JP6410572B2 - Current diagnostic device and current diagnostic method - Google Patents

Description

  The present invention relates to a current diagnosis apparatus and a current diagnosis method. More specifically, the present invention relates to an abnormality diagnosis technique using a current diagnosis method.

  Diagnosis technology for diagnosing equipment composed of a motor, a load device driven by the motor, and a coupling connecting both of them, large-scale important rotating equipment including a turbine and a blower, and a compressor It is used in various facilities such as high-speed rotating equipment.

  As such a diagnostic technique, a method using axial vibration by an eddy current sensor or bearing box vibration by a piezoelectric acceleration sensor has been proposed. For example, if a spectrum pattern obtained by applying fast Fourier transform (FFT) to waveform data such as vibration and sound generated from a bearing is compared with a preset spectrum pattern at the time of abnormality, the comparison result It is possible to diagnose the bearing based on the above.

  As described above, since the vibration diagnosis technology requires measurement of vibration in the diagnosis target device, a vibration measurement sensor must be installed in the vicinity of the vibration target device, and the sensor must be installed. For example, the sensor must be installed in the vicinity of the vibration measuring device. However, since such installation work is actually difficult, there may be a situation where it is extremely difficult to evaluate the soundness by monitoring the state at the site by applying the vibration diagnosis technique.

  For example, when monitoring the status of rotating equipment that is difficult to directly sense in high radiation areas or high places / narrow places (such as in pits), submersible pumps, high-temperature facilities, etc. Data collection is difficult from the viewpoint of ensuring work safety and personal safety. Therefore, it is difficult to evaluate the soundness of rotating equipment in the facility.

  On the other hand, paying attention to such problems of vibration diagnosis technology, as another technology for diagnosing equipment abnormality, the load current of the motor driving the equipment is measured, the harmonic content contained in the load current is detected, the load A current diagnosis method for diagnosing an abnormality in equipment can be exemplified by comparing absolute values and relative values of current, detecting sudden changes in load current, and the like (see, for example, Patent Documents 1 and 2).

  Motor current signature analysis (MCSA), which is one of current diagnosis methods, has an advantage that data can be collected from a place away from the facility because a signal is detected from a power cable. In other words, since the current waveform obtained from the power cable of the motor can be used for analysis, it is not necessary to install a sensor in the target facility on the site, and a power source installation place such as a power panel in an electrical room away from the site. Data collection is possible. Therefore, it is an effective method for monitoring the state of equipment in an area where measurement is impossible because a human cannot install a sensor.

  Moreover, such a current diagnosis technique can be applied to state monitoring of movable equipment (equipment whose measurement point moves, such as equipment traveling on rails or a robot). Furthermore, the current diagnosis technique can be applied not only to an abnormality of the motor but also to an abnormality detection of a load facility (a driven facility such as a pump or a fan connected to the motor).

JP 2011-257362 A JP 2010-288352 A

  However, in the motor current sign analysis, when an abnormality occurs, it cannot be determined whether the motor is abnormal or the load facility (pump, etc.) is abnormal. For this reason, although it does not know whether it is a motor and its load equipment, it can only judge that the abnormality has arisen in the said equipment. Also, in the current spectrum, the level of sideband generated around the power supply frequency and around the slot passing frequency (= number of rotations x number of rotor bars) is very small. In comparison, it is difficult to see the difference, and the abnormality detection capability may be inferior. For this reason, the present situation is that it has not established as a diagnostic method which can grasp | ascertain an abnormal condition reliably now.

  The present invention can collect diagnostic data at a location away from the device to be diagnosed to perform abnormality diagnosis of the device, improve the abnormality detection capability, and clarify which device has the abnormality. It is an object of the present invention to provide a current diagnostic apparatus and a current diagnostic method which can be diagnosed in a simple manner.

In order to solve such a problem, the present invention is a diagnostic device for diagnosing a diagnosis target device including a motor, a load device driven by the motor, and a coupling connecting both of them.
Current measuring means for measuring the load current of the motor;
Filtering means for determining a frequency range corresponding to a diagnostic item of the diagnostic target device;
Frequency analysis means for frequency analysis of the current waveform filtered by the filtering means;
From the frequency analysis result by the frequency analysis means, calculate the difference between the power supply frequency level of the motor and the rotational frequency sideband level of the diagnosis target device, and collate the calculated difference value with the first criterion. First abnormality determination means for determining presence or absence of a rotation system abnormality in the diagnosis target device based on the collated result;
A magnification calculation means for calculating and outputting a value obtained by dividing the spectrum of the frequency analysis result of the current waveform by a normal spectrum stored in advance as a magnification with respect to a normal value;
The magnification is checked against a second determination criterion set based on the correlation between the fluid abnormality in the diagnosis target device and the magnification, and the presence / absence of the fluid abnormality is determined based on the comparison result. A second abnormality determining means;
Spectral level calculation means for obtaining an average spectral level in a frequency range limited by filtering of the frequency analysis result by the frequency analysis means;
A result of collating the spectral level with a third criterion set based on a correlation between an abnormality of a bearing constituting the diagnosis target device and a magnitude of a change in the spectral level due to the presence or absence of the abnormality. A third abnormality determining means for determining the presence or absence of a bearing-derived abnormality derived from the bearing,
Diagnostic result output means for outputting at least one of the determination result by the first to third abnormality determination means and the notification content corresponding to the determination result;
Is included.

  The present inventor aimed at further practical application of the motor current sign analysis technique, and as a result of studying it as an aid to the application to the state monitoring of the rotating equipment, as a result, the sideband generated around the power supply frequency in the current spectrum We found a correlation between the wave level and the degree of anomaly degradation. In other words, when an abnormality such as coupling alignment is out of order or the blades of the load device are unbalanced, the rotor in the motor is shaken by vibrations caused by the abnormality, so that the air between the stator and the stator The gap interval varies and amplitude modulation occurs in the current waveform. As a result, the knowledge that the sideband level is increased was obtained. In the present invention, a determination criterion formulated based on the found correlation is used. That is, a first abnormality determination unit that compares the first determination criterion to determine the presence / absence of a rotating system abnormality, and a second abnormality determination unit that determines the presence / absence of a fluid abnormality by comparing the second determination criterion. And make a diagnosis based on the established criteria. Furthermore, in the present invention, the presence or absence of a bearing-derived abnormality is determined by collating with the third determination criterion. As described above, according to this current diagnostic apparatus, it is possible to diagnose whether there is an abnormality that has not been noticed by the conventional method, such as a rotation system abnormality, a fluid abnormality, and a bearing-derived abnormality in the diagnosis target device. In addition, according to such current diagnosis, it is not necessary to measure the vibration in the actual machine at the site as in the conventional vibration diagnostic technology, but by measuring the load current at a place away from the actual machine and analyzing it, It becomes possible to monitor the state of the equipment.

  In the present invention, a value obtained by dividing the spectrum of the frequency analysis result of the current waveform by the normal spectrum stored in advance is used as a magnification with respect to the normal value. As described above, the sideband generated around the power supply frequency is difficult to identify. However, in the present invention, it is easy to identify an abnormality by using a function of calculating a magnification with a normal value.

  In this current diagnostic device, the motor or the rotational system abnormality in the diagnostic target device is based on the occurrence of a sideband FL ± fr of the rotational frequency fr of the shaft around the power supply frequency FL in the current spectrum. It can be detected that an imbalance of the load device or a coupling misalignment has occurred.

  The current diagnosis device may determine the wear state of the bearing of the induction motor by calculating an average spectral level in a frequency range limited by the filtering. Since there is a correlation between the amount of wear of the rolling bearing and the level of the spectrum in the predetermined frequency range of the current, abnormality can be determined by such a current diagnostic device.

  In the current diagnostic apparatus, any one of the O / A value, the RMS value, and the average value can be calculated as the average spectrum level in the frequency range limited by the filtering.

  Furthermore, the current diagnostic apparatus may calculate the average spectral level in a frequency range of a power supply frequency FL ± 20 Hz. The fluid abnormality of the load equipment (driven equipment) can be detected by the level of the power supply frequency FL ± 20 Hz. Incidentally, in imbalance, misalignment, and the like, the rotor of the motor is excited according to the rotation frequency (vibrates once per rotation), and thus a sideband of the rotation frequency is generated. Further, when subjected to amplitude modulation, the frequency is generated on the plus side and the minus side of the power supply frequency FL. However, when air flows into the fluid of the load device (pump, etc.) from the valve or flange, the flow is disturbed or the flow rate suddenly changes, so there is no periodicity, and the magnitude of the load change is random and changes over time. Therefore, when such amplitude modulation is applied, an infinite number of spectra increase around the power supply (fluid abnormality).

Further, the present invention is a diagnostic method for diagnosing a diagnosis target device including a motor, a load device driven by the motor, and a coupling connecting both of them,
Measuring the load current of the motor;
Filtering the measured load current according to the frequency range corresponding to the diagnostic item of the diagnostic target device;
Frequency analyzing the filtered current waveform;
The difference between the power supply frequency level of the motor and the rotational frequency sideband level of the diagnosis target device is calculated from the frequency analysis result, the calculated difference value is checked against the first determination criterion, and the checking result is A step of determining the presence or absence of a rotating system abnormality in the diagnostic target device, based on
Calculating and outputting a value obtained by dividing the spectrum of the frequency analysis result of the current waveform by the normal spectrum stored in advance as a magnification with respect to the normal value;
The magnification is checked against a second determination criterion set based on the correlation between the fluid abnormality in the diagnosis target device and the magnification, and the presence / absence of the fluid abnormality is determined based on the comparison result. Process,
Obtaining an average spectral level of the frequency analysis result in a frequency range limited by filtering;
A result of collating the spectral level with a third criterion set based on a correlation between an abnormality of a bearing constituting the diagnosis target device and a magnitude of a change in the spectral level due to the presence or absence of the abnormality. A step of determining the presence or absence of a bearing-derived abnormality derived from the bearing,
Outputting at least one of the determination result and the notification content corresponding to the determination result;
Is included.

  According to the present invention, it is possible to collect diagnostic data at a location away from the device to be diagnosed to perform abnormality diagnosis of the device, and to improve abnormality detection capability so that any device has an abnormality. Can be clearly diagnosed.

It is a figure which shows the structural example of an electric current diagnostic apparatus. It is a figure which shows an example of a diagnostic object apparatus. It is a block diagram showing the function of a computer. It is a figure which shows the kind of coupling misalignment. It is a figure which shows an example of the spectrum at the time of misalignment. It is the graph which showed the relationship between the amount of unbalance at the time of an unbalance test, and FL ± fr sideband level. It is the graph which showed the relationship between the amount of imbalance and a vibration speed value level based on the data at the time of an unbalance test. 4B is a graph showing data obtained by dividing a current spectrum obtained by measuring the current spectrum of FIG. 4A on the vertical axis by a current spectrum in a normal state, and frequency on the horizontal axis. It is a figure which shows an example of the diagnostic reference | standard in the case of monitoring a state of a rotary machine with a vibration diagnostic technique. It is a graph which shows an example of the relationship between the spectrum level [dB] of the sideband of the current waveform at the time of imbalance, and a vibration speed value [mm / sec]. It is a graph which shows the current sideband level at the time of offset misalignment of coupling. It is a graph which shows the current sideband level at the time of angle misalignment. It is a graph which shows the current spectrum comparison at the time of rolling bearing wear and a normal time. It is a graph which shows the relationship between a rolling bearing wear amount and the current spectrum level of 900-1500Hz. It is a graph which shows the comparison of the current spectrum at the time of a pump flow rate change. It is a graph which shows the magnification with the time of normal current spectrum at the time of pump flow rate change. It is a graph which shows the comparison of the current spectrum at the time of air entrainment. It is a graph which shows the magnification with the time of normal current spectrum at the time of air entrainment. It is a graph which shows the comparison of the current spectrum at the time of the oil leak of a bearing. It is a graph which shows the magnification with the current spectrum normal time at the time of oil leakage of a bearing. It is a graph which shows the comparison of the current spectrum at the time of unbalance of a motor direct connection fan. It is a graph which shows the magnification with the normal time of the current spectrum at the time of imbalance of a motor direct connection fan. It is a graph which shows the magnification with the normal time after envelope-processing the current spectrum at the time of imbalance of a motor direct connection fan. It is a graph which shows the magnification with the normal time of the current spectrum at the time of fan (belt drive) imbalance. It is a table | surface which shows an example of the 1st determination criterion in an electric current diagnostic apparatus. It is a table | surface which shows an example of the 2nd determination criterion in an electric current diagnostic apparatus. It is a table | surface which shows an example of the 3rd determination criterion in an electric current diagnostic apparatus. It is a graph which shows the comparison of the current spectrum at the time of misalignment. It is a graph which shows the magnification with the normal time of the current spectrum at the time of misalignment. It is a graph which shows the change rate of the frequency around an angle misalignment amount and fc.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 shows a configuration example of the current diagnostic apparatus 1. The current diagnostic apparatus 1 includes a clamp ammeter (current measuring means) 2, a current data recording device 3, and a computer 10. The clamp ammeter 2 is installed on a power panel or the like and collects current data such as a current waveform. The current data recording device 3 records the current data collected by the clamp ammeter 2. The computer 10 has current waveform analysis software, and analyzes the current data recorded in the current data recording device 3 and outputs the result.

  In FIG. 2, an example of the diagnostic object apparatus 100 by the electric current diagnostic apparatus 1 is shown. The diagnosis target device 100 connects a motor (induction motor) 110 installed on a concrete foundation 140, a pump (an example of a load device) 120 driven by the motor 110, and the motor 110 and the pump 120. Coupling. The motor 110 includes a stator 112 and a rotor 114. The rotor 114 rotates the rotating shaft 130 supported by the bearing 160. One end of the rotary shaft 130 is attached with a pumping blade 170 constituting the pump 120. The rotating shaft 130 functions as a coupling that connects the motor 110 and the pump 120. Further, a flywheel 150 is attached to the rotor 114 as necessary during an abnormality test or the like.

  FIG. 3A is a block diagram showing functions of the computer 10 and the like. The computer 10 stores in advance a diagnostic program including current waveform analysis software and the like. According to the diagnostic program, the computer 10 (CPU) performs filtering means 12, frequency analyzing means 14, envelope processing means 16, normal spectrum storing means 18, magnification calculating means 20, rotating system abnormality determining means 22, and spectral level calculation. It functions as means 24, fluid abnormality determination means 26, and bearing-derived abnormality determination means 28. Further, the computer 10 causes the display unit 30 to display the diagnosis result.

  The filtering unit 12 determines a frequency range to be used for a diagnosis item of the diagnosis target device 100 by filtering. The frequency range is, for example, a range of 0 to 200 Hz, a range of 1 k to 2 kHz, and the like.

  The envelope processing unit 16 performs envelope processing (envelope processing) on the current waveform filtered by the filtering unit 12 to generate data after envelope detection.

  The frequency analysis unit 14 performs frequency analysis on the current waveform filtered by the filtering unit 12 and the data after envelope detection subjected to the envelope processing by the envelope processing unit 16. The signal subjected to frequency analysis by the frequency analysis unit 14 is transmitted to the magnification calculation unit 20, the rotation system abnormality determination unit 22, and the spectrum level calculation unit 24. Further, the frequency analysis signal when the diagnosis target device 100 is normal is stored in the normal spectrum storage means 18.

  The magnification calculation means 20 divides the spectrum of the current waveform signal frequency-analyzed by the frequency analysis means 14 by the normal spectrum stored in advance, and calculates the magnification for the normal value. While the conventional method of identifying sidebands generated around the slot passing frequency is difficult to identify, according to the current diagnostic apparatus 1 using the magnification with respect to the normal value, it is easy to identify the abnormality, and particularly the abnormal state is slight. This is especially true.

  The rotation system abnormality determination means 22 calculates the difference between the power supply frequency level of the motor 110 and the rotation frequency sideband level of the diagnosis target device 100 from the frequency analysis result by the frequency analysis means 14, and uses the calculated difference value as the first difference value. 1 is compared with the determination criterion 1, and the presence or absence of a rotating system abnormality in the diagnosis target device 100 is determined based on the comparison result.

  Here, the rotation system abnormality means an abnormality in the rotation system. Specifically, the misalignment of the coupling that occurs in the form of misalignment (offset misalignment), surface misalignment (angle misalignment), and misalignment and surface misalignment as described later (see FIG. 3B). ). When a mechanical abnormality such as a rotation system abnormality occurs in the motor 110 or the pump 120 (or a fan or the like), the rotating shaft 130 changes, and the rotor 114 of the motor 110 changes. As a result, the rotor 114 of the motor 110 vibrates via the coupling, so that the electromagnetic force changes and the current waveform changes.

  The first criterion is a criterion set for diagnosis based on the difference between the power frequency level of the motor 110 and the rotational frequency sideband level. An example of the first determination criterion is shown in FIG. The first determination criteria are the target frequency range, diagnosis method, reference value (determination content criteria), and abnormality diagnosis comments that correspond to the determination results and are notified as necessary. It is determined.

  The abnormality diagnosis comment may include not only a comment to be transmitted at the time of abnormality or attention, but also a comment to that effect when it is good (see FIG. 22). Alternatively, it can be shown that there is no abnormality or the like by not showing a comment when good. The same applies to the second determination criterion (FIG. 23) and the third determination criterion (FIG. 24) described later.

  The spectrum level calculation unit 24 obtains the spectrum level in the frequency range limited by the filtering of the filtering unit 12 of the frequency analysis result by the frequency analysis unit 14. As the spectrum level, an O / A value (overall value: sum of products of power spectra (Y-axis values) of each frequency subjected to FFT analysis) can be calculated. As an alternative to the O / A value, an RMS value (effective value) and an average value can also be calculated.

  The fluid abnormality determination unit 26 collates the magnification calculated by the magnification calculation unit 20 with the second determination criterion, and determines whether there is a fluid abnormality in the diagnosis target device 100 based on the comparison result.

  The fluid abnormality is an abnormality that can occur through the fluid of the load device, for example, the flow is disturbed when air enters the fluid of the pump. When a fluid abnormality occurs in the motor 110, the pump 120 (or a fan, etc.), the rotating shaft 130 changes, and the rotor of the motor 110 changes. As a result, the rotor 114 of the motor 110 vibrates via the rotating shaft (coupling) 130, so that the electromagnetic force changes and the current waveform changes.

  The second determination criterion is a determination criterion set based on the correlation between the fluid abnormality in the diagnosis target device 100 and the magnification described above. Further, the second determination criterion may define an abnormality diagnosis comment (notification content) that corresponds to the determination result collated with the determination criterion and is notified as necessary. An example of the second determination criterion is shown in FIG.

  The bearing-derived abnormality determination unit 28 collates the spectrum level transmitted from the spectrum level calculation unit 24 with a third determination criterion (see FIG. 24), and based on the collation result, the bearing constituting the diagnosis target device 100. The presence / absence of a bearing-derived abnormality resulting from 160 abnormality is determined.

  The third criterion is the abnormality of the bearing 160 and the magnitude of the change in the spectrum level due to the presence or absence of the abnormality (in other words, the difference between the spectrum level when the bearing 160 is abnormal and the spectrum level when the bearing 160 is normal). ) Is a determination criterion set based on the correlation with. An example of the third determination criterion is shown in FIG. In addition, the third determination criterion may define an abnormality diagnosis comment (notification content) that corresponds to the determination result collated with the determination criterion and is notified as necessary.

  Here, the determination based on the third determination criterion will be described. Here, it is determined whether or not the rolling bearing 160 is worn. When bearing wear occurs, the spectral level in a predetermined frequency region (for example, 900 to 1500 Hz) increases. This is because when the bearing 160 is worn, the clearance inside the bearing is expanded, and the rotor 114 of the motor 110 is swung around when the shaft is swung around. When the rotor 114 swings around, the space (air gap) between the stator 112 and the stator 112 fluctuates, so that the current waveform changes as the electromagnetic force acting on the motor 110 fluctuates. This fluctuation is a fluctuation that has undergone amplitude modulation due to the rotational frequency in unbalance or misalignment, and therefore, a sideband of the rotational frequency is generated around the power supply frequency in the current spectrum. The fluid level abnormality of the pump 120, the oil leakage of the bearing 160, and the like, since the modulation level and frequency are random, various spectra are generated around the power supply frequency. In the case of bearing wear, since the fluctuating frequency is high, it is assumed that a high frequency signal is superimposed on the current waveform, and an increase in the high frequency component of the current waveform is observed.

  The display means 30 is an abnormality that is a determination result by the rotation system abnormality determination means 22, a determination result by the fluid abnormality determination means 26, a determination result by the bearing-derived abnormality determination means 28, and a notification content of countermeasures corresponding to the determination result. Output and display diagnostic comments. The display means 30 may be a display for a device (such as a personal computer) including the computer 10 or a projector. Or the device etc. which transmit and display an output to a remote place may be sufficient. Note that, as described above, when a comment indicating that is good when it is displayed, three abnormality diagnosis comments corresponding to each of the first to third determination criteria are output. On the other hand, if the specification does not indicate a comment when the condition is good, at least one abnormality diagnosis comment is output when the condition is abnormal.

[Outline of diagnosis by current diagnosis device 1]
The diagnosis by the current diagnosis apparatus 1 of the present embodiment will be described using the graph shown in FIG. 4A and the like.

  Here, the terms are explained. Unbalance means that a scale is attached, damaged, worn, or the like on a rotating part (for example, a blade of a pump or a fan), resulting in an unbalanced state and vibration due to centrifugal force. It is the most popular abnormal vibration phenomenon that occurs at production sites. By the way, any rotating object has some degree of unbalance, but here, unacceptable is called unbalance.

  There are three types of coupling misalignment: misalignment (offset misalignment), surface misalignment (angle misalignment), and a combination of these misalignment and surface misalignment (see FIG. 3B). Misalignment may occur due to poor construction or shaft elongation or deformation due to temperature rise during operation, causing abnormal vibration.

<Coupling misalignment>
In response to an abnormality such as coupling misalignment, a rotation frequency (fr) sideband around the power supply frequency (FL) is generated (the frequency of the sideband is FL ± fr) (see FIG. 4A). This is because the current waveform is subjected to slight amplitude modulation by the rotation frequency.

  FIG. 5 shows the data obtained by dividing the current spectrum of the current spectrum of FIG. 4A on the vertical axis by the normal current spectrum and the frequency on the horizontal axis. Compared to FIG. 4A, the generation of sideband waves can be clearly displayed. Thereby, the presence or absence of the generation of sidebands is confirmed.

<Unbalance>
Similarly, when an imbalance occurs, the rotation frequency (fr) sideband around the power supply frequency (FL) (the frequency of the sideband is FL ± fr) is generated and correlated with the degree of abnormality. Judgment criteria were formulated in the form.

  Here, similarly, when an imbalance occurs, a rotation frequency (fr) sideband around the power supply frequency (FL) (the frequency of the sideband is FL ± fr) is generated and correlated with the degree of abnormality. The grounds for this are as follows. FIG. 4B shows the relationship between the unbalance amount and the FL ± fr sideband level during the unbalance test. When the weight (flywheel 150, etc.) is attached to the rotating part (rotor 114) and the unbalance amount is increased, the sideband (FL ± fr) level of the rotating frequency fr around the power supply frequency FL increases. It can be seen that there is a correlation between the degree of imbalance abnormality and the sideband level.

  FIG. 4C shows the relationship between the unbalance amount and the vibration speed value level based on the same unbalance test data. When monitoring the condition of rotating machinery, the vibration speed criterion applied to the pump is good if it is less than 4.0 mm / s, careful if it is 4.0 mm / s or more and less than 8.0 mm / s, or 8.0 mm / s or more but less than 16.0 mm / s. In case of 16.0mm / s or more, it is judged as dangerous.

<Unbalance criteria>
FIG. 6 shows an example of diagnostic criteria (hereinafter referred to as “AMD speed determination criteria”) when the state of a rotating machine such as the motor 110 or the bearing 160 is monitored by vibration diagnostic technology. FIG. 7 shows an example of the relationship between the spectral level [dB] of the sideband of the current waveform during unbalance and the vibration speed value [mm / sec]. Here, the horizontal axis represents the O / A value [mm / s] of the vibration speed when imbalance is generated in a motor of 15 kW capacity, and the level of the power frequency FL ± rotational frequency fr and the level of the power frequency in the current spectrum. The difference [dB] is shown as the vertical axis.

  When attention is paid to the contents of these figures (particularly, the contents of FIG. 7), it is found that the sideband spectrum level of the current waveform is correlated with the degree of abnormality of the motor. In other words, it can be seen that as the spectrum level of the sideband of the current waveform increases, the vibration speed value, which is one element representing the degree of abnormality, also increases. Therefore, an attempt is made to formulate a criterion using this current waveform spectrum. The vibration management standard for this motor is 2 mm / s or less is good, 4 to 8 mm / s is careful, 8 mm / s to 16 mm / s deteriorates, and 16 mm / s or more is dangerous (see FIG. 6). When this is applied to the relationship of FL + fr indicated by ● in FIG. 7, the vibration speed value corresponds to 4 mm / s is about −70 dB, and that corresponding to 8 mm / s is about −65 dB. Therefore, instead of vibration diagnosis using the vibration velocity value, use the sideband spectrum level of the current waveform, good if the difference between the power supply frequency level and the sideband level is 70 dB or more, be careful at 70 to 65 dB, 65 dB or less Can be determined as abnormal. Thus, in the current diagnostic device 1 of the present embodiment, the diagnosis target device 100 can be diagnosed by obtaining the difference between the sideband level of the rotation frequency around the power supply frequency and the power supply frequency level.

  The characteristics of the current diagnostic apparatus 1 of the present embodiment described so far are summarized as follows.

  (1) The correlation between the level of the sideband generated around the power supply frequency and the degree of abnormality deterioration is found in the current spectrum, a determination criterion is established, and the diagnosis target device 100 is diagnosed based on this determination criterion. According to this, since current diagnosis can be performed instead of vibration diagnosis, it is possible to monitor the state at the site by formulating such a determination criterion.

  (2) Since the sideband generated around the conventional slot passing frequency is very difficult to discriminate, the magnification calculating means 20 is used to display the magnification relative to the normal value. Thereby, since the S / N ratio and the visibility are improved by displaying the amount of change at the time of abnormality (spectrum) as compared with the normal time, it is easy to identify the abnormality. In addition, a magnification display is used around the power supply frequency so that it can be easily identified when the abnormal state is slight.

  (3) The wear phenomenon of the rotating equipment in the diagnosis target equipment such as the rolling bearing 160 can be diagnosed by a level in a specific frequency range (for example, 900 to 1500 Hz). This is a diagnostic method that did not exist before, and a criterion was formulated.

  (4) The fluid abnormality of the load device (pump) can be detected by the level of the power supply frequency ± 20 Hz. This is also a diagnostic method that was not available in the past, and criteria were formulated.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

  Here, this inventor tested about applying the electric current diagnostic apparatus 1 of this embodiment to various diagnoses. Hereinafter, it demonstrates as an Example.

<Alignment criteria>
The alignment tolerance at 1800 rpm for the coupling of Pruftechnik Co.
・ Offset: Acceptable 0.08mm, Excellent 0.05mm
・ Angle: Acceptable 0.05mm, Excellent 0.03mm <Surface opening at coupling diameter 160mm>
Since the coupling used in this testing machine is 160 mm, the “acceptable” angle is 0.08 mm and the “excellent” is 0.048 mm. A test using the current diagnostic apparatus 1 of the present embodiment was performed when the degree of misalignment abnormality was variously changed for this coupling. The results are shown in FIGS.

  FIG. 8 is a graph showing the current sideband level during offset misalignment due to coupling misalignment, and FIG. 9 is a graph showing the current sideband level during angle misalignment due to surface misalignment. As shown in FIGS. 8 and 9, both the offset misalignment and the angle misalignment are good when the difference between the power supply frequency level and the sideband level is 70 dB or more, but the current sideband level difference corresponding to the alignment allowable value. Below (for example, 70 dB), the allowable value is exceeded.

<Bearing wear criteria>
Generally, when the lubrication state of the rolling bearing deteriorates, wear occurs on the rolling elements (balls and rollers) and the transfer surfaces of the inner ring and the outer ring. When wear of the rolling bearing progresses, rattling may occur and the bearing may be damaged due to damage to the cage. Further, when the vibration is vibrated to an amplitude close to the air gap, the rotor 114 and the stator 112 are contacted and short-circuited, Sudden stoppage may occur.

  Here, the present inventor tried to formulate the wear judgment criteria of the rolling bearing. A test was conducted to measure the current spectrum when the inner ring thickness of the same bearing was worn by 50 μm, 100 μm, 150 μm, and 200 μm, and the level of the current spectrum in various frequency ranges at each wear was compared with the normal spectrum. FIG. 10 is a graph showing a comparison of current spectra when the rolling bearing is worn and when it is normal, and FIG. 11 is a graph showing a relationship between the amount of wear of the rolling bearing and a current spectrum level of 900 to 1500 Hz.

  As a result, it was confirmed that the wear of the rolling bearing can be diagnosed by focusing on the current spectrum level of 900 to 1,500 Hz.

<Detection of air entrainment>
Attempt to detect air entrainment. FIG. 12 is a graph showing a comparison of current spectra when the pump flow rate is changed, FIG. 13 is a graph showing a magnification with respect to the normal current spectrum when the pump flow rate is changed, and FIG. 14 is a comparison of current spectra when air is involved. FIG. 15 is a graph showing the magnification with respect to the normal current spectrum at the time of air entrainment.

  Air entrainment (to the fluid) refers to an event in which air is mixed in due to deterioration of the packing at the flange (joint of piping), deterioration of the valve gland, etc., or air is mixed into the fluid in the reducer. It is. When air is entrained in the fluid, it becomes turbulent and adversely affects the performance of the pump.

When the pump flow rate change (for example, valve throttle 40m ³ / Hr → 16m ³ / Hr) or when air is entrained in the fluid, an increase in the level in the range of power supply frequency -20Hz to power supply frequency + 20Hz was observed. Is remarkable).

<Detection of out of oil>
A test was carried out in which the amount of lubricating oil in the rolling bearing was reduced to make it oil-spilled, and the current spectrum at this time was measured. FIG. 16 is a graph showing a comparison of the current spectrum when the bearing is leaked, and FIG. 17 is a graph showing a magnification with respect to the normal current spectrum when the bearing is leaked. Even in the case of poor lubrication of the rolling bearing (for example, oil leakage), an increase in level in the region of power supply frequency −20 Hz to power supply frequency +20 Hz was observed as in the above-described embodiment. In the case of a fluid abnormality, the level in the ± 20 Hz region around the power supply frequency rises, whereas in this embodiment, it is confirmed that the level in the ± 20 Hz region around the power supply frequency rises in the same way even when the rolling bearing is oiled. It was done.

<Unbalance of motor direct fan>
FIG. 18 is a graph showing a comparison of current spectra when the motor direct connection fan is unbalanced, and FIG. 19 is a graph showing a magnification of the current spectrum when the motor direct connection fan is unbalanced with a normal state. FIG. 20 is a graph showing the magnification of the spectrum obtained by enveloping the current waveform when the motor-directly connected fan is unbalanced and performing frequency analysis.

Specific specifications in Example 5 are as follows.
(Equipment specifications)
Motor capacity: 22kw
Power frequency (FL): 50Hz
Actual rotation frequency (fr): 49.6Hz
FL + fr = 99.6Hz
(Vibration diagnosis result)
When the vibration measurement was carried out, the vibration speed value was 9.0 mm / sec, which was in the deterioration (D zone) region in the AMD speed determination criteria. In addition, when the vibration waveform was subjected to frequency analysis, the dominant frequency was the rotation frequency (fr), and it was determined that the fan was unbalanced.
(Current diagnosis result)
When current diagnosis was performed using the current diagnosis device 1 of the present embodiment, the level difference between the FL + fr component and the FL component at the time of abnormality in the current spectrum is 67.0 dB, and if it is unbalanced, attention (C zone) If it was misalignment, it was determined to be greater than the allowable value.

  When the fan was stopped and the blade was inspected for opening, dust was found to adhere to the surface of the blade. As a result, it was determined that an imbalance had occurred, cleaning was performed, and operation was started again. When the vibration measurement was performed, the vibration velocity value decreased to a favorable range of 2.6 mm / s. In addition, when current diagnosis was performed using the current diagnosis device 1 of the present embodiment, the level of FL + fr component in the current spectrum decreased after cleaning, and the level difference between FL + fr and FL component was 75.5 dB, which was a favorable range. .

  Even when the motor direct fan was unbalanced, an increase in the sideband level of the power supply frequency ± the rotation frequency was observed as in the above-described embodiment.

<Fan (belt drive) imbalance>
FIG. 21 is a graph showing the magnification of the current spectrum when the fan (belt drive) is unbalanced. Specific specifications in Example 6 are as follows.
(Equipment specifications)
Motor capacity: 15kw
Power frequency (FL): 50Hz
Motor actual rotation frequency (fr): 24.0Hz
Fan actual rotation frequency (fr1): 26.8Hz
FL ± fr = 26.0Hz, 74.0Hz
(Vibration diagnosis result)
When the vibration measurement was performed, it was determined that the vibration speed value was 10.1 mm / sec and the area was deteriorated (D zone) in the AMD speed criterion. In addition, frequency analysis of the vibration waveform revealed that the dominant frequency was fr1 (fan rotation frequency), and the fan was unbalanced.
(Current diagnosis result)
When current diagnosis is performed using the current diagnosis device 1 of the present embodiment, the level difference between the FL-fr component and the FL component in the current spectrum is 62.5 dB, and if it is unbalanced, the deterioration (D zone) region If it is misalignment, it was determined to be greater than the allowable value.

  Even when the fan (belt drive) is unbalanced, an increase in power supply frequency ± rotational frequency sideband level was observed as in the above-described embodiment.

<Criteria>
An example of the determination standard that has been formulated from the above-described embodiment and the results of each example is shown as Example 7 in FIGS. By finding the frequency band linked to the abnormal level of the diagnosis target device by the above-mentioned diagnosis technology, the equipment diagnosis can be classified into “good”, “caution”, “abnormal”, etc. Established technology.

Comparative Example 1

  The present inventor has verified a conventional diagnostic method for determination at a sideband level around the slot frequency fc. Hereinafter, the result is described as Comparative Example 1 for reference. Here, it verified in the range around a slot frequency.

  FIG. 25 is a graph showing a comparison of current spectra at the time of coupling misalignment, and FIG. 26 is a graph showing the magnification of the current spectrum at the time of misalignment with that at normal time. FIG. 27 is a graph showing the angle misalignment amount and the frequency change rate around the slot frequency fc. In FIG. 27, the horizontal axis represents the angle misalignment amount [°], and the vertical axis represents the rate of change (magnification value).

  As can be seen from the contents of FIG. 27, no correlation was observed between the degree of abnormality (abnormal level) and the rate of change of the frequency around the slot frequency fc used in the conventional method.

  The present invention is suitable for application to an apparatus for diagnosing a device constituted by a motor, a load device driven by the motor, and a coupling connecting both of them.

DESCRIPTION OF SYMBOLS 1 ... Current diagnostic apparatus 2 ... Clamp ammeter (current measuring means)
3 ... Current data recording device 10 ... Computer 12 ... Filtering means 14 ... Frequency analysis means 18 ... Normal spectrum storage means 20 ... Magnification calculation means 22 ... Rotational system abnormality determination means (first abnormality determination means)
24... Spectral level calculation means 26... Fluid abnormality determination means (second abnormality determination means)
28 ... Bearing-derived abnormality determination means (third abnormality determination means)
30: Display means (diagnosis result output means)
100 ... Diagnosis target device 110 ... Motor 120 ... Pump (load device)
130 ... Rotating shaft (coupling)
160 ... Bearing

Claims (6)

A diagnostic device for diagnosing a diagnosis target device including a motor, a load device driven by the motor, and a coupling connecting both of them,
Current measuring means for measuring the load current of the motor;
Filtering means for determining a frequency range corresponding to a diagnostic item of the diagnostic target device;
Frequency analysis means for frequency analysis of the current waveform filtered by the filtering means;
From the frequency analysis result by the frequency analysis means, calculate the difference between the power supply frequency level of the motor and the rotational frequency sideband level of the diagnosis target device, and collate the calculated difference value with the first criterion. First abnormality determination means for determining presence or absence of a rotation system abnormality in the diagnosis target device based on the collated result;
A magnification calculation means for calculating and outputting a value obtained by dividing the spectrum of the frequency analysis result of the current waveform by a normal spectrum stored in advance as a magnification with respect to a normal value;
The magnification is checked against a second determination criterion set based on the correlation between the fluid abnormality in the diagnosis target device and the magnification, and the presence / absence of the fluid abnormality is determined based on the comparison result. A second abnormality determining means;
Spectral level calculation means for obtaining an average spectral level in a frequency range limited by filtering of the frequency analysis result by the frequency analysis means;
A result of collating the spectral level with a third criterion set based on a correlation between an abnormality of a bearing constituting the diagnosis target device and a magnitude of a change in the spectral level due to the presence or absence of the abnormality. A third abnormality determining means for determining the presence or absence of a bearing-derived abnormality derived from the bearing,
Diagnostic result output means for outputting at least one of the determination result by the first to third abnormality determination means and the notification content corresponding to the determination result;
A current diagnostic device.   Based on the occurrence of a sideband FL ± fr of the rotational frequency fr of the shaft around the power supply frequency FL in the current spectrum, the motor or the load device is unbalanced, which is the rotational system abnormality in the diagnosis target device, Alternatively, the current diagnostic apparatus according to claim 1, wherein the occurrence of coupling misalignment is detected.   The current diagnosis apparatus according to claim 2, wherein the wear state of the bearing of the motor is determined by calculating an average spectral level in a frequency range limited by the filtering.   The current diagnosis apparatus according to claim 3, wherein any one of an O / A value, an RMS value, and an average value is calculated as an average spectrum level in a frequency range limited by the filtering.   The current diagnosis apparatus according to claim 4, wherein the average spectrum level in a frequency range of a power supply frequency FL ± 20 Hz is calculated. A diagnostic method for diagnosing a diagnosis target device including a motor, a load device driven by the motor, and a coupling connecting both of the motor,
Measuring the load current of the motor;
Filtering the measured load current according to the frequency range corresponding to the diagnostic item of the diagnostic target device;
Frequency analyzing the filtered current waveform;
The difference between the power supply frequency level of the motor and the rotational frequency sideband level of the diagnosis target device is calculated from the frequency analysis result, the calculated difference value is checked against the first determination criterion, and the checking result is A step of determining the presence or absence of a rotating system abnormality in the diagnostic target device, based on
Calculating and outputting a value obtained by dividing the spectrum of the frequency analysis result of the current waveform by the normal spectrum stored in advance as a magnification with respect to the normal value;
The magnification is checked against a second determination criterion set based on the correlation between the fluid abnormality in the diagnosis target device and the magnification, and the presence / absence of the fluid abnormality is determined based on the comparison result. Process,
Obtaining an average spectral level of the frequency analysis result in a frequency range limited by filtering;
A result of collating the spectral level with a third criterion set based on a correlation between an abnormality of a bearing constituting the diagnosis target device and a magnitude of a change in the spectral level due to the presence or absence of the abnormality. A step of determining the presence or absence of a bearing-derived abnormality derived from the bearing,
Outputting at least one of the determination result and the notification content corresponding to the determination result;
A current diagnostic method.