KR102079034B1 - Method and device for diagnosing rotor bar fault and load fault in the squirrel cage induction motors using current space vector and fourier or wavelet transform - Google Patents

Abstract

Various embodiments of the present invention relate to a method for diagnosing a rotor defect and a load defect of an induction motor and an apparatus thereof. According to various embodiments of the present invention, an apparatus for diagnosing a rotor defect and a load defect of an induction motor comprises: a current data acquisition unit which acquires current data output from the induction motor; a state determination unit which checks the state of the induction motor based on the current data received from the current data acquisition unit; a data conversion unit which acquires frequency spectrum data based on the current data; and a defect diagnosis unit which determines whether the induction motor is defective based on the frequency spectrum data. When the state of the induction motor is a steady state, the data conversion unit acquires the frequency spectrum data by using Fourier transform and when the state of the induction motor is a transient state, acquires the frequency spectrum data by using wavelet transform. Other embodiments may be possible. The present invention can diagnose defects of an induction motor regardless of the state of the induction motor.

Description

TECHNICAL AND DEVICE FOR DIAGNOSING ROTOR BAR FAULT AND LOAD FAULT IN THE SQUIRREL CAGE INDUCTION MOTORS USING CURRENT SPACE VECTOR AND FOURIER OR WAVELET TRANSFORM}

The present invention relates to a method and apparatus for diagnosing a defect of an induction motor, and more particularly, to a method of diagnosing a rotor defect and a load defect of an induction motor using a current space vector and Fourier or wavelet transformation according to two or more currents. And to an apparatus.

In general, an induction motor is a device in which a coil is wound on the outside of the stator and the rotor is located in the outside. An induction motor is a device for driving a motor by flowing an AC power to a coil of the stator so that an induction current flows through the rotor.

When a three-phase voltage or three-phase current having a phase difference of 120 ° is applied to the three-phase winding of the stator, the magnetic field Фs of the induction motor rotate at a constant speed according to the frequency of the input power. In the case of an induction motor, the rotor field generates current in the conductor of the rotor to generate magnetic flux Фr in the rotor. In this way, the induction motor operates according to the torque τ induced by the magnetic flux generated in the stator and the rotor.

In general, the squirrel cage induction motor corresponding to one of the types of induction motor is a main power device widely used in the industry because the rotor structure is simple, easy to operate and durable. Therefore, when the rotor and the load of the squirrel cage induction motor are defective, the entire process can be stopped without simply ending the induction motor failure in most complex continuous processes. The enormous economic consequences of this are accompanied by the need for a proactive monitoring system to prevent defects.

성분과 또다른 측파대(sideband) 주파수(부하결함주파수,

성분을 연산하고, 전원 주파수 대비 상대적 크기(dB)를 기준으로 결함을 진단했다.

In accordance with the necessity, industrial sites using induction motors perform induction motor condition monitoring and preventive maintenance of individual induction motors. For example, the condition monitoring system uses a fast fourier transform on one of the acquired current signals to obtain a sideband frequency (rotary defect frequency,

Components and other sideband frequencies (load fault frequency,

The component was calculated and the fault diagnosed based on the relative magnitude in dB relative to the supply frequency.

However, the conventional Fourier transform method can analyze only a steady state current signal and cannot diagnose a load or frequency that changes with time (for example, a transient state current signal). In addition, since the existing monitoring system utilizes the frequency spectrum data obtained using only one phase current, there is a problem of not distinguishing a rotor defect from a load defect as a limit of frequency conversion and misdiagnosing.

The present invention has been made to solve the above problems, by applying a Fourier transform or wavelet transform in accordance with the state of the induction motor by using a current signal in the steady state and transition state to accurately diagnose the defect of the induction motor and The purpose is to provide a device.

It is also an object of the present invention to provide a method and apparatus for accurately diagnosing a rotor defect and a load defect of an induction motor by using a current space vector generated based on two or more currents.

According to various embodiments of the present disclosure, an apparatus for diagnosing rotor defects and load defects of an induction motor may include: a current data acquisition unit configured to acquire current data output from an induction motor; A state determination unit checking a state of the induction motor based on the current data received by the current data acquisition unit; A data converter configured to obtain frequency spectrum data based on the current data; And a defect diagnosis unit configured to determine whether the induction motor is defective based on the frequency spectrum data, and wherein the data converter is configured to perform a Fourier transform when the state of the induction motor is in a steady state. The frequency spectrum data may be acquired using the wavelet transform, and the frequency spectrum data may be obtained using a wavelet transform when the state of the induction motor is in a transient state.

According to the present invention as described above, has the following various effects.

The present invention can diagnose a defect of an induction motor regardless of the state of the induction motor by applying the Fourier transform to the steady state current signal and the wavelet transform to the current signal in the transition state.

In addition, the present invention can accurately diagnose rotor defects and load defects of an induction motor by using a current space vector generated based on two or more currents.

In addition, the present invention can more accurately analyze the current signal of the transition state by using a continuous wavelet transform.

1 is a block diagram illustrating a rotor defect and a load defect diagnosis apparatus of an induction motor according to an exemplary embodiment of the present invention.
2 is a flowchart illustrating a method of diagnosing a rotor defect and a load defect of an induction motor according to an exemplary embodiment of the present invention.
3A and 3B illustrate an envelope, a rotor speed curve, a slip curve, a rotor defect frequency spectrum, and a load defect frequency spectrum of stator current peak values of an induction motor according to an exemplary embodiment of the present invention.
4A and 4B illustrate a frequency spectrum of a single phase current according to a Fourier transform and a frequency spectrum of a space vector calculated using two or more phase currents according to an embodiment of the present invention.
FIG. 5 illustrates frequency spectra of single-phase currents according to wavelet transformation when an induction motor according to an embodiment of the present invention is a normal, rotor bar defect or a load defect.
6 illustrates frequency spectra of two or more phase currents according to wavelet transformation when an induction motor according to an embodiment of the present invention is a normal, rotor bar defect or a load defect.
7 is a flowchart illustrating a method of diagnosing a defect of an induction motor by a defect diagnosing unit according to an embodiment of the present invention.

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. And, in describing the embodiments of the present invention, if it is determined that the detailed description of the related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of the functions of the present invention, and may vary according to the intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete and complete the scope of the invention to those skilled in the art. It is provided to inform you.

Various embodiments of the present disclosure may be implemented in software (eg, a program) that includes instructions stored in a machine (eg, a computer) readable storage medium. The device is a device capable of calling a stored command from a storage medium and operating according to the called command, and may include an electronic device (eg, a server) according to the disclosed embodiments. The instructions can include code generated or executed by a compiler or interpreter. The device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, 'non-temporary' means that the storage medium does not include a signal and is tangible, and does not distinguish that data is stored semi-permanently or temporarily on the storage medium.

According to an embodiment of the present disclosure, a method according to various embodiments of the present disclosure may be included in a computer program product. The computer program product may be traded between the seller and the buyer as a product. The computer program product may be distributed online in the form of a device-readable storage medium (eg compact disc read only memory (CD-ROM)) or through an application store (eg Play StoreTM). In the case of an online distribution, at least a portion of the computer program product may be stored at least temporarily on a storage medium such as a server of a manufacturer, a server of an application store, or a relay server, or may be temporarily created.

Each component (eg, a module or a program) according to various embodiments may be composed of a singular or plural number of objects, and some of the above-described subcomponents may be omitted, or other subcomponents may be omitted. It may be further included in various embodiments. Alternatively or additionally, some components (eg, modules or programs) may be integrated into one entity to perform the same or similar functions performed by each corresponding component prior to integration. In accordance with various embodiments, the operations performed by a module, program, or other component may be executed sequentially, in parallel, repeatedly, or heuristically, or at least some of the operations may be executed in a different order, may be omitted, or other operations may be added. Can be.

Unless otherwise defined, all terms used in the present specification (including technical and scientific terms) may be used in a sense that can be commonly understood by those skilled in the art. In addition, terms that are defined in a commonly used dictionary are not ideally or excessively interpreted unless they are specifically defined clearly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” does not exclude the presence or addition of one or more other components in addition to the mentioned components.

In general, the method of diagnosing a fault of an induction motor may be performed while the induction motor is stopped or in operation. When the induction motor diagnoses a defect while stopped, the accuracy may be high because it is directly disassembled and visually checked for defects, but this is not efficient because it consumes a lot of time. On the other hand, a method of diagnosing a defect during operation of the induction motor can easily diagnose a defect at any time, but has a disadvantage in inaccuracy than a method of diagnosing a defect during stop.

Therefore, in order to increase the accuracy of the method of diagnosing a fault during the operation of the induction motor, a motor spectrum analysis analysis (MCSA) diagnosis method has been developed and commercialized. The MCSA diagnostic method observes the frequency spectrum extracted based on the current data and determines that a specific frequency component rises as a defect of the induction motor. For example, the rotor defect frequency (frequency detected when the rotor defect) corresponding to one of the specific frequency components is a multiple of 2 * slip frequency, which is the sideband frequency (based on the power source frequency fs = 60Hz), as shown in Equation 1 below.

[Equation 1]

Where S is the slip of the induction motor, fs is the power supply frequency, and k is a positive integer.

In addition, the load fault frequency (frequency detected in case of a load fault) corresponding to another one of the specific frequency components is a multiple of components of the mechanical rotation frequency (fr) of the rotor, which is the sideband frequency (based on the power frequency fs = 60 Hz). Same as 2.

[Formula 2]

,

,

Where S is the slip of the induction motor, fs is the power source frequency, P is the pole number of the induction motor, and k is a positive integer.

MCSA, which is a conventional diagnostic method, may diagnose rotor defects and load defects by analyzing current of one phase using the rotor defect frequency and the load defect frequency described above. However, since the analysis is performed in the frequency domain, the analysis is possible only when the state of the induction motor is in a steady state, and there is a problem that the diagnosis is impossible when the load is changed. In addition, when analyzing the frequency spectrum with a current of one phase, there was a problem that it is difficult to distinguish the rotor defect from the load defect as the frequency bands of the rotor defect frequency and the load defect frequency overlap.

Therefore, in order to solve the existing problem, the rotor defect and load defect diagnosis apparatus 100 of the induction motor according to an embodiment of the present invention uses wavelet transformation to induce a load or frequency fluctuation condition (variation state). The motor can be diagnosed accurately. In addition, the rotor fault and load fault diagnosis apparatus 100 of the induction motor analyzes the frequency spectrum of the current space vector, which is a complex value, rather than a single-phase current, which is a real value, so that the motor unbalance (forward) and the external coupling or load of the motor may be reduced. By separating the opposite rotational components, the sensitivity and reliability of the induction motor diagnosis can be greatly increased.

Specific configurations and operations of the present invention according to the above object will be described in detail with reference to FIGS. 1 to 7.

1 is a block diagram illustrating a rotor defect and a load defect diagnosis apparatus of an induction motor according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the apparatus 100 for diagnosing rotor defects and load defects of an induction motor according to an exemplary embodiment of the present invention may be an induction motor 200 or a switchboard through a network or a direct connection (eg, a direct connection with a cable). 300, a potential transformer (PT) and a current transformer (CT) may be connected. The network may include a wireless network and a wired network. For example, the network may be a local area network (e.g. Bluetooth, WiFi direct or infrared data association) or a telecommunications network (e.g. cellular network, Internet, or computer network (e.g. LAN or WAN)). have.

In an embodiment, the rotor defect and load defect diagnosis apparatus 100 of the induction motor may include a control unit 110, a current data acquisition unit 120, a state determination unit 130, a data conversion unit 140, and a defect diagnosis unit. 150 and database 160.

In an embodiment of the present disclosure, the controller 110 may control various operations for diagnosing a defect of the induction motor 200, and may include a current data acquirer 120, a state determiner 130, and a data converter 140. ), The defect diagnosis unit 150 and the database 160 may be connected and controlled.

In an embodiment, the current data acquisition unit 120 may acquire current data from the induction motor 200 or the switchboard 300. For example, the current data acquisition unit 120 may acquire current data of two or more phases from the induction motor 200 or the switchboard 300.

In an embodiment, the state determiner 130 may check the state of the induction motor 200 based on the current data received by the current data acquirer 120.

In an embodiment, the data converter 140 may acquire frequency spectrum data based on the current data. For example, when the state of the induction motor 200 is a steady state, the data converter 140 may acquire frequency spectrum data using a Fourier transform, and the induction motor 200 In the case where the state of) is a transient state, frequency spectrum data may be obtained by using a wavelet transform. In addition, the data converter 140 may calculate a current space vector.

In an embodiment, the defect diagnosis unit 150 may determine whether the induction motor 200 is defective based on the frequency spectrum data. For example, the defect diagnosis unit 150 may determine whether the rotor defect frequency component and the load defect frequency component are detected in the frequency spectrum data based on the slip value and the power supply frequency value, and each component is detected. Can be diagnosed as rotor fault or load fault.

In an embodiment of the present disclosure, the database 160 may include a fault diagnosis history of the induction motor 200, basic information of a past diagnosed induction motor, and the like.

In one embodiment, the rotor defect and load defect diagnosis device 100 of the induction motor, for example, a smartphone (tablet), tablet PC (tablet personal computer), mobile phone (mobile phone), video phone, electronic E-book readers, desktop PCs, laptop PCs, netbook computers, workstations, servers, personal digital assistants, and PMPs A portable multimedia player, an MP3 player, a mobile medical device, a camera, or a wearable device may be included.

In one embodiment, the induction motor 200 includes a stator winding forming a rotor magnetic field, a stator iron core forming a passage of magnetic flux generated by the rotor field, and a rotor conductor and a rotor iron core rotating under induction current. And the rotor conductor may be a rotor bar.

2 is a flowchart illustrating a method of diagnosing a rotor defect and a load defect of an induction motor according to an exemplary embodiment of the present invention. 3A and 3B illustrate an envelope, a rotor speed curve, a slip curve, a rotor defect frequency spectrum, and a load defect frequency spectrum of stator current peak values of an induction motor according to an exemplary embodiment of the present invention. 4A and 4B illustrate a frequency spectrum of one phase current and a frequency spectrum of two or more currents according to a Fourier transform according to an embodiment of the present invention. FIG. 5 illustrates frequency spectra of single-phase currents according to wavelet transformation when an induction motor according to an embodiment of the present invention is a normal, rotor bar defect or a load defect. FIG. 6 illustrates frequency spectra of spatial vectors calculated using two or more phase currents according to wavelet transformation when an induction motor according to an embodiment of the present invention is a normal, rotor bar defect or a load defect.

2 may be performed by the rotor fault and load fault diagnosis apparatus 100 of the induction motor of FIG. 1. The operations of FIG. 2 are not limited to the configurations according to the following description, and may be performed by the controller 110 of FIG. 1 or other components.

Referring to FIG. 2, in an embodiment, the current data acquisition unit 120 may acquire current data of two or more phases in an induction motor in operation 21. For example, the current data acquisition unit 120 may acquire two-phase or three-phase current data of stator currents of the induction motor 200 connected through a network or a cable. For example, the current data acquirer 120 may transmit the obtained current data to the state determiner 130 and the data converter 140. The current data may include an envelope 31 of stator current peak values shown in FIG. 3A. In addition, the current data acquisition unit 120 acquires data including the rotor speed curve 33 and the slip curve 32 shown in FIG. It may be transmitted to the diagnosis unit 150.

In an embodiment, the data converter 140 may calculate a current space vector based on current data of two or more phases in operation 22.

For example, if one phase of a stator current of an induction motor is measured at a sampling frequency of fsampling [Hz] and the frequency spectrum is observed by Fourier transform, the frequency component from 0 Hz to fsampling / 2 Hz contained in the stator current (rotor defect) Frequency component, load defect frequency component) can be observed. Theoretically, as shown in FIG. 3A, the rotor defect frequency component 34 and the load defect frequency component 35 are observed identically to each other symmetrically on the X axis. In the case of Fourier transformed frequency spectrum in one phase, the negative region (reverse) frequency section cannot be identified, and the negative region (reverse) frequency component is matched to the positive region by the X-axis symmetry, so that the two defects cannot be distinguished. (Curve 36 in Fig. 3B) This shows that the two defects overlap and merge at the (43) frequency position in Fig. 4A, and in Fig. 5, the two defects (second and third) show the same pattern.

This is because, in one phase, the direction of rotation of the current vector cannot be distinguished. A forward component and a small reverse component that are not ideal are simultaneously present at the power source frequency fs, and the rotor defect frequency component is likewise the positive component due to the rotor defect (34). ) And the inverse motor component 35 (load fault frequency component) may be present at the same time due to induction motor imbalance, load influence, etc. The component can be observed.

Since the actual rotor defect is proportional to the magnitude of the forward component due to the rotor defect frequency component, only the influence of the forward component due to the rotor defect can be used for sensitive diagnosis. An accurate diagnosis can be made only when the electronic defect frequency component is observed. However, since the rotor defect frequency component is observed as shown in the curve 36 of FIG. 3B, accurate diagnosis of the rotor defect can be difficult. In addition, the reverse component caused by external factors such as load inequality of the induction motor may be large enough to affect the diagnosis results, and even if the reverse component is not large, the three-phase fault frequency components are different from each other if they are not zero. May affect. Therefore, in order to solve the problem, the present invention can calculate the current space vector as shown in Equation 3 below.

[Equation 3]

Where a is a complex number of magnitude 1 and phase 120 degrees.

When the Fourier transform is applied as a vector having a rotation direction, the current space vector can be observed by separately separating negative (reverse) and positive (forward) regions with components between -fsampling / 2Hz and fsampling / 2Hz. This makes it possible to distinguish between the forward and reverse components. Therefore, the sensitivity and reliability of the diagnosis can be improved by observing only the forward component, which is the rotor defect component, without the interference of the reverse component irrelevant to the rotor defect. 3A (34), that is, only the component (47) (forward component) of FIG. 4B is observed, and only the second pattern of FIG. 6 is checked.

On the other hand, according to an embodiment of the present invention, as shown in the drawing, the data converter 140 may perform a current space vector calculation operation in operation 25 or operation 26 after operation 24 is performed.

In an embodiment, the state determiner 130 may calculate a rate of change of current root mean square (RMs) values based on the current data in operation 23. For example, the state determiner 130 may obtain current rms values by subtracting an average value (DC component) from the original signal of the current data and calculating a section that crosses the zero point of the remaining signals, and the rate of change of the current rms values. Can be computed in real time.

In an embodiment, the state determiner 130 may determine whether the rate of change of the current rms values is within a reference range in operation 24. For example, when the load of the induction motor varies, the area of the envelope 31 of the stator current peak values may vary as in the transition state a of the stator current shown in FIG. 3A. Accordingly, when the rate of change of the current rms values exceeds the preset reference range, the state determiner 130 may determine that the load is changing. Therefore, the state determination unit 130 determines the state of the induction motor as a normal state when the rate of change of the current rms values is within the reference range, and determines the state of the induction motor when the rate of change of the current rms values exceeds the reference range. It can be judged as a transition state. Here, the steady state may be a state in which the current rms value is little changed, and the transition state may mean a state in which the load or frequency of the induction motor is changed. The reference range may be determined to an appropriate value in consideration of the steady state in which the load does not change.

In an embodiment, when the state of the induction motor is in a transition state, the data converter 140 may convert the current space vector into frequency spectrum data using wavelet transform in operation 25.

A wavelet is a signal consisting of a wave that repeats increasing and decreasing around 0, and can be set to have a characteristic useful for signal processing. The wavelet transform is one of time-frequency analysis techniques, and unlike the Fourier transform using a sinusoidal cosine and a sine function, the wavelet transform transforms current data into a time-frequency space using a wavelet function such as Equation 4 below. That is, the wavelet transform can extract time information and frequency information from the original signal at the same time. For example, the present invention can extract a rotor defect frequency component and a load defect frequency component by generating a space vector from two-phase or more current data. .

[Equation 4]

는 웨이블릿 패밀리라는 함수로 웨이블릿 모 함수(mother wavelet,

)에 압축 계수 s와 전이 계수 τ의 합성으로 얻어지고, x(t)는 전류 데이터이다. 웨이블릿 함수는 허용가능 조건을 만족한다면 얼마든지 다른 형태를 가질 수 있고, 예컨대, 복소수 웨이블릿을 포함할 수 있다. 또한, 웨이블릿 함수는 모를렛웨이블릿(morlet wavelet), Modulated 가우스 웨이블릿, Barrat웨이블릿, Gabor 웨이블릿, Frequency B-Splines (FBS) 웨이블릿 중 적어도 하나일 수 있고, 바람직하게는 Gabor 웨이블릿, Frequency B-Splines (FBS) 웨이블릿이 농형 유도 전동기에 적합할 수 있다.In Equation 4,

Is a function called wavelet family. The wavelet parent function (mother wavelet,

) Is obtained by combining the compression coefficient s and the transition coefficient τ, and x (t) is current data. The wavelet function may have any other form as long as it satisfies the allowable condition, and may include, for example, a complex wavelet. The wavelet function may be at least one of a morlet wavelet, a modulated gaussian wavelet, a barrat wavelet, a gabor wavelet, and a frequency b-splines (fbs) wavelet. Wavelets may be suitable for squirrel cage induction motors.

가 된다. 기동 시에 슬립은 1에서 0에 가깝게 떨어진다. (예: 회전자가 멈추어 있으면 슬립은 1, 정격속도(정상상태)에 도달하면 0에 가까운 정격 슬립으로 동작하고 모터마다 정격 슬립은 다를 수 있다.) 즉, (1-2*1)*60 = -60 에서 (1-2*0)*60 = 60 근처로 변하게 된다. 부하 결함 주파수 성분의 경우, 수식 2 에서

인 경우에,

가 되고, 이를 계산해보면,

또는

가 되는데 후자의 경우에 대해서

성분과 부호만 다르고 크기는 같은 값을 갖게 된다. 부하 결함 주파수 성분은 기동 시에 slip은 1에서 0에 가깝게 떨어지므로, (-1+2*1)*60 = 60 에서 (-1+2*0)*60 = -60 근처로 변하게 되어서, 회전자 결함 주파수 성분과 x축 대칭의 그래프가 산출될 수 있다.Specifically, when the state of the induction motor 200 is a steady state, the data converter 140 may acquire frequency spectrum data using a Fourier transform, and the induction motor 200 When the state of the transition state (transient state), the frequency spectrum data can be obtained by using a wavelet transform (wavelet transform). The defect diagnosis unit 150 may derive the rotor defect frequency curve or the load defect frequency curve, and may derive the rotor defect frequency component or the load defect frequency component. For example, for the rotor fault frequency component, when k = 1 in equation 1,

Becomes At start-up the slip falls close to one to zero. (E.g. when the rotor is stopped, the slip will be 1, and when the rated speed (steady state) is reached, the slip will be close to 0 and the rated slip may vary for each motor.) From -60 to (1-2 * 0) * 60 = 60. For the load fault frequency component,

in case of,

If you calculate this,

or

For the latter case

Only the components and signs are different and the magnitudes are the same. The load fault frequency component changes at (-1 + 2 * 1) * 60 = 60 to (-1 + 2 * 0) * 60 = -60 at slip, since the slip drops from 1 to 0 at startup. A graph of electronic defect frequency components and x-axis symmetry can be calculated.

가 항등식이기 때문에, 모든 상태(정상상태, 운전 상태, 변이상태)에 대해서 항상 대칭이므로, 한 상의 전류를 이용하면 구분해 낼 수 없고, 따라서, 본 발명은 전류 공간 벡터를 이용한다.On the other hand, in the above description

Since is an identity equation, it is always symmetrical with respect to all states (steady state, operating state, transition state), so it cannot be distinguished by using one phase current, and therefore, the present invention uses a current space vector.

[Equation 1]

[Formula 2]

,

,

According to an embodiment of the present disclosure, the data transformer 140 may acquire frequency spectrum data by using a continuous wavelet transform. The wavelet transform is divided into continuous wavelets and discrete wavelets. The continuous wavelet transform is a time-frequency that is useful for representing and analyzing scale characteristics such as non-stationary signals and wideband signals. Discrete wavelet transform is a time-scale transform for data processing and analysis of a signal based on filter bank theory, using a scale function that is a normal orthogonal basis and the wavelets obtained therefrom. . Therefore, in a load or frequency fluctuation condition, the continuous wavelet transform may be easier to identify the rotor defect frequency spectrum and the load defect frequency spectrum than the discrete wavelet transform.

According to an embodiment, when the state of the induction motor is in a normal state, the data converter 140 may convert the current space vector into frequency spectrum data using a Fourier transform in operation 26. For example, when the data converter 140 performs Fourier transform of the current space vector, such as the frequency spectrum shown in FIG. 4B (45 is a power frequency component, 46 is a reverse phase component of the power frequency, and fp is a sampling frequency). The diagnosis unit 150 may distinguish between the rotor defect frequency components 47 and (1-2s) fs and the load defect frequency components 48 and-(1-2s) fs. In contrast, when only one phase of current is used without using the current space vector, the frequency spectrum in which the rotor defect frequency component and the load defect frequency component cannot be distinguished is shown in FIG. Sampling frequency). The frequency components 43 and 44 shown in FIG. 4A are not distinguished from the rotor defect frequency components and the load defect frequency components, and thus the values thereof may overlap each other in comparison with 4b, or may be larger and offset from each other. This can cause a malfunction of the fault. Therefore, the present invention can distinguish the rotor fault frequency component and the load fault frequency component even by using the Fourier transform by using the current space vector, and can accurately diagnose the fault of the induction motor.

In an embodiment of the present disclosure, the defect diagnosis unit 150 may diagnose a defect of the induction motor based on the frequency spectrum data in operation 27. More details will be described later with reference to FIG. 7.

For example, the first frequency spectrum shown in FIG. 5 and obtained by the conventional method is a frequency spectrum when the induction motor acquired according to one phase current is normal and the second frequency spectrum is a rotor of the induction motor obtained according to one phase current. The frequency spectrum when two bars fail. The third frequency spectrum is the frequency spectrum when there is a load defect of an induction motor acquired according to the one-phase current. That is, as shown in FIG. 5, when only one phase current is used, the superimposition component (load defect frequency component) and the forward component (rotor defect frequency component) cannot be distinguished because they overlap as shown in FIG. 3B.

However, the first normal spectrum shown in FIG. 6 and obtained by the method of the present invention is the frequency spectrum when the induction motor acquired according to the three-phase current is normal and the second frequency spectrum is the rotor of the induction motor acquired according to the three-phase current. The frequency spectrum when two bars fail. The third frequency spectrum is the frequency spectrum when there is a load defect of an induction motor acquired according to three-phase current. That is, the present invention can prevent the diagnosis due to the reverse component by using the current space vector and can be diagnosed using only the forward component. Therefore, the defect of the induction motor can be diagnosed precisely.

7 is a flowchart illustrating a method of diagnosing a defect of an induction motor by a defect diagnosing unit according to an embodiment of the present invention. The operations of FIG. 7 may be performed by the rotor fault and load fault diagnosis apparatus 100 of the induction motor of FIG. 1. The operations of FIG. 7 may be an embodiment embodying operation 27 of FIG. 2.

Referring to FIG. 7, in an embodiment, the defect diagnosis unit 150 may identify a rotor defect frequency component or a load defect frequency component in acquired frequency spectrum data in operation 71.

In an embodiment, the defect diagnosis unit 150 may check data within a power frequency range of the frequency spectrum data in operation 72. For example, when the power supply frequency is 60 Hz, the power supply frequency range may be -60 Hz to 60 Hz, and when the power supply frequency is 50 Hz, the power supply frequency range may be -50 Hz to 50 Hz. In addition to the power source frequency can be set in various ways, such as 30, 20Hz, only the frequency spectrum data within the power source frequency range determined according to the power source frequency can be confirmed.

According to an embodiment, the defect diagnosis unit 150 may convert each result value into dB based on the maximum value among the result values calculated based on the confirmed data in operation 73. For example, each value may be redefined in dB based on the maximum value of the calculated results. For example, dB = 20 log (each value / maximum value) yields 0 dB for the maximum value, and parts of 1/10 and 1/100 of the maximum value may be -20 dB or -40 dB.

In an embodiment, the fault diagnosis unit 150 may determine that the induction motor is defective when the dB is higher than the defect reference value in operation 74. For example, the defect reference value may be -50 dB or more, and when higher than the defect reference value, it may be determined that the induction motor is defective. For example, a -40dB derivation can be determined as a defect.

According to various embodiments of the present disclosure, an apparatus for diagnosing rotor defects and load defects of an induction motor may include: a current data acquisition unit configured to acquire current data output from an induction motor; A state determination unit checking a state of the induction motor based on the current data received by the current data acquisition unit; A data converter configured to obtain frequency spectrum data based on the current data; And a defect diagnosis unit configured to determine whether the induction motor is defective based on the frequency spectrum data, and wherein the data converter is configured to perform a Fourier transform when the state of the induction motor is in a steady state. The frequency spectrum data may be acquired using the wavelet transform, and the frequency spectrum data may be acquired using a wavelet transform when the state of the induction motor is a transient state.

According to various embodiments of the present disclosure, the current data acquisition unit may acquire current data of two or more phases from the induction motor.

According to various embodiments of the present disclosure, the state determination unit may calculate a rate of change of root mean squre (rms) values based on the current data, compare the rate of change of the current rms values with a reference range, and rate of change of the current rms values. When it is within this reference range, the state of the induction motor may be determined as a normal state, and when the rate of change of the current rms values exceeds the reference range, the state of the induction motor may be determined as a transition state.

According to various embodiments of the present disclosure, the data converter may calculate a current space vector based on current data of two or more phases received from the current data acquirer.

According to various embodiments of the present disclosure, when the state of the induction motor is in a steady state, the data converter converts the current space vector into the frequency spectrum data using a Fourier transform, and induces the induction motor. When the state of the motor is a transient state, the current space vector may be transformed into the frequency spectrum data using a wavelet transform.

According to various embodiments of the present disclosure, the defect diagnosis unit may identify a rotor defect frequency component or a load defect frequency component from the frequency spectrum data.

According to various embodiments of the present disclosure, the defect diagnosis unit may check data within a power frequency range from the frequency spectrum data.

According to various embodiments of the present disclosure, the defect diagnosis unit may determine whether a rotor defect of the induction motor is based on data in the power frequency range.

According to various embodiments of the present disclosure, the defect diagnosis unit may convert each result value into dB based on a maximum value among the result values calculated based on the frequency spectrum data, and when the dB is higher than the defect reference value, the induction motor is defective. You can judge that.

According to various embodiments of the present disclosure, the data converter may acquire the frequency spectrum by using a continuous wavelet transform.

In the above, the present invention has been described by specific embodiments such as specific components and the like, but the drawings are provided to help a more general understanding of the present invention, and the present invention is limited to the above embodiments. However, those skilled in the art may make various modifications and variations from this description.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, fall within the scope of the spirit of the present invention. will be.

100-rotor and load fault diagnosis device of induction motor
110-control unit
120-current data acquisition unit
130-Status Judgment
140-data conversion unit
150-Fault Diagnosis
160-Database
200-induction motor
300-switchboard

Claims (10)

A current data acquisition unit for acquiring current data output from the induction motor;
A state determination unit checking a state of an induction motor based on the current data received by the current data acquisition unit;
A data converter configured to obtain frequency spectrum data based on the current data; And
A defect diagnosis unit determining whether a defect of the induction motor is based on the frequency spectrum data,
The data converter,
When the state of the induction motor is in a steady state, the frequency spectrum data is obtained by using a Fourier transform,
And when the state of the induction motor is in a transient state, the frequency spectrum data is obtained by using a wavelet transform.
The apparatus of claim 1, wherein the current data acquisition unit acquires current data of two or more phases from the induction motor.
The method of claim 2, wherein the state determination unit,
Calculating a rate of change of current root mean squre (rms) values based on the current data,
Compare the rate of change of the current rms values with a reference range,
When the rate of change of the current rms values is within the reference range, it is determined that the state of the induction motor as a normal state,
When the rate of change of the current rms value exceeds the reference range, it is determined that the state of the induction motor as a transition state, characterized in that the rotor fault and load fault diagnosis apparatus of the induction motor.
The apparatus of claim 2, wherein the data converter calculates a current space vector based on two-phase or more current data received from the current data acquirer.
The method of claim 4, wherein the data conversion unit,
When the state of the induction motor is in a steady state, the current space vector is transformed into the frequency spectrum data using a Fourier transform,
When the state of the induction motor is a transient state, the rotor defect and the load defect diagnosis of the induction motor, characterized in that for converting the current space vector to the frequency spectrum data using a wavelet transform (wavelet transform) Device.
The apparatus of claim 1, wherein the defect diagnosis unit identifies a rotor defect frequency component or a load defect frequency component in the frequency spectrum data.
The apparatus of claim 1, wherein the defect diagnosis unit checks data within a power frequency range among the frequency spectrum data.
The apparatus of claim 7, wherein the defect diagnosis unit determines whether a rotor defect of the induction motor is determined based on data within the power frequency range.
The method of claim 1, wherein the defect diagnosis unit,
Convert each result to dB based on the maximum value among the result values calculated based on the frequency spectrum data
The rotor fault and load fault diagnosis apparatus of the induction motor, characterized in that it is determined that the induction motor is defective when the dB is higher than the defect reference value.
The apparatus of claim 1, wherein the data transformer acquires the frequency spectrum using a Fourier transform or a continuous wavelet transform.

Images