q) of the synchronous motor.

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