Method for measuring time constant of asynchronous motor rotor on line based on impedance value

Abstract

The invention provides a method for on-line measurement of a time constant of an asynchronous motor rotor based on an impedance value. The method comprises the following steps: carrying out frequency self-correction on a test instrument before measurement; frequency self-correction is carried out on a test instrument before measurement, and a characteristic impedance value of the asynchronous motor rotor is input into an LCR characteristic test circuit; the test instrument is matched with the voltage phase oscillography device through a built-in automatic calibration circuit to carry out frequency self-correction; when correction is carried out, firstly, an instrument is powered on and initialized, frequency f set by the instrument is input into the LCR characteristic test circuit, and the working frequency of the LCR characteristic test circuit is correspondingly adjusted; meanwhile, the test instrument is adjusted to a phase measurement mode, and then the test instrument inputs the capacitance value, the loss characteristic and the equivalent series resistance parameter into the capacitor; and comparing with a standard capacitor with known accuracy for measurement until the measurement result of the test instrument is consistent with a standard value, and then completing calibration.

Description

Technical Field

[0001] The invention belongs to the field of motor rotor measurement, and in particular relates to a method for measuring an asynchronous motor rotor time constant online based on impedance value. Background Art

[0002] At present, in the field of asynchronous motor control, accurate determination of the rotor time constant (Sr=Lr / Rr) is crucial for optimizing motor performance. The rotor time constant not only affects the rotor flux detection accuracy in the motor flux closed-loop control system, but is also directly related to the control effect of the electromagnetic torque. However, the existing rotor time constant determination method has many shortcomings, which limits the application of asynchronous motors in high-performance drive control applications.

[0003] Traditional methods for determining rotor time constants mainly include measuring and calculating motor constants through stalled and no-load tests, and online identification using algorithms such as the EKF and MRAC. Although these methods can achieve the determination of rotor time constants to a certain extent, they all have significant disadvantages. For example, stalled and no-load tests need to be performed when the motor is offline, and cannot reflect the parameter changes of the motor during operation in real time; while the Kalman filter method and the MRAC law rely on a large amount of real-time calculations and are highly dependent on the stator resistance Rs, making these methods unsatisfactory in high-performance drive control applications.

[0004] Although the Kalman filter method can realize online identification of motor parameters, its algorithm complexity is relatively high and requires an accurate motor model and high computing power, which is often difficult to achieve in practical applications. At the same time, the sensitivity of this method to stator resistance also limits its widespread application in asynchronous motor control. Although the model reference adaptive method can overcome the shortcomings of the Kalman filter method to a certain extent, its identification accuracy and convergence speed are often affected by the motor operating state and parameter changes, making it difficult to ensure the stability and accuracy of the identification results.

[0005] The existing rotor time constant calculation formula derived from the voltage equation also depends on parameters such as stator resistance, voltage and current. This means that during the operation of the motor, parameter changes caused by factors such as temperature rise and magnetic field saturation will directly affect the measurement results of the rotor time constant. Therefore, the application of these methods in high-performance drive control of asynchronous motors is greatly limited.

[0006] The existing asynchronous motor rotor time constant measurement method has many shortcomings and cannot meet the needs of real-time and accurate measurement of motor parameters in high-performance drive control situations. Therefore, a new method for online measurement of asynchronous motor rotor time constant based on impedance value is studied to overcome the shortcomings of the existing technology and improve the overall performance of the asynchronous motor control system, which has important theoretical significance and practical application value. Now there is an urgent need for a method for online measurement of asynchronous motor rotor time constant based on impedance value. Summary of the invention

[0007] The present invention proposes a method for measuring the time constant of an asynchronous motor rotor online based on impedance value, which solves the problems of insufficient accuracy, complex operation and strong dependence on test instruments in the process of measuring the time constant of an asynchronous motor rotor in the prior art, and realizes accurate online measurement based on impedance value.

[0008] The technical solution of the present invention is implemented as follows: a method for measuring the time constant of an asynchronous motor rotor online based on impedance value, the method comprising the following steps: The test instrument is frequency-self-calibrated before measurement; The test instrument is frequency-self-calibrated before measurement, and the characteristic impedance value of the asynchronous motor rotor is input into the LCR characteristic test circuit; The test instrument performs frequency self-calibration through the built-in automatic calibration circuit and the voltage phase oscilloscope device; When performing calibration, firstly, the instrument is powered on and initialized, and the frequency f set by the instrument is input into the LCR characteristic test circuit, and the working frequency of the LCR characteristic test circuit is adjusted accordingly; at the same time, the test instrument is adjusted to the phase measurement mode, and then the test instrument inputs the capacitance value, loss characteristics and equivalent series resistance parameters into the capacitor; the calibration is completed by comparing and measuring with a standard capacitor of known accuracy until the measurement result of the test instrument is consistent with the standard value, and the asynchronous motor rotor is tested with the LCR characteristic test circuit, and the sinusoidal AC signal of its voltage and current values ​​is obtained through the test of the LCR characteristic test circuit; The sinusoidal AC signal is processed to obtain the phase difference and amplitude attenuation of the corresponding sinusoidal wave; the corresponding phase difference and amplitude attenuation are obtained by comparing the impedance value of the asynchronous motor rotor obtained by actual measurement and the frequency value of the test instrument after self-calibration with the standard LCR value table; The equivalent impedance value of the asynchronous motor rotor is calculated; and after the calculation, the equivalent circuit of the asynchronous motor is calculated in combination with the geometric structure characteristics of the asynchronous motor; according to the equivalent circuit of the asynchronous motor, the time constant τ is obtained from the impedance formula of the RL and RC circuits associated with the asynchronous motor.

[0009] Compared with the prior art, the present technical solution places special emphasis on the frequency self-calibration step of the test instrument in the measurement process, which is a link that is often overlooked in the prior art. In the prior art, the frequency accuracy of the test instrument often depends on the calibration at the factory. In actual use, due to factors such as ambient temperature and circuit aging, the frequency of the test instrument may deviate, thereby affecting the accuracy of the measurement result. In the present method, the frequency of the test instrument can be calibrated in real time through the frequency self-calibration step to ensure the frequency accuracy of the test instrument during the measurement process, thereby improving the accuracy of the measurement result.

[0010] In terms of the test principle, this method uses an LCR characteristic test circuit to test the asynchronous motor rotor, and processes the sinusoidal AC signal obtained from the test to obtain its corresponding phase difference and amplitude attenuation. This step is not common in the prior art. The prior art usually directly measures the voltage, current and other parameters of the motor, and then uses these parameters to calculate the rotor time constant. However, this method is often affected by various factors such as the operating state of the motor and parameter changes, resulting in the accuracy of the measurement results being limited. In this method, through the LCR characteristic test circuit and the processing of the sinusoidal AC signal, the impedance characteristics of the asynchronous motor rotor can be obtained more directly and accurately, thereby further improving the accuracy of the rotor time constant measurement.

[0011] When calculating the rotor time constant of the asynchronous motor, this method combines the geometric structure characteristics of the asynchronous motor, calculates the equivalent circuit of the asynchronous motor, and obtains the time constant based on the equivalent circuit of the asynchronous motor and the impedance formula of the associated RL and RC circuits. This step is also relatively rare in the prior art. The prior art usually obtains the rotor time constant through formula derivation or numerical calculation based on known motor parameters. However, this method often ignores the influence of the geometric structure characteristics of the motor on the motor parameters, resulting in the accuracy of the calculation results being limited. In this method, by combining the geometric structure characteristics and equivalent circuit of the motor, the rotor time constant can be calculated more accurately, thereby further improving the accuracy and reliability of the measurement results.

[0012] As a preferred embodiment, when performing frequency self-calibration, a voltage phase oscilloscope is used to measure the phase difference of the measured frequency before and after correction, and the frequency obtained by the test instrument and the capacitance parameter value of the measuring capacitor are input into the automatic calibration circuit to obtain the corrected phase difference and frequency, thereby obtaining the corrected sinusoidal wave phase difference.

[0013] As a preferred implementation, the method for testing the asynchronous motor rotor by the LCR characteristic test circuit is as follows: The voltage phase difference of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The current phase difference between two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The amplitude attenuation of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the amplitude attenuation of the impedance value is calculated through the automatic calibration circuit, where the amplitude attenuation refers to the ratio of the impedance value to the standard impedance value; By comparing the phase difference of the impedance value, the amplitude attenuation of the impedance value and the equivalent frequency of the motor stator, the resistance value of the motor stator coil and the equivalent reactance of the stator coil are obtained under the corresponding impedance value; The stator winding equivalent impedance is calculated by the stator coil resistance value and the stator coil equivalent reactance; the motor winding self-inductance is calculated by the stator coil resistance value and the stator coil equivalent reactance, combined with the winding turns and the stator wire gauge geometric dimensions; the motor stator equivalent internal resistance impedance is calculated by the stator coil equivalent inductance and the motor winding self-inductance; the stator coil equivalent inductance is calculated by the motor stator equivalent internal resistance impedance value; the motor stator equivalent leakage inductance is calculated based on the motor stator coil equivalent inductance and the motor winding self-inductance, combined with the motor stator winding turns and the stator wire diameter geometric dimensions; the equivalent mutual inductance between the three-phase windings of the motor is calculated by the motor stator equivalent leakage inductance, and the voltage and current values ​​of the asynchronous motor are tested by the equivalent mutual inductance.

[0014] As a preferred implementation, on the test instrument, the R, L, and C values ​​of the standard asynchronous motor are used as a reference sample of the motor to be tested, and the standard LCR value table is compared to obtain the corresponding impedance value as an actual value of the test motor. When the rotor impedance values ​​R, L, and C meet the standards, the test motor can be represented by the R, L, and C values, thereby calculating the equivalent impedance value of the rotor of the asynchronous motor to be tested.

[0015] As a preferred embodiment, the equivalent circuit of the asynchronous motor is to use the two-phase lines of the motor as the flow channels of the rotor current and voltage, and the motor rotor and the stator coil form a series-parallel impedance network; the impedance values ​​of the motor rotor and the motor coil are equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit; the time constant of the motor rotor is obtained by combining the measured rotor impedance value and the calculated rotor frequency value.

[0016] After adopting the above technical solution, the beneficial effect of the present invention is: in terms of measurement accuracy, since the method adopts the frequency self-correction step and the LCR characteristic test circuit, the impedance characteristics of the asynchronous motor rotor can be obtained in real time and accurately, thereby improving the accuracy of the rotor time constant measurement. This is crucial for high-performance asynchronous motor control systems, because accurate rotor time constants can ensure the stability and response speed of the motor during the control process.

[0017] In terms of measurement accuracy, since this method uses a frequency self-correction step and an LCR characteristic test circuit, the impedance characteristics of the asynchronous motor rotor can be obtained in real time and accurately, thereby improving the accuracy of the rotor time constant measurement. This is crucial for high-performance asynchronous motor control systems, because an accurate rotor time constant can ensure the stability and response speed of the motor during the control process.

[0018] In terms of measurement accuracy, since this method uses a frequency self-correction step and an LCR characteristic test circuit, the impedance characteristics of the asynchronous motor rotor can be obtained in real time and accurately, thereby improving the accuracy of the rotor time constant measurement. This is crucial for high-performance asynchronous motor control systems, because an accurate rotor time constant can ensure the stability and response speed of the motor during the control process.

[0019] This technical solution has significant advantages over the existing technology in terms of measurement accuracy, operation convenience, and test instrument dependence. It not only improves the accuracy of asynchronous motor rotor time constant measurement, but also reduces the difficulty and cost of operation, and enhances the versatility and adaptability of the method. This is of great significance for promoting the research and application of high-performance control systems for asynchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 The figure is a flow chart of the method of the present invention.

[0022] Figure 2 This is a test circuit diagram of the capacitor capacity C of the present invention.

[0023] Figure 3 Schematic diagram of the test circuit of the inductor element L of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example: like Figure 1 As shown, a method for measuring the time constant of an asynchronous motor rotor based on an impedance value online comprises the following steps: The test instrument is frequency-self-calibrated before measurement; The test instrument is frequency-self-calibrated before measurement, and the characteristic impedance value of the asynchronous motor rotor is input into the LCR characteristic test circuit; The test instrument performs frequency self-calibration through the built-in automatic calibration circuit and the voltage phase oscilloscope device; When performing calibration, firstly, the instrument is powered on and initialized, and the frequency f set by the instrument is input into the LCR characteristic test circuit, and the working frequency of the LCR characteristic test circuit is adjusted accordingly; at the same time, the test instrument is adjusted to the phase measurement mode, and then the test instrument inputs the capacitance value, loss characteristics and equivalent series resistance parameters into the capacitor; the calibration is completed by comparing and measuring with a standard capacitor of known accuracy until the measurement result of the test instrument is consistent with the standard value, and the asynchronous motor rotor is tested with the LCR characteristic test circuit, and the sinusoidal AC signal of its voltage and current values ​​is obtained through the test of the LCR characteristic test circuit; The sinusoidal AC signal is processed to obtain the phase difference and amplitude attenuation of the corresponding sinusoidal wave; the corresponding phase difference and amplitude attenuation are obtained by comparing the impedance value of the asynchronous motor rotor obtained by actual measurement and the frequency value of the test instrument after self-calibration with the standard LCR value table; The equivalent impedance value of the asynchronous motor rotor is calculated; and after the calculation, the equivalent circuit of the asynchronous motor is calculated in combination with the geometric structure characteristics of the asynchronous motor; according to the equivalent circuit of the asynchronous motor, the time constant τ is obtained from the impedance formula of the RL and RC circuits associated with the asynchronous motor.

[0026] This method measures the time constant of the asynchronous motor rotor online based on the impedance value. The core of this method is to accurately measure the impedance characteristics of the asynchronous motor rotor through precise testing instruments and LCR characteristic test circuits, combined with automatic frequency correction technology, and derive the rotor time constant based on this. This method makes full use of the advantages of LCR (inductance, capacitance, resistance) testing technology, can reflect the electrical characteristics of the asynchronous motor rotor online and in real time, and provide key parameters for high-performance control of the motor.

[0027] The frequency self-calibration step before measurement is the key to ensure test accuracy. Since the test instrument may be affected by factors such as environment and aging during use, resulting in frequency deviation, the test instrument needs to be self-calibrated before formal measurement. This process is achieved through automatic calibration circuit and voltage phase oscilloscope device to ensure that the frequency output by the test instrument during the measurement process is accurate.

[0028] The asynchronous motor rotor is tested using the LCR characteristic test circuit. The LCR characteristic test circuit is a circuit specifically used to measure inductance, capacitance and resistance. It can provide a stable sinusoidal AC signal and measure the voltage and current values ​​in the circuit. In order to obtain the phase difference and amplitude attenuation of the asynchronous motor rotor, the sinusoidal AC signal needs to be processed. The processing process includes steps such as signal acquisition, filtering, and amplification to ensure the accuracy and stability of the signal. By analyzing the processed signal, the two key parameters of phase difference and amplitude attenuation can be obtained. These two parameters are closely related to the impedance characteristics of the asynchronous motor rotor and are the basis for deriving the time constant.

[0029] After obtaining the phase difference and amplitude attenuation, combined with the impedance value of the asynchronous motor rotor obtained by actual measurement and the frequency value of the test instrument after self-calibration, the corresponding theoretical values ​​of the phase difference and amplitude attenuation can be obtained by comparing the standard LCR value table. By comparing the actual measured value with the theoretical value, the accuracy and reliability of the measurement result can be verified. Calculate the equivalent impedance value of the asynchronous motor rotor. The equivalent impedance value is an important parameter reflecting the electrical characteristics of the asynchronous motor rotor. It can be obtained by processing and calculating the measured voltage and current values. In the calculation process, the geometric structure characteristics of the asynchronous motor need to be considered, because the geometric structure of the motor has an important influence on its electrical characteristics. After obtaining the equivalent impedance value, combined with the geometric structure characteristics of the asynchronous motor, the equivalent circuit of the asynchronous motor can be calculated. The equivalent circuit is a simplified circuit model that can reflect the main electrical characteristics of the asynchronous motor. Through the equivalent circuit, the impedance formula of the RL and RC circuits of the asynchronous motor can be further derived, thereby obtaining the time constant τ.

[0030] The time constant τ is an important parameter that reflects the dynamic characteristics of asynchronous motors. It determines the response speed and stability of the motor after receiving external excitation. The time constant τ measured by this method can provide key parameter support for the high-performance control of the motor, which helps to optimize the control strategy and performance of the motor.

[0031] In this application document, the time constant is determined by the frequency response, and the capacitor capacity C test method is as follows Figure 2 As shown, the calculation formula is as follows:

[0032] Among them U in is the function signal generator, U OUT For oscilloscope.

[0033] The test method of the inductor element L is as follows Figure 3 As shown, the calculation formula is as follows:

[0034] Among them U in is the function signal generator, U OUT For oscilloscope.

[0035] like Figure 2 and Figure 3 As shown, the method of the present application document only measures the amplitude-frequency response of the voltage of the component to be tested, and can directly convert the parameter value of the component to be tested, without measuring the current of the component to be tested and the phase difference between its terminal voltage and current.

[0036] The specific workflow of the method of this application document is as follows: Assume that in an industrial automation production line, an asynchronous motor needs to be optimized and upgraded. In order to ensure that the upgraded motor can meet the requirements of high-performance control, the rotor time constant of the motor needs to be accurately measured. At this time, this method can be used for measurement.

[0037] Connect the test instrument to the LCR characteristic test circuit and make sure the test instrument is in good working condition. Then, perform frequency self-calibration on the test instrument to ensure that the frequency it outputs is accurate. This step can be achieved through an automatic calibration circuit and a voltage phase oscilloscope device.

[0038] Next, connect the asynchronous motor to the LCR characteristic test circuit and start the test program. The test program will output a stable sinusoidal AC signal to the asynchronous motor rotor and measure the voltage and current values ​​in the circuit. These values ​​will serve as the basis for subsequent processing and calculations.

[0039] In order to obtain the phase difference and amplitude attenuation of the asynchronous motor rotor, the collected sinusoidal AC signal needs to be processed. The processing process includes signal filtering, amplification and other steps to ensure the accuracy and stability of the signal. At the same time, the phase difference and amplitude attenuation of the processed signal also need to be calculated.

[0040] After calculating the phase difference and amplitude attenuation, combined with the actual measured impedance value of the asynchronous motor rotor and the frequency value of the test instrument after self-calibration, the corresponding theoretical values ​​of the phase difference and amplitude attenuation can be obtained by comparing the standard LCR value table. By comparing the actual measured value with the theoretical value, the accuracy and reliability of the measurement result can be verified.

[0041] The equivalent impedance value and equivalent circuit of the asynchronous motor are calculated using the processed voltage and current values ​​and the geometric structure characteristics of the asynchronous motor. In the calculation process, it is necessary to fully consider the influence of the geometric structure of the motor on the electrical characteristics to ensure the accuracy of the calculation results. After obtaining the equivalent circuit, the impedance formula of the RL and RC circuits of the asynchronous motor can be further derived, and the time constant τ can be calculated accordingly. This step is the key to the measurement process, because the time constant τ is an important parameter reflecting the dynamic characteristics of the asynchronous motor.

[0042] The measured time constant τ is compared and analyzed with the performance requirements of the motor. If the time constant τ meets the performance requirements, it means that the high-performance control strategy of the motor is feasible; if it does not meet the requirements, the control strategy of the motor needs to be optimized and adjusted according to the value of the time constant τ. Through this process, high-performance control of the asynchronous motor can be achieved, and the operating efficiency and stability of the motor can be improved.

[0043] When performing frequency self-correction, a voltage phase oscilloscope is used to measure the phase difference of the measured frequency before and after correction, and the frequency obtained by the test instrument and the capacitance parameter value of the measuring capacitor are input into the automatic calibration circuit to obtain the corrected phase difference and frequency, thereby obtaining the corrected sinusoidal wave phase difference. The prior art often only focuses on the accuracy of the frequency during the frequency correction process, while ignoring the change in the phase difference. However, this preferred embodiment not only takes into account the accuracy of the frequency, but also further ensures the stability and accuracy of the test signal by measuring the phase difference before and after correction. By inputting the capacitance parameter value of the capacitor, the corrected phase difference can be calculated more accurately, thereby improving the accuracy and reliability of the test results. This improvement enables the test instrument to achieve higher accuracy in both frequency and phase dimensions, providing more accurate basic data for the subsequent determination of the rotor time constant of the asynchronous motor.

[0044] The method for testing the asynchronous motor rotor by the LCR characteristic test circuit is as follows: The voltage phase difference of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The current phase difference between two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The amplitude attenuation of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the amplitude attenuation of the impedance value is calculated through the automatic calibration circuit, where the amplitude attenuation refers to the ratio of the impedance value to the standard impedance value; By comparing the phase difference of the impedance value, the amplitude attenuation of the impedance value and the equivalent frequency of the motor stator, the resistance value of the motor stator coil and the equivalent reactance of the stator coil are obtained under the corresponding impedance value; The stator winding equivalent impedance is calculated by the stator coil resistance value and the stator coil equivalent reactance; the motor winding self-inductance is calculated by the stator coil resistance value and the stator coil equivalent reactance, combined with the winding turns and the stator wire gauge geometric dimensions; the motor stator equivalent internal resistance impedance is calculated by the stator coil equivalent inductance and the motor winding self-inductance; the stator coil equivalent inductance is calculated by the motor stator equivalent internal resistance impedance value; the motor stator equivalent leakage inductance is calculated based on the motor stator coil equivalent inductance and the motor winding self-inductance, combined with the motor stator winding turns and the stator wire diameter geometric dimensions; the equivalent mutual inductance between the three-phase windings of the motor is calculated by the motor stator equivalent leakage inductance, and the voltage and current values ​​of the asynchronous motor are tested by the equivalent mutual inductance.

[0045] The equivalent circuit of the asynchronous motor uses the two-phase line of the motor as the flow channel of the rotor current and voltage, and the motor rotor and stator coil form a series-parallel impedance network. The impedance value of the motor rotor and the motor coil is equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit. Compared with the prior art, this step is different in that: The prior art usually simplifies the equivalent circuit of the asynchronous motor into a single impedance model, while ignoring the complex electrical structure inside the motor. However, the preferred embodiment constructs a more accurate equivalent circuit model, and equates the impedance values ​​of the motor rotor and stator coil to an LC series oscillation circuit and a series resistor-capacitor oscillation circuit, respectively, to more accurately reflect the electrical characteristics inside the motor. This improvement makes the equivalent circuit model more in line with the actual situation and provides more accurate circuit model support for subsequent time constant calculations. At the same time, by combining the measured rotor impedance value and the calculated rotor frequency value, the time constant of the motor rotor can be obtained more accurately, providing key parameters for high-performance control of the motor.

[0046] On the test instrument, the R, L, and C values ​​of the standard asynchronous motor are used as a reference sample of the motor to be tested, and the corresponding impedance value is obtained as an actual value of the test motor by comparing with the standard LCR value table. When the rotor impedance values ​​R, L, and C meet the standards, the test motor can be represented by the R, L, and C values, thereby calculating the equivalent impedance value of the rotor of the asynchronous motor to be tested. The equivalent circuit of the asynchronous motor uses the two-phase lines of the motor as the flow channel for the rotor current and voltage, and the motor rotor and the stator coil form a series-parallel impedance network. The impedance value of the motor rotor and the motor coil is equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit. Compared with the prior art, the difference between this step and the prior art is: The prior art usually simplifies the equivalent circuit of the asynchronous motor into a single impedance model, while ignoring the complex electrical structure inside the motor. However, the preferred embodiment constructs a more accurate equivalent circuit model, and equates the impedance values ​​of the motor rotor and stator coil to an LC series oscillation circuit and a series resistor-capacitor oscillation circuit, respectively, to more accurately reflect the electrical characteristics inside the motor. This improvement makes the equivalent circuit model more in line with the actual situation and provides more accurate circuit model support for subsequent time constant calculations. At the same time, by combining the measured rotor impedance value and the calculated rotor frequency value, the time constant of the motor rotor can be obtained more accurately, providing key parameters for high-performance control of the motor.

[0047] The equivalent circuit of the asynchronous motor is to use the two-phase lines of the motor as the flow channels of the rotor current and voltage, and the motor rotor and the stator coil form a series-parallel impedance network; the impedance values ​​of the motor rotor and the motor coil are equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit; the time constant of the motor rotor is obtained by combining the measured rotor impedance value and the calculated rotor frequency value.

[0048] The equivalent circuit of the asynchronous motor uses the two-phase line of the motor as the flow channel of the rotor current and voltage, and the motor rotor and stator coil form a series-parallel impedance network. The impedance value of the motor rotor and the motor coil is equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit. Compared with the prior art, this step is different in that: The prior art usually simplifies the equivalent circuit of the asynchronous motor into a single impedance model, while ignoring the complex electrical structure inside the motor. However, the preferred embodiment constructs a more accurate equivalent circuit model, and equates the impedance values ​​of the motor rotor and stator coil to an LC series oscillation circuit and a series resistor-capacitor oscillation circuit, respectively, to more accurately reflect the electrical characteristics inside the motor. This improvement makes the equivalent circuit model more in line with the actual situation and provides more accurate circuit model support for subsequent time constant calculations. At the same time, by combining the measured rotor impedance value and the calculated rotor frequency value, the time constant of the motor rotor can be obtained more accurately, providing key parameters for high-performance control of the motor.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the time constant of an asynchronous motor rotor based on impedance value online, characterized in that: The method comprises the following steps: Before the test, the test instrument is frequency-self-calibrated, and the characteristic impedance value of the asynchronous motor rotor is input into the LCR characteristic test circuit; the test instrument performs frequency self-calibration through the built-in automatic calibration circuit and the voltage phase oscilloscope device; When performing calibration, firstly, the instrument is powered on and initialized, and the frequency f set by the instrument is input into the LCR characteristic test circuit, and the working frequency of the LCR characteristic test circuit is adjusted accordingly; at the same time, the test instrument is adjusted to the phase measurement mode, and then the test instrument inputs the capacitance value, loss characteristics and equivalent series resistance parameters into the capacitor; the calibration is completed by comparing and measuring with a standard capacitor of known accuracy until the measurement result of the test instrument is consistent with the standard value, and the asynchronous motor rotor is tested with the LCR characteristic test circuit, and the voltage and current value data are obtained through the test of the LCR characteristic test circuit; The voltage and current data are processed to obtain the phase difference and amplitude attenuation of the corresponding sine wave; the corresponding phase difference and amplitude attenuation are obtained by comparing the impedance value of the asynchronous motor rotor obtained by actual measurement and the frequency value of the test instrument after self-calibration with the standard LCR value table; The equivalent impedance value of the asynchronous motor rotor is calculated; and after the calculation, the equivalent circuit of the asynchronous motor is calculated in combination with the geometric structure characteristics of the asynchronous motor; according to the equivalent circuit of the asynchronous motor, the time constant τ is obtained from the impedance formula of the RL and RC circuits associated with the asynchronous motor.

2. A method for measuring the time constant of an asynchronous motor rotor based on impedance value online according to claim 1, characterized in that: When performing frequency self-calibration, a voltage phase oscilloscope is used to measure the phase difference of the measured frequency before and after correction. The frequency obtained by the test instrument and the capacitance parameter value of the measuring capacitor are input into the automatic calibration circuit to obtain the corrected phase difference and frequency, thereby obtaining the corrected sinusoidal wave phase difference.

3. The method for measuring the time constant of an asynchronous motor rotor based on impedance value online according to claim 1, characterized in that: The method for testing the asynchronous motor rotor by the LCR characteristic test circuit is as follows: The voltage phase difference of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The current phase difference between two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the phase difference of the impedance value is calculated through the automatic calibration circuit; The amplitude attenuation of two phases of the three-phase stator winding of the motor is measured. After completing the frequency self-calibration and inputting the parameters of the two-phase winding of the motor, the amplitude attenuation of the impedance value is calculated through the automatic calibration circuit, where the amplitude attenuation refers to the ratio of the impedance value to the standard impedance value; By comparing the phase difference of the impedance value, the amplitude attenuation of the impedance value and the equivalent frequency of the motor stator, the resistance value of the motor stator coil and the equivalent reactance of the stator coil are obtained under the corresponding impedance value; The stator winding equivalent impedance is calculated by the stator coil resistance value and the stator coil equivalent reactance; the motor winding self-inductance is calculated by the stator coil resistance value and the stator coil equivalent reactance, combined with the winding turns and the stator wire gauge geometric dimensions; the motor stator equivalent internal resistance impedance is calculated by the stator coil equivalent inductance and the motor winding self-inductance; the stator coil equivalent inductance is calculated by the motor stator equivalent internal resistance impedance value; the motor stator equivalent leakage inductance is calculated based on the motor stator coil equivalent inductance and the motor winding self-inductance, combined with the motor stator winding turns and the stator wire diameter geometric dimensions; the equivalent mutual inductance between the three-phase windings of the motor is calculated by the motor stator equivalent leakage inductance, and the voltage and current values ​​of the asynchronous motor are tested by the equivalent mutual inductance.

4. The method for measuring the time constant of an asynchronous motor rotor based on impedance value online according to claim 1, characterized in that: On the test instrument, the R, L, and C values ​​of the standard asynchronous motor are used as a reference sample of the motor to be tested. At the same time, the corresponding impedance value is obtained by comparing it with the standard LCR value table as an actual value of the test motor. When the rotor impedance values ​​R, L, and C meet the standards, the test motor can be represented by the R, L, and C values, thereby calculating the equivalent impedance value of the asynchronous motor rotor to be tested.

5. The method for measuring the time constant of an asynchronous motor rotor based on impedance value online according to claim 1, characterized in that: The equivalent circuit of the asynchronous motor is to use the two-phase lines of the motor as the flow channels of the rotor current and voltage, and the motor rotor and the stator coil form a series-parallel impedance network; the impedance values ​​of the motor rotor and the motor coil are equivalent to an LC series oscillation circuit, and the impedance value of the stator coil is equivalent to a series resistor-capacitor oscillation circuit; the time constant of the motor rotor is obtained by combining the measured rotor impedance value and the calculated rotor frequency value.

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