KR20190099861A - System and method for detecting damper bar breakage of 3-phase salient pole synchronous machines - Google Patents

Abstract

Disclosed are a system and a method for diagnosing a damper bar fault of a three-phase alternating-current salient-pole synchronizer and a recording medium having a computer-readable program for performing the same. The system for diagnosing a damper bar fault of a three-phase alternating-current salient-pole synchronizer comprises a magnetic flux measurement unit, a frequency analysis unit, and a damper bar diagnosis unit. The magnetic flux measurement unit measures the magnetic flux in a gap between a rotor and a stator of a three-phase alternating-current salient-pole synchronizer. The frequency analysis unit calculates the magnitude of the measured magnetic flux in response to a frequency. The damper bar diagnosis unit diagnoses a fault of a damper bar of the three-phase alternating-current salient-pole synchronizer if the calculated magnitude of the magnetic flux is larger than a preset reference value in a preset diagnosis frequency band. The diagnosis frequency band (f_damper) is calculated by the equation of: f_damper = f_s +/- k(1-s/p)f_s = (1 +/- k(1-s)/p)fs, wherein f_s is a power frequency of the synchronizer, p is the number of pole pairs, s is a slip of the synchronizer, and k is a positive integer excluding multiples of 2p.

Description

A recording medium recording a damper bar failure diagnosis system, method, and a computer-readable program for executing the method of a three-phase alternating current pole type synchronizer.

TECHNICAL FIELD The present invention relates to power equipment, and more particularly, to a system and method for diagnosing a defect of a synchronizer such as an electric motor or a generator.

One-third of the synchronous generators, which make up 95% of the generators, have damper bars, and most of the synchronous motors, which make up 5-10% of the high-voltage motors, have damper bars. 1 is a view schematically showing the structure of a synchronous rotor with a damper bar.

For the operation of a three-phase AC synchronous motor, a three-phase voltage or current having an electrical phase difference of 120 ° is applied to the three-phase winding of the stator. In this case, a rotating magnetic field is generated which rotates at a constant speed according to the frequency of the input power. . 2 is a schematic diagram illustrating stator flux generated in a three-phase AC motor.

The damper bar is a short-circuit conductor structure that generates starting torque of the motor due to the current generated in the damper bar by the rotating magnetic field generated by the stator winding, thereby enabling the starting of the motor. In addition to starting the motor, the damper bar also maintains the speed to stabilize the rotation of the motor.

The damper bar is essential for starting the synchronous motor. However, the damper bar is often broken when the upright maneuver is repeated. Since the damper bar must withstand a large starting current and rotate at high speed, the damper bar is cracked or broken due to heat shrinkage expansion and centrifugal stress.

Such a defect causes the starting torque to become small, but gradually lowers the efficiency of the apparatus and further causes the starting of the apparatus itself. If there is a fault, sufficient current is not induced and the torque will be weakened or unable to start.

However, this unexpected failure of the motor will cause a large economic loss. Normally, when the motor is not started, it is only known when the motor is broken and can be used after the repair. In some cases, the motor stops causing a huge cost.

However, there are no commercially available diagnostic methods for diagnosing the damper bar of the synchronous machine yet. Just use the endoscope to directly inspect the inside of the motor or generator to observe the failure of the damper bar, or Most of the methods used for visual inspection after disassembly are used.

The paper on the diagnosis of damper bar failure is described in “H.C. Karmaker, “Broken damper bar detection studies using flux probe measurements and time-stepping finite element analysis for salient-pole synchronous machines”, 4th IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives, 2003. SDEMPED 2003. In this case, we use a very basic current monitoring technique.

If the rotor damper bar is broken, the airgap flux and current distribution of the salient-pole synchronous machine will change during startup. When the damper bar is broken, the current flowing through the damper bars of the corresponding pole decreases, and the average value is reduced by measuring the current flowing through the damper bars of each pole when compared with the normal state.

Therefore, installing the Flux probe on the stator bore surface allows online monitoring of whether the damper bar is swollen. This is a very rudimentary technology, which has a problem of low sensitivity and is not used in the field.

On the other hand, the rotor of the synchronizer may be classified into a salient pole rotor and a cylindrical rotor according to its shape. 3 and 4 are schematic diagrams showing the structure of a synchronous motor having a salient pole rotor and a cylindrical rotor, respectively. However, due to the influence of the salient pole motor, it is more difficult to diagnose a defect of the motor than the cylindrical rotor motor.

KR 100928536 B1 US 20150088444 A1

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a system and method for diagnosing a damper bar defect of a three-phase AC synchronizer such as a synchronous motor or a generator, in particular, a salient-type synchronizer.

In order to achieve the above object, a damper bar failure diagnosis system of a three-phase AC salient synchronous device according to the present invention includes a magnetic flux measuring part, a frequency analyzer, and a damper bar diagnosis part. The magnetic flux measuring unit measures the magnetic flux in the gap between the rotor and the stator of the three-phase alternating current pole type synchronizer, the frequency analyzer calculates the magnitude of the measured magnetic flux corresponding to the frequency, and the damper bar diagnosing unit If it exceeds the preset reference value in the preset diagnostic frequency band, it is diagnosed that the three-phase AC salient synchronous damper bar is faulty.

At this time, the diagnostic frequency band (f _damper ) is

의 수학식에 의해 산출되며, f_s는 상기 동기기의 전원 주파수, p는 상기 동기기의 회전자 극쌍수, s는 상기 동기기의 슬립, k는 2p의 배수를 제외한 양의 정수이다. 여기서 동기기의 슬립은 회전자 속도와 회전자계의 속도(동기속도)와의 차이를 회전자계의 속도(동기속도)로 나눈 값이다.

A is calculated by the following equation, f _s is the power frequency of the synchronous machine, p is the pole of the synchronous machine rotor pair number, s is the slip of the synchronous machine, k is a positive integer other than multiples of 2p. Here, the slip of the synchronizer is a value obtained by dividing the difference between the rotor speed and the rotor speed (synchronous speed) by the rotor speed (synchronous speed).

According to such a configuration, it is possible to easily diagnose the damper bar failure of the three-phase AC salient type synchronizer by using the magnetic flux measured by the magnetic flux sensor generally installed in the synchronizer.

In addition, the diagnosis of the damper bar can be performed for a preset start time. According to such a configuration, the diagnosis of the damper bar for the synchronous start time for which a large damper bar current is induced makes it easier to diagnose the electro-magnetic imbalance due to the failure of the damper bar.

의 수학식에 의해 산출되며, s는 동기기의 슬립, f_s는 동기기의 전원 주파수이다. In addition, the damper bar failure diagnosis system of the three-phase AC salient type synchronizer according to the present invention includes a current measuring unit, a feature value calculation unit, and a failure diagnosis unit. The current measuring unit measures the stator current of the three-phase AC salient type synchronizer, the feature value calculating unit calculates one or more feature values of the synchronous resistance, reactance, and impedance in the preset fault frequency band, and the fault diagnosis unit calculates the calculated feature values. Is diagnosed as a failure of the damper bar by comparing with the preset fault reference feature. In this case, the fault frequency band f _d is

S is the slip of the synchronizer, and f _s is the power supply frequency of the synchronizer.

According to such a configuration, it is possible to easily diagnose the damper bar failure of the three-phase AC salient type synchronizer by using the current measured by the current sensor generally installed in the synchronizer.

The apparatus may further include a failure number calculator configured to calculate the number of failures of the damper bar by comparing the calculated feature value with a preset number reference feature value. According to such a configuration, it is possible to easily determine whether the damper bar of the three-phase AC salient type synchronous device is damaged and the number of failed damper bars by using the current measured using the current sensor installed in the synchronous device.

의 수학식에 의해 산출되며, s는 동기기의 슬립, f_s는 동기기의 전원 주파수이다.In addition, the damper bar failure diagnosis system of the three-phase AC salient type synchronizer according to the present invention includes a current measuring unit, a vector sum calculation unit, and a failure diagnosis unit. The current measuring unit measures the stator current of the three-phase alternating current pole type synchronizer, the vector sum calculating unit calculates the three-phase vector sum of the stator current in the preset fault frequency band, and the fault diagnosis unit calculates the calculated vector sum and the preset fault reference feature. Diagnose the damper bar for failure by comparing the values. In this case, the fault frequency band f _d is

S is the slip of the synchronizer, and f _s is the power supply frequency of the synchronizer.

Even with such a configuration, it is possible to easily diagnose the damper bar failure of the three-phase AC salient type synchronizer using the current measured by the current sensor generally installed in the synchronizer.

In addition, an invention in which the system is implemented in the form of a method and a recording medium recording a computer readable program for executing the method are disclosed.

According to the present invention, it is possible to easily diagnose a damper bar failure of a three-phase alternating current pole type synchronous machine by using a magnetic flux measured by a magnetic flux sensor provided for diagnosing a field winding short circuit in the synchronous machine.

In addition, it is possible to easily determine whether the damper bar of the three-phase alternating current pole type synchronous device is damaged or the number of failed damper bars by using the current measured using the current sensor installed in the synchronous machine.

In addition, by diagnosing the damper bar for the synchronous start time for which a large damper bar current is induced, the electro-magnetic unbalance diagnosis due to the failure of the damper bar is facilitated.

In addition, it is possible to easily diagnose the damper bar failure of the three-phase alternating current pole type synchronizer by using the current measured by the current sensor generally installed in the synchronizer.

1 schematically shows the structure of a synchronous rotor with a damper bar;
2 is a schematic diagram illustrating stator flux generated in a three-phase alternating current motor;
3 and 4 are schematic diagrams showing the structure of a synchronous motor having a salient pole rotor and a cylindrical rotor, respectively.
Figure 5 is a schematic block diagram of a damper bar failure diagnosis system of a three-phase AC salient synchronous according to an embodiment of the present invention.
6 and 7 show time-frequency analysis waveforms of air gap magnetic flux of a three-phase four-pole salient synchronous motor for normal and defective motors, respectively.
8 is a table showing, for example, a four-pole electric motor as a diagnostic frequency band that changes according to a slip change.
9 and 10 show resistance and reactance versus time and frequency, respectively.
11 and 12 show the results of plotting the maximum (max) values of the 2s * f frequency components of the resistance and reactance of the synchronizer for the damper bars 0, 1, 2, and 3 faulty synchronizers. It is a graph.
11 and 12 show the results of plotting the maximum (max) values of the 2s * f frequency components of the resistance and reactance of the synchronizer for the damper bars 0, 1, 2, and 3 faulty synchronizers. It is a graph.
13 to 15 are graphs of the frequency response that change with time when the damper bars are broken at 0, 1 and 2, respectively.
Fig. 16 is a graph showing the vector sum of three-phase currents in the fault frequency band.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

5 is a schematic block diagram of a damper bar failure diagnosis system of a three-phase AC salient synchronous machine according to an embodiment of the present invention. In FIG. 5, the damper bar failure diagnosis system 100 of the three-phase AC salient type synchronizer includes a magnetic flux measuring unit 110, a frequency analyzing unit 120, a current measuring unit 130, a feature value calculating unit 140, and a vector sum. The calculator 150 and the failure diagnosis unit 160 are included.

In FIG. 5, the failure diagnosis system 100 includes both the magnetic flux measuring unit 110 and the current measuring unit 120, but the magnetic flux measuring unit 110 and the current measuring unit 120 may be selectively included. In addition, although only the current measuring unit 120 is illustrated in FIG. 5, a separate voltage measuring unit (not shown) for measuring the voltage of the stator current may be further included.

In FIG. 5, the components of the three-phase AC salient synchronous failure diagnosis system 100 may be implemented only in hardware, but may be generally implemented together in hardware and software operating on the hardware.

The magnetic flux measuring unit 110 measures the magnetic flux in the gap between the rotor and the stator of the three-phase AC salient synchronous machine. At this time, the magnetic flux sensor for measuring the magnetic flux can measure the magnetic flux in the axial direction (radial direction), radial direction (circumferential direction) of the inside of the motor.

The frequency analyzer 120 calculates the magnitude of the measured magnetic flux corresponding to the frequency, and the failure diagnosis unit 160 generates a three-phase alternating current pole type when the magnitude of the calculated magnetic flux is greater than a preset reference value in a preset diagnostic frequency band. Diagnose that the synchronous damper bar is faulty.

At this time, the diagnostic frequency band (f _damper ) is

의 수학식에 의해 산출되며, f_s는 상기 동기기의 전원 주파수, p는 상기 동기기의 회전자 극쌍수, s는 상기 동기기의 슬립, k는 2p의 배수를 제외한 양의 정수이다.

A is calculated by the following equation, f _s is the power frequency of the synchronous machine, p is the pole of the synchronous machine rotor pair number, s is the slip of the synchronous machine, k is a positive integer other than multiples of 2p.

In addition, the preset reference value at this time may be a value preset by the user or the like, and may be, for example, a frequency response in a diagnostic frequency band in a steady state.

For example, in the case of a pole type synchronous motor having a pole pair of p, rotor defects (eccentricity or damper bar defects, field winding defects, etc.) or load defects (unbalanced, misaligned, etc.) as the motor operates. , Eccentricity, etc.), the torque pulsation of the rotor rotational frequency fr as shown in equation (1) occurs.

(1)

(One)

Where k is a positive integer, s is slip of the motor (synchronous speed-rotor speed) / synchronous speed), p is the number of pole pairs of the motor, and f _s is the frequency of the power source (60 Hz). In general, this component appears when the vibration is analyzed, and when analyzing the frequency spectrum of the current or the magnetic flux, it appears as a sideband of the power frequency as shown in Equation (2).

(2)

(2)

In the case of a P (= 2p) pole motor, k is induced by vibration or electric current regardless of a defect due to the spin pole type rotor. For example, for a four-pole (p = 2) motor, k = 4, 8, 12,... The ingredients are always organic.

If a magnetic flux sensor is installed, in the case of a P (= 2p) pole motor, k is a drainage component of P induced in the flux signal regardless of the defect due to the rotor rotor. If there is a damper bar fault, the damper bar fault can be diagnosed by considering that the component is induced at all positive integers k in the current, vibration and flux signals.

On the other hand, the diagnosis of the damper bar can be performed for a preset start time. According to such a configuration, the diagnosis of the damper bar for the synchronous start time for which a large damper bar current is induced makes it easier to diagnose the electro-magnetic imbalance due to the failure of the damper bar.

This is because the damper bar fault component is particularly sensitive during synchronous start-up, and an increase in this component can be observed during operation as well as during synchronous start-up. As an example, the time-frequency analysis waveforms of the air gap flux in the start and steady state of a three-phase four-pole salient synchronous motor are shown in FIGS. 6 and 7, respectively, for a normal and a defective motor.

6 and 7 show time-frequency analysis waveforms of air gap flux of a three-phase four-pole salient synchronous motor for a normal and a defective motor, respectively, and FIG. 8 shows four diagnostic frequency bands that change according to a slip change. The table shows an example of a pole motor.

In Figures 6 and 7, it can be seen that different components appear during startup (1-3 seconds) and during operation (3.5 seconds later). The example motor is a 4-pole motor with k = 4, 8, 12, 16,... For all cases, all components appear during start-up and operation, but k = 1, 2, 3, 5, 6, 7, 9, 10, 11,... It can be seen that the components of are only present in the defective motor or increase greatly.

It can be seen that these components increase significantly, especially during start-up, and observing these components in the flux, current, and vibration signals can reliably monitor the damper bar for defects.

의 수학식에 의해 산출되며, s는 동기기의 슬립, f_s는 동기기의 전원 주파수이다. 댐퍼 바에 고장이 발생하는 경우, 슬립 주파수의 2배에 해당하는 사이드밴드 성분이 전류, 자속 스펙트럼에 나타나기 때문이다. The current measuring unit 130 measures the stator current of the three-phase AC salient synchronous type, and the feature value calculating unit 140 calculates one or more characteristic values of the synchronous resistance, reactance, and impedance in the preset fault frequency band. . In this case, the fault frequency band f _d is

S is the slip of the synchronizer, and f _s is the power supply frequency of the synchronizer. When a failure occurs in the damper bar, the sideband component corresponding to twice the slip frequency appears in the current and magnetic flux spectra.

 In this case, the failure diagnosis unit 160 compares the calculated feature value with a preset failure reference feature value to diagnose whether the damper bar has failed. In this case, the failure reference characteristic value may be a value preset by a user or the like, and may be, for example, one or more of resistance, reactance, and impedance of the synchronizer in a steady state.

According to such a configuration, it is possible to easily diagnose the damper bar failure of the three-phase AC salient type synchronizer by using the current measured by the current sensor generally installed in the synchronizer.

In addition, the failure diagnosis unit 160 may calculate the number of failures of the damper bar by comparing the calculated feature value with a preset number reference feature value. The preset number reference feature value is also a value preset by the user or the like, and may be, for example, one or more of resistance, reactance, and impedance of the synchronous device set corresponding to each failure number.

According to such a configuration, it is possible to easily determine whether the damper bar of the three-phase AC salient type synchronous device is damaged and the number of failed damper bars by using the current measured using the current sensor installed in the synchronous device.

More specifically, the resistance (R) and the reactance (X) of the motor can be obtained using the voltage and current applied to the stator of the synchronous machine. When the damper bar of the rotor is broken, the resistance R and the reactance X may be plotted through the STFT as shown in FIGS. 9 and 10. 9 and 10 show resistance and reactance versus time and frequency, respectively.

 The 2s * f component, which is prominent when the DC value is excluded, tends to increase as R and X increase as the number of broken bars increases. In other words, it is possible to determine whether the damper bar is broken by increasing the sizes of R and X. 11 and 12 are graphs showing the results of plotting the max value of the 2s * f frequency components of the resistance and the reactance of the synchronous device.

의 수학식에 의해 산출되며, s는 동기기의 슬립, f_s는 동기기의 전원 주파수일 수 있다. The vector sum calculator 150 calculates a three-phase vector sum of the stator currents in a preset fault frequency band. In this case, the fault diagnosis unit 160 compares the calculated vector sum with a preset fault reference characteristic value to provide a damper bar. Diagnose whether there is a fault. In this case, the fault frequency band f _d is

S is a slip of the synchronizer, and f _s may be a power supply frequency of the synchronizer.

More specifically, STFT may be performed as shown in three plots shown in FIGS. 13 to 15 by obtaining a vector sum of three-phase currents flowing through the stator. 13 to 15 are graphs of a frequency response that changes with time when the damper bars are broken into zero, one, or two, respectively.

By tracking the maximum value of the (1-2 s) fs component prominent in this STFT, the plot shown in FIG. 16 can be obtained. 16 is a graph showing the vector sum of three-phase currents in the fault frequency band. Referring to the plot in FIG. 16, it can be easily confirmed that as the number of broken bars of the damper bar increases, the magnitude of the STFT current increases.

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited thereby, but should be construed as modifications or improvements of the embodiments supported by the claims.

100: Damper bar fault diagnosis system for three-phase AC pole type synchronizer
110: magnetic flux measuring unit
120: frequency analyzer
130: current measuring unit
140: feature value calculator
150: vector sum calculation unit
160: fault diagnosis unit

Claims (13)

A magnetic flux measuring unit for measuring magnetic flux in a gap between the rotor and the stator of the three-phase alternating current pole type synchronizer;
A frequency analyzer for calculating the magnitude of the magnetic flux corresponding to the frequency; And
Including a fault diagnosis unit for diagnosing that the three-phase AC salient synchronous damper bar is a failure when the magnitude of the calculated magnetic flux in the preset diagnostic frequency band is larger than a preset reference value,
The diagnostic frequency band f _damper

_S is a power frequency of the synchronizer, p is the number of poles of the rotor of the synchronizer, s is the slip of the synchronizer, and k is a positive integer excluding a multiple of 2p. Damper bar failure diagnosis system of AC salient type synchronizer.
The method according to claim 1,
Diagnosis of the damper bar is a damper bar failure diagnosis system of a three-phase AC salvo type synchronous, characterized in that performed for a predetermined start time.
A current measuring unit measuring a stator current of the three-phase AC salient synchronous machine;
An impedance calculator for calculating at least one characteristic value of resistance, reactance, and impedance of the synchronizer in a preset fault frequency band; And
A failure diagnosis unit for diagnosing a failure of the damper bar by comparing the calculated feature value with a preset failure reference feature value;
The fault frequency band f _d is

The damper bar failure diagnosis system of a three-phase AC salient type synchronizer, wherein _s is slip of the synchronous device, and f _s is a power frequency of the synchronous device.
The method according to claim 3,
And wherein the fault diagnosis unit further calculates the number of faults of the damper bar by comparing the feature value with a preset number reference feature value.
A current measuring unit measuring a stator current of the three-phase AC salient synchronous machine;
A vector sum calculator configured to calculate a three-phase vector sum of the stator currents in a preset fault frequency band; And
A failure diagnosis unit for diagnosing a failure of the damper bar by comparing the vector sum with a preset failure reference feature value;
The fault frequency band f _d is

The damper bar failure diagnosis system of a three-phase AC salient type synchronizer, wherein _s is slip of the synchronous device, and f _s is a power frequency of the synchronous device.
The method according to claim 5,
And wherein the fault diagnosis unit further calculates the number of faults of the damper bar by comparing the vector sum with a preset number reference feature value.
As a fault diagnosis method performed by the damper bar fault diagnosis system of a three-phase alternating current pole type synchronizer,
A magnetic flux measuring step of measuring magnetic flux in the gap between the rotor and the stator of the three-phase alternating current pole type synchronous machine;
A frequency analysis step of calculating the magnitude of the magnetic flux corresponding to the frequency; And
And a fault diagnosis step of diagnosing that the three-phase AC salient type synchronous damper bar is faulty when the magnitude of the calculated magnetic flux becomes larger than a preset reference value in a preset diagnosis frequency band.
The diagnostic frequency band f _damper

_S is a power frequency of the synchronizer, p is the number of poles of the rotor of the synchronizer, s is the slip of the synchronizer, and k is a positive integer excluding a multiple of 2p. Method of diagnosing damper bar failure in AC salient type synchronizer.
The method according to claim 7,
Diagnosis of the damper bar is a damper bar failure diagnosis system of a three-phase AC salvo type synchronous, characterized in that performed for a predetermined start time.
As a fault diagnosis method performed by the damper bar fault diagnosis system of a three-phase alternating current pole type synchronizer,
A current measuring step of measuring a stator current of the three-phase AC salient synchronous machine;
Calculating a characteristic value of at least one of resistance, reactance, and impedance of the synchronizer in a preset fault frequency band; And
A fault diagnosis step of diagnosing a failure of the damper bar by comparing the feature value with a preset fault reference impedance;
The fault frequency band f _d is

S is the slip of the synchronizer, and f _s is the power frequency of the synchronizer.
The method according to claim 9,
In the fault diagnosis step, the fault number of the damper bar fault diagnosis method of the three-phase AC salvo type synchronizer further comprises calculating the number of faults of the damper bar by comparing the feature value with a preset number reference feature value.
As a fault diagnosis method performed by the damper bar fault diagnosis system of a three-phase alternating current pole type synchronizer,
A current measuring step of measuring a stator current of the three-phase AC salient synchronous machine;
A vector sum calculation step of calculating a three-phase vector sum of the stator currents in a preset fault frequency band; And
And a fault diagnosis step of diagnosing the failure of the damper bar by comparing the vector sum with a preset fault reference feature value.
The fault frequency band f _d is

The damper bar failure diagnosis system of a three-phase AC salient type synchronizer, wherein _s is slip of the synchronous device, and f _s is a power frequency of the synchronous device.
The method according to claim 11,
In the fault diagnosis step, the damper bar fault diagnosis method of the three-phase AC salient type synchronizer further comprises calculating the number of faults of the damper bar by comparing the vector sum with a preset number reference feature value.
A recording medium having recorded thereon a computer readable program for executing the method of any one of claims 7 to 12.

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