ANOMALIA DIAGNOSTIC DEVICE, ANOMALIA DIAGNOSTIC PROCEDURES AND ANOMALIA DIAGNOSTIC SYSTEM

Abstract

An anomaly diagnostic device comprising: - a data acquisition unit configured to acquire a current waveform and drive frequency of an electric motor driven by an energy conversion device; - an operating pattern storage unit storing a combination of a current value of the current waveform and the drive frequency acquired by the data acquisition unit at the same time; - a data determination unit configured to determine whether a current value of the current waveform and the drive frequency, acquired by the data acquisition unit at the same time, match the combination stored in the operating pattern storage unit as a diagnostic target;- an analysis unit configured to perform a frequency analysis on the current waveforms that have been determined by the data determination unit to be congruent, to extract sideband waves, and to calculate the spectral intensity of the sideband waves; and - an anomaly diagnostic unit configured to perform a diagnosis that an anomaly has occurred when the spectral intensity of the sideband waves is equal to or greater than a threshold value.

Description

Technical field The present invention relates to an anomaly diagnosis for an electric motor driven by an energy conversion device. State of the art An electric motor is a key component, serving as a drive unit for assembly line equipment or mechanical devices in industrial plants. Therefore, its continuous, normal, and stable operation is essential. However, many electric motors operate in highly demanding environments, such as high temperatures, heavy loads, corrosion, and wear. Consequently, there is a high probability of sudden malfunctions. To prevent such sudden failures, there is a significant need for technology that continuously monitors electric motors. Recently, a continuous monitoring technology has been developed with an anomaly diagnostic device that diagnoses an anomaly in an electric motor by measuring the current applied to the motor. For example, in patent document 1, the current applied to an electric motor driven by a mains power supply is measured and subjected to frequency analysis, and it is diagnosed whether or not an anomaly has occurred based on the spectral intensity of sideband waves resulting from the anomaly, which occur at frequencies close to the power supply frequency. Patent document 2 relates to a diagnostic device for electric motors which is able to diagnose the presence or absence of a fault in an electric motor by detecting sideband waves that arise in peak values ​​on both sides in the range of the mains frequency, even in an electric motor in which the load torque fluctuates. Bibliography Patent document Patent document 1: JP 2016 - 090 546 APatent document 2: JP 2016 - 195 524 A Summary of the invention Problems to be solved with the invention However, if an electric motor is driven by an energy conversion device, the following applies: If the current and drive frequency change, the spectral intensity of sideband waves, which serves as an anomaly diagnostic criterion, also changes. Therefore, it cannot be determined whether the change in the spectral intensity of the sideband waves is caused by the degree of anomaly or by a change in the current and drive frequency, and thus it is difficult to diagnose whether or not an anomaly has occurred. The present invention was designed to solve the above problem, and it is an object of the present invention to provide an anomaly diagnostic device, an anomaly diagnostic method and an anomaly diagnostic system which are capable of diagnosing whether or not an anomaly has occurred, even for an electric motor in which the current value and the drive frequency change as a result of the energy conversion device. Problem solving An anomaly diagnostic device according to the present invention comprises: a data acquisition unit configured to acquire a current waveform and a drive frequency of an electric motor driven by an energy conversion device; an operating pattern storage unit that stores a combination of a current value of the current waveform and the drive frequency acquired by the data acquisition unit at the same time; a data determination unit configured to determine whether a current value of the current waveform and the drive frequency, acquired by the data acquisition unit at the same time, correspond to the combination stored in the operating pattern storage unit;an analysis unit configured to perform a frequency analysis on the current waveforms that have been determined by the data determination unit to be consistent, to extract sideband waves, and to calculate the spectral intensity of the sideband waves; and an anomaly diagnostic unit configured to perform a diagnosis that an anomaly has occurred when the spectral intensity of the sideband waves is equal to or greater than a threshold value. An anomaly diagnostic method according to the present invention comprises: a data acquisition step in which a current waveform and a drive frequency of an electric motor driven by an energy conversion device are acquired; an operating pattern storage step in which a combination of a current value of the current waveform and the drive frequency, which are acquired at the same time in the data acquisition step, is stored; a data determination step in which it is determined whether or not a current value of the current waveform and the drive frequency, as a diagnostic target, which are acquired at the same time in the data acquisition step, correspond to the combination that is stored in the operating pattern storage step;an analysis step in which a frequency analysis of the current waveforms, which have been determined to be identical in the data determination step, is performed, sideband waves are extracted, and the spectral intensity of the sideband waves is calculated; and an anomaly diagnosis step in which a diagnosis is made that an anomaly has occurred if the spectral intensity of the sideband waves is equal to or greater than a threshold value. An anomaly diagnostic system according to the present invention comprises: an energy conversion device configured to read the current waveform and the drive frequency of the electric motor; an anomaly diagnostic device configured to detect the current waveform and the drive frequency read by the energy conversion device, determine whether or not a current value of the current waveform and the drive frequency matches the combination stored in the operating pattern memory unit, and diagnose whether or not an anomaly has occurred based on the current waveforms that have been determined to match; and a monitoring device configured to output at least one indication and one alarm based on a diagnostic result from the anomaly diagnostic device. Effect of the invention According to the present invention, a combination of the current value of a current waveform and a drive frequency, which are acquired at the same time, is specified, and a current waveform that matches the specified combination of current value and drive frequency is subjected to anomaly diagnosis. Consequently, it becomes possible to detect anomalies even for an electric motor in which the current value and drive frequency change as a result of the energy conversion device. Brief description of the drawings Fig. 1 is a schematic configuration diagram showing an anomaly diagnostic device according to embodiment 1 of the present invention. Fig. 2 is a schematic configuration diagram showing the anomaly diagnostic device according to embodiment 1 of the present invention. Fig. 3 is a schematic configuration diagram showing the anomaly diagnostic device according to embodiment 1 of the present invention. Fig. 4 is a schematic configuration diagram showing a data acquisition unit according to embodiment 1 of the present invention. Fig. 5 is a graph showing an example of an operating pattern of an electric motor according to embodiment 1 of the present invention. Fig. 6 shows the processing procedure of the anomaly diagnostic device according to embodiment 1 of the present invention. Fig. 7 is a diagram to explain the anomaly diagnostic device according to embodiment 1 of the present invention.Figure 8 is a schematic configuration diagram of a preset information storage unit according to embodiment 1 of the present invention. Figure 9 is a graph showing an example of a frequency spectrum waveform according to embodiment 1 of the present invention. Figure 10 is a schematic configuration diagram showing an analysis unit according to embodiment 1 of the present invention. Figure 11 is a graph showing an example of a frequency spectrum waveform according to embodiment 1 of the present invention. Figure 12 shows the processing procedure in the anomaly diagnostic device according to embodiment 1 of the present invention. Figure 13 is a schematic configuration diagram showing a dq-axis analysis unit according to embodiment 2 of the present invention. Figure 14 is a graph showing an example of a q-axis frequency spectrum waveform according to embodiment 2 of the present invention.Figure 15 is a schematic configuration diagram showing an anomaly diagnostic system according to embodiment 3 of the present invention. Description of embodiments The following describes embodiments according to the present invention with reference to the drawings. Figure 1 is a schematic configuration diagram showing the installation conditions of an anomaly diagnostic device according to the present invention. As shown in Figure 1, a plurality of circuit breakers 2, a power conversion device 6, an anomaly diagnostic device 10, and an electric motor 3 are connected by power supply lines 1. The electric motor 3 is driven by the power conversion device 6 and is connected to a mechanical device 4 as a load via a drive energy transmission mechanism for transferring drive energy. A current detection unit 5 is attached to lines connecting the power conversion device 6 and the electric motor 3, and it detects currents supplied to the electric motor 3. A drive frequency detection unit 7 is attached to the energy conversion unit 6 and detects the drive frequency of the electric motor 3 based on a command signal generated in the energy conversion unit 6. The anomaly diagnostic unit 10 diagnoses whether or not an anomaly has occurred in the electric motor 3 based on the current detected by the current detection unit 5 and the drive frequency provided by the drive frequency detection unit 7. Examples of anomalies in the electric motor 3 include: a bearing anomaly, shaft eccentricity, misalignment, and imbalance. The current detection unit 5, shown in Fig. 1, is provided for each phase of the three-phase power supply lines. However, a measurement can be performed for any one of the phases. Since the detection accuracy is hardly affected by the measurement location, the location where the current detection unit 5 is mounted is also not limited, as long as the current supplied to the electric motor 3 can be measured. Anomaly diagnostics for a plurality of electric motors 3 can be performed by a single anomaly diagnostic device 10. Instead of the current detection unit 5, a sensor mounted in the energy conversion device 6 can also be used. Next, the configuration of the anomaly diagnostic device 10 is described with reference to Fig. 2. Fig. 2 is a schematic configuration diagram of the anomaly diagnostic device. The anomaly diagnostic device 10 includes, for example, a processing unit 11, a storage unit 12, a display unit 13, an alarm unit 14, and a communication unit 15. The processing unit 11 executes a predetermined process based on various types of data stored in the storage unit 12. If the electric motor 3 is diagnosed as abnormal, the display unit 13 and the alarm unit 14 receive signals and issue a display message and an alarm to inform an observer of the anomaly. Only one of the display unit 13 and alarm unit 14 can be used to provide the above functions. The anomaly diagnostic device 10 is, for example, a server, a personal computer (PC), a microcomputer, etc., connected to a network. Next, the configuration for implementing the functions of the anomaly diagnostic device 10 is described with reference to Fig. 3. Fig. 3 is a schematic configuration diagram of the anomaly diagnostic device. The anomaly diagnostic device 10 comprises: a data acquisition unit 100, a data determination unit 120, an analysis unit 150, and an anomaly diagnostic unit 170 in the processing unit 11, and it comprises: an operating pattern storage unit 110, a threshold storage unit 130, a default information storage unit 140, and an analysis result storage unit 160 in the storage unit 12. In the event that necessary information is not stored in the storage unit 12, the anomaly diagnostic device 10 can also be equipped with an input unit so that the necessary information can be entered. In the anomaly diagnostic device 10, the data acquisition unit 100 records a drive frequency and a current waveform of the current supplied to the electric motor 3. The data determination unit 120 then determines whether or not a combination of the RMS value of the current waveform and the drive frequency, recorded at the same time, matches a combination stored in the operating pattern storage unit 110. The analysis unit 150 performs a frequency analysis on the current waveforms that have been determined to be consistent by the data determination unit 120, calculates the spectral intensity of sideband waves resulting from an anomaly based on the preset information stored in the preset information storage unit 140, and stores the spectral intensity in the analysis result storage unit 160. If the calculated spectral intensity of the sideband waves is equal to or greater than the threshold stored in the threshold storage unit 130, the anomaly diagnosis unit 170 diagnoses that the anomaly has occurred. Fig. 4 is a schematic configuration diagram showing the data acquisition unit. The data acquisition unit 100 comprises a current waveform acquisition unit 101, a current value acquisition unit 102, and a drive frequency acquisition unit 103. The current waveform acquisition unit 101 acquires a current waveform from the current detected by the current detection unit 5. The current value acquisition unit 102 calculates and acquires the RMS value (hereinafter referred to as the current value) from the current waveform acquired by the current waveform acquisition unit 101. The current value is calculated, for example, as the square root of the value obtained by averaging the square of the instantaneous value of the current waveform over one period. The drive frequency detection unit 103 detects the drive frequency, which is detected by the drive frequency detection unit 7 of the energy conversion device 6. The drive frequency can be the position of the spectral peak value that has the greatest intensity in the frequency analysis performed by the analysis unit 150 on the current waveform acquired by the current waveform detection unit 101. The operating pattern storage unit 110 acquires the current value and drive frequency from the data acquisition unit 100 and stores a combination of current value and drive frequency, acquired at the same time, a large number of times. A stage in which the current waveform and drive frequency are detected to specify such a combination to be stored in the operating pattern storage unit 110 is referred to below as learning stage 503. A further stage in which the current waveform and drive frequency are detected to perform anomaly diagnosis is referred to as diagnostic stage 504. It is preferred that the electric motor 3 operates normally in learning stage 503. Fig. 5 is a graph showing an example of an operating pattern of the electric motor. The vertical axis 506 indicates the current value of the drive frequency. The horizontal axis 505 indicates the time. The operating pattern of the electric motor 3 in learning stage 503 and diagnostic stage 504 is shown. Here, the operating pattern is a pattern of current value or drive frequency output by the energy conversion device 6, repeated at predetermined time intervals. In the example shown in Fig. 5, a first waveform 501a and a second waveform 501b in learning stage 503 and a third waveform 501c in diagnostic stage 504 have identical current values ​​or drive frequencies. Therefore, the electric motor 3 has the same operating pattern in learning stage 503 and diagnostic stage 504. Here, the identical current values ​​or drive frequencies contain a measurement error. For example, they can be considered identical if the error is approximately ± 0.01 A to 0.1 A or ± 0.01 Hz to 0.1 Hz. Next, the processing procedure for storing a combination of the current value and the drive frequency in the operating pattern storage unit 110 in learning stage 503 is described with reference to Fig. 6. Fig. 6 shows an example of the processing procedure of the anomaly diagnostic device in the learning stage. First, the data acquisition unit 100 acquires the current waveform and the drive frequency at predetermined time intervals from the current detection unit 5 and the drive frequency detection unit 7, respectively (step S1). The data acquisition unit 100 calculates the current value from the current waveform and outputs the current value of the current waveform and the drive frequency, which are acquired at the same time, as a combination. Among the combinations of current values ​​and drive frequencies recorded at identical times, the next step is to count the number of times an identical combination is recorded (step S2). As a counting method, for example, as shown in Fig. 7, in the operating pattern storage unit 110, which stores current values ​​and drive frequencies in card form, each combination of current value and drive frequency recorded at the same time is stored, so that the number of times an identical combination is recorded can be counted. In the example shown in Fig. 7, combinations of current value and drive frequency, recorded at the same time (i: current value, f: drive frequency), are counted 100 times each for combinations of 4 A and 52 Hz, 4.5 A and 56 Hz, and 5 A and 60 Hz, which is the largest number of times. Then, combinations of 3.5 A and 52 Hz, 4 A and 56 Hz, and 4.5 A and 60 Hz are each counted 60 times, which is the next largest number of times. Next, for example, the number of times is compared with a predetermined target value, and a combination of current value and drive frequency is specified for which the number of times is equal to or greater than the target value (step S3). If the target value is 80, combinations of current values ​​and drive frequencies of 4 A and 52 Hz, 4.5 A and 56 Hz, and 5 A and 60 Hz are specified. The specified combinations of current values ​​and drive frequencies for which the counted number of times is equal to or greater than the target value are stored in the operating pattern memory unit 110 (step S4). As described above, the operating pattern memory unit 110 stores combinations that are recorded a large number of times as the combination of current value, current waveform, and drive frequency to be used for anomaly diagnosis. The data determination unit 120 acquires a combination of current value, current waveform, and drive frequency as a diagnostic target, acquired at the same time by the data acquisition unit 100. It then checks this acquired combination of current value and drive frequency against a combination of current value and drive frequency stored in the operating pattern storage unit 110 to determine whether they match. The current waveform found to match is output to the analysis unit 150 and subjected to anomaly diagnosis. The threshold storage unit 130 stores a threshold value for the spectral intensity of sideband waves as a diagnostic criterion for anomalies. Generally, the higher the degree of anomaly, the greater the spectral intensity of sideband waves, and the spectral intensity of sideband waves depends on the drive frequency and the current value of the electric motor 3. Threshold values ​​are predefined and associated with specific combinations of current values ​​and drive frequencies stored in the operating pattern storage unit 110. For example, the threshold value is determined as follows. In the normal state of the electric motor 3, the data acquisition unit 100 records the current waveform and the drive frequency, whereby the current waveform, which has been determined by the data determination unit 120 to correspond with the combination of current value and drive frequency stored in the operating pattern storage unit 110, is subjected to a frequency analysis and the spectral intensity of sideband waves is calculated. Then, based on the calculation result, the threshold is determined. Since the data exhibit a distribution due to the error, for example, a standard deviation σ of the spectral intensities of sideband waves is calculated, and the range in which data are present within 3σ is used as the threshold. As described above, in learning stage 503, combinations of current values ​​and drive frequencies to be used for anomaly diagnosis are stored in the operating pattern memory unit 110, and in diagnostic stage 504, the current waveform which is determined to match the combination stored in the operating pattern memory unit 110 is subjected to anomaly diagnosis. The anomaly diagnosis can therefore be carried out using the threshold value that corresponds to the combination of current value and drive frequency, and it is therefore possible to detect an anomaly, even in the case of the electric motor 3, in which the spectral intensity of sideband waves, which serves as a diagnostic criterion, changes as a result of the change in current value and drive frequency by the energy conversion device 6. The current waveform used for anomaly diagnosis is the waveform corresponding to the combination of current value and drive frequency, which is captured a large number of times. Therefore, the number of current waveform samples used for diagnosis can be increased, thus improving anomaly detection accuracy. Fig. 8 is a schematic configuration diagram of the setpoint information storage unit. The setpoint information storage unit 140 comprises a nominal value information storage unit 141, a frequency storage unit 142, and a load information storage unit 143. The setpoint information storage unit 140 stores information required to specify the frequencies at which sideband waves occur. In the nominal value information storage unit 141, nominal value information such as the power supply frequency, the number of poles and the nominal speed is stored, based on information from a nominal value table attached to the electric motor 3. The frequency storage unit 142 comprises a rotational frequency storage unit 142a and a bearing natural frequency storage unit 142b. The frequency storage unit 142 stores the rotational frequency of the electric motor 3 and the bearing natural frequency. As shown in Fig. 9, sideband waves occur on both sides near the drive frequency, at positions that vary depending on the type of anomaly. In the event of an anomaly, such as misalignment or imbalance, sideband waves occur, for example, at positions separated from the drive frequency (the center frequency) by the rotation frequency in both directions. Furthermore, in the event of an anomaly due to the bearing of electric motor 3, sideband waves occur at positions separated from the drive frequency (the center frequency) by the bearing's natural frequency in both directions. The rotation frequency storage unit 142a stores the rotation frequency of the electric motor 3. The rotation frequency of the electric motor 3 is, for example, in a range between the rotation frequency in the case of no load and the rotation frequency in the case of rated rotation. The rotation frequency in the case of no load is calculated as 2·fs / p (fs: power supply frequency, p: number of poles), from the power supply frequency and the number of poles stored in the rated value information storage unit 141. The rotation frequency in the case of rated rotation is also calculated from the rated speed, which is stored in the rated value information storage unit 141. The bearing natural frequency storage unit 142b stores the bearing natural frequency based on the bearing information. The load information storage unit 143 stores load information. This load information includes, for example, the type of device, such as a pump, fan, or compressor, the presence or absence of a belt or chain, and the like. The rotational frequency changes depending on the load on the electric motor 3. For example, if a belt or chain is used, an external load is exerted on the shaft of the electric motor 3, and therefore the rotational frequency tends to be high. When the load information is stored in the load information storage unit 143, it becomes possible to correct the rotational frequency, which is stored in the rotational frequency storage unit 142a. Next, the analysis unit 150 will be described with reference to Fig. 10. Fig. 10 is a schematic configuration diagram of the analysis unit. The analysis unit 150 comprises the following: a current frequency analysis unit 151, a current spectrum averaging unit 152, a sideband wave extraction unit 153, and a spectral intensity calculation unit 154. The current frequency analysis unit 151 performs a frequency analysis on the current waveform, which has been determined by the data determination unit 120 to correspond to the combination of current value and drive frequency stored in the operating pattern storage unit 110. The current waveform is analyzed, for example, by a fast Fourier transform analysis (FFT) of the current, a discrete Fourier transform, or the like. The current spectrum averaging unit 152 averages frequency spectrum waveforms obtained multiple times by the current frequency analysis unit 151. As shown in Fig. 11, the frequency spectrum waveform includes disturbances resulting from the switching process of the energy conversion device 6, in addition to a spectrum resulting from the anomaly of the electric motor 3. Averaging the frequency spectrum waveforms can reduce the spectral intensity of the disturbances occurring near the drive frequency, and consequently, the detection accuracy for sideband waves resulting from anomalies can be improved. The sideband wave extraction unit 153 detects all spectral peak positions from the frequency spectrum waveform obtained by the current frequency analysis unit 151. Preferably, the detection range is from 0 Hz to 1000 Hz. The sideband wave extraction unit 153 extracts—as sideband waves—spectral peak positions that occur at equal frequencies on either side of the center frequency. At this point, the drive frequency can be the drive frequency obtained by means of the data acquisition unit 100 simultaneously with the current waveform, or it can be calculated from the position of the spectral peak value that has the greatest intensity among the detected spectral peak values. The spectral intensity calculation unit 154 comprises a rotation frequency calculation unit 154a and a bearing natural frequency calculation unit 154b, each of which calculates the spectral intensity of sideband waves. The rotation frequency calculation unit 154a acquires the rotation frequency stored in the rotation frequency storage unit 142a and extracts positions separated from the drive frequency by the rotation frequency. The rotation frequency calculation unit 154a then calculates the spectral intensities of spectral peak values ​​occurring at the extracted positions. Similarly, the bearing natural frequency calculation unit 154b acquires the bearing natural frequency, which is stored in the bearing natural frequency storage unit 142b, and extracts positions separated from the drive frequency by the bearing natural frequency. The bearing natural frequency calculation unit 154b then calculates the spectral intensities of spectral peak values ​​occurring at the extracted positions. These calculated spectral intensities are stored in the analysis result storage unit 160, along with the current value and the drive frequency at the time the current waveform was acquired. The calculation of the spectral intensity of sideband waves can be performed here in at least one of rotation frequency calculation unit 154a and bearing natural frequency calculation unit 154b, and an input unit can be provided for the anomaly diagnostic device 10, so that one of the calculation units is selected according to the type of anomaly to be diagnosed. As described above, in learning stage 503, combinations of current values ​​and drive frequencies are stored in the operating pattern memory unit 110, and in diagnostic stage 504, the current waveform that matches the stored combination is subjected to a frequency analysis. Even if the positions of sideband waves change as a result of the change in drive frequency by the energy conversion unit 6, the positions of the sideband waves can be accurately extracted. The anomaly diagnostic unit 170 obtains the threshold, which corresponds to the drive frequency and the current value of the analyzed current waveform, from the threshold storage unit 130, and it performs a diagnosis that the anomaly has occurred when the calculated spectral intensity of sideband waves is equal to or greater than the threshold. As described above, the anomaly diagnostic device 10 according to the present embodiment is configured such that in the learning stage 503, combinations of current values ​​and drive frequencies used for anomaly diagnosis are stored in the operating pattern storage unit 110, and that in the diagnostic stage 504, a frequency analysis is performed for the current waveform that matches the combination stored in the operating pattern storage unit 110, and diagnoses whether or not an anomaly has occurred, based on the calculated spectral intensity of sideband waves. With this configuration, the spectral intensity of sideband waves is compared to the threshold value corresponding to the combination of the drive frequency and current value of the analyzed current waveform, thus diagnosing whether or not an anomaly has occurred. Even if the current value and drive frequency change as a result of the energy conversion device 6, and the spectral intensity of sideband waves, which serves as an anomaly diagnosis criterion, changes, an anomaly can still be detected. With reference to Fig. 12, the operation in diagnostic stage 504 is described, in which the anomaly diagnostic device 10 performs an anomaly diagnosis. Fig. 12 shows an example of the processing procedure in the anomaly diagnostic device. The anomaly diagnostic device 10 starts the anomaly diagnosis when, through learning stage 503, the current value of the current waveform and the drive frequency to be used for the diagnosis have been stored in the operating pattern memory unit 110, and the necessary information has also been stored in the threshold value memory unit 130 and the target information memory unit 140 (YES). First, in step S101, the data acquisition unit 100 records the current waveform and the drive frequency as a diagnostic target at predetermined time intervals and calculates and records the current value from the current waveform. In step S102, the data determination unit 120 determines whether the combination of current value of the current waveform and drive frequency, recorded at the same time, matches the combination of current value and drive frequency stored in the operating pattern storage unit 110. If they match (YES), the data determination unit 120 outputs the current waveform at that time to the analysis unit 150. In step S103, the current waveform, which is determined to be identical, is subjected to frequency analysis using the analysis unit 150. The analysis unit 150 extracts positions at which sideband waves occur from the drive frequency and calculates the spectral intensity of the sideband waves. In step S104, the anomaly diagnostic unit 170 compares the calculated spectral intensity of the sideband waves with the threshold that corresponds to the drive frequency and the current value of the analyzed current waveform, and if the calculated spectral intensity is equal to or greater than the threshold (JA), then the anomaly diagnostic unit 170 makes a diagnosis that an anomaly has occurred. If an anomaly is indicated by the diagnostic system, display unit 13 and alarm unit 14 issue a corresponding message and alarm in step S105. At this point, at least one of the operations of display unit 13 and alarm unit 14 can be performed. Operation in learning stage 503 can always be carried out before diagnostic stage 504, or, if the operating pattern has been established, the diagnosis can be carried out on the basis of combinations of current values ​​and drive frequencies that have been stored in advance in the operating pattern storage unit 110, without carrying out operation in learning stage 503. As described above, the following applies: Whether or not an anomaly has occurred is diagnosed on the basis of the current waveform, which corresponds to the combination of current value and drive frequency, stored in the operating pattern storage unit 110 in learning stage 503, so that it is possible to detect the anomaly even for the electric motor 3, which is driven by the energy conversion device 6. Design 2 In embodiment 2, the current waveform acquired by the data acquisition unit 100 according to embodiment 1 is subjected to a coordinate conversion, and the frequency analysis is performed on the d-axis current and the q-axis current in a dq-axis coordinate system. Fig. 13 is a schematic configuration diagram of a dq-axis analysis unit. A dq-axis analysis unit 1500 comprises the following: a coordinate conversion unit 1501 for the dq-axis, a current frequency analysis unit 1502 for the dq-axis, a current spectrum averaging unit 1503 for the dq-axis, a sideband wave extraction unit 1504 for the dq-axis, and a spectral intensity calculation unit 1505 for the dq-axis. Here, the d-axis indicates the direction of the magnetic flux of the electric motor 3, and the q-axis indicates the direction perpendicular to the d-axis. The d-axis current is the current corresponding to the magnetic flux, and the q-axis current is the current corresponding to the torque. Fig. 14 shows a q-axis frequency spectrum waveform of the electric motor. The vertical axis indicates the spectral intensity, and the vertical axis indicates the frequency. As shown in Fig. 14, the sideband waves, which serve as a diagnostic criterion for the presence / absence of an anomaly, are also extracted from the frequency spectrum waveform of the current waveform that has undergone the dq-axis coordinate transformation. Even with this configuration, as with embodiment 1, it is possible to perform anomaly diagnostics for the electric motor 3, whereby the current value and the drive frequency change as a result of the energy conversion device 6. Furthermore, the current waveform, which is recorded by the data acquisition unit 100, is subjected to a dq-axis conversion, so that it becomes possible to accurately detect the anomaly due to an air gap variation, such as an eccentricity, based on the d-axis current, as well as the anomaly due to a load pulsation based on the q-axis current. In the present embodiment, a coordinate conversion into the d-axis current and the q-axis current in a dq-axis coordinate system is performed. However, a conversion into an α-axis current and a β-axis current in an αβ-axis coordinate system can also be performed to carry out a frequency analysis. embodiment 3 An anomaly diagnostic system according to embodiment 3 for carrying out the present invention is described with reference to Fig. 15. Fig. 15 is a schematic configuration diagram showing an example of the anomaly diagnostic system. In the present embodiment, the same reference numerals as those in embodiment 1 denote identical or corresponding parts. An anomaly diagnostic system 500 comprises an anomaly diagnostic device 200, a monitoring device 300, and an energy conversion device 400. In embodiment 1, an example is shown in which the anomaly diagnostic device 10, which is connected to the electric motor 3, acquires and processes data. If the diagnostic device indicates an anomaly, a notification and an alarm are issued accordingly. In the present embodiment, the following applies: Each of the energy conversion devices 400, which are connected to the electric motors 3, reads data. The anomaly diagnostic device 200 acquires the read data and diagnoses whether or not the anomaly has occurred. Then, based on the result of the diagnosis, the monitoring device 300 issues a notification and an alarm. The energy conversion unit 400 comprises the following: a current detection unit 401, a drive frequency detection unit 402, a data reading unit 410, a display unit 413, an alarm unit 414, and a communication unit 415. The energy conversion unit 400 drives the electric motor 3. Using the data reading unit 410, the energy conversion unit 400 reads the current waveform and the drive frequency from the current detection unit 401 and the drive frequency detection unit 402. The current detection unit 401 is a current sensor installed in the energy conversion unit 400. The current waveform and the drive frequency, which are read by the data reading unit 410, are transmitted to a communication unit 215 of the anomaly diagnostic device 200 via the communication unit 415. The anomaly diagnostic device 200 comprises a processing unit 211, a storage unit 212, and a communication unit 215. The anomaly diagnostic device 200 acquires the current waveform and the drive frequency using the communication unit 215 as the data acquisition unit 100. The anomaly diagnostic device 200 comprises the data determination unit 120, the analysis unit 150, and the anomaly diagnostic unit 170 in the processing unit 211, and it comprises the operating pattern storage unit 110, the threshold storage unit 130, the target information storage unit 140, and the analysis result storage unit 160 in the storage unit 212. The current waveform and the drive frequency transmitted by the energy conversion unit 400 are acquired by the communication unit 215, which serves as the data acquisition unit 100. The data determination unit 120 determines whether the current value of the current waveform and the drive frequency obtained match one of the combinations stored in the operating pattern storage unit 110. The analysis unit 150 performs a frequency analysis on the current waveform that has been determined to match and thus calculates the spectral intensity of the sideband waves. The anomaly diagnostic unit 170 compares the calculated spectral intensity of sideband waves with the threshold value and diagnoses whether or not the anomaly has occurred. The diagnostic result obtained is transmitted by the communication unit 215 of the anomaly diagnostic device 200 to a communication unit 315 of the monitoring device 300 and to the communication unit 415 of the energy conversion device 400. The monitoring device 300 comprises a display unit 313, an alarm unit 314, and a communication unit 315. The monitoring device 300 is installed at a location where an observer is present, and it issues a notification and an alarm through the display unit 313 and the alarm unit 314 according to the diagnostic result. The diagnostic result is also transmitted to the energy conversion unit 400, and if an anomaly is indicated by the diagnostics, the display unit 413 and the alarm unit 414 issue a warning and an alarm. At least either the display units 313, 413 or the alarm units 314, 414 can issue such warnings and alarms. Such a configuration enables anomaly detection for the electric motor 3, which is driven by the energy conversion device 6, whereby the current value and the drive frequency are changed, as according to embodiment 1. In addition, in the present embodiment, data provided by the energy conversion device 400 for each electric motor 3 are acquired by the communication unit 215 of the anomaly diagnostic device 200 and thus processed, and the diagnostic result is transmitted to the monitoring device 300 and the energy conversion device 400. Thanks to this configuration, even in a large factory where multiple electric motors 3 and multiple mechanical devices 4 are in operation, the observer can locate the device based on the information displayed on the monitoring device 300. This allows the electric motors 3 and the mechanical devices 4 to be observed and monitored. Furthermore, since each energy conversion device 400 is equipped with the display unit 413 and the alarm unit 414 to show the diagnostic result, it is easy to identify the electric motor 3 that has been diagnosed as having an anomaly. The current detection unit 401 does not necessarily need to be installed in the energy conversion device 400, and an external sensor can be used for this purpose. In the example shown in Fig. 15, two energy conversion devices 400 are provided. However, the number of energy conversion devices 400 can be increased to three, four, etc., depending on the number of electric motors 3 and the number of mechanical devices 4, and each energy conversion device 400 can transmit the acquired data to the anomaly diagnostic device 200. Furthermore, each energy conversion device 400 can also be equipped with a storage unit 412, and after the recorded data have been stored in the storage unit 412 for a certain period of time, the data can be collectively transferred to the anomaly diagnostic device 200. It is preferred that a malfunction database 600, in which past malfunction information is accumulated, is connected to the anomaly diagnostic system 500. New malfunction information about the diagnostics, indicating an anomaly, should be registered in the malfunction database 600. The malfunction information represents, for example, a current waveform that is detected when a malfunction has occurred. The threshold for the spectral intensity of sideband waves, which serves as an anomaly diagnostic criterion, can be determined based on the results of frequency analysis of the current waveform when the malfunction has occurred. Consequently, the anomaly diagnostic criterion can be clarified, thus improving anomaly detection accuracy. In embodiments 1 to 3, the anomaly diagnostic device 10 and the anomaly diagnostic device 200 are shown in a configuration separate from the energy conversion device 6 and the energy conversion device 400, which drive the electric motors 3. However, the energy conversion device 6 or the energy conversion device 400 can also be equipped with a microcomputer in which a program is implemented that has a function equivalent to the anomaly diagnostic device 10 or the anomaly diagnostic device 200. Such a configuration, in which the anomaly diagnostic device 10 or the anomaly diagnostic device 200 is installed in the energy conversion device 6 or the energy conversion device 400, which drives the electric motor 3, makes it possible to perform the anomaly diagnosis without the restrictions regarding the installation location due to the increase in the number of wires. Description of reference symbols 1 Power supply line 2 Circuit breaker 3 Electric motor 4 Mechanical device 5 Current detection unit 6 Energy conversion unit 7 Drive frequency detection unit 10 Anomaly diagnostic unit 11 Processing unit 12 Storage unit 13 Display unit 14 Alarm unit 15 Communication unit 100 Data acquisition unit 101 Current waveform acquisition unit 102 Current value acquisition unit 103 Drive frequency acquisition unit 110 Operating pattern storage unit 120 Data determination unit 130 Threshold value storage unit 140 Target information storage unit 150 Analysis unit 160 Analysis result storage unit 170 Anomaly diagnostic unit 141 Nominal value information storage unit 142 Frequency storage unit 143 Load information storage unit 151 Current frequency analysis unit 152 Current spectrum average unit 153 Sideband wave extraction unit 154 Calculation unit for spectral intensity 1501 Coordinate conversion unit for the dq axis 1502Current frequency analysis unit for the dq axis 1503 Current spectrum averaging unit for the dq axis 1504 Sideband wave extraction unit for the dq axis 1505 Spectral intensity calculation unit for the dq axis 200 Anomaly diagnostic device 300 Monitoring device 400 Energy conversion device 500 Anomaly diagnostic system 600 Malfunction database

Claims

An anomaly diagnostic device comprising: - a data acquisition unit configured to acquire a current waveform and drive frequency of an electric motor driven by an energy conversion device; - an operating pattern storage unit storing a combination of a current value of the current waveform and the drive frequency acquired by the data acquisition unit at the same time; - a data determination unit configured to determine whether a current value of the current waveform and the drive frequency, acquired by the data acquisition unit at the same time, match the combination stored in the operating pattern storage unit as a diagnostic target;- an analysis unit configured to perform a frequency analysis on the current waveforms that have been determined by the data determination unit to be congruent, to extract sideband waves, and to calculate the spectral intensity of the sideband waves; and - an anomaly diagnostic unit configured to perform a diagnosis that an anomaly has occurred when the spectral intensity of the sideband waves is equal to or greater than a threshold value. Anomaly diagnostic device according to claim 1, wherein the operating pattern storage unit stores a combination of a current value of the current waveform and the drive frequency, which are recorded a predetermined number of times or more by the data acquisition unit at the same time. Anomaly diagnostic device according to claim 1 or 2, wherein the analysis unit extracts the sideband waves that occur at positions separated from the drive frequency as the center by at least one rotation frequency and a bearing natural frequency. Anomaly diagnostic device according to one of claims 1 to 3, wherein the analysis unit converts the current waveform into a d-axis current or a q-axis current. An anomaly diagnostic procedure comprising: - a data acquisition step in which a current waveform and a drive frequency of an electric motor driven by an energy conversion device are acquired; - an operating pattern storage step in which a combination of a current value of the current waveform and the drive frequency, acquired at the same time in the data acquisition step, is stored; - a data determination step in which it is determined whether or not a current value of the current waveform and the drive frequency, acquired at the same time in the data acquisition step, match the combination stored in the operating pattern storage step as a diagnostic target;- an analysis step in which a frequency analysis of the current waveform, which has been determined to be identical in the data determination step, is performed, sideband waves are extracted, and the spectral intensity of the sideband waves is calculated; and - an anomaly diagnosis step in which a diagnosis is made that an anomaly has occurred if the spectral intensity of the sideband waves is equal to or greater than a threshold value. An anomaly diagnostic system comprising: - an energy conversion device configured to read the current waveform and the drive frequency of the electric motor; - an anomaly diagnostic device according to any one of claims 1 to 4, configured to detect the current waveform and the drive frequency read by the energy conversion device, determine whether or not a current value of the current waveform and the drive frequency matches the combination stored in the operating pattern memory unit, and diagnoses whether or not an anomaly has occurred based on the current waveform that has been determined to match; and - a monitoring device configured to output at least one of a warning and one alarm based on a diagnostic result by the anomaly diagnostic device. Anomaly diagnostic system according to claim 6, wherein the energy conversion device reads the current waveform from a current sensor mounted in the energy conversion device.

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