79 results about "Rotor time constant" patented technology

A method and apparatus to provide continuous and reliable rotor temperature estimates for line-connected induction motors during steady-state and / or dynamic motor operations. Rotor temperature is calculated from voltage and current measurements without any temperature or speed sensors. First, complex space vectors are synthesized from voltage and current measurements. Second, the instantaneous rotor speed is detected by calculating the rotational speed of a single rotor slot harmonic component with respect to the rotational speed of the fundamental frequency component. Third, the positive sequence fundamental frequency components are extracted from complex space vectors. Fourth, the rotor time constant is estimated in a model-reference adaptive system based on a dynamic induction motor equivalent circuit model. Finally, the rotor temperature is calculated according to the linear relationship between the rotor temperature and the estimated rotor time constant. Real-time induction motor thermal protection is achieved through this continuous tracking of the rotor temperature.

The invention discloses a linear induction motor constant slip frequency vector control method. The method comprises the steps as follows: detecting the rotation speed of a rotor of a linear induction motor, calculating the magnetic chain space position angle Theta<s> of the rotor according to the given slip frequency electric angular velocity Wsl; calculating the excitation voltage Usm and torque voltage Ust according to the magnetic chain space position angle Theta<s> and the given slip frequency electric angular velocity Wsl and combining a given torque T and a rotor time constant Tr; generating modulation pulses by pulse-modulating the excitation voltage Usm and the torque voltage Ust and the DC voltage output by the power supply; converting the DC voltage output by the power supply into the AC electricity so as to be supplied to the linear induction motor according to the modulation pulse. The invention also discloses a linear induction motor constant slip frequency vector control system. The linear induction motor constant slip frequency vector control method and system of the invention can realize the constant slip frequency vector control of the linear induction motor.

A method and apparatus to provide continuous and reliable rotor temperature estimates for line-connected induction motors during steady-state and / or dynamic motor operations. Rotor temperature is calculated from voltage and current measurements without any temperature or speed sensors. First, complex space vectors are synthesized from voltage and current measurements. Second, the instantaneous rotor speed is detected by calculating the rotational speed of a single rotor slot harmonic component with respect to the rotational speed of the fundamental frequency component. Third, the positive sequence fundamental frequency components are extracted from complex space vectors. Fourth, the rotor time constant is estimated in a model-reference adaptive system based on a dynamic induction motor equivalent circuit model. Finally, the rotor temperature is calculated according to the linear relationship between the rotor temperature and the estimated rotor time constant. Real-time induction motor thermal protection is achieved through this continuous tracking of the rotor temperature.

The invention discloses a motor parameter detection method and a motor parameter detection apparatus. The motor parameter detection method comprises the following steps that: open circuit is carried out on a phase winding of the motor; a motor stator resistance detection step is realized; that is, a pulse direct current voltage is applied between other two phases of the motor and the motor stator resistance is detected; and a motor rotor time constant detection step is realized; that is, a stepped direct current voltage is applied between the other two phases of the motor; different time and current values of the time are measured as well as a current-time linear equation is obtained; a current value at zero time and the motor stator resistance are introduced into the current-time linear equation to obtain an approximate value of the rotor time constant. According to the invention, a motor parameter detection method and a motor parameter detection apparatus are provided on the condition that an induction machine rotor is in a static state; and high accuracy of motor parameter detection can be realized only by successively applying currents or voltages at different frequencies between two phases of the motor as well as reducing voltage errors and an influence of a sink effect.

The invention discloses an online calibrating method and device for a rotor time constant of an asynchronous motor, and an asynchronous motor driving control system. The calibrating method comprises the following steps: measuring the angular velocity of a rotor, the current of a stator and the voltage of the stator; calculating a given reactive power and an actual reactive power of a motor based on a formula; making a comparison between the given reactive power and the calculated actual reactive power served as a feedback reactive power, so as to generate a deviation signal; adjusting the deviation signal through a proportional-integral controller in order to output an adjusting value of a rotor time constant; calibrating the setting value of the rotor time constant based on the adjusting value, thus meeting the setting value of the rotor time constant in line with the actual value. The calibrating method is simple, and is low in requirement on hardware.

The invention relates to a method for measuring the time constant of an asynchronous motor rotor on line. The method comprises the following steps of: giving initial parameters in advance; obtaining induced electromotive force of a rotor flux linkage on a stator winding; processing the induced electromotive force of the rotor flux linkage on the stator winding to obtain a value of synchronous angular speed; obtaining a value of slip frequency from the synchronous angular speed; and obtaining a value of time constant of the rotor according to a slip frequency formula. The invention further relates to a device for implementing the method for measuring the time constant of the asynchronous motor rotor on line. The method and device for measuring the time constant of the asynchronous motor rotor on line, disclosed by the invention, have the beneficial effects of simple algorithm, small occupying area on CPU (Central Processing Unit) resources and higher precision of measured time constant of the rotor.

The invention discloses a method for identifying the stator resistance and the rotor resistance online in an asynchronous motor speed sensorless system. According to the method, a controller constructs an adaptive observer using direct or indirect field-oriented control. First, the given signal of the motor rotor flux amplitude is a trapezoidal wave (including DC component), and the given signal can be composed of a flat given part and a slope given part; and then, the observer self-adapts to the stator resistance and speed when the actual rotor flux amplitude keeps up with the flat given part, and the observer self-adapts to the rotor time constant and speed when the actual rotor flux amplitude tracks the slope given part. The method is of high universality. The problem that simultaneous identification of the stator resistance and the rotor resistance in a speed sensorless system is difficult is overcome. The accuracy of speed identification is improved. The control performance of rotors in a full-speed range is improved.

A method for identifying a traction induction motor parameter of a high-speed train is disclosed. The method comprises the steps of: running two magnetic flux linkage observers synchronously and calibrating main model parameters such as a magnetic inductance and a rotor time constant set in a controller respectively in high-speed and low-speed running regions of the traction induction motor by utilizing respective advantages of a voltage type observer and a current type observer to enable the traction induction motor to be in a full-speed running range and enable the observation effects of the two magnetic flux linkage observers to be optimal. The method for identifying the traction induction motor parameter of the high-speed train can overcome the negative influence such as temperature rise of the motor and the excitation characteristic change, and realizes high-performance traction control.

The invention discloses an induction motor parameter identification method. The method comprises steps of S10, identifying motor stator phase resistance Rs; S2, identifying motor stator phase leakage inductance Lssigma; S30, identifying motor stator / rotor equivalent excitation inductance Lm, equivalent stator self-inductance Ls and equivalent rotor self-inductance Lr; S40, detecting a motor rotor time constant initial value Tr0; S50, calculating a rotor resistor initial value Rr0; S60, calculating a rotor resistor correction value Rr; and S70, calculating a motor rotor time constant correction value Tr. Through the method, not any equipment is required to add such as a three-phase voltage regulator and a three-phase power meter, and online induction motor parameter identification vector control is carried out. The method is advantaged in that the method is simple and easy for operation, and quite high accuracy is realized.

The invention discloses a method for measuring a time constant of a rotor of an asynchronous machine. An inverter or a servo driver connected with the asynchronous machine comprises an inverter bridge; when the inverter bridge is in an inversion state, stator current is given to be Is0 and the working time is given to be tm under the condition that the stator current and voltage are zero, and the magnetizing current reaches the maximum Im0 which is recorded; after excitation is carried out for tm, the inverter bridge is immediately in a closed state, and the stator current is zero after a period of time; after a stator is cut off, the inverter bridge is set to be in a three-phase short circuit state, the stator current Is is gradually raised from zero, when the Is reaches the maximum Isz, the Isz is recorded, and the current of the asynchronous machine is waited to be subjected to excitation attenuation to reach zero; and the Isz is compared with IszO, and when the compared difference is in a set error range, the time constant of the rotor of the asynchronous machine is working time tm1. By the method, calculation can be simplified and measurement errors can be effectively reduced.

The invention provides an asynchronous motor rotor time constant on-line identification system. The system comprises a decomposition angle calculation unit, a feedforward voltage decomposition unit, a feedback voltage sampling unit, a feedback voltage decomposition unit and a time constant calculation unit, wherein the decomposition angle calculation unit is used for acquiring a decomposition angle according to exciting current and torque current; the feedforward voltage decomposition unit is used for performing decomposition calculation on the feedforward voltage by using the decomposition angle; the feedback voltage sampling unit is used for sampling the output end of a controlled motor to acquire the feedback voltage; the feedback voltage decomposition unit is used for performing decomposition calculation on the feedback voltage by using the decomposition angle; and the time constant calculation unit is used for calculating and updating the rotor time constant according to the decomposition results of the feedforward voltage and the feedback voltage. The system realizes on-line real-time identification of the rotor time constant through voltage decomposition, and the process is not influenced by the change of stator resistance.

The invention provides a method for determining an optimal time constant of a three-phase asynchronous motor rotor. The method includes the step s11 of setting a rotor time constant reference value tau[r]_ref, the step s12 of selecting an excitation current value id and a corresponding torque current value iq, wherein at the moment, iq=id; the step s13 of calculating the slip ratio Ws=iq / (tau[r]_ref*id) at the moment, the step s14 of conducting vector control, the step s15 of judging whether the torque progressively increases or not, the step s16 of enabling tau[r]_ref to be equal to tau[r]_ref plus delta tau[r] if the torque progressively increases, and executing the step s13 again, wherein delta tau[r] is the increment; the step s17 of determining the optimal time constant tau[r] which is equal to tau[r]_ref if the torque does not progressively increase. According to the method, the defects in the prior art are overcome, the executing efficiency of software is improved, the characteristics of parameter dynamic changes is also taken into consideration, and the method can be easily achieved in terms of projects under the condition that efficient output of a system is ensured.

A system and method for determining a rotor time constant of an AC induction machine is disclosed. During operation of the induction motor, a flux signal is injected into a rotor flux command so as to generate a time-variant rotor flux. A voltage-current flux observer determines amplitudes of rotor flux variations resulting from the time-variant rotor flux, with the amplitudes of the rotor flux variations comprising an amplitude of a rotor flux variation based on a current model of the voltage-current flux observer and an amplitude of a rotor flux variation based on a combined voltage-current model of the voltage-current flux observer. A rotor time constant of the induction motor is then estimated based on the determined amplitudes of the rotor flux variations.

The invention discloses a torque calibration method for an AC induction motor of an electric vehicle. The torque calibration method comprises the following steps: when the AC induction motor of the electric vehicle controls the electric vehicle, adopting the torque computational formula to convert an expected torque T<o>e into an expected torque current I<0>g, and realizing the torque control according to the directional vector control algorithm of the rotor field; before the torque calibration is carried out, adjusting the time constant parameter Tt and the mutual induction parameter Lm of the motor rotor by comparing the error tendency between an expected torque curve and an actual torque curve, so as to enable the actual torque to be close to the expected torque and to realize the actual torque calibration. According to the torque calibration method, on the basis of the conventional vector control algorithm, by the calibration of the time constant Tt and the mutual induction Lm of the motor rotor based on the conventional motor parameters in sequence, the actual torque calibration is completed; in the entire calibration process, a control motor is smooth and accurate in torque output, the requirement on torque control accuracy of a driving system of the electric vehicle can be met, and cumbersome torque calibration by adopting the table look-at method is further avoided.

A method for identifying the discrete instantaneous angular speed of electromechanical systems in which electrical rotating machinery is used and in which at least one electrical signal is measured during an operation of the electromechanical system. The method includes measuring analog stator current signals and analog stator voltage signals for at least one phase A, B, C, converting the measurements into a digital discrete form, transmitting the digital discrete signals to a computer device wherein data analysis is performed in a processor unit on the basis of a simplified mathematical model of the dynamics of the motor or generator. During the data analysis an average rotor time constant is calculated, an average supply frequency value is identified, an average angular speed is obtained, and an instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals is determined. The discrete instantaneous angular speed is identified by combining the average supply frequency value, the instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals, the average rotor time constant, and a number of pole pairs of the electric motor, given by the user. The result of combining the data is stored in a memory of the processor unit.

The invention discloses an asynchronous motor parameter online correction method based on a rotor flux observer. The method is characterized by comprising the following steps: getting an accurate counter electromotive force e through a high-order current sliding-mode observer according to a motor stator voltage vector v, a stator current vector i and a rotor electrical angular velocity omega(r) under a two-phase static coordinate system (alpha-beta) obtained through acquisition and operation; setting up an asynchronous motor state space expression based on the relationship between the counter electromotive force and the rotor flux; constructing a rotor flux sliding-mode observer according to the space expression to observe a rotor flux vector phi(r); getting the calculated value phi<hat>(ri) of the rotor flux vector according to a current flux model; and further getting the phase difference sinusoidal quantity sin(delta theta) and the amplitude difference delta|phi(r)|; and using the phase difference sinusoidal quantity sin(delta theta) to correct a given rotor resistance R<hat>(r) in the system, and using the amplitude difference delta|phi(r)| to correct a given excitation inductance L<hat>(m) in the system. The integral problem caused by flux is overcome. Moreover, there is no transient flux problem, an accurate rotor time constant can be obtained, and online identification of excitation inductance is realized.

The invention provides a power calculation based slip estimation system. The power calculation based slip estimation system comprises a current sampling unit, a current conversion unit, a current regulation unit and a slip calculation unit, wherein the current sampling unit is used for sampling three-phase current of an asynchronous motor, the current conversion unit is used for obtaining feedback current D-axis component and Q-axis component, the current regulation unit is used for obtaining D-axis stator voltage and Q-axis stator voltage, and the slip calculation unit is used for obtaining slip according to the D-axis stator voltage, the Q-axis stator voltage, the feedback current D-axis component, the Q-axis component and a rotor time constant. The invention further provides a corresponding method. The system and the method have the advantages that the slip is estimated according to the ratio of active power to reactive power to enable rotor field orientation error caused by the rotor time constant Tr during speed regulation to become smaller, so that rotor field orientation effect of the asynchronous motor is improved effectively, and torque control precision is improved.

The invention discloses an asynchronous motor rotor time constant online recognition method based on an improved reactive power model. According to the invention, a feed-forward for a motor stator frequency, subjected to the amplitude limiting treatment, is introduced in a conventional reactive power model. The method comprises the steps of sampling and obtaining the actual reactive power Q of a motor by an actual reactive power calculation unit; obtaining the stator inductance Ls of the motor by a stator inductance calculation unit; obtaining the reference value Isdref of the d-axis component of the stator current of the motor by an excitation controller; obtaining the theoretical reactive power Qref of the motor by a theoretical reactive power calculation unit; obtaining the reactive power deviation delta Q by a deviation calculation unit; obtaining a feed-forward value omega Q by an amplitude limiting unit; obtaining a correction value delta Tr for the rotor time constant Tr of the motor by a proportional-integral controller; and calculating the rotor time constant Tr of the motor by an arithmetic operation unit. The above method can be applied in the four-quadrant operation scenarios for the motor. By means of the method, the proportional-integral controller of the reactive power model is easy to set. At the same time, the similar rotor time constant convergence dynamic process can be obtained during the high-speed and low-speed operation process of the motor.

The invention relates to a method for measuring a parameter of an asynchronous motor. The method comprises the following steps of: presetting a reference exciting current and a reference torque current, setting a first rotor time constant and a second rotor time constant; obtaining a first slip frequency and a second slip frequency which respectively correspond to the first rotor time constant and the second rotor time constant by using a slip frequency formula; respectively obtaining a first output torque and a second output torque which correspond to the first rotor time constant and the second rotor time constant; and respectively substituting the first output torque, the second output torque, the first slip frequency and the second slip frequency into a torque formula to work out an actual rotor time constant, wherein an output torque in the torque formula is a product of a first coefficient and an expression including the rotor time constants and the slip frequency product. The invention also relates to a method for realizing the device. The method and device for measuring the parameter of the asynchronous motor have the beneficial effect that the measured rotor time constant is high in accuracy.

The invention discloses a method for automatically identifying asynchronous motor rotor time constant by a frequency converter. The method comprises following steps: a, calculating the probable value tau of the rotor time constant; b, selecting at least five numbers including tau[1], tau[2] and the like...tau[n] between 0.1 tau to 3 tau as primary screening rotor time constants; c, driving the asynchronous motor to rotate by the frequency converter according to the selected first primary screening rotor time constant tau[1], and obtaining a first primary screening speed deviation accumulated value after the asynchronous motor finishing the operation process; d, obtaining a primary second screening speed deviation accumulated value based on a similar way of the step c; e, performing the same process until obtaining the n-th primary screening speed deviation accumulated value by the frequency converter; f, comparing the obtained n primary screening speed deviation accumulated values, and using the primary screening rotor time constant corresponding to the minimum primary screening speed deviation accumulated value as an identification result. Through adoption of the method, neither debugging performed by professional staff nor additional hardware equipment is needed, and the method has good identification effect.

The invention discloses an asynchronous motor rotor time constant adjusting method. The asynchronous motor rotor time constant adjusting method comprises the steps: judging whether the rated field current is accurate; commanding the motor to operate with high speed under zero load, recording and extracting several practical modulation coefficients for a frequency converter in different rotating speed stages, obtaining the due theoretical modulation coefficient in the normal situation through calculation, comparing the values of the two modulation coefficients and adjusting the excitation current value set by the system until the two modulation coefficients for several different speed points become approximate; and on the basis of determining that the excitation current value set by the system is approximate to the rated excitation current value, commanding the motor to run with moderate load or heavy load in the high speed stage, recording and extracting several practical modulation coefficients for the frequency converter in different rotating speed stages, calculating the modulation coefficients under the corresponding rotating speed at the same time, and comparing the values of the two coefficients at several different speed points. The asynchronous motor rotor time constant adjusting method is high in efficiency and low in consumed time, and can be quickly mastered and applied to field debugging to enable the motor rotor time constant to be approximate to a true value so as to guarantee the motor to work in the optimal state.

The invention discloses a method for verifying an induction motor rotor time constant based on magnetic field orientation accuracy. The implementation steps are as follows: firstly, in an indirect rotor magnetic field orientation controller a given torque current and exciting current are ensured to be equal; secondly, a motor drags a direct current generator load to rotate in an operation mode with given torque; then, a rotor time constant value in the controller is constantly changed, and corresponding motor steady state rotation speed values are recorded; and finally, when the steady state rotation speed of the motor corresponding to a certain rotor time constant value reaches the highest is observed, and the rotor time constant value is an accurate value. The method can automatically run and complete verification, and does not need people to judge an experiment phenomenon, and a result is fairly accurate.

The invention relates to an asynchronous motor vector control rotor winding temperature on-line monitoring method comprising the following steps: 1) carrying out rotor magnetic field accurate orientation based on load angle compensation correction according to current and voltage signals under d-q synchronous rotation coordinates; 2) estimating a rotor time constant on the basis of accurate orientation of a rotor magnetic field and correction and compensation of slip frequency; 3) estimating the rotor time constant value in a short time when the motor is started for the first time to reach stable rotating speed, and obtaining a motor cooling medium detection temperature; 4) estimating the current rotor time constant value in the normal working process of the motor, obtaining the motor cooling medium detection temperature corresponding to the moment, and estimating the rotor winding temperature in real time; and 5) obtaining the temperature rise of the rotor winding. Compared with the methods in the prior art, the method has the advantages that the rotor magnetic field orientation is accurate, the robustness is good, the temperature monitoring of the rotor winding is conveniently realized, and the method is not influenced by the characteristics of hardware equipment, the electromagnetic interference of a working environment and the like.

The invention discloses a low switching frequency operation control method for a new-type high power asynchronous motor. The method comprises the steps of signal collection, flux linkage observation, flux linkage outer ring control and rotation speed outer ring control, and prediction current inner ring control. An inverter direct current side voltage and a motor stator current are obtained through utilization of collection signals; rotor flux linkage is obtained through calculation; flux linkage closed loop is realized to obtain a d-axis current reference value; the rotation speed of an asynchronous motor is obtained through utilization of the collection signals; rotation speed closed loop is realized to obtain a q-axis current reference value; and a switching signal is directly generated through the prediction current inner ring control, thereby realizing the control of the inverter over the motor. According to the method, a boundary is appointed to be an oval with a long d-axis and a short q-axis in a dq synchronous coordinate system, so the switching frequency operation control with a relatively low linear modulation mode is realized; the switching frequency is reduced by releasing relatively high errors to a d-axis; moreover, the problem of increasing an additional harmonic current is avoided through utilization of the feature that a motor rotor time constant is relatively high; and the motor system operation reliability and high efficiency under the low switching frequency are improved.

The invention relates to a self-setting method in a vector control system of an asynchronous motor, which mainly adopts rotor time constant self testing under the magnetic circuit saturation. The self-setting method aims to achieve the effect of controlling the performance in a speed control system of the vector control asynchronous motor through the rotor time constant self testing under the magnetic circuit saturation. The rotor time constant self testing is carried out through a voltage type inverter. When direct current voltage is excited and added, the current of a rotor circuit of the asynchronous motor is zero, and the current of a stator is a steady-state current value Id. If a transient process occurs in the current of the stator, the current initial value of the rotor circuit is not zero. Therefore, the zero current of a rotor can be determined through the characteristic, so that a rotor time constant is obtained by adopting a least square method. The self-tested rotor time constant particularly considers the measurement and the acquisition of the rotor time constant under the magnetic circuit saturation and the dead-time compensation, so that the performance of the vector control system of the asynchronous motor is improved.

The invention provides a rotor time constant online identifying system based on a flux estimator. The system comprises a sampling unit, a magnetic field angle calculating unit, a first current converting unit, a second current converting unit, a controlled quantity calculating unit and a time constant calculating unit, wherein the sampling unit is used for sampling the three-phase voltage and three-phase current of the output end of an asynchronous motor; the magnetic field angle calculating unit is used for calculating an estimated magnetic field angle; the first current converting unit is used for acquiring practical exciting current and practical torque current; the second current converting unit is used for acquiring control exciting current and control torque current; the controlled quantity calculating unit is used for calculating a controlled quantity; and the time constant calculating unit is used for calculating and updating a rotor time constant. The invention further discloses a corresponding method. According to the system and method, the rotor time constant is calculated by a relation between estimated magnetic field angle decomposing current and control angle decomposing current, so that the torque control accuracy is increased.

The invention discloses a method for calibrating key parameters of an asynchronous motor of an electric vehicle. The method comprises the steps: on a motor twin-trawling table, for different rotatingspeeds n and different torque instructions Te* under a current rotating speed, calibrating a d-axis given current value, a q-axis given current value and a rotor time constant value of the asynchronous motor of the electric vehicle by adopting a Proximal Policy Optimization (PPO) algorithm; storing a calibrated result in a motor controller in a form of a table so that the asynchronous motor of theelectric vehicle queries and uses the parameter can be inquired during actual operation. According to the method, the rotor time constant of the asynchronous motor of the electric vehicle is calibrated, and the d-axis given current and the q-axis given current of the motor are also calibrated; meanwhile, the calibrated parameters can enable the motor to have the maximum torque-current ratio characteristic under any rotating speed n and torque instruction Te*.

The invention relates to induction motor feedback type indirect vector control system and a control method thereof.The control system includes a speed controller, an Lm parameter division arithmetic unit, an addition operation controller, an integral controller, a division operation controller, a Tr parameter division arithmetic unit, a high cut-off frequency low-pass filter, a three-phase static / two-phase rotating coordinate transformation circuit, a two-phase rotating / three-phase static coordinate transformation circuit, a current hysteresis tracking PWM signal generator, a voltage source inverter and an induction motor.Compared with the prior art, the induction motor feedback type indirect vector control system needs an Lm parameter multiplication arithmetic unit and a rotor time constant Tr inertial link circuit no longer, and the high cut-off frequency low-pass filter is added, so that the problem that the rotor flux linkage vector amplitude of a traditional control system monotonically rises, dynamic response is slow and the induction motor cannot perform constant acceleration and quick starting at an accelerating-starting stage, and the dynamic response of the induction motor feedback type indirect vector control system is improved.

The invention discloses an asynchronous motor rotor resistance and excitation inductance decoupling correction method. The method comprises the steps of obtaining accurate counter electromotive force e via a high-order sliding-mode observer according to the acquired and calculated motor stator voltage vector V, stator current vector i and rotor electrical angular velocity omega r under a two-phase static coordinate system alpha beta, and establishing an asynchronous motor state space expression according to the relation between the counter electromotive force and the rotor flux, thus realizing accurate observation of a rotor flux vector phi r; obtaining a rotor flux vector calculation value which is defined in the specification according to a current flux model, then obtaining a phase difference delta theta and an amplitude difference which is defined in the specification, analyzing and deducing a correlation function of a parameter error and a flux error to obtain a weighting coefficient, correcting given rotor resistance which is defined in the specification in the system by using a decoupling correction function I which is defined in the specification, and correcting given excitation inductance in the system by using a decoupling correction function II which is defined in the specification. The method does not have the flux transient problem while solving the problem of integration of flux acquisition, and can obtain an accurate rotor time constant and realize on-line identification of the excitation inductance.

A method for estimating the rotor time constant (τr) of an induction machine when the stator resistance (Rs) and rotor resistance (Rr) of the induction machine are known. The method comprises the steps of feeding a DC current to the stator of the induction machine, injecting a sine-wave current component into the stator of the induction machine, the current having an amplitude (isc) and an angular frequency (ωc), measuring the voltage component (uscd) of the stator voltage of the induction machine in the same direction and with the same angular frequency as the injected current, and calculating the rotor time constant using equationτr=1ωc⁢uscd-Rs⁢isc(Rs+RR)⁢isc-uscd.