KR20150115415A - Method of hindance diagnose of electromotor - Google Patents

Abstract

The present invention relates to a method for diagnosing the fault of an electric motor and, more particularly, to a method for diagnosing the fault of an electric motor, capable of determining a fault state according to the size or presence of a specific frequency element by converting a current supplied to the electric motor into a complex number of an exponential type and performing the Fourier transform of the complex exponents of the complex number.

Description

[0001] The present invention relates to a method of diagnosing an electric motor,

More particularly, the present invention relates to a fault diagnosis method for an electric motor, and more particularly, to a fault diagnosis method of an electric motor, more particularly, to a fault diagnosis method of an electric motor that converts a current supplied to an electric motor into an exponential complex number, performs Fourier transform on the complex number index of the exponential complex number, And more particularly, to a fault diagnosis method for an electric motor for determining whether or not a fault exists.

Although the motor is widely used as a rotating device, fault diagnosis is indispensable because it can cause great damage if a fault occurs.

The failure of the motor can be divided into electrical, mechanical and maintenance failures. Among them, insulation breakdown and baying failure of the stator winding account for more than 78% of the total faults. [1]

The fault diagnosis method of the electric motor includes diagnosis by electric signal, diagnosis by temperature or infrared measurement, diagnosis through noise and vibration monitoring, diagnosis by speed and torque measurement, chemical analysis, sound, noise measurement, There is a method. [2]

Among them, MESA (Motor Electrical Signature Analysis) method using electrical signals is preferred because it does not require a separate accessory for diagnosis of faults. However, if a slight change in electrical signal such as a short circuit of the stator is sufficient, There are difficulties in analyzing. [3] [4]

Conventionally, there is a Park's Vector Approach as a typical fault diagnosis method using an electrical signal, which converts a three-phase current input to an electric motor into a d-axis current (i _d ) and a q-axis current (i _q ) And diagnoses the fault by analyzing the pattern form of the Pax vector on the dq plane.

FIG. 1 shows a Pax vector pattern when the motor is in a normal state, and FIG. 2 shows a Pax vector pattern when a motor fails.

As can be seen from FIGS. 1 and 2, when the motor is normal, the pattern of the Pax vector is represented by a circle centered at the origin, and when a fault occurs, the shape of the pattern is represented by an ellipse.

In addition, the faux vector pattern at the time of fault occurrence can be calculated by the distortion ratio (DR) as shown in the following equation, and the calculated distortion rate is used as a measure of the fault diagnosis.

[Mathematical Expression]

Where r _max is the long axis radius of the Pax vector pattern and r _min is the short axis radius of the ellipse's Pax vector pattern.

However, in the fault diagnosis method using the conventional Pax vector pattern, there is a problem that it is difficult to diagnose the fault when the value of the distortion rate is small, and the specific cause of the fault can not be diagnosed only by the magnitude of the distortion.

[1] Song, Myung - Hyun, Park, Kyu - Nam, Lee, Tae - Hoon, Han, Dong - Ki, and Kyung - Han Park, "Fault Diagnosis System of Induction Motor Stator Winding Using LabVIEW," Summer Meeting of the Korean Institute of Electrical Engineers, 7.18. - 15, 2005. [2] Nandi, S. and Toliyat, H. A "Condition Monitoring and Fault Diagnosis of Electrical Machines-A Review," Record of the IEEE Industry Applications Conference, Seattle, 1999, pp. 197-204. [3] Kim, K., and Parlos, A.G., "Non-Stationary Signal Segmentation Using Induction Motors," Mechanical Systems and Signal Processing, Vol. 16, 2002, no. 2-3, pp. 223-253. [4] A. Bellini, F. Filippetti, G. Franceschini, C. Tassoni, G. B. Kliman, "Quantitative evaluation of induction motor broken bars by means of electrical signature analysis," IEEE Trans. Ind. Appl., Vol. 37, no. 5, Sept / Oct, 2001, pp. 1248-1254 [5] Nejjari, H., Benbouzid, M., "Monitoring and Diagnosis of Induced Motors Electrical Faults Using a Current Park's Vector Pattern Learning Approach," IEEE Transactions on Industry Applications, vol.36, May / June 2000, -735. [6] A. J. M. Cardoso, S. M. A. Cruz, D. S. B. Fonseca, "Inter-Turn Stator Winding Fault Diagnosis in 3-phase Induction Motors," IEEE Trans. on Energy Conversion, Vol. 3, Sept. 1999, pp. 595-598. [7] Song, Myung-Hyun, Park, Gyu-Nam, Han-Dong, Kang, Oh, "Automatic diagnosis of stator winding fault using Park's vector pattern distortion", Trans. KIEE. Vol. 57p, No. 2, 2008.

It is an object of the present invention to provide a fault diagnosis method of an electric motor which can effectively perform fault diagnosis even if a distortion factor of a Pax vector pattern is low.

It is also an object of the present invention to provide a fault diagnosis method for a motor capable of diagnosing a specific cause of a fault.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a fault diagnosis method of an electric motor for receiving a three-phase current of a motor and diagnosing a fault state of the motor, the method comprising: receiving a three- Converting the three-phase current into a d-axis current and a q-axis current on a d-q coordinate system; Converting the complex number that makes the d-axis current into a real number and the q-axis current to be an imaginary number into an exponential complex number according to an Euler formula; Analyzing a frequency component of the complex number index of the exponential complex number through a Fourier transform; And determining whether the motor is faulty according to the presence or absence of a specific frequency component or the magnitude of a specific frequency component.

Converting the d-axis current and the q-axis current into a complex number on a complex plane using Equation (1): < EMI ID = 1.0 > And transforming the complex number into an exponential complex number using an Euler formula as shown in Equation (2) below.

[Equation 1]

&Quot; (2) "

Here, I _d is the d-axis current, I _q is the q-axis current, I _s is the complex number, r is the absolute value of the complex number, θ is the declination of the complex number, and re ^jθ is the complex number index.

In addition, the present invention further provides a computer-readable storage medium having stored thereon a fault diagnosis program for performing the fault diagnosis method by functioning as a computer.

The present invention further provides a computer that functions by the fault diagnosis program to perform the fault diagnosis method.

According to another aspect of the present invention, there is provided a fault diagnosis system, comprising: a data storage device storing a fault diagnosis program for performing a fault diagnosis by functioning as a computer; A communication device capable of transmitting data to the outside via a communication network; And a central processing unit for transmitting the fault diagnosis program to an external client computer system through the communication device.

The present invention has the following excellent effects.

First, according to the fault diagnosis method of the present invention, fault diagnosis is diagnosed by using a phase angle that is not the size of a Pax vector, so that fault diagnosis can be effectively performed even if the distortion rate of the Pax vector magnitude is low on the dq plane.

Further, according to the fault diagnosis method of the present invention, since the complex number index on the complex plane can be calculated as the frequency component through the Fourier transform, the fault diagnosis can be performed according to the existence or the size of the specific frequency band. There is an advantage to be able to do.

1 is a view showing a Pax vector pattern when the motor is in a normal state,
2 is a view showing a Pax vector pattern when a motor fails,
3 is a diagram illustrating an environment in which a fault diagnosis method according to an embodiment of the present invention is performed;
4 is a diagram for explaining complex numbers of a fault diagnosis method according to an embodiment of the present invention;
FIG. 5 is a view showing a conventional Pax vector pattern simulated on a dq plane,
6 is a graph showing a result of simulating a Pax vector pattern according to the conventional Pax vector size in a time domain when the motor is normal,
FIG. 7 is a graph showing a result of simulating a Pax vector pattern according to a conventional Pax vector size in a time domain when the motor is in a fault state;
FIG. 8 is a Fourier transformed result of the simulation result of FIG. 7,
FIG. 9 is a diagram illustrating a simulation of a complex number index, which is a phase angle of a Pax vector, on a dq plane according to an embodiment of the present invention;
10 is a view showing simulation results of the simulation pattern of the present invention in the time domain when the motor is normal,
11 is a view showing a result of simulating the simulation pattern of the present invention in the time domain when the motor is in a failure state,
FIG. 12 is a Fourier transformed result of the simulation result of FIG. 11,
FIG. 13 shows Fourier transform performed by the fault diagnosis method according to an embodiment of the present invention when the motor is normal,
FIG. 14 shows Fourier transform performed by the fault diagnosis method according to an embodiment of the present invention when the motor is short-circuited for two turns. As a result,
15 is a result of Fourier transform using a fault diagnosis method according to an embodiment of the present invention when the motor is short-circuited for four turns.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Hereinafter, the technical structure of the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

Referring to FIG. 3, a fault diagnosis method according to an embodiment of the present invention is a fault diagnosis method of an electric motor using an electric signal as a method of diagnosing a fault of an electric motor by monitoring a power supply 20 supplied to the electric motor 10 .

The fault diagnosis method according to an embodiment of the present invention is performed by a computer 100 that receives a current value supplied to an electric motor 10 and determines whether the fault has occurred, ) To function as a failure diagnostic program for performing a failure diagnosis.

In addition, the malfunction diagnostic program may be stored in a computer-readable storage medium such as a CD, a USB, or a hard disk, and may be provided separately from the computer 100.

However, the malfunction diagnostic program may be provided not only in the above-described removable storage media but also by being stored in a server computer system and transmitted to a client computer system via a communication network.

The server computer system may further comprise a data storage device capable of storing the fault diagnosis program, a communication device capable of transmitting data through a communication network, and a central data transmission / Or a computer device including a processing device.

Hereinafter, a fault diagnosis method according to an embodiment of the present invention will be described in detail.

In the fault diagnosis method according to an embodiment of the present invention, the computer 100 receives a three-phase current supplied to the motor 10.

Also, the three-phase current may be input from a current sensor or a hall sensor for measuring a current input to the motor 10, and may be digital or analog information.

In addition, when the three-phase current is analog information, the computer 100 may include an AD converter for converting analog information into digital information.

Next, the computer 100 converts the three-phase current into a d-axis current and a q-axis current on the d-q coordinate system.

Also, the d-axis current and the q-axis current are substantially the same as the d-axis current (i _d ) and the q-axis current (i _q ) of the conventional Pax vector technique and can be expressed by the following equation (a).

[Mathematical expression a]

Where i _m is the maximum value of the supply current, ω is the supply angular frequency, and t is the time variable.

Next, as shown in Fig. 4, the d-axis current I _d and the q-axis current I _q are converted into a complex number I _s on the complex plane.

Also, the complex number I _s is a complex number that real numbers the d-axis current I _d and the imaginary q-axis current I _q , and can be calculated by Equation 1 below.

Next, the complex number (I _s ) is converted into an exponential complex number using an Euler formula as shown in the following equation (2).

Here, r denotes a magnitude of the complex number (I _s ) as an absolute value of the complex number (I _s ), and? Denotes a declination of the complex number.

Also, the complex number exponent e ^{j [ theta]} in the exponential complex number re ^{j [ theta]} means the direction of the complex number I _s .

In addition, the fault diagnosis of the present invention is performed based on the complex number index.

That is, the conventional fault diagnosis method using the Pax vector is a method using the size of the Pax vector, and the fault diagnosis method of the present invention is a method using the direction (phase angle) of the Pax vector on the complex plane.

Next, the complex number index re ^{j? Is} converted into a time domain magnitude and the Fourier transform is performed to obtain a frequency component.

Next, it is determined whether or not the electric motor is faulty according to the presence of a specific frequency component or the magnitude of a specific frequency component.

5 (a) and 5 (b) illustrate a pattern simulated on a dq plane according to the conventional Pax vector size. FIG. 5 (a) shows a pattern when a steady state is present, and FIG. 5 .

FIG. 6 is a diagram showing a result of simulating the pattern (a) in FIG. 5 on the time domain, and FIG. 7 is a diagram showing a result of simulating the pattern (b) on the time domain in FIG.

5 to 7, when a fault occurs, the conventional Pax vector pattern is compared with the pattern at the time of occurrence of a fault, and a difference in shape of the pattern occurs. Therefore, the distortion rate can be used as a measure of the occurrence of faults. However, It is difficult to use the vector as a measure of the occurrence of the fault because there is little difference in the shape of the vector only in a slight phase difference.

8 shows the result of Fourier transform of the size of the Pax vector according to the time at the time of occurrence of a failure, and frequency components other than the fundamental wave component hardly appeared even in the event of a failure.

This means that even when the frequency component of the Pax vector is converted, the frequency components are almost the same when the motor is in the normal state and in the fault state, so that it can not be used as a measure of the fault diagnosis.

Extremely conventional Pax vector diagnostic techniques have failed, but fail diagnosis can not be performed if the distortion of the Pax vector pattern is insignificant.

On the other hand, Figure 9 is a (b) in (a) of Figure 9 to show a pattern negotiation simulate the complex index re ^jθ according to one embodiment of the present invention on a dq plane is a pattern when the normal state, and FIG. 9 This is a pattern when a failure occurs.

Fig. 10 shows the result of simulating the pattern (a) of Fig. 9 on the time domain, and Fig. 11 shows the result of simulating the pattern (b) of Fig. 9 on the time domain.

That is, referring to FIGS. 9 to 11, it can be seen that there is almost no difference in pattern shape on the dq plane when a fault occurs, but the shape of the complex number index re ^jθ varies with time.

In addition, FIG. 12 shows a result of Fourier transform of the complex number index re ^jθ according to the passage of time in the event of a failure, and a specific frequency component other than the fundamental wave component occurred in the occurrence of a failure.

This means that if the distortion of the conventional Pax vector pattern is insignificant, the complex number index can be Fourier transformed to perform the fault diagnosis.

FIG. 13 shows a result of Fourier transform of the complex number index re ^jθ according to an embodiment of the present invention when the motor is in a normal state, FIG. 14 shows a result of the Fourier transform of the complex number index re ^jθ according to an embodiment the complex index re ^jθ according to a result of a Fourier transform, Figure 15 is the result of a complex index re ^jθ according to one embodiment of the present invention: 4-turn short circuit of the motor, applying a Fourier transform.

As can be seen from FIGS. 13 to 15, when the frequency is normal, a specific frequency component exists in the vicinity of 160 [Hz] in addition to the fundamental wave, and since the magnitude of a specific frequency component changes in a two- The fault diagnosis method according to an embodiment of the present invention can determine not only whether a fault has occurred in an electric motor, but also what type of fault has occurred.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation in the present invention. Various changes and modifications will be possible.

10: electric motor 20: power source
100: Computer

Claims (5)

A fault diagnosis method for an electric motor in which a computer receives a three-phase current of a motor and diagnoses a fault condition of the motor,
Receiving a three-phase current of an electric motor;
Converting the three-phase current into a d-axis current and a q-axis current on a dq coordinate system;
Converting the complex number having the d-axis current as a real number and making the q-axis current as an imaginary number into an exponential complex number according to an Euler formula;
Analyzing a frequency component of the complex number index of the exponential complex number through a Fourier transform; And
And determining whether the motor is faulty according to the presence or absence of a specific frequency component or the magnitude of a specific frequency component.
The method according to claim 1,
Transforming into an exponential complex number:
Converting the d-axis current and the q-axis current into a complex number on a complex plane using Equation (1) below; And
And converting the complex number into an exponential complex number using the Euler's formula as shown in Equation (2) below.
[Equation 1]

&Quot; (2) "

Here, I _d is the d-axis current, I _q is the q-axis current, I _s is the complex number, r is the absolute value of the complex number, θ is the declination of the complex number, and re ^jθ is the complex number index.
A computer-readable storage medium having stored thereon a fault diagnosis program for performing the fault diagnosis method according to claim 1 or 2 by functioning as a computer.
A computer that functions by the fault diagnosis program and performs the fault diagnosis method of claim 1 or 2.
A data storage device storing a fault diagnosis program for performing a fault diagnosis method according to any one of claims 1 to 3 by functioning as a computer;
A communication device capable of transmitting data to the outside via a communication network; And
And a central processing unit for transmitting the fault diagnosis program to an external client computer system through the communication device.

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