Measurement and evaluation of magnetic flux of permanent magnet synchronous motor

Abstract

The invention relates to a method for measuring the magnetic flux (psi d, psi q) of a permanent magnet synchronous motor, the motor voltage of which is generated by a rectifier, on the basis of the motor current (id, iq) of the synchronous motor. A plurality of individual measurements (E1 to E4) are carried out. In each individual measurement (E1 to E4), a motor voltage is generated as a voltage pulse using an initial minute motor current. A d component (psi d) of the magnetic flux is derived from the d component (Ud) of the motor voltage by integration during the pulse duration of the voltage pulse, a q component (psi q) of the magnetic flux is derived from the q component (Uq) of the motor voltage by integration during the pulse duration of the voltage pulse, and a measured value of the d component (id) and a measured value of the q component (iq) of the motor current are detected. The invention also relates to a measurement and evaluation system (3) for measuring and evaluating a magnetic flux (psi d, psi q) of a permanent magnet synchronous motor.

Description

Technical Field

[0001] The invention relates to a method for measuring the magnetic flux of a permanent-magnet synchronous motor based on its motor current, the motor voltage of which is generated by a rectifier, and to a measuring and evaluation system for measuring and evaluating the magnetic flux of such a synchronous motor. Background Art

[0002] In permanent magnet synchronous motors, there is a trend toward smaller motors with greater overload capacity. This results in more pronounced nonlinear behavior in the motors, necessitating expansion of motor control models to account for these effects. This requires measured data describing these nonlinearities. The magnetic flux as a function of the motor current has proven to be a particularly advantageous description, particularly the d-component and q-component of the magnetic flux as functions of the d-component and q-component of the motor current in a d / q coordinate system fixed to the rotor. The d-component of a variable such as the motor current, magnetic flux, or motor voltage is often referred to as the d-component of the variable in the d / q coordinate system or as the component of the variable in the d direction in the d / q coordinate system. The same applies to the q-component of the variable.

[0003] For example, until now, motor data identification has involved measuring the differential inductance in the d- and q-directions. This measurement is performed using a current offset and a superimposed sinusoidal measurement current. While measurements in the d-direction can be performed when the synchronous motor's rotor is stationary, measurements in the q-direction cause the motor's rotor to move and accelerate violently. This movement sometimes prevents the measurement from being completed, as it would otherwise cause the maximum motor speed to be exceeded. Using this measurement, the magnetic flux can be calculated by integrating the inductance, which, of course, results in a flux that is related to only one variable. However, performing such measurements using two varying variables is time-consuming.

[0004] US2017 / 0179859 A1 discloses a method for diagnosing the condition of permanent magnets in a permanent magnet excitation motor. For example, based on detected current and voltage information of the motor, the q-axis current, d-axis current, q-axis voltage, and / or d-axis voltage of the motor are determined. This information is used to determine magnetic flux information about the magnetic flux of the motor. This magnetic flux information is used to assess the condition of the motor's permanent magnets. This assessment can be used to identify permanent magnet degradation or damage that may occur as a result of increased temperature, physical, or chemical degradation.

[0005] 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 current reference voltage based on a requested maximum AC current and an estimated maximum AC current, and to control a DC current reference voltage based on a requested DC current and an estimated DC current. The signal demodulation circuit is configured to generate an estimated maximum AC current and an estimated DC current for the signal modulation circuit. The resistance and inductance estimation circuit is configured to determine the inductance of the electrical load based on the estimated maximum AC current and a phase shift. Summary of the Invention

[0006] The basic object of the present invention is to provide an improved method for measuring the magnetic flux of a permanent-magnet synchronous motor as a function of the motor current of the synchronous motor. The present invention also provides a measuring and evaluation system for measuring and evaluating the magnetic flux of a permanent-magnet synchronous motor.

[0007] According to the invention, this object is achieved by a method having the features of claim 1 and a measuring and evaluation system having the features of claim 15 .

[0008] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0009] In the method according to the invention for measuring the magnetic flux of a permanent-magnet synchronous motor from its motor current, the motor voltage of the permanent-magnet synchronous motor is generated by a rectifier, a plurality of individual measurements are performed, wherein for each individual measurement,

[0010] - Using the initial small motor current to generate the motor voltage as a voltage pulse,

[0011] - deriving the d component of the magnetic flux from the d component of the motor voltage by integration during the pulse duration of the voltage pulse,

[0012] - deriving the q component of the magnetic flux from the q component of the motor voltage by integrating over the pulse duration of the voltage pulse, and

[0013] - Detecting the measured value of the d component and the measured value of the q component of the motor current.

[0014] A voltage pulse is understood to be a voltage that assumes a non-zero value of a specific amplitude only during a short pulse duration. The voltage can assume the value zero multiple times during the pulse duration, meaning it consists of multiple individual pulses. For example, voltage pulses are generated by PDM signals (Pulse Duration Modulation signals).

[0015] In other words, the method according to the present invention therefore performs multiple individual measurements, wherein the d and q components of the magnetic flux are each determined using an initially small motor current, and the d and q components of the motor current are measured. The d and q components of the magnetic flux are each determined by integrating the corresponding component of the motor voltage over the pulse duration of the voltage pulse that generates the motor voltage in the individual measurement. By appropriately selecting the voltage pulse for the individual measurement, the d and q components of the magnetic flux can be determined as a function of the d and q components of the motor current. Because the motor current is extinct at the beginning of each individual measurement and the voltage pulse is relatively short, the individual measurements can be performed while the synchronous motor's rotor is nearly stationary, thus avoiding the aforementioned problems caused by excessive rotor motion.

[0016] In one embodiment of the invention, the d component of the motor voltage is the difference between the d component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor, wherein the d component of the magnetic flux is obtained by integrating the d component of the motor voltage, and the q component of the motor voltage is the difference between the q component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor, wherein the q component of the magnetic flux is obtained by integrating the q component of the motor voltage.

[0017] The above-described embodiment of the invention therefore uses the measured value of the motor-side output voltage of the rectifier applied to the terminals of the synchronous motor and takes into account the ohmic component of the voltage drop at the stator winding of the synchronous motor.

[0018] In an alternative embodiment of the present invention to the above-described embodiment, the d component of the motor voltage is the difference between a setpoint value for the d component of the rectifier output voltage and a voltage mapping error modeled between an ohmic component of the voltage drop across the stator winding of the synchronous motor and the d component of the rectifier output voltage, wherein the integration of the d component of the motor voltage yields the d component of the magnetic flux, and the q component of the motor voltage is the difference between a setpoint value for the q component of the rectifier output voltage and a voltage mapping error modeled between an ohmic component of the voltage drop across the stator winding of the synchronous motor and the q component of the rectifier output voltage, wherein the integration of the q component of the motor voltage yields the q component of the magnetic flux. The voltage mapping error of a component of the rectifier output voltage is understood to be the difference between a setpoint value for that component of the rectifier output voltage and an actual value of that component of the rectifier output voltage.

[0019] Therefore, the above-described embodiment of the present invention uses a set value for the rectifier output voltage instead of a measured value to derive the magnetic flux. Therefore, due to an inaccurate understanding of the voltage mapping error, the accuracy of the set value is slightly lower than the accuracy of deriving the magnetic flux based on the measured value of the rectifier output voltage. However, the advantage is that it is not necessary to measure the rectifier output voltage.

[0020] In the two above-described embodiments of the invention, the ohmic voltage drop at the stator winding of the synchronous motor is calculated, for example, from the ohmic resistance of the stator winding and the motor current.

[0021] Preferably, the measured value of the d component of the motor current detected during the individual measurement period is the value at which the absolute value of the d component of the motor current is at its maximum, and the measured value of the q component of the motor current detected during the individual measurement period is the value at which the absolute value of the q component of the motor current is at its maximum. This embodiment of the present invention takes into account that the motor current increases from zero to a maximum value during the individual measurement period, and this maximum value is used for the measured values ​​of the d and q components of the motor current. For example, if only the average value of the motor current over a pulse-width modulated clock cycle is measured during the current measurement period, a small motor voltage is still generated for each clock cycle after the voltage pulse generated during the individual measurement period. Since the motor current still has approximately its maximum value, the motor current is measured for that clock cycle.

[0022] In a further embodiment of the invention, a measurement sequence of four consecutive individual measurements is respectively carried out, wherein for each measurement sequence,

[0023] - generating for the individual measurements at least approximately the same absolute value of the d component of the motor voltage and at least approximately the same absolute value of the q component of the motor voltage,

[0024] for the second individual measurement following the first individual measurement and for the third individual measurement following the second individual measurement, the sign of the q component of the motor voltage is reversed compared to the first individual measurement, and

[0025] For the fourth individual measurement following the third individual measurement, a q component of the motor voltage is generated that has the same sign as for the first individual measurement.

[0026] The above-described embodiments of the present invention are intended to minimize the movement and position changes of the synchronous motor rotor during measurement. This is achieved, in part, by inverting the sign of the q component of the motor voltage in the second individual measurement of a measurement sequence compared to the sign of the first individual measurement in order to stop the rotor movement 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 rotor position caused by the first individual measurement. In the fourth individual measurement of the measurement sequence, the sign of the q component of the motor voltage is inverted compared to the sign of the third individual measurement in order to stop the rotor movement caused by the third individual measurement. Consequently, after the measurement sequence, the motor is in at least approximately the same state as before the measurement sequence.

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

[0028] In another embodiment of the invention, for each measurement sequence, an average value is formed of the q component of the magnetic flux determined during the first individual measurement and the fourth individual measurement, and an average value is formed of the measured values ​​of the q component of the motor current detected during the first individual measurement and the fourth individual measurement.

[0029] In another embodiment of the invention, for each measurement sequence, an average value is formed of the q component of the magnetic flux determined during the second individual measurement and the third individual measurement, and an average value is formed of the measured values ​​of the q component of the motor current detected during the second individual measurement and the third individual measurement.

[0030] The three aforementioned embodiments of the invention combine the individual measurements of a measurement sequence by averaging the values ​​of the corresponding components of the magnetic flux and motor current determined during the individual measurements. This compensates for differences between the individual measurements and measurement inaccuracies caused by the movement and position changes of the rotor.

[0031] In another embodiment of the present invention, each measurement sequence is performed for an initial, slight movement of the synchronous motor's rotor, or more precisely, for an initial, slight relative movement of the rotor and stator of the synchronous motor. For example, after each measurement sequence, the relative movement of the rotor and stator is stopped by a voltage pulse that counteracts the relative movement.

[0032] The above-described embodiments of the invention are also intended to perform measurements with as little rotor movement as possible.

[0033] In another embodiment of the present invention, a value pair consisting of a target value for the d component and a target value for the q component of the motor current is set, and a measurement sequence is performed for each value pair, wherein the measured values ​​of the d component and the q component of the motor current in the measurement sequence match the corresponding target values ​​of the value pair with a set minimum accuracy. For example, to perform a measurement sequence corresponding to the value pair, multiple measurement sequences are iterated.

[0034] The above-described embodiments of the present invention aim to distribute the measured values ​​of the d and q components of the motor current over a measurement range in a manner defined by value pairs, so as to cover the measurement range as completely as possible. For example, value pairs are selected to uniformly grid the measurement range. To determine the measurement points characterized by the value pairs, for example, multiple measurement sequences are iterated until the measured values ​​of the d and q components of the motor current match the target values ​​of the value pairs with a defined minimum accuracy.

[0035] In another embodiment of the present invention, the d and q components of the magnetic flux are respectively approximated by parameterized functions of the d and q components of the motor current, and the parameters of the functions are determined from the d and q components of the magnetic flux determined during the measurement and the associated d and q components of the motor current. The functions thus determined can advantageously be used for various quantitative calculations of the motor characteristics of the synchronous motor, for example, for calculating the so-called MTPA operating point (MTPA = Maximum Torque Per Ampere). This operating point is the operating point at which the desired torque is achieved with the minimum motor current required for this purpose.

[0036] The measuring and evaluation system according to the invention is used for measuring and evaluating the magnetic flux of a permanent-magnet synchronous motor as a function of the motor current of the synchronous motor, the motor voltage of the permanent-magnet synchronous motor being generated by a rectifier, the measuring and evaluation system comprising:

[0037] a measuring unit designed to measure the magnetic flux of the synchronous motor as a function of the motor current of the synchronous motor according to the method according to the invention, and

[0038] an evaluation unit designed to calculate the inductance of the synchronous motor and / or the torque of the synchronous motor and / or the reluctance torque constant of the synchronous motor and / or the torque-to-current ratio from the measurement results of the measuring unit as a function of the motor current of the synchronous motor.

[0039] The measuring and evaluation system according to the present invention utilizes the fact that, according to the present invention, the magnetic flux is measured as a function of the motor current of the synchronous motor. This allows calculation of various characteristic variables relevant to the operation of the synchronous motor, such as inductance, torque, torque-to-current ratio, and reluctance torque constant, based on the motor current of the synchronous motor. Specific formulas for calculating these parameters are given below in the description of the figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above characteristics, features and advantages of the present invention and the manner and method of achieving them will become more clear and easier to understand with reference to the following description of the embodiments, which will be explained in more detail with reference to the accompanying drawings.

[0041] Figure 1 shows the time curves of various variables of a permanent-magnet synchronous motor during the measurement of the magnetic flux, which are dependent on the motor current.

[0042] Figure 2 shows the inductance related to the motor current of a permanent magnet synchronous motor,

[0043] Figure 3 shows a characteristic curve of a permanent-magnet synchronous motor calculated using measurements carried out according to the method of the invention and a characteristic curve measured while the rotor of the synchronous motor rotates,

[0044] Figure 4 The optimal load angle calculated based on the torque of the permanent magnet synchronous motor is shown.

[0045] Figure 5 shows the optimal d and q components of the motor current calculated based on the torque of the permanent magnet synchronous motor and the calculated optimal absolute value of the motor current,

[0046] Figure 6 A block diagram shows an exemplary embodiment of a measuring and evaluation system for measuring and evaluating the magnetic flux as a function of the motor current of a permanent-magnet synchronous motor.

[0047] Corresponding components are provided with the same reference numerals in the figures. DETAILED DESCRIPTION

[0048] Figure 1 (Attached Figure 1 ) shows an embodiment of the method according to the invention for determining the motor current of a synchronous motor by means of different variables i which are dependent on the time t. d 、i q 、U d 、U q The magnetic flux of the permanent magnet synchronous motor is measured by the curves of , n and α. d represents the d component of the motor current, i q represents the q component of the motor current, U d represents the d component of the motor voltage, U q The q component of the motor voltage is represented by n, the rotational speed, and α, the rotor position angle of the synchronous motor. The motor voltage is generated by a rectifier, for example by pulse-duration modulation of a PDM signal of the rectifier.

[0049] For example, the d component of the motor voltage U d is the difference between the d component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor, and the q component of the motor voltage U q is the difference between the q component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor. Alternatively, the d component of the motor voltage U d is the difference between the set value of the d component of the output voltage of the rectifier and the modeled voltage mapping error of the ohmic component of the voltage drop at the stator winding of the synchronous motor and the d component of the output voltage of the rectifier, and the q component of the motor voltage U qThe q component of the rectifier output voltage is the difference between the set value and the voltage mapping error between the ohmic component of the voltage drop across the synchronous motor's stator winding and the modeled q component of the rectifier output voltage. The ohmic component of the voltage drop across the synchronous motor's stator winding is calculated from the ohmic resistance of the stator winding and the motor current.

[0050] In this method, a measurement sequence S of four consecutive individual measurements E1 to E4 is performed. With each individual measurement E1 to E4, the motor voltage is generated as a voltage pulse with an initially small motor current. The d component U of the motor voltage is obtained by integration during the pulse duration of the voltage pulse. d The d component of the magnetic flux is obtained by integrating the q component of the motor voltage U during the pulse duration of the voltage pulse. q This yields the q component of the magnetic flux.

[0051] Furthermore, in each individual measurement E1 to E4, the d component i of the motor current is detected. d The measured value and q component i q For example, the d component of the motor current i d The measured value is the d component of the motor current i d The absolute value of the maximum value, and the q component of the motor current i q The measured value is the q component of the motor current i q The value when the absolute value of is maximum.

[0052] For each measurement sequence S, in the individual measurements E1 to E4, at least approximately the same d component U of the motor voltage is generated in each case. d and the q component of the motor voltage U q In the second individual measurement E2 following the first individual measurement E1 and in the third individual measurement E3 following the second individual measurement E2, the q component U of the motor voltage q The sign of is reversed compared to the first individual measurement E1. In the fourth individual measurement E4 following the third individual measurement E3, a q component U of the motor voltage having the same sign as for the first individual measurement E1 is generated. q .

[0053] For each measurement sequence S, the mean value of the d-components of the magnetic flux obtained during the individual measurements is formed, and the d-component i of the motor current is formed. d The average value of the measured values ​​detected during the individual measurements E1 to E4 is formed. In addition, for each measurement sequence S, the average value of the q component of the magnetic flux obtained during the first individual measurement E1 and the fourth individual measurement E4 is formed, and the q component i of the motor current is formed. qThe average value of the measured values ​​detected during the first individual measurement E1 and the fourth individual measurement E4 is formed. Accordingly, for each measurement sequence S, the average value of the q component of the magnetic flux obtained during the second individual measurement E2 and the third individual measurement E3 is formed, and the q component i of the motor current is formed. q The average value of the measurement values ​​detected during the second individual measurement E2 and the third individual measurement E3.

[0054] Each measurement sequence S is performed for an initial slight relative movement of the rotor and stator of the synchronous motor. For this purpose, after each measurement sequence S, the relative movement of the rotor and stator is stopped by a voltage stop pulse H which counteracts the relative movement and has only a d component.

[0055] Preferably, the measurement settings are respectively composed of the d component i of the motor current d The target value i ds and q component i q The target value i qs The value pair i ds 、i qs For each value pair, a measurement sequence S is performed, wherein the d component i of the motor current is d and q component i q The measured value of the value pair matches the corresponding target value i with the set minimum accuracy ds 、i qs For example, set the value pair so that it evenly meshes the d component of the motor current i d and q component i q range.

[0056] To perform the operation corresponding to the value pair (i ds 、i qs ), for example, performing a plurality of iterations of the measurement sequence S, wherein the motor voltage U is corrected separately in each case d and U q , so as to reach the target value i with the required minimum accuracy ds and i qs For example, the motor voltage U of the first step of the iteration can be estimated or calculated via the parameterized motor inductance d and U q Then, you can use i d and i q The settings are corrected using the actual measured values ​​and the measurements are repeated until the target value i is reached with the required minimum accuracy. ds and i qs If multiple measurements have been performed, the measured differential inductances around the corresponding measurement points can be used to speed up the convergence of the iterations.

[0057] Figure 1 The target value i is shown as an example ds and i qs At the time points t1 and t2, two measurement sequences S are performed after each time point, and the target value i is reached with the required minimum accuracy during the second measurement sequence S. ds and i qs .

[0058] However, with Figure 1 Different, it is not actually necessary to change the two target values ​​i at the same time ds and i qs For example, starting with a small target value i ds and i qs , then first continuously increase the target value i according to the confirmed grid qs , until the desired i is covered q Then, change the target value i ds And pass through the target value i again for the changed target value qs Here, for the d component i d , target values ​​must always be set for both signs of the current i ds For example, it is possible to start with a smaller absolute value of the current and first process the positive target value i ds , and then also starting from a smaller absolute value of the current, the negative target value i is processed ds This is necessary because the permanent magnet synchronous motor is about i d It is neither point-symmetric nor axis-symmetric. In the measurement sequence S, q components i with different signs appear q In the q component i q There is usually an axial symmetry in the , so that the target value i is set for the symbol qs Of course, measurements have shown that the symmetry does not exist for all motors, so that it is not always possible to exploit the symmetry and it is necessary to use the target value i for both signs. qs Furthermore, the maximum current of the synchronous motor or the rectifier is taken into account in the measurement, so that no target value is set which would result in the maximum current being exceeded.

[0059] A lot of information can be derived from the measurement of the d and q components of the magnetic flux. On the one hand, the inductance L can be calculated by differentiating the components of the magnetic flux according to the corresponding components of the motor current. dd (i d ,i q ) and L qq (i d ,i q ). Furthermore, if the components of the magnetic flux are differentiated with respect to the corresponding other components of the motor current, the transverse inductance L is obtained dq (i d ,iq ) and L qd (i d ,i q ):

[0060]

[0061] or

[0062]

[0063] or

[0064]

[0065] or

[0066]

[0067] or

[0068] Here, ψ d represents the d component of the magnetic flux, ψ q represents the q component of the magnetic flux.

[0069] The flux measurement in the d direction is still missing the permanent magnet flux ψ dPM The offset cannot be measured when the synchronous motor is stationary. This missing value can be measured by measuring the voltage constant k E The understanding is calculated as follows

[0070]

[0071] Here, z p is the number of pole pairs, and the voltage constant k E It is the effective voltage of the link at no load divided by the speed of the synchronous motor. dPM The value of must be added to the measured d component of the magnetic flux in order to obtain ψ d .

[0072] Alternatively, the motor voltage can also be measured at an appropriate speed while the synchronous motor is idling (from which k can also be determined). E ) to measure ψ dPM .

[0073] Figure 2 (Attached Figure 2 ) exemplarily shows the d and i q Determine the inductance L dd results.

[0074] According to id and i q The measurement of the magnetic flux, i.e., the measurement of the d and q components of the magnetic flux, also operates in principle position-dependently, i.e., as a function of the synchronous motor's rotor position angle α, and with kinematic uncertainties. Synchronous motors with single-tooth windings generally exhibit position-dependency of the magnetic flux, making it possible to measure the magnetic flux as a function of the rotor position.

[0075] The torque of the synchronous motor can also be calculated using the magnetic flux as follows

[0076]

[0077] In this case, the cogging torque is neglected or has to be considered separately.

[0078] The torque calculated from the measured magnetic flux takes into account the saturation dependence. For example, with the help of the torque, the torque to current ratio k can be calculated as follows T K T Characteristic curve k T (i q ), the torque to current ratio describes the torque to the q component of the motor current i q Relationship:

[0079]

[0080] Or calculate the reluctance torque constant k at all operating points according to the following TRei (i d ,i q )

[0081]

[0082] Figure 3 (Attached Figure 3 ) and k measured when the synchronous motor rotor rotates T Characteristic curve 2 shows by way of example the k calculated in this way. T Characteristic curve 1. It can be clearly seen that the two results are in good agreement.

[0083] Another possibility is to use i d and i q The optimal operating point can be calculated by approximating the magnetic flux with a suitable parameterized function. For example, such a function is as follows:

[0084]

[0085] In this case, ka0 to ka4 , b0 to kb4 , kc0 to kc2 and kd0 value kd5 are parameters which are determined from the d and q components of the magnetic flux and the associated d and q components of the motor current which are determined during the measurement.

[0086] For example, the MTPA operating point is calculated using the magnetic flux parameterized in this way.

[0087] Figure 4 (Attached Figure 4 )and Figure 5 (Attached Figure 5 ) shows, for example, the MTPA operating point of a synchronous motor calculated in this way. Figure 4 Shown with torque M i The optimal load angle ρ is calculated, and Figure 5 Shown according to the torque M d The calculated optimal d and q current components i do and i qo And the motor current depends on the torque M d The calculated optimal current absolute value |i o |.

[0088] Figure 6 (Attached Figure 6 ) shows the motor current i for a synchronous motor d 、i q Measuring and evaluating the magnetic flux ψ of permanent magnet synchronous motors d , ψ q Block diagram of an embodiment of a measuring and evaluation system 3, wherein the motor voltage of a permanent magnet synchronous motor is generated by a rectifier. The measuring and evaluation system 3 comprises a measuring unit 4, which is designed to measure the motor current i of the synchronous motor according to the method according to the invention as described above. d 、i q To measure the magnetic flux ψ of the synchronous motor d , ψ q Furthermore, the measuring and evaluation system 3 comprises an evaluation unit 5 which is designed to determine the value of the motor current i of the synchronous motor. d 、i q The inductance L of the synchronous motor is calculated from the measurement result of the measuring unit 3. dd 、L qq 、L dq 、L qd , synchronous motor torque M i , torque to current ratio k T and the magnetic drag torque constant k TRel The evaluation unit 5 is designed, for example, as a computer program that is executed on a processor and calculates the above-mentioned variable L of the synchronous motor according to the formula explained above. dd 、Lqq 、L dq 、L qd 、M i 、k T and k TRel .

[0089] While the present invention has been illustrated and described in detail by way of preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art will be able to devise other variations therefrom without departing from the scope of the present invention.

Claims

1. A method for determining the motor current (i d ,i q )Measure the magnetic flux (ψ) of the permanent magnet synchronous motor d , ψ q ), wherein the motor voltage of the permanent magnet synchronous motor is generated by a rectifier, wherein A plurality of individual measurements (E1 to E4) are performed, and during each individual measurement (E1 to E4), - Using the initial small motor current to generate the motor voltage as a voltage pulse, - Determine the d component of the motor voltage (U d ) yields the d component of the magnetic flux (ψ d ), - from the q component of the motor voltage (U q ) yields the q component of the magnetic flux (ψ q ),and - Detecting the d component of the motor current (i d ) and the q component (i q )’s measured value.

2. The method according to claim 1, wherein The d component of the motor voltage (U d ) is the difference between the d component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor, and the q component of the motor voltage (U q ) is the difference between the q component of the measured output voltage of the rectifier and the ohmic component of the voltage drop at the stator winding of the synchronous motor.

3. The method according to claim 1, wherein The d component of the motor voltage (U d ) is the difference between the set value of the d component of the output voltage of the rectifier and the modeled voltage mapping error of the ohmic component of the voltage drop at the stator winding of the synchronous motor and the d component of the output voltage of the rectifier, and the q component of the motor voltage (U q ) is the difference between the set value of the q component of the output voltage of the rectifier and the modeled voltage mapping error of the ohmic component of the voltage drop at the stator winding of the synchronous motor and the q component of the output voltage of the rectifier.

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

5. A method according to any one of the preceding claims, wherein The d component of the motor current (i d ) is the d component of the motor current (i d ) is the value when the absolute value is the largest, and the q component of the motor current (i q ) is the q component of the motor current (i q ) is the value at which its absolute value is maximum.

6. A method according to any one of the preceding claims, wherein A measurement sequence (S) of four consecutive individual measurements (E1 to E4) is respectively performed, wherein for each measurement sequence (S) - for the individual measurements (E1 to E4) an at least approximately identical d component (U d ) and the q component of the motor voltage (U q ) have at least approximately the same absolute value, For the second individual measurement (E2) following the first individual measurement (E1) and for the third individual measurement (E3) following the second individual measurement (E2), the q component (U q ) is inverted in sign compared to said first individual measurement (E1), and - for a fourth individual measurement (E4) following the third individual measurement (E3), a q component (U) of the motor voltage having the same sign as for the first individual measurement (E1) is generated q ).

7. The method according to claim 6, wherein: For each measurement sequence (S), the d component (ψ) of the magnetic flux obtained during the individual measurements (E1 to E4) is formed. d ) and forms the d component of the motor current (i d ) is the average value of the measurement values ​​detected during the individual measurements (El to E4).

8. The method according to claim 6 or 7, wherein: For each measurement sequence (S), the q component (ψ) of the magnetic flux obtained during the first individual measurement (E1) and the fourth individual measurement (E4) is formed. q ) and forms the q component of the motor current (i q ) is the average value of the measurement values ​​detected during the first individual measurement (El) and the fourth individual measurement (E4).

9. The method according to any one of claims 6 to 8, wherein For each measurement sequence (S), the q component (ψ q ) and forms the q component of the motor current (i q ) is the average value of the measurement values ​​detected during the second individual measurement (E2) and the third individual measurement (E3).

10. The method according to any one of claims 6 to 9, wherein Each measurement sequence (S) is performed for an initial small relative movement of the rotor and stator of the synchronous motor.

11. The method according to any one of claims 6 to 10, wherein After each measurement sequence (S), the relative motion of the rotor and stator is stopped by a voltage stop pulse (H) which counteracts the relative motion.

12. The method according to any one of claims 6 to 11, wherein Set the d component of the motor current (i d ) target value (i ds ) and q component (i q ) target value (i qs ) and for each value pair a measurement sequence (S) is performed, the measurement sequence for the d component (i d ) and q component (i q ) matches the corresponding target value (i ds ,i qs ).

13. The method according to claim 12, wherein: Iterations are performed during the plurality of measurement sequences (S) to perform the measurement sequences (S) corresponding to the value pairs.

14. A method according to any one of the preceding claims, wherein The d component of the motor current (i d ) and q component (i q ) are parameterized functions that approximate the d component of the magnetic flux (ψ d ) and the q component of the magnetic flux (ψ q ), and the d component of the magnetic flux (ψ d ) and q component (ψ q ) and the associated d component of the motor current (i d ) and q component (i q ) determines the parameters of the function.

15. A method for determining the motor current (i d ,i q )Measure and evaluate the magnetic flux (ψ) of permanent magnet synchronous motors d , ψ q ), wherein the motor voltage of the permanent magnet synchronous motor is generated by a rectifier, and the measuring and evaluation system (3) comprises: a measuring unit (4) designed to measure the motor current (i d ,i q ) measures the magnetic flux of the synchronous motor (ψ d , ψ q ),and - an evaluation unit (5) designed to, based on the motor current (i d ,i q ), the inductance (L) of the synchronous motor is calculated from the measurement result of the measurement unit (4) dd , L qq , L dq , L qd ) and / or the torque of the synchronous motor (M i ) and / or the reluctance torque constant (k TRel ) and / or torque to current ratio (k T ).

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