JP2010288352A - Method for diagnosing fault in facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate detection of a fault in a facility including a motor and equipment driven by the motor. <P>SOLUTION: At least either a load current or a zero-phase current of an induction motor 14 that drives equipment 17 is measured. Based on the result of analyzing frequency, both or either of the following is compared with a predetermined condition: at least one of the presence/absence, frequency, and magnitude of a side band that occurs both on the high-frequency and low-frequency sides of an operating frequency f<SB>L</SB>and at least one of disturbance and undulation of the waveform of the frequency analysis. Based on the result of the comparison, a fault is diagnosed in the facility including the induction motor 14, equipment 17, and coupling 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a facility abnormality diagnosis method, and is suitable for use in diagnosing an abnormality in a facility including an induction motor (hereinafter referred to as a motor if necessary) and equipment driven by the motor. .

As a conventional method for diagnosing equipment abnormality of an industrial machine, there are roughly the following diagnostic methods (a) to (e).
(A) Current diagnostic method In the current diagnostic method, the load current of the motor that drives the equipment is measured, the harmonic content contained in the load current is detected, the absolute and relative values of the load current are compared, and the load current is suddenly changed. Diagnose equipment abnormalities by detecting
(B) Vibration diagnosis method In the vibration diagnosis method, a vibration sensor that measures vibration amplitude, acceleration, etc. is installed in the equipment (part) to be diagnosed, and the inherent frequency and magnitude of the vibration when the equipment to be diagnosed is abnormal. By detecting, abnormality of equipment is diagnosed.

(C) Acoustic diagnostic method In the acoustic diagnostic method, an acoustic microphone is installed in the vicinity of a diagnosis target facility (part), and an abnormality of the facility is diagnosed by analyzing a specific acoustic frequency when the diagnosis target facility is abnormal.
(D) Temperature diagnosis method In the temperature diagnosis method, a thermometer is installed in a diagnosis target facility (part), and an abnormality of the facility is diagnosed by detecting a temperature change when the diagnosis target facility is abnormal.
(E) Torque diagnosis method In the torque diagnosis method, a strain gauge is installed on the drive shaft of an electric motor to detect torque fluctuations, thereby diagnosing equipment abnormality.

Any of these methods (a) to (e) is a method of detecting and diagnosing equipment abnormality by installing a large number of various detectors at the location to be diagnosed and processing signals obtained from the detectors. .
For example, in the vibration diagnosis method, in order to diagnose bearing abnormalities (bearing breakage, seizure, eccentricity of load rotating bodies, etc.), a vibration detector is installed in the bearing section, and abnormalities are detected by the behavior of vibration frequency and amplitude. There was a way to diagnose. In addition, the current of the motor is taken out in place of many equipment diagnosis detectors, the maximum value, the minimum value, the average value, etc. of the current are obtained, and the abnormality of the equipment is determined by comparing with the preset value. There are methods and current diagnosis methods such as detecting the rate of change of the current and comparing it with a preset value to determine an abnormality of the equipment.

  As this current diagnosis method, there are techniques described in Patent Documents 1 to 3 that detect a phase difference by analyzing the frequency of an alternating current waveform of an electric motor to determine an abnormality of equipment. Further, there are techniques described in Patent Documents 4 and 5 for diagnosing equipment abnormality by obtaining a phase and amplitude imbalance rate of a current waveform. In addition, a method for determining an abnormality of equipment by an absolute value comparison diagnosis that compares an effective value of a current obtained by detecting a current of an electric motor that drives a mechanical system and a fixed upper limit value and a lower limit set value, and a current signal Patent Document 6 discloses a method for determining an abnormality of equipment by a relative value comparison diagnosis in which the latest moving average value and a time-dependent change result based on a deviation value are compared with each other as a reference. Further, Patent Documents 7 to 9 measure the interphase voltage and current of the motor, and measure the magnitude of each order of the voltage imbalance ratio and current imbalance ratio and the harmonic component of the magnetic field included in the current. An electrical equipment deterioration diagnosis method is disclosed that specifies the degree of deterioration of a motor, its cause and location based on a deterioration judgment value consisting of the obtained harmonic content.

JP 61-151477 A JP 61-151478 A JP 61-151479 A JP-A-61-186870 JP 61-186871 A Japanese Patent No. 1960047 Japanese Patent No. 3561882 Japanese Patent No. 3671367 Japanese Patent No. 3661155

  In the conventional equipment abnormality diagnosis with various detectors installed, the detector is installed directly at the location to be diagnosed, so the diagnosis accuracy is high, but many expensive detectors are installed on site to maintain the detector. Enormous labor is required, and it is difficult to maintain a constant detection accuracy.

  Moreover, although there exists a technique of patent documents 1-5 as a method of diagnosing by the load current of the electric motor which drives a machine, in this technique, an expensive rotation detector is required in order to diagnose an abnormality of equipment, There is a problem that maintenance of the rotation detector is required. Although it is an effective means for diagnosis when the motor is operated alone, it is necessary to measure multiple load currents and rotation detection at the same time with a load such as a reducer and a bearing connected to the motor. However, there is a problem that it becomes an expensive device.

Further, in Patent Document 6, an absolute value comparison diagnosis is performed in which the current value of the motor driving the mechanical system is compared with the upper limit value of about 80% and the lower limit value of about 20% of the rated current of the motor. In absolute value comparison diagnosis, the range of current change judged to be normal is as wide as 20% to 80% of the rated current, so a slight increase in current due to lack of lubricating oil for reducers, bearings, etc. is buried in the load current. In addition, there is a problem that if the upper limit value and the lower limit value are narrowed, a current change in a normal load state is erroneously detected as an abnormality.
Further, in the relative value comparison diagnosis, a certain number of data (in Patent Document 6, the number of data L = 0 to 30 and the sampling time ΔT = 6 seconds or less) is necessary to perform the moving average of the latest current values. This means that the time for detecting an abnormality is delayed by L × ΔT ÷ 2. Therefore, in order to prevent an abnormality detection delay, it is necessary to reduce the number of data L or the sampling time ΔT. However, if this is reduced, the moving average value and the deviation value will approach the obtained current value as much as possible. There is a problem that it is impossible to detect the abnormality of the equipment. In addition, when the current gradually increases or decreases over a long period of time as an abnormal phenomenon of the equipment (for example, load increase due to reduction of lubricating oil or grease such as a reduction gear or a bearing), the change over time based on the deviation value There is a problem that equipment abnormalities cannot be detected by comparison based on actual results. For this reason, there is a problem that cannot be said to be a diagnostic method with high utility value.

  On the other hand, in Patent Documents 7 to 9, in order to calculate the voltage imbalance rate and current imbalance rate of an electric motor, a large number of detectors that measure the voltage and current of each phase are required, and furthermore, a magnetic field generated by the current. It is also necessary to have a detector for detecting. In addition, currents in various frequency bands depending on the situation appear as abnormal forms that occur in various devices (such as bearings such as bearings, load devices such as speed reducers, couplings, and compressors) that constitute the facility. Therefore, it is difficult to uniquely determine the abnormality of the facility simply by the harmonic content of each order and the level of the level. Therefore, it is necessary to create a criterion by combining multiple harmonic orders according to the abnormal form of each device, and to evaluate the state of the equipment depending on whether or not the criterion is met. There is a problem that it is enormous and the judgment criteria are enormous and is not practical.

  Furthermore, in any of the above-described methods, a great deal of labor is required to determine the reference value for determining abnormality. For example, in a method of diagnosing equipment abnormality using the load current of the motor that drives the equipment, the behavior due to equipment abnormality composed of a wide variety of parts and devices can be expressed simply by the maximum value, minimum value, and average value of the load current. Difficult to diagnose. Furthermore, in order to improve the diagnostic accuracy, it is important to determine a reference value for abnormality determination that matches the situation of the facility. Therefore, initially set the reference value relatively high or low based on the motor specifications and test report, check the situation after operating for several days, and change whether the reference value is gradually lowered or raised. It is necessary to repeat trial and error to see the situation further. For this reason, there is a problem that enormous time and labor are required.

  The present invention has been made in view of the above-described problems, and is intended to make it possible to more easily detect an abnormality in equipment including an electric motor and a device driven by the electric motor. Objective.

The facility abnormality diagnosis method of the present invention is a facility abnormality diagnosis method for diagnosing an abnormality of a facility having an induction motor, a device driven by the induction motor, and a coupling that interconnects the induction motor and the device. In the current measuring step of measuring a load current for at least one phase of the induction motor, a frequency analyzing step of analyzing the frequency of the measured load current, and a waveform obtained by the frequency analysis, the induction motor Based on the presence or absence of sidebands appearing on both the high frequency side and low frequency side of the operating frequency, which is the frequency of the voltage applied to the, and the position and size of the sidebands, An abnormality determining step of determining whether or not there is an abnormality and determining the type of abnormality of the equipment when there is an abnormality of the equipment.
Another feature of the facility abnormality diagnosis method according to the present invention is that the facility includes an induction motor, a device driven by the induction motor, and a coupling that interconnects the induction motor and the device. An abnormality diagnosis method for equipment for diagnosing an abnormality, wherein a current measurement step for measuring a load current for at least one phase of the induction motor, a frequency analysis step for frequency analysis of the measured load current, and the frequency analysis Based on the obtained waveform disturbance and undulation state, it is determined whether or not there is an abnormality in the equipment, and when there is an abnormality in the equipment, there is an abnormality determination step for determining the type of abnormality in the equipment. In the point.

  According to the present invention, from the waveform obtained by frequency analysis of the load current / zero phase current of the induction motor, sidebands appearing on both the high frequency side and the low frequency side of the operating frequency, or waveform disturbance and Anomalies in equipment were determined based on the state of swell. Therefore, it is possible to set a criterion for determining an abnormality more easily than in the past, and it is possible to more easily detect an abnormality in equipment including the electric motor and a device driven by the electric motor.

It is a figure which shows the single phase equivalent circuit of an induction motor. It is a figure which shows an example of the load characteristic of an induction motor. It is a figure which shows an example of the result of the waveform of the load current at the time of torque fluctuation, and its frequency (FFT) analysis. It is a figure which shows an example of the result of the frequency analysis of the load current of a normal induction motor. It is a figure which shows an example of the waveform of the load current of an induction motor in case a load fluctuation is intense, and the result of the frequency analysis. It is a figure which shows an example of the result of the frequency analysis of the load current of an induction motor when a minute torque fluctuation arises in the rotating shaft of the induction motor. It is a figure which shows an example of the result of the frequency analysis of the load current of an induction motor when bearings, such as a bearing (part), and bearings, such as a bearing, are damaged. It is a figure which shows an example of the result of a frequency analysis of the load current of an induction motor when there is a change in the state of lubricating oil in a bearing such as a bearing. It is a figure which shows an example of the result of the frequency analysis of the load current of an induction motor in the case where there is no case where there is no vibration of an induction motor by installation bolt loosening. It is a figure which shows an example of a structure of the abnormality diagnosis apparatus of an installation. It is a figure which shows the 1st example of the waveform obtained by frequency-analyzing the load current of an induction motor. It is a figure which shows the 2nd example of the waveform obtained by frequency-analyzing the load current of an induction motor. It is a figure which shows Example 1 and shows the waveform obtained by frequency-analyzing the load current of an induction motor. It is a figure which shows Example 2 and shows the waveform obtained by frequency-analyzing the zero phase current of an induction motor.

Before describing embodiments of the present invention, the meaning of frequency analysis of the load current and zero-phase current of an induction motor will be described. FIG. 1 is a diagram showing an equivalent circuit of an induction motor. In FIG. 1, the impedance Z _{2 of the} secondary circuit (converted from the secondary side to the primary side) is expressed by the following (formula 1). Here, s is slip, n ₀ is the synchronization speed, and n is the rotation speed.

If the frequency of the power supply voltage applied to the induction motor (hereinafter referred to as the operating frequency) is f _L , its angular velocity is ω _L (= 2πf _L ), and I _m0 is the _{peak value} of the current I ₀ , the current I _{1 of} each part, I ₂ is represented by the following (formula 2).

Here, if there is no load fluctuation and it is constant, the slip is also constant. Therefore, when the frequency analysis is performed on the load current I ₁ of the induction motor, only the operating frequency f _L exists. On the other hand, as shown in FIG. 2, when the load torque fluctuates by ± 20% with a constant period (frequency f _S ) centering on 60%, the sliding s also fluctuates with amplitude B and frequency f _S centering on s _0. Thus, the load current I ₁ of the induction motor is as shown in the following (formula 3).

As shown in FIG. 3A, the amplitude of the waveform 31 of the load current I ₁ in (Equation 3) fluctuates at the frequency f _S , and the result of the frequency analysis (the waveform 31 of the load current I ₁ is As a result of the FFT, as shown in FIG. 3B, f _L ± f _S sidebands (sideband frequencies) 32 and 33 appear on both sides with the operating frequency f _L as the center. Also, the level height (size) of the sideband frequencies 32 and 33 corresponds to the magnitude of torque fluctuation. On the other hand, in a three-phase induction motor, a rotating magnetic field is generated by the current flowing in the stator coil of the three-phase induction motor, but the magnetic flux distribution of the magnetic field generated in the stator coil forms a square wave, and its counter electromotive force Is superimposed on the load current, the load current and the zero-phase current of each phase of the three-phase motor are normally expressed by the following (formula 4). Here, I _um is the _{peak value} of the U-phase current I _u , I _vm is the _peak value of the V-phase current I _v , I _wm is the _peak value of the W-phase current I _w , and n is an odd integer value of 3 or more. .

Odd harmonics corresponding to a square wave of the magnetic flux distribution are superimposed on the current value of each phase, and the zero-phase current I _z is the sum of the currents I _u , I _v , I _w of each phase and is normally zero. Become. If the currents I _u , I _v , and I _w of each phase are subjected to frequency analysis, an odd harmonic nf _L having an operating frequency f _L and a positive value n that is an odd multiple thereof appears. Based on this, the equipment abnormality diagnosis method by frequency analysis of the load current of the induction motor according to the present embodiment will be described below.

(1) Behavior of Frequency Analysis Result in Normal Induction Motor First, FIG. 4 shows an example of a result of frequency analysis of a load current of a new induction motor or a normal induction motor after maintenance. The induction motor used to obtain the analysis result shown in FIG. 4 is a new rotor, the stator coil replaced, the bearing replaced, and the rated output is 650 kW 3.3 kV 136A, the number of poles 8P, rated rotational speed is 735 min ⁻¹ , and insulation class is B type. FIG. 4 shows the result of frequency analysis by measuring the current of the induction motor alone with no load. The current of the induction motor was measured in a stable state after sufficient lubrication and running-in of the bearing. As a result of the frequency analysis of this current, as shown in FIG. 4, it is attenuated gently like a mountain foot around the operating frequency f _L (50 Hz) in the region of 100 Hz or less, and the waveform is distorted (the waveform is less than the swell below). There is no waviness (vibration in the vertical waveform that is gentler than the above-mentioned disturbance affecting the outline of the waveform). Moreover, the side band of a rotation frequency is not recognized. On the other hand, in the region of 100 Hz or higher, since the magnetic flux density distribution of the stator magnetic field is a square wave, an odd harmonic nf _L (n is an odd integer value of 3 or more) of the operating frequency f _L is recognized.

(2) When load fluctuation is severe FIG. 5 shows an example of the result of frequency analysis of the load current of the induction motor when the load current is severe. The induction motor used to obtain the analysis result shown in FIG. 5 has a rated output of 260 kW 3.3 kV 157A, a pole number of 6P, a rated rotational speed of 980 min ⁻¹ , and an insulation class of B type. In the result of the frequency analysis shown in FIG. 5, the fluctuation of the load current is 28A to 56A, resulting in a waveform as shown in FIG. When this is subjected to frequency analysis, as shown in FIG. 5B, a wide region of ± several Hz is generated in the vicinity of the operating frequency f _L (50 Hz). This is because there is no single sideband frequency on both sides of the operating frequency f _L , and the slip also fluctuates with load fluctuation, and the fluctuation frequency is ± 0 to ± several Hz. In addition, since the frequency fluctuates continuously, the sideband frequency corresponding to each fluctuating frequency also varies continuously. An abnormality of the facility can be diagnosed based on a wide region of ± several Hz in the vicinity of the operating frequency f _L (50 Hz). In addition, the broken line of FIG.5 (b) represents the theoretical waveform of a normal induction motor.

(3) When a slight torque fluctuation occurs on the rotating shaft If an abnormality occurs on the equipment, such as the coupling misalignment of the induction motor or load imbalance, the rotational frequency (shaft rotation speed ÷ 60 seconds) torque fluctuation occurs. FIG. 6 shows an example of the result of frequency analysis of the load current at this time. The induction motor used to obtain the analysis result shown in FIG. 6A has a rated output of 165 kW 3 kV 39A, a pole number of 6 P, a rated rotational speed of 990 min ⁻¹ , and an insulation class of B type. The amount of misalignment of the ring is 0.23 mm. On the other hand, the induction motor used to obtain the analysis result shown in FIG. 6 (b) has a rated output of 95kW 3kV 23A, a pole number of 4P, a rated rotational speed of 1460min- ¹ , and an insulation class of B type. The amount of misalignment of the coupling is 0.1 mm.

In the waveforms shown in FIGS. 6A and 6B, torque fluctuation occurs at the rotational frequency (16.5 Hz for 6P, 24.8 Hz for 4P), and therefore, the sideband frequency corresponding to the rotational frequency ( ± 16.5 Hz at 6P, and ± 24.8 Hz at 4P) are notable. The amount of torque fluctuation appears as the level of the sideband frequency, and when the amount of coupling misalignment is large or when the load factor of the induction motor is high, a sideband frequency twice the rotational frequency appears. . In this way, when a misalignment of the coupling, bending of the drive shaft, and load imbalance on the driven machine side occur, minute torque fluctuations corresponding to the rotational frequency occur on the drive shaft of the induction motor. It will be the same sideband frequency and rotation frequency on both sides of the load current frequency analysis to the operation frequency f _L of the induction motor is generated. Accordingly, generated on both sides of the operation frequency f _L, based on the presence and magnitude of the same sideband frequency and rotational frequency, it can be diagnosed abnormality equipment.

(4) When a bearing such as a bearing is broken FIG. 7A shows an example of the structure of a bearing (a part thereof), and FIG. 7B shows a frequency analysis of the load current of the induction motor when the bearing is broken. An example of the result is shown. The bearing has different dimensions and quantities of the rolling elements (balls or rollers) 7 depending on the dimensions and model, and has a frequency specific to the bearing (the revolution frequency f _{C of} the rolling elements 7 and the rotation speed f _Z of the rolling elements 7). ing. When the load current of the induction motor is subjected to frequency analysis in a state where there is an abnormality in the bearing (the rolling element 7, the inner ring 9, the outer ring 10, etc.), as shown in FIG. Alternatively, the relative speed f _m (= f _N −f _C ), which is the difference between the rotational frequency f _N of the drive shaft 15 and the revolution frequency f _C 12 of the rolling element 7, is a sideband frequency on both sides of the operating frequency f _L. Appears as Therefore, the difference between the natural frequency of the bearing (the revolution frequency f _{C of} the rolling element 7, the rotation speed f _Z of the rolling element 7), the rotation frequency f _N of the drive shaft 15 and the revolution frequency f _C 12 of the rolling element 7. By paying attention to the relative speed f _m , the abnormality of the facility can be diagnosed based on the sideband frequency appearing on both sides of the operating frequency f _L from the result of frequency analysis of the load current of the induction motor.

(5) Behavior of frequency analysis results due to changes in the state of lubricating oil in bearings such as bearings Figure 8 shows the results of frequency analysis of the load current of an induction motor when there is a change in the state of lubricating oil in bearings and other bearings. An example is shown. Specifically, FIG. 8A shows the result of frequency analysis of the load current of the induction motor in a state where the grease of the bearing is insufficient. Moreover, FIG.8 (b) shows the result of the frequency analysis of the load current of the induction motor in the stable state after supplying grease. The induction motor used to obtain the analysis result shown in FIG. 8 has a rated output of 95 kW 3 kV 24 A, a pole number of 4 P, a rated rotational speed of 1460 min ⁻¹ , and an insulation class of B type. Comparing the two, the lack of grease on the bearing causes disturbance in the attenuation curve at the foot of the mountain centering on the operating frequency (50 Hz) (see FIG. 8A). When the rolling element 7 of the bearing rolls the inner ring 9 and the outer ring 10 due to the lack of grease, friction is generated between the rolling element 7 and the inner ring 9 and the outer ring 10, thereby preventing the bearing from rotating smoothly. Since a minute torque fluctuation occurs in the drive shaft 15, the waveform resulting from the frequency analysis of the load current of the induction motor is disturbed. In this state, when the grease is replenished and the frequency analysis of the load current of the induction motor is performed in a stable state, the grease spreads in the bearing, and friction between the rolling element 7 and the inner ring 9 and the outer ring 10 is reduced. As shown in FIG. 8 (b), there is no disturbance in the attenuation curves at the mountain skirts on both sides of the operating frequency (50 Hz). In this way, if there is any abnormality (such as adhesion or lack of grease) in the lubricating oil of a bearing such as a bearing, a minute torque of the drive shaft 15 is generated. As a result, in the result of the frequency analysis of the load current, in the low frequency region, disturbance occurs in the attenuation curve of the mountain skirt extending on both sides centering on the operation frequency (50 Hz). An equipment abnormality can be diagnosed based on this disturbance.

(6) Behavior of frequency analysis result due to vibration such as loose installation bolt FIG. 9 shows the phenomenon that appears in the result of frequency analysis of the load current of the induction motor when the installation bolt of the induction motor is loosened. Shows the results of the experiment. In order to remove disturbances acting other than loosening of the installation bolts of the induction motor, the induction motor was fixed to a surface plate, and the induction motor was fixed with bolts. FIG. 9A shows the result of frequency analysis of the current of the induction motor with no load in this state. Further, anti-vibration rubber (thickness 10 mm) was inserted between the induction motor and the surface plate, assuming that the installation bolts of the induction motor were loosened. FIG. 9B shows the result of frequency analysis of the current of the induction motor with no load in this state. The induction motor used for obtaining the analysis result shown in FIG. 9 has a rated output of 110 kW 400 V 190 A, a pole number of 2 P, a rated rotational speed of 2980 min ⁻¹ , and an insulation class of F type.

When both are compared, in FIG. 9A, the same result as in the case of the normal induction motor described above (FIG. 4) is obtained. In other words, in the region of 100 Hz or less, the operation frequency f _L (50 Hz) is attenuated gently like a mountain skirt, and the waveform is not disturbed. On the other hand, in the region of 100 Hz or higher, since the magnetic flux density distribution of the stator magnetic field is a square wave, an odd harmonic nf _L (n is an odd integer value of 3 or more) of the operating frequency f _L appears. In FIG. 9B, there is no significant difference from the waveform shown in FIG. 9A in the region of 500 Hz or higher. However, in the region of 500 Hz or less, the waveform does not gently attenuate like the mountain skirt centering on the operating frequency f _L (50 Hz), and large waveform undulations and disturbances appear in the attenuation curve. This is because the induction motor is not fixed, and the vibration of the rotation is transmitted to the stator, the stator coil vibrates, or the air gap between the rotor of the induction motor and the stator fluctuates. This happens because the rotor rotates. In this way, vibrations due to loosening of the installation bolts of the induction motor, insufficient rigidity of the installation base, or vibrations due to severe damage to the bearings are also transmitted to the stator coil of the induction motor and rotate together with the vibration of the stator coil. When the rotor (rotor) vibrates and the air gap between the stator and the rotor fluctuates during the rotation of the rotor, the waveform disturbance and the undulation occur in the waveform obtained by frequency analysis of the load current of the induction motor. An equipment abnormality can be diagnosed based on the disturbance and undulation of the waveform.

(7) Behavior of frequency analysis result of zero-phase current As described above, the zero-phase current of the induction motor is normally zero from the equation (4), and the operating frequency that is characteristic in the result of the frequency analysis is as follows. f _L and its odd harmonic nf _L (n is an odd integer value of 3 or more) do not appear. For example, if the load of the equipment or equipment driven by the induction motor varies, the current of each phase of the induction motor varies according to the load, but the zero-phase current is offset and the load variation appears. Absent. On the other hand, if any abnormality (local insulation drop, rare short, etc.) occurs in the stator coil of the induction motor, the abnormality information is superimposed on the current of the relevant phase, so in the result of the frequency analysis of the zero-phase current The operating frequency f _L or its odd harmonic nf _L (n is an odd integer value of 3 or more) appears. In particular, as described above, since the magnetic flux distribution of the magnetic field generated in the stator coil forms a square wave and the counter electromotive force is superimposed on the load current, an odd harmonic is generated when the stator coil is abnormal. Will appear prominently, and based on this fact, the abnormality of the stator coil of the induction motor can be diagnosed.

  As described above, each phase current of the induction motor diagnoses a minute torque fluctuation caused by an abnormality in the rotating system including the rotor of the motor, and the zero-phase current of the induction motor The abnormality of the stator coil of the electric motor will be diagnosed. Accordingly, in the present embodiment, at least one of the load current and the zero-phase current of at least one phase of each phase current of the induction motor is measured, and the sidebands appearing on both sides of the operating frequency from the result of the frequency analysis. By examining the position and size of the frequency (sideband) and the behavior of the attenuation curve like the mountain hem extending on both sides around the operating frequency (waveform disturbance and undulation), the induction motor is of course Abnormalities in equipment and facilities driven by the induction motor are diagnosed.

FIG. 10 is a diagram illustrating an example of the configuration of the equipment abnormality diagnosis apparatus.
In FIG. 10, the facility is configured by connecting a drive shaft 15 of an induction motor 14 and devices 17 driven by the induction motor 14 with a coupling 16. In the control panel 18 that controls the induction motor 14, at least one phase of the induction motor 14 is detected using a current detector 19 that detects the load current of the induction motor 14 and a data collection device 20 that stores the value of the load current. One or both of the minute current and the zero-phase current are measured, the data is taken into the frequency analysis device 21, and the frequency analysis is performed.
The frequency analysis device 21 can be realized using, for example, a personal computer. The devices 17 are a speed reducer, a mechanical device, and the like. The current detector 19 can be realized by using a clamp meter or a current transformer. In FIG. 11, the data collection device 20 and the frequency analysis device 21 are separate devices, but the data collection and the frequency analysis may be performed by the same device. In this case, it is preferable to collect data on the load current of the induction motor 14 at high speed. In addition, when there are many induction motors to be diagnosed, a current detector is prepared for each control panel provided for each induction motor, and load current data for each induction motor is automatically collected at once. Then, they may be taken in and subjected to frequency analysis. These configurations belong to the free design range of the embodiment of the present invention.

The data collection device 20 desirably processes data at a sampling frequency of 2 kHz or higher in order to increase the resolution of the result of frequency analysis. Further, since the abnormality of the facility is diagnosed by the behavior of the analysis waveform (waveform disturbance, swell, etc.), it is desirable to use the Hamming window function as the window function used in the frequency analysis device 21.
The frequency analysis device 21 compares the behavior of the waveform obtained by frequency analysis with the behavior of a predetermined waveform, and determines the presence / absence of an abnormality and the location of the abnormality based on the result. Normally, a waveform with a mixture of multiple waveforms is displayed depending on the location of the abnormality and the form of the abnormality. However, the equipment configuration and installation status of the equipment, as well as information on equipment specifications and equipment operating status, etc. Therefore, it is possible to easily identify an abnormal part. Information on the behavior of the predetermined waveform includes, for example, a wide area shown in FIG. 5B, a sideband frequency corresponding to the rotation frequency shown in FIGS. 6A and 6B, and a diagram. The sideband frequency corresponding to the natural frequency and relative speed of the bearing shown in FIG. 7B, the waveform disturbance shown in FIG. 8A, the waveform swell and disturbance shown in FIG. 9B, and the operating frequency f _{And information on L} and its odd harmonic nf _L (n is an odd integer value of 3 or more), and the like. Such information is stored in advance in a storage device in the frequency analysis device 21 based on, for example, an operation by the user.

FIG. 11 is a diagram illustrating an example of the behavior of a waveform obtained by frequency analysis.
In the waveform shown in FIG. 11-1 (a), around the operating frequency f _L, is gently attenuated as foot of the mountain. Further, the line width of the waveform is narrow without any disturbance. Furthermore, there is no undulation in the waveform. When such a waveform is obtained as a result of the frequency analysis, the equipment is in a normal state (the state where the induction motor 14 is new, the stator coil is replaced or overhauled, and then the induction motor 14 is placed on the surface plate. It is determined that the vehicle is in a fixed state with no load and fully acclimated.
In the waveform shown in FIG. 11-1 (b), the operating frequency f _L not gradually attenuate mainly, the operation frequency f _L by ± several Hz trapezoidal wider range of the level also becomes higher. If such a waveform is obtained as a result of the frequency analysis, it is basically determined that the load fluctuation is normal. However, when the left and right balance of the wide portion is shifted or undulated, it is determined that the load fluctuation is abnormal.

In the waveform shown in FIG. 11A, the waveform is distorted along the attenuation curve at the crest of the waveform shown in FIG. 11A, and the attenuation curve at the crest is thick. If such a waveform is obtained as a result of the frequency analysis, it is determined that the bearing / speed reducer is deficient in grease or slightly stuck.
In the waveform shown in FIG. 11-2 (a), the attenuation curve at the crest of the waveform shown in FIG. 11-1 (c) is wavy. This phenomenon is also observed in a frequency band of 100 Hz or higher. If such a waveform is obtained as a result of the frequency analysis, it is determined that the bearing is damaged, the induction motor 14 or the mounting bolt of the bearing is loose, the rigidity of the mounting base is insufficient, and the like.
In the waveform shown in FIG. 11-2 (b), on both sides of the operation frequency f _L, sideband frequency corresponding to the rotational frequency has appeared. Further, when the torque fluctuation is large, a sideband frequency twice that appears. If such a waveform is obtained as a result of frequency analysis, damage to the inner ring or outer ring of the bearing, misalignment of the coupling, load imbalance, uneven wear of the shaft of the bearing, etc. To be judged.
In the waveform shown in FIG. 11-2 (c), on both sides of the operation frequency f _L, a number of sideband frequencies different from the rotation frequency has appeared. This sideband frequency matches the natural frequency of the bearing or the rotational frequency of each axis of the speed reducer. If such a waveform is obtained as a result of frequency analysis, bearing damage (generation of surface defects on the rolling elements and generation of defects on the rolling surfaces of the inner and outer rings), abnormalities and damage to the speed reducer (missing gear of the speed reducer) It is judged that there has been a breakage or tooth meshing failure).

The induction motor 14 is a power source for driving the equipment, and is also a highly sensitive high-sensitivity sensor. The load current of the induction motor 14 is not limited to the induction motor 14 itself for driving the equipment. Various operating statuses and abnormality information on the equipments 17 (speed reducer, mechanical device, etc.) to be processed are included. Under such knowledge, in this embodiment, at least one of the load current and the zero-phase current of the induction motor 14 that drives the devices 17 is measured. And from the result of the frequency analysis (especially 100 Hz or less), at least one of the frequency (position) and size of the sideband appearing on both the high frequency side and the low frequency side of the operating frequency f _L , and the frequency analysis The at least one of the turbulence and undulation of the waveform is compared with both or any one of the predetermined conditions. And the abnormality of the installation containing the induction motor 14, the equipment 17, and the coupling 16 is diagnosed from the result of the comparison. Thereby, in this embodiment, the effect shown to the following (1)-(5) etc. is acquired.

(1) Since it is possible to diagnose the abnormality of the equipment in the normal operation state without stopping the induction motor 14 that drives the equipment and the equipment 17 that is driven by the induction motor 14, it is possible to avoid the operation stop due to troubles, maintenance work Cost reduction such as simplification and cost reduction becomes possible.
(2) Since the induction motor 14 and its control device (frequency analysis device 20) are separated and usually the control devices are aggregated and an electric room is installed, the operator installs the induction motor 14 It is safe to check the operating status and abnormalities of equipment in the electrical room without going to the site.
(3) Since the amount of information contained in the load current of the induction motor 14 is abundant, and based on the load current of the induction motor 14, the operating state / abnormal state of the equipment can be grasped at an early stage. Can be formulated.
(4) Since the induction motor 14 itself is a high-sensitivity sensor with high accuracy, the only new sensor necessary for diagnosis is the current detector 19, and therefore, a very inexpensive and highly reliable facility diagnosis is possible.
(5) In order to determine equipment abnormalities, the criteria for judging equipment abnormalities can be determined by the position and size of sidebands, waveform disturbances and undulations, operating frequencies and odd harmonics. It is no longer necessary to determine the criteria by trial and error. Therefore, it is possible to reduce the time and labor for creating a standard for determining an abnormality of equipment as compared with the conventional case.

Next, examples of the present invention will be described.
Example 1
FIG. 12 shows the result of frequency analysis when the induction motor 14 is operated with no load after the bearing of the induction motor 14 is replaced with a new one. The induction motor 14 used to obtain the analysis result shown in FIG. 12 has a rated output of 95 kW 3 kW 23 A, a pole number of 4 P, a rated rotational speed of 1460 min ⁻¹ , and an insulation class of B type.

FIG. 12A shows the result of frequency analysis of the load current of the induction motor 14 immediately after startup. In the waveform shown in FIG. 12A, the decay curve of the mountain skirt extending to both sides with the operating frequency (50 Hz) as the center is severely disturbed, and the undulation of the decay curve is also large. Further, the sideband frequency of ± 24.93 Hz corresponding to the rotation frequency, ± 7.23 Hz corresponding to the natural frequency of the bearing (the revolution frequency f _C of the rolling element 7), and ± 14.43 Hz which is twice the frequency thereof. The sideband frequency of appears. This is a phenomenon that appears in the early stages of new bearings. The bearing has a gap defined by the standard. Immediately after the induction motor 14 is started, the temperature of the bearing does not rise, and therefore, in the initial stage of a new bearing, the bearing rotates with this gap existing. Therefore, a minute torque fluctuation accompanying the rotation appears on the drive shaft 15 as a sideband frequency of the rotation frequency. Further, since the grease supplied to the bearing does not spread everywhere, the rolling element 7 cannot smoothly rotate between the outer ring 10 and the inner ring 9 of the bearing, and as a result, the drive shaft 15 has a minute amount corresponding to the natural frequency of the bearing. Torque fluctuations appear as disturbances and undulations in the sideband frequency and attenuation curve.

  FIG. 12B shows the result of frequency analysis of the load current of the induction motor 14 after two hours have passed since the start. Compared with the waveform shown in FIG. 12 (a), the waveform shown in FIG. 12 (b) has no undulation of the attenuation curve at the foot of the mountain extending to both sides around the operating frequency (50Hz), and the waveform is less disturbed. . This is because with the operation of the induction motor 14, the temperature of the bearing rises, and the rolling element 7, the outer ring 10, and the inner ring 9 are expanded by heat, so that the gap originally in the bearing is reduced.

  FIG. 12C shows the result of frequency analysis of the load current of the induction motor 14 after 3 hours have passed since the start. As the operating time elapses, the grease softens as the temperature rises and reaches the inside of the bearing, so that the rolling element 7 can rotate smoothly between the outer ring 10 and the inner ring 9 of the bearing. As a result, FIG. As shown in the waveform of c), the disturbance of the decay curve of the mountain skirt extending to both sides with the operating frequency (50 Hz) as the center is eliminated.

  In other words, this phenomenon shows that a new bearing faithfully describes the process of getting used as the operating time elapses. If the operation of the induction motor 14 is further continued, the result of the frequency analysis of the load current of the induction motor 14 this time due to the deterioration of the grease or the like is changed from the waveform shown in FIG. 12C to the waveform shown in FIG. Transition to the state. If the grease further deteriorates and the grease loses its function as a lubricating oil, the rolling element 7 of the bearing or the outer ring 10 and the inner ring 9 are damaged, and the state of the waveform shown in FIG. Thus, it is possible to diagnose a bearing abnormality.

(Example 2)
FIG. 13 shows the result of frequency analysis of the zero-phase current of the induction motor 14. The induction motor 14 used to obtain the analysis result shown in FIG. 13 has a rated output of 1.5 kW 400 V 3.6 A, a pole number of 6 P, a rated rotational speed of 935 min ⁻¹ , and an insulation class of B type. . Specifically, FIG. 13 (a) shows the result of frequency analysis of the zero-phase current when the stator coil of the induction motor 14 is normal, and FIG. 13 (b) shows an abnormality in the stator coil of the induction motor 14 ( The result of the frequency analysis of the zero-phase current when a (rare short) occurs is shown.

As described above, the zero-phase current of the induction motor 14 is normally zero from (Equation 4), and as a result of frequency analysis, the characteristic operating frequency f _L and its odd harmonic nf _L (n is An odd integer value of 3 or more) does not appear or is a very small value. The state is the state shown in FIG. 13A, and the frequency analysis result of the zero-phase current shown in FIG. 13A shows that the operating frequency f _L and its odd harmonic nf _L (n is 3 or more). An odd integer value). This indicates that the stator coil of the induction motor is in a normal state with no abnormality.

On the other hand, in FIG. 13B, sideband frequencies (± 16.63 Hz and twice the frequency) corresponding to the rotation frequency appear on both sides with the operating frequency f _L as the center. In addition, odd harmonics (particularly the third, fifth, and seventh orders) appear greatly (see the part indicated by the downward arrow line in FIG. 13B). Further, similarly to the vicinity of the operating frequency f _L , an attenuation curve like a mountain tail appears around each odd harmonic nf _L and a sideband frequency of the rotational frequency also appears. Since the magnetic flux distribution of the rotating magnetic field generated by the stator coil forms a square wave, odd harmonics are superimposed on the phase current of the induction motor 14, but if normal, the odd harmonics nf _L are generated at zero phase current. The fact that the odd-numbered harmonic nf _L appears conspicuously when it becomes zero or a very small value indicates that the stator coil is abnormal. Based on this result, when the induction motor 14 was opened and investigated, the first coil of the U phase was rarely short-circuited. Further, the sideband frequency of the rotational frequency exists on both sides of the operating frequency f _L and the odd harmonic nf _{L because} the rotating magnetic field is unbalanced due to the rare short of the stator coil. This is because a slight torque fluctuation is generated in FIG. In addition, you may make it confirm the disturbance and the wave | undulation of the attenuation curve of the odd harmonic vicinity instead of the odd harmonic itself.

The embodiment of the present invention described above can be realized by a computer executing a program. Further, a means for supplying the program to the computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium for transmitting such a program may be applied as an embodiment of the present invention. it can. A program product such as a computer-readable recording medium that records the program can also be applied as an embodiment of the present invention. The programs, computer-readable recording media, transmission media, and program products are included in the scope of the present invention.
In addition, the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  The present invention provides a facility including an induction motor by measuring at least one of a load current and a zero-phase current of an induction motor that drives a device and comparing the result of frequency analysis with a predetermined behavior. This makes it possible to diagnose abnormalities in the components that make up the equipment, and enables inexpensive and effective equipment diagnosis and wide application in industries that have enormous facilities such as the steel industry and chemical plants.

7 Rolling elements of bearing 8 Drive shaft 9 Inner ring of bearing 10 Outer ring of bearing 14 Induction motor to be diagnosed 15 Induction motor drive shaft 16 Coupling 17 Equipment 18 Control board of induction motor 19 Current detector 20 Data collection device 21 Frequency Analysis device

Claims (4)

An equipment abnormality diagnosis method for diagnosing abnormality of equipment having an induction motor, a device driven by the induction motor, and a coupling that interconnects the induction motor and the device,
A current measuring step of measuring a load current for at least one phase of the induction motor;
A frequency analysis step for frequency analysis of the measured load current;
In the waveform obtained by the frequency analysis, the presence or absence of sidebands appearing on both the high frequency side and the low frequency side of the operating frequency, which is the frequency of the voltage applied to the induction motor, the position of the sidebands, and An abnormality determination step of determining whether there is an abnormality in the equipment based on at least one of the sizes, and determining the type of abnormality in the equipment when there is an abnormality in the equipment, An abnormality diagnosis method for equipment to be used. An equipment abnormality diagnosis method for diagnosing abnormality of equipment having an induction motor, a device driven by the induction motor, and a coupling that interconnects the induction motor and the device,
A current measuring step of measuring a load current for at least one phase of the induction motor;
A frequency analysis step for frequency analysis of the measured load current;
Abnormality determination step of determining the presence or absence of abnormality of the equipment based on the state of waveform disturbance and undulation obtained by the frequency analysis, and determining the type of abnormality of the equipment when there is abnormality of the equipment And an abnormality diagnosis method for equipment. In the current measuring step, instead of a load current for at least one phase of the induction motor, a zero-phase current of the induction motor is measured,
The equipment abnormality diagnosis method according to claim 1, wherein the frequency analysis step performs frequency analysis on the measured zero-phase current. In the current measurement step, in addition to the load current for at least one phase of the induction motor, further measure the zero-phase current of the induction motor,
3. The facility abnormality diagnosis method according to claim 1, wherein the frequency step performs frequency analysis of both the measured load current and zero phase current.

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