阅读说明：本技术 一种基于电流矢量模长的异步电机故障的判定方法 (Asynchronous motor fault determination method based on current vector modular length ) 是由 徐国卿 陈梦南 于 2021-07-26 设计创作，主要内容包括：本发明公开了一种诊断异步电机故障的方法,将电机定子三相电流变换到三相同步速旋转的dq轴上,电流dq分量以直流为主,定子电流综合矢量长度也为直流。定子匝间短路、转子断条、转子偏心、轴承损坏等故障体现在dq电流和矢量长度的脉动变化。根据脉动频率,很容易判别电机故障。由于电机通常由逆变器供电,电机定子上的三相电流有很多谐波含量,电机故障后,三相交流电流上既有逆变器或变频器供电产生得谐波,也有故障后产生的谐波,很不容易把这些谐波区分。本发明提供的方法,克服了这个缺点,具有检测方便、算法简单的优点；本发明使用了同步旋转坐标系dq0下的电流分量和综合电流矢量长I-(l)为特征量,使得对异步电机故障诊断的结果更加准确。(The invention discloses a method for diagnosing faults of an asynchronous motor, which is characterized in that three-phase currents of a stator of the motor are converted to dq axes rotating at three same step speeds, the current dq components are mainly direct currents, and the comprehensive vector length of the stator current is also direct currents. Faults such as stator turn-to-turn short circuit, rotor broken bar, rotor eccentricity and bearing damage are reflected in the pulse change of dq current and vector length. According to the pulse frequency, the motor fault can be easily judged. Because the motor is usually powered by an inverter, the three-phase current on the stator of the motor has a plurality of harmonic contents, and after the motor fails, the existing inverter or transformer is arranged on the three-phase alternating currentThe harmonic waves generated by the power supply of the frequency device and the harmonic waves generated after the fault are generated, and the harmonic waves are not easy to distinguish. The method provided by the invention overcomes the defect and has the advantages of convenient detection and simple algorithm; the invention uses the current component and the integrated current vector length I under the synchronous rotating coordinate system dq0 l The method is a characteristic quantity, so that the fault diagnosis result of the asynchronous motor is more accurate.)

1. A method for judging the fault of an asynchronous motor based on the current vector modular length is characterized by comprising the following operation steps:

(1) obtaining three-phase stator current i of asynchronous motor to be fault detected_sa、i_sb、i_sc；

(2) Will i_sa、i_sb、i_scConversion into a current component i in a synchronously rotating coordinate system dq0_sd、i_sq；

(3) To i_sd、i_sqCarrying out spectrum analysis;

(4) will i_sa、i_sb、i_scCurrent component i transformed into two-phase stationary α β 0 coordinate system_sα、i_sβ；

(5) Calculate the sum of_sα、i_sβThe formed comprehensive current vector has a modular length;

(6) carrying out frequency spectrum analysis on the current vector modular length;

(7) and judging the fault form of the asynchronous motor to be monitored according to the result of the frequency spectrum analysis.

2. The method for determining the fault of the asynchronous motor based on the current vector mode length according to the claim 1, wherein the step (2) comprises the following specific operation steps:

i in the synchronously rotating dq0 coordinate system_sd、i_sqThe following equation was used to obtain:

wherein theta is_eIs the synchronous electrical angle.

3. The method for determining the fault of the asynchronous motor based on the current vector mode length according to the claim 1, wherein the step (3) comprises the following specific operation steps:

performing discrete Fourier transform on the direct current component under the synchronous rotating coordinate system, wherein the calculation formula is as follows:

wherein: i is_dqIn the current amount in the frequency domain, N is the sequence length of the sampling current, N is the ordinal number on the time axis, and k is the ordinal number on the frequency axis.

4. The method for judging the fault of the asynchronous motor based on the current vector mode length is characterized in that the step (4) specifically comprises the following operation steps:

i in two-phase stationary alpha beta 0 coordinate system_sα、i_sβObtained by the following formula：

5. The method for determining the fault of the asynchronous motor based on the current vector mode length as claimed in claim 1, wherein the step (5) comprises the following specific operation steps:

the calculation of the modulo length of the current vector is:

wherein: i_lAnd | is the current vector modulo length.

6. The method for determining the fault of the asynchronous motor based on the current vector mode length as claimed in claim 1, wherein the step (6) comprises the following specific operation steps:

performing discrete Fourier transform on the current vector mode length, wherein the calculation formula is as follows:

wherein: i is_LIs the current vector modulo length in the frequency domain, and N is the length of the sampled current.

7. The method for judging the fault of the asynchronous motor based on the current vector mode length is characterized in that the step (7) specifically comprises the following operation steps:

when the component of the stator current under the synchronous rotation coordinate axis is direct current and has no obvious pulse change, and the vector length of the stator current is a fixed value, the motor has no fault;

when the component of the stator current under the synchronous rotation coordinate axis has the pulsation 2 times of the fundamental frequency and the vector length of the stator current also has the pulsation 2 times of the fundamental frequency, the motor has turn-to-turn short circuit fault;

when stator currents are synchronizedComponent in the axis of rotation is present at 2ksf₁The pulsation of the frequency and the vector length of the stator current also exist 2ksf₁When the frequency is in pulsation, the motor has a rotor broken bar fault;

when component of stator current under synchronous rotation coordinate axis exists kf_outerThe pulsation of the frequency and the vector length of the stator current also exist kf_outerWhen the frequency is in pulsation, the motor has a bearing outer rail fault;

when component of stator current under synchronous rotation coordinate axis exists kf_innerThe pulsation of the frequency and the vector length of the stator current also exist kf_innerWhen the frequency pulsates, the motor has a track fault in the bearing;

when component of stator current under synchronous rotation coordinate axis exists kf_ballThe pulsation of the frequency and the vector length of the stator current also exist kf_ballWhen the frequency pulsates, the motor has a bearing ball failure;

when component of stator current under synchronous rotation coordinate axis exists kf_rThe pulsation of the frequency and the vector length of the stator current also exist kf_rWhen the frequency is in pulsation, the motor has mixed eccentric faults;

where k is an integer and s is the slip f₁，f_outer、f_inner、f_ballFundamental frequency, characteristic frequency f of failure of the outer track, inner track and ball of the bearing_rIs the rotational frequency of the motor.

Technical Field

The invention relates to the technical field of motor state monitoring, in particular to a method for motor fault diagnosis, which is a fault diagnosis method based on dq-axis direct-current components and current comprehensive vectors.

Background

As a transmission machine, the asynchronous motor is widely applied to the industrial and national defense fields of power plants, steel plants, naval vessels and the like, and the safe operation of the asynchronous motor is very important. The asynchronous motor is generally in a long-time continuous operation state, and the working environment is severe, so that the fault is inevitable. The failure of an asynchronous motor not only damages the machine body, but also affects the whole transmission system. If the device cannot be found and overhauled in time, accidents and shutdown can be caused, economic loss is caused, and even casualties are caused.

At present, the mode of regular maintenance (such as half-year minor repair and one-year major repair) is usually adopted to avoid the accident shutdown of the asynchronous motor. However, due to the existence of the overhaul period, the asynchronous motor may have faults and accidents within the overhaul period, and the "regular overhaul" mode cannot be used for the fault, which is called "failure inspection" in the engineering field; on the other hand, when the maintenance period comes, the asynchronous motor may not have a fault, and even the state is good, and the "regular maintenance" mode will cause the so-called "over-inspection" on the engineering site. "failure" will result in an asynchronous motor failure, shutdown, with self-evident losses. "over-inspection" will result in unnecessary maintenance costs, down time. The dismounting of the casing only once requires tens of thousands of yuan of money, no mention of disassembling the asynchronous motor, overhauling the stator and rotor, etc. Thus, "over-testing" would result in significant waste.

The emergence, development and application of asynchronous motor fault detection and diagnosis technology has triggered a revolution of asynchronous motor maintenance system, and the traditional after-repair and regular maintenance mode is gradually changed into a predicted maintenance mode.

Statistics shows that the faults of the asynchronous motor mainly comprise stator winding turn-to-turn short circuit faults, rotor broken bar faults and bearing faults, the occurrence probability of the faults is about 6%, 30%, 10% and 40%, and the faults are progressive and become accidents through the occurrence and development stages.

A great deal of research and application also appear aiming at the faults of the motor dragging system, such as faults of a rolling bearing, a gear, a shaft system and the like. In recent years, with the development of computer simulation technology, documents for fault diagnosis theoretical modeling, simulation analysis and the like for broken bars, eccentricity, bearings and the like have been increasing. The application range is gradually expanded to the fields of variable frequency, direct current and alternating current servo motors and the like.

No matter what kind of mode obtains the motor stator electric signal, its frequency component all takes power supply frequency as the main, and real fault signal component is very weak, therefore how to extract weak fault signal, rejects useless power supply frequency component is asynchronous machine fault detection and diagnostic method can obtain the basis that extensively uses.

For amplitude modulation of electrical signals, the most basic analysis approach is to use a sideband analysis method of amplitude spectrum or refined spectrum. Due to the existence of instability of the sideband, the Hilbert transform can be adopted to obtain the envelope spectrum and the instantaneous frequency spectrum of the electric signal for analysis. The envelope spectrum can remove the main power frequency with larger amplitude in the electric signal and highlight the fault characteristic frequency, and the expression form of the frequency spectrum is the same as that of the conventional vibration signal frequency spectrum, so that the analysis and the comparison are convenient; the instantaneous frequency spectrum is better suited to extract the frequency modulated components of the current signal. The Hilbert transform demodulation spectrum analysis also has the disadvantage that the demodulation spectrum generates additional demodulation frequency components for modulated signals exceeding the carrier frequency, which is called overmodulation, and the additional frequency components appearing in the demodulation spectrum are called overmodulation folding frequency components. Some scholars adopt a square demodulation method or a frequency shift demodulation method for performing quadratic power on current, but fault characteristic frequency shift can be generated in a frequency spectrum, and extra harmonic components and the like can also appear, so that the identification and diagnosis of frequency spectrum characteristics are not facilitated.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art, and provides a method for judging the fault of an asynchronous motor based on the current vector modular length, which uses the current component and the comprehensive current vector length I under a synchronous rotating coordinate system dq0_lThe method is a characteristic quantity, so that the result of fault diagnosis of the asynchronous motor is more accurate, and the method has the advantages of convenience in detection and simple algorithm.

In order to achieve the purpose of the invention, the invention adopts the following technical scheme:

a method for judging the fault of an asynchronous motor based on the current vector modular length comprises the following operation steps:

(1) obtaining three-phase stator current i of asynchronous motor to be fault detected_sa、i_sb、i_sc；

(2) Will i_sa、i_sb、i_scConversion into a current component i in a synchronously rotating coordinate system dq0_sd、i_sq；

(3) To i_sd、i_sqCarrying out spectrum analysis;

(4) will i_sa、i_sb、i_scCurrent component i transformed into two-phase stationary α β 0 coordinate system_sα、i_sβ；

(5) Calculate the sum of_sα、i_sβThe formed comprehensive current vector has a modular length;

(6) carrying out frequency spectrum analysis on the current vector modular length;

(7) and judging the fault form of the asynchronous motor to be monitored according to the result of the frequency spectrum analysis.

Preferably, the specific operation steps of the step (2) are as follows:

i in the synchronously rotating dq0 coordinate system_sd、i_sqThe following equation was used to obtain:

wherein theta is_eIs the synchronous electrical angle.

Preferably, the specific operation steps of step (3) are as follows:

performing discrete Fourier transform on the direct current component under the synchronous rotating coordinate system, wherein the calculation formula is as follows:

wherein: i is_dqIs the frequency domainThe current amount, k, is the ordinal number on the frequency axis, N is the ordinal number on the time axis, and N is the length of the sampled current.

Preferably, the specific operation steps of step (4) are as follows:

i in two-phase stationary alpha beta 0 coordinate system_sα、i_sβThe following equation was used to obtain:

preferably, the specific operation steps of step (5) are as follows:

the calculation of the modulo length of the current vector is:wherein: i_lAnd | is the current vector modulo length.

Preferably, the specific operation steps of step (6) are as follows:

performing discrete Fourier transform on the current vector mode length, wherein the calculation formula is as follows:wherein: i is_LIs the current vector modulo length in the frequency domain, k is the ordinal number on the frequency axis, N is the ordinal number on the time axis, and N is the length of the sampled current.

Preferably, the specific operation steps of step (7) are as follows:

when the component of the stator current under the synchronous rotation coordinate axis is direct current and has no obvious pulse change, and the vector length of the stator current is a fixed value, the motor has no fault;

when the component of the stator current under the synchronous rotation coordinate axis has the pulsation 2 times of the fundamental frequency and the vector length of the stator current also has the pulsation 2 times of the fundamental frequency, the motor has turn-to-turn short circuit fault;

when the component of stator current under the synchronous rotation coordinate axis exists 2ksf₁The pulsation of the frequency and the vector length of the stator current also exist 2ksf₁When the frequency is in pulsation, the motor has a rotor broken bar fault;

when component of stator current under synchronous rotation coordinate axis exists kf_outerThe pulsation of the frequency and the vector length of the stator current also exist kf_outerWhen the frequency is in pulsation, the motor has a bearing outer rail fault;

when component of stator current under synchronous rotation coordinate axis exists kf_innerThe pulsation of the frequency and the vector length of the stator current also exist kf_innerWhen the frequency pulsates, the motor has a track fault in the bearing;

when component of stator current under synchronous rotation coordinate axis exists kf_ballThe pulsation of the frequency and the vector length of the stator current also exist kf_ballWhen the frequency pulsates, the motor has a bearing ball failure;

when component of stator current under synchronous rotation coordinate axis exists kf_rThe pulsation of the frequency and the vector length of the stator current also exist kf_rWhen the frequency is in pulsation, the motor has mixed eccentric faults;

where k is an integer, s is the slip, f₁、f_outer、f_inner、f_ballFundamental frequency, characteristic frequency f of failure of the outer track, inner track and ball of the bearing_rIs the rotational frequency of the motor.

Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:

1. compared with the traditional detection method based on the sensor, the method has the advantages of convenience in detection and simple algorithm;

2. the method solves the problem that the fault diagnosis of the asynchronous motor fails due to a large amount of harmonic waves caused by power supply of an inverter or a frequency converter in the stator current;

3. the invention uses the current component and the integrated current vector length I under the synchronous rotating coordinate system dq0_lThe method is a characteristic quantity, so that the fault diagnosis result of the asynchronous motor is more accurate.

Drawings

Fig. 1 is a flow chart of motor fault diagnosis.

FIG. 2 is a matlab/simulink simulation model during turn-to-turn short circuit fault detection of a three-phase asynchronous motor.

FIG. 3 is a matlab/simulink simulation model during three-phase asynchronous motor rotor broken bar fault detection.

FIG. 4 is a matlab/simulink simulation model during three-phase asynchronous motor bearing fault detection.

Fig. 5 is a simulation result when an asynchronous motor has a turn-to-turn short circuit fault.

Fig. 6 is a simulation result of an asynchronous motor when a rotor bar breakage fault occurs.

Fig. 7 is a simulation result when a hybrid eccentric fault occurs in the asynchronous motor.

Fig. 8 is a simulation result when an external rail fault occurs in the asynchronous motor.

Fig. 9 is a simulation result when an internal track fault occurs in the asynchronous motor.

Fig. 10 shows simulation results when a ball failure occurs in the asynchronous motor.

Detailed Description

The invention is described in further detail below with reference to the figures and specific embodiments. It should be understood that the following examples are illustrative only and do not represent or limit the scope of the present invention, which is defined by the claims.

The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:

the first embodiment is as follows:

in this embodiment, a method for determining an asynchronous motor fault based on a current vector modulus length includes the following operation steps:

(1) obtaining three-phase stator current i of asynchronous motor to be fault detected_sa、i_sb、i_sc；

(2) Will i_sa、i_sb、i_scConversion into a current component i in a synchronously rotating coordinate system dq0_sd、i_sq；

(3) To i_sd、i_sqCarrying out spectrum analysis;

(4) will i_sa、i_sb、i_scCurrent component i transformed into two-phase stationary α β 0 coordinate system_sα、i_sβ；

(5) Calculate the sum of_sα、i_sβThe formed comprehensive current vector has a modular length;

(6) carrying out frequency spectrum analysis on the current vector modular length;

(7) and judging the fault form of the asynchronous motor to be monitored according to the result of the frequency spectrum analysis.

In the embodiment, the current component and the comprehensive current vector length Il under the synchronous rotating coordinate system dq0 are used as characteristic quantities, so that the result of fault diagnosis of the asynchronous motor is more accurate, and the method has the advantages of convenience in detection and simple algorithm. The method is characterized in that three-phase currents of a motor stator are converted to dq axes rotating at three same step speeds, the current dq components are mainly direct currents, and the comprehensive vector length of the stator current is also direct currents. Faults such as stator turn-to-turn short circuit, rotor broken bar, rotor eccentricity and bearing damage are reflected in the pulse change of dq current and vector length. According to the pulse frequency, the motor fault can be easily judged. Because the motor is usually supplied by an inverter, three-phase current on a stator of the motor has a plurality of harmonic contents, after the motor fails, the harmonic generated by the power supply of the inverter or a frequency converter on the three-phase alternating current and the harmonic generated after the failure are not easy to distinguish. The method of the embodiment overcomes the defect and improves the efficiency.

Example two:

this embodiment is substantially the same as the first embodiment, and is characterized in that:

in this embodiment, the specific operation steps in the step (2) are as follows:

i in the synchronously rotating dq0 coordinate system_sd、i_sqThe following equation was used to obtain:

wherein theta is_eIs the synchronous electrical angle.

In this embodiment, the specific operation steps in the step (3) are as follows:

performing discrete Fourier transform on the direct current component under the synchronous rotating coordinate system, wherein the calculation formula is as follows:

wherein: i is_dqIn the current amount in the frequency domain, N is the sequence length of the sampling current, N is the ordinal number on the time axis, and k is the ordinal number on the frequency axis.

In this embodiment, the specific operation steps in the step (4) are as follows:

i in two-phase stationary alpha beta 0 coordinate system_sα、i_sβThe following equation was used to obtain:

in this embodiment, the specific operation steps of step (5) are as follows:

the calculation of the modulo length of the current vector is:wherein: i_lAnd | is the current vector modulo length.

In this embodiment, the specific operation steps of step (6) are as follows:

performing discrete Fourier transform on the current vector mode length, wherein the calculation formula is as follows:wherein: i is_LIs the current vector modulo length in the frequency domain, and N is the length of the sampled current.

In this embodiment, the specific operation steps of step (7) are as follows:

when the component of the stator current under the synchronous rotation coordinate axis is direct current and has no obvious pulse change, and the vector length of the stator current is a fixed value, the motor has no fault;

when the component of the stator current under the synchronous rotation coordinate axis has the pulsation 2 times of the fundamental frequency and the vector length of the stator current also has the pulsation 2 times of the fundamental frequency, the motor has turn-to-turn short circuit fault;

when the component of stator current under the synchronous rotation coordinate axis exists 2ksf₁The pulsation of the frequency and the vector length of the stator current also exist 2ksf₁When the frequency is in pulsation, the motor has a rotor broken bar fault;

when component of stator current under synchronous rotation coordinate axis exists kf_outerThe pulsation of the frequency and the vector length of the stator current also exist kf_outerWhen the frequency is in pulsation, the motor has a bearing outer rail fault;

when component of stator current under synchronous rotation coordinate axis exists kf_innerThe pulsation of the frequency and the vector length of the stator current also exist kf_innerWhen the frequency pulsates, the motor has a track fault in the bearing;

when component of stator current under synchronous rotation coordinate axis exists kf_ballThe pulsation of the frequency and the vector length of the stator current also exist kf_ballWhen the frequency pulsates, the motor has a bearing ball failure;

when component of stator current under synchronous rotation coordinate axis exists kf_rThe pulsation of the frequency and the vector length of the stator current also exist kf_rWhen the frequency is in pulsation, the motor has mixed eccentric faults;

where k is an integer, s is the slip, f₁、f_outer、f_inner、f_ballFundamental frequency, characteristic frequency f of failure of the outer track, inner track and ball of the bearing_rIs the rotational frequency of the motor.

Compared with the traditional detection method based on the sensor, the method has the advantages of convenience in detection and simple algorithm; the method of the embodiment solves the problem that the fault diagnosis of the asynchronous motor fails due to the fact that a large number of harmonic waves are caused by power supply of an inverter or a frequency converter in stator current.

Example three:

this embodiment is substantially the same as the above embodiment, and is characterized in that:

in this embodiment, as shown in fig. 1, a flowchart of a method for diagnosing a motor fault according to this embodiment is shown, and the method includes the following steps:

step 1: obtaining three-phase stator current i_sa、i_sb、i_sc；

Step 2: will i_sa、i_sb、i_scConversion into a current component i in a synchronously rotating coordinate system dq0_sd、i_sq；

And step 3: performing discrete Fourier transform on the direct current component under the synchronous rotating coordinate system, wherein the calculation formula is as follows:

and 4, step 4: will i_sa、i_sb、i_scCurrent component i transformed into two-phase stationary coordinate system alpha beta 0_sα、i_sβ：

And 5: according to i_sα、i_sβCalculating the modular length of the current vector:

step 6: performing discrete Fourier transform on the current vector mode length, wherein the calculation formula is as follows:

and 7: judging the type of the fault according to the diagnosis result:

when the component of the stator current under the synchronous rotation coordinate axis is direct current and has no obvious pulse change, and the vector length of the stator current is a fixed value, the motor has no fault;

when the component of the stator current under the synchronous rotation coordinate axis has the pulsation 2 times of the fundamental frequency and the vector length of the stator current also has the pulsation 2 times of the fundamental frequency, the motor has turn-to-turn short circuit fault;

when the component of stator current under the synchronous rotation coordinate axis exists 2ksf₁The pulsation of the frequency and the vector length of the stator current also exist 2ksf₁When the frequency is in pulsation, the motor has a rotor broken bar fault;

when component of stator current under synchronous rotation coordinate axis exists kf_outerThe pulsation of the frequency and the vector length of the stator current also exist kf_outerWhen the frequency is in pulsation, the motor has a bearing outer rail fault;

when component of stator current under synchronous rotation coordinate axis exists kf_innerThe pulsation of the frequency and the vector length of the stator current also exist kf_innerWhen the frequency pulsates, the motor has a track fault in the bearing;

when component of stator current under synchronous rotation coordinate axis exists kf_ballThe pulsation of the frequency and the vector length of the stator current also exist kf_ballWhen the frequency pulsates, the motor has a bearing ball failure;

when component of stator current under synchronous rotation coordinate axis exists kf_rThe pulsation of the frequency and the vector length of the stator current also exist kf_rWhen the frequency is in pulsation, the motor has mixed eccentric faults;

where k is an integer, s is the slip, f₁Is the frequency of the power supply, f_outer、f_inner、f_ballCharacteristic frequency, f, of failure of the outer bearing track, inner bearing track and balls, respectively_rIs the rotational frequency of the motor.

Fig. 2 to 4 show a fault motor open-loop system simulation model constructed on Matlab/Simulink simulation software, and a fault diagnosis method is constructed according to the design steps described above.

Fig. 5 to 10 show the modulus lengths of the dc component and the current comprehensive vector of dq axis obtained by simulation, and the following results can be obtained by performing spectrum analysis on the simulation results:

compared with the traditional detection method based on the sensor, the method has the advantages of convenience in detection and simple algorithm; the method of the embodiment solves the problem that the fault diagnosis of the asynchronous motor fails due to a large amount of harmonic waves caused by power supply of an inverter or a frequency converter in the stator current; the method of the embodiment uses the current component and the integrated current vector length I under the synchronous rotating coordinate system dq0_lThe method is a characteristic quantity, so that the fault diagnosis result of the asynchronous motor is more accurate.

The embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the embodiments, and various changes and modifications can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be equivalent substitutions, as long as the purpose of the present invention is met, and the present invention shall fall within the protection scope of the present invention without departing from the technical principle and inventive concept of the present invention.