Monitoring device

Abstract

To provide a monitoring device capable of accurately diagnosing deterioration of an apparatus equipped with a motor connected to a three phase alternating current.SOLUTION: In a monitoring device 100 of an apparatus equipped with a motor 30, the motor is connected to three phase alternating current, and the device includes two current detectors CT1 and CT2 of a system for acquiring a current of one phase of the three phase alternating current and passing a line supplied with the three phase alternating current. The monitoring device includes an acquisition unit 111 that acquires currents for two phases from the two current detectors, a correction unit 112 that corrects a positive or negative polarity of one of the acquired currents for two phases when a phase difference between the currents for two phases output from the acquisition unit is smaller than a phase difference when the two current detectors are attached in the same direction, a calculation unit 113 that calculates a current for the remaining one phase from the currents for two phases corrected by the correction unit, and an output unit 115 that outputs information on deterioration of a device using information including at least the current for the remaining one phase calculated by the calculation unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to monitoring devices. [Background technology]

[0002] Patent Document 1 discloses an abnormality judgment device that includes a judgment unit that makes a judgment regarding an abnormality in a mechanical element of an equipment that mounts an electrically driven rotating machine based on an electrical characteristic amount of the rotating machine, the electrical characteristic amount being a specific frequency component of a signal that is correlated with the current of an electric motor that drives the rotating machine, and the specific frequency component being a component that is a predetermined positive integer multiple of the rotational frequency of the rotating machine, and the judgment unit makes the judgment by taking into account fluctuations in the relationship between the abnormality in the mechanical element and the electrical characteristic amount due to changes in the rotational frequency of the rotating machine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-28644 Summary of the Invention [Problem to be solved by the invention]

[0004] When diagnosing the deterioration of equipment equipped with a motor connected to three-phase AC, from the viewpoint of work space and cost, two current detectors are sometimes used to acquire the current for two phases of the three-phase AC, and the current for the remaining phase is calculated from the acquired current for the two phases to diagnose the deterioration of the equipment.If the current detectors are not installed in the correct relationship with the two phases, the current for the remaining phase cannot be calculated correctly, and an accurate diagnosis cannot be made when diagnosing the deterioration using the calculated current for the remaining phase. The present disclosure aims to diagnose deterioration of an equipment equipped with a motor connected to three-phase AC by acquiring current for two phases using two current detectors, calculating the current for the remaining phase, and using the calculated current for the remaining phase to diagnose deterioration of the equipment more accurately than when diagnosing deterioration of the equipment without making corrections for the installation direction of the current detectors for the two phases. [Means for solving the problem]

[0005] The monitoring device disclosed herein is a monitoring device for equipment equipped with a motor, the motor being connected to three-phase AC, and comprising two current detectors that pass through lines through which the three-phase AC is supplied to acquire current for one phase of the three-phase AC, an acquisition unit that acquires current for two phases from the two current detectors, a correction unit that corrects the positive and negative polarity of one phase of the acquired current for two phases when the phase difference of the current for two phases output from the acquisition unit is smaller than the phase difference when the two current detectors are installed in the same direction, a calculation unit that calculates the current for the remaining phase from the current for the two phases corrected by the correction unit, and an output unit that outputs information regarding deterioration of the equipment using information including at least the current for the remaining phase calculated by the calculation unit. In this case, for an equipment equipped with a motor connected to three-phase AC, when the current for two phases is acquired using two current detectors and the current for the remaining phase is calculated, and the deterioration of the equipment is diagnosed using the calculated current for the remaining phase, a more accurate diagnosis can be made than when the deterioration of the equipment is diagnosed without making any correction for the installation direction of the current detectors for the two phases. The monitoring device according to the present disclosure outputs information about the deterioration of the device using the currents for the two phases corrected by the correction unit and the current for the remaining one phase calculated by the calculation unit, thereby enabling a more accurate diagnosis than when the deterioration diagnosis is performed using the current for one phase. Here, the acquisition unit includes an offset correction unit that corrects the offsets of the currents for two phases acquired from the current detectors, respectively, so that the phase difference between the acquired currents for two phases can be accurately calculated. Furthermore, when the amplitude of the composite wave of the currents for the two phases output from the acquisition unit is greater than the amplitude of the currents output from the acquisition unit, the correction unit determines that the phase difference between the currents for the two phases output from the acquisition unit is smaller than the phase difference when the two current detectors are installed in the same direction. In this case, it is possible to determine whether the phase difference between the currents for the two phases acquired is smaller than the phase difference when the two current detectors are installed in the same direction without calculating the phase difference. The acquisition unit also includes a gain correction unit that corrects the gain of at least one of the two phases of current acquired from the current detector, thereby making it possible to accurately calculate a composite wave of the acquired two phases of current. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a diagram illustrating an example of the configuration of a monitoring system to which a monitoring device according to an embodiment of the present invention is applied. [Figure 2] 1 is a diagram illustrating an example of the configuration of a monitoring device according to an embodiment of the present invention. [Figure 3] 10A and 10B show waveforms of two phases of current output from the acquisition unit, where (a) shows the waveform when two current sensors are installed in the same direction, and (b) shows the waveform when two current sensors are installed in alternating directions. [Figure 4] 10A and 10B are diagrams illustrating a method for calculating a phase difference, in which (a) shows an example of a waveform of a current detected by a first current sensor and a second current sensor, and (b) shows an example of a measured value of the amplitude of the current at each detection time. [Figure 5] 10 is a diagram showing an example of the flow of a process for diagnosing deterioration of a motor-equipped device by a monitoring device according to the present embodiment. FIG. [Figure 6] 10A and 10B show the waveform of a composite wave obtained by combining two phases of current output from the acquisition unit, where (a) shows the waveform of the composite wave when two current sensors are installed in the same direction, and (b) shows the waveform of the composite wave when two current sensors are installed in alternating directions. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. <Monitoring system configuration> FIG. 1 is a diagram showing an example of the configuration of a monitoring system 1 to which a monitoring device 100 according to this embodiment is applied. The monitoring system 1 includes an inverter device 10, a motor 30, and a monitoring device 100.

[0008] The inverter device 10 is connected to, for example, a three-phase AC power supply (commercial power supply), and uses AC power supplied from the AC power supply to drive the motor 30. The configuration of the inverter device 10 will be described in detail later.

[0009] The motor 30 is, for example, an interior permanent magnet motor (IPM motor). The motor 30 drives, for example, a compressor of a refrigerant circuit provided in an air conditioner. The inverter device 10 and the motor 30 are connected by three electric wires 21U, 21V, and 21W through which a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw flow, respectively. Hereinafter, when there is no need to distinguish between the three electric wires 21U, 21V, and 21W, they may be referred to as electric wires 21.

[0010] The monitoring device 100 diagnoses the deterioration of the equipment equipped with the motor 30. The equipment equipped with the motor 30 is, for example, a compressor. The deterioration of the equipment includes, for example, wear of the bearings of the motor 30 (hereinafter referred to as "bearing wear"), an increase in friction fluctuation of the bearings of the motor 30, insulation deterioration leading to a ground fault or a layer short, etc. Furthermore, if the equipment is a compressor equipped with the motor 30, the deterioration of the equipment includes a decrease in the oil sealing performance of the compressor, liquid compression in which liquid refrigerant enters and is compressed in the compression chamber of the compressor, etc.

[0011] The monitoring device 100 includes a first current sensor CT1 and a second current sensor CT2 that detect current. Hereinafter, when there is no need to distinguish between the first current sensor CT1 and the second current sensor CT2, they may be referred to as current sensors CT. Furthermore, the first current sensor CT1 and the second current sensor CT2 may be collectively referred to as two current sensors CT. FIG. 1 shows a case where the two current sensors CT are attached to an electric wire 21 between a motor 30 and an inverter device 10 that drives the motor 30. The current sensor CT is an example of a current detector.

[0012] The first current sensor CT1 and the second current sensor CT2 are attached to any two of the three electric wires 21 and detect the current in the attached electric wires 21. FIG. 1 shows a case where the first current sensor CT1 is attached to the electric wire 21U and the second current sensor CT2 is attached to the electric wire 21V. The current sensor CT is a current detector that passes through the electric wire 21, and is, for example, a clamp-type current transformer that can be attached / detached by clamping the electric wire 21. The current transformer detects the current flowing through the electric wire 21 by detecting the magnetic field generated around the electric wire 21. In the example shown in FIG. 1, the current sensor CT is circular, and the tip of the current sensor CT rotates around a fulcrum S, opening the tip of the current sensor CT and allowing it to be attached to or detached from the electric wire 21.

[0013] The monitoring device 100 is used, for example, by a service engineer. The service engineer carries the monitoring device 100 to a measurement location, attaches the current sensor CT to the electric wire 21 to detect the current, and obtains a diagnosis result of the deterioration of the equipment to be diagnosed. When current sensors CT are attached to electric wires 21 to detect current in this way, it is possible that the two current sensors CT may be attached in a direction other than the correct direction. In this embodiment, the monitoring device 100 has the configuration shown in Fig. 2, so that it is possible to accurately diagnose the deterioration of the equipment even if the two current sensors CT are attached in a direction other than the correct direction.

[0014] 2 is a diagram showing an example of the configuration of the monitoring device 100 according to this embodiment. In FIG. 2, the configuration of the inverter device 10 is also shown. The inverter device 10 includes a converter circuit 11, a reactor 12, a capacitor 13, and an inverter circuit 14. The converter circuit 11 is a circuit that converts AC to DC. The converter circuit 11 is, for example, a diode bridge circuit. The capacitor 13 smoothes the output of the converter circuit 11. The inverter circuit 14 converts the DC smoothed by the capacitor 13 into AC of a predetermined frequency and a predetermined voltage. The inverter circuit 14 includes, for example, a plurality of (here, six) bridge-connected switching elements. The switching elements switch the input DC to convert the DC into three-phase AC. The converted three-phase AC drives the motor 30.

[0015] The monitoring device 100 includes an acquisition unit 111 , a correction unit 112 , a calculation unit 113 , a diagnosis unit 114 , and an output unit 115 . The acquisition unit 111 acquires currents for two phases from the two current sensors CT, performs conversion and correction as described below, and then outputs the corrected currents for two phases to the correction unit 112. The acquisition unit 111 includes an A / D conversion unit 116, a current conversion unit 117, an offset correction unit 118, and a gain correction unit 119.

[0016] The A / D conversion unit 116 acquires the currents detected by the two current sensors CT as analog signals, and digitizes the acquired analog signals by A / D conversion. The current conversion unit 117 converts the signal digitized by the A / D conversion unit 116 into a current dimension signal.

[0017] The offset correction unit 118 corrects the offset of the two phases of current acquired from the two current sensors CT. If there is a discrepancy in the offset of the two current sensors CT, the average level of the acquired current cannot be recognized as 0 A. The offset correction unit 118 corrects the offset by, for example, adjusting the detection value when no current is flowing to 0 A. The gain correction unit 119 corrects the gain of the two phases of current acquired from the two current sensors CT. If there is a discrepancy in the gain of the two current sensors CT, the amplitude level of the acquired current will be recognized as different from the actual level. The gain correction unit 119 corrects the gain by, for example, correcting one of the acquired two phases of current to make the amplitude the same as the other current.

[0018] The correction unit 112 corrects the positive / negative polarity of one of the acquired two phases of current when the phase difference between the two phases of current output from the acquisition unit 111 is smaller than the phase difference when two current sensors CT are installed in the same direction. The correction unit 112 includes a phase difference determination unit 120 and a polarity correction unit 121. The phase difference determining unit 120 determines whether the phase difference between the two phases of current output from the acquiring unit 111 is smaller than the phase difference when the two current sensors CT are attached in the same direction. The polarity corrector 121 corrects the positive / negative polarity of one of the two phases of current output from the acquirer 111.

[0019] The calculation unit 113 calculates the current for the remaining one phase from the currents for two phases detected by the two current sensors CT. The diagnosing unit 114 diagnoses the deterioration of the equipment including the motor 30 using information including at least the current for the remaining one phase calculated by the calculating unit 113. The diagnosing unit 114 outputs information on the deterioration of the equipment using, for example, the current for two phases corrected by the polarity correcting unit 121 and the current for the remaining one phase calculated by the calculating unit 113. The diagnosing unit 114 calculates, for example, a current vector of the three-phase current flowing through the electric wire 21 from the current for three phases, and diagnoses the deterioration of the equipment based on the calculated current vector. The current vector Ia is expressed as Ia=√(Iu 2 +Iv 2 +Iw 2 ) can be calculated as follows.

[0020] The output unit 115 outputs information relating to the deterioration of the equipment including the motor 30. The output unit 115 outputs the information relating to the deterioration of the equipment to a display screen (not shown) provided in the monitoring device 100, for example. Each function of the acquisition unit 111, correction unit 112, calculation unit 113, diagnosis unit 114, and output unit 115 can be configured using, for example, a microcomputer and a memory device in which software for operating it is stored.

[0021] <Current calculation> The U-phase current Iu, V-phase current Iv, and W-phase current Iw flowing through the three electric wires 21U, 21V, and 21W satisfy the relationship Iu+Iv+Iw=0. Therefore, by detecting the currents for two phases, the current for the remaining phase can be calculated. Here, the current sensor CT has a fixed measurement direction relative to the current it measures, and if the current sensor CT is installed in the opposite direction, the measured value will be multiplied by -1. Therefore, if the two current sensor CTs are not installed in the correct relationship, the current for the remaining phase cannot be calculated correctly.

[0022] Consider a case where the first current sensor CT1 is attached to the electric wire 21U and the second current sensor CT2 is attached to the electric wire 21V, and the current for the remaining one phase is calculated from the currents for two phases detected by the two current sensors CT. When the two current sensors CT are attached in the same direction, the W-phase current Iw flowing through the electric wire 21W is correctly calculated as Iw = -(Iu + Iv). On the other hand, when the two current sensors CT are attached in alternate directions (here, it is assumed that the current sensor CT attached to the electric wire 21V is oriented in the opposite direction), the W-phase current Iw is calculated as Iw = -(Iu - Iv), which is not a correct value. In this case, even if the calculated W-phase current Iw is used to diagnose the deterioration of the equipment equipped with the motor 30, the diagnosis will not be accurate.

[0023] Therefore, in this embodiment, when diagnosing the deterioration of equipment equipped with a motor 30, the positive / negative polarity of the acquired current is corrected according to the installation direction of the two current sensors CT, and the corrected current is used to diagnose the deterioration. The mounting directions of the two current sensors CT are determined from the phase difference between the two phases of current output from the acquisition unit 111, for example.

[0024] <Calculation of phase difference> 3A and 3B are diagrams showing waveforms of two phases of current output from the acquisition unit 111, where (a) shows the waveform when two current sensors CT are installed in the same direction, and (b) shows the waveform when two current sensors CT are installed in alternate directions. The two waveforms shown in Fig. 3A and 3B are waveforms of phase currents detected by the two current sensors CT, respectively. In Fig. 3, the horizontal axis represents time and the vertical axis represents amplitude, with half the current period being set to 1 on the horizontal axis and the amplitude of the current waveform being set to 1 on the vertical axis.

[0025] As shown in Figure 3(a), when two current sensors CT are installed in the same direction, the phase difference between the detected two-phase currents is 2 / 3π. On the other hand, as shown in Figure 3(b), when two current sensors CT are installed in alternate directions, the phase difference between the detected two-phase currents is π / 3. The phase difference (2 / 3π) when two current sensors CT are installed in the same direction is larger than the phase difference (π / 3) between the detected two-phase currents when two current sensors CT are installed in alternate directions. In other words, if the phase difference between the two-phase currents detected by the two current sensors CT is smaller than the phase difference when two current sensors CT are installed in the same direction, it can be determined that the two current sensors CT are installed in alternate directions.

[0026] The phase difference between the currents for two phases output from the acquisition unit 111 is calculated by the phase difference determination unit 120. The phase difference determination unit 120 calculates, for example, zero cross points where the currents for two phases output from the acquisition unit 111 change polarity, and calculates the phase difference from the zero cross points. 4A and 4B are diagrams illustrating a method for calculating the phase difference. (a) shows an example of the waveforms of the currents detected by the first current sensor CT1 and the second current sensor CT2, and (b) shows an example of the measured amplitude of the current at each detection time. The two waveforms shown in Fig. 4A were calculated based on the measurements by the two current sensors CT at each detection time shown in Fig. 4B. In Fig. 4A, the horizontal axis represents time and the vertical axis represents amplitude, with half the current period representing 1 and the vertical axis representing the amplitude of the current waveform representing 1.

[0027] In Figure 4(a), t 1+ is the zero crossing point where the current detected by the first current sensor CT1 changes from positive to negative, and t 1- indicates the zero crossing point where the current detected by the first current sensor CT1 changes from negative to positive. 1- is the current detected by the first current sensor CT1. 1+ The next zero crossing point of t 2+ indicates the zero crossing points where the current detected by the second current sensor CT2 changes from positive to negative. These zero crossing points are calculated from the detection times just before and just after the current changes polarity. For example, t 1+ When calculating the current detected by the first current sensor CT1, the adjacent detection times immediately before and after the change in sign are defined as t + , t - The current at that time is i + , i - Then, t 1+ = (t - i + -t + i - ) / ( i + -i - ) can be calculated as follows. In the example shown in FIG. 4(b), t + = 0.666667, t - = 0.833333, i + = 0.244688, i - = -0.2729, t 1+ = 0.745458. Similarly, t 1-, t 2+ is calculated.

[0028] Since the calculated time difference between the two zero crossing points of the current detected by the first current sensor CT1 is half the current period T, the current period T is T = 2 | t 1+ -t 1- The zero crossing point t 1+ and the zero crossing point t 2+ From the current period T, the phase difference φ is φ = 2π | t 1+ -t 2+ | / T.

[0029] <Diagnosis of deterioration> Fig. 5 is a diagram showing an example of the flow of a process for diagnosing deterioration of equipment equipped with a motor 30 by the monitoring device 100 according to this embodiment. Fig. 5 shows a case where the first current sensor CT1 is attached to the electric wire 21U and the second current sensor CT2 is attached to the electric wire 21V. 5, first, the monitoring device 100 detects a current using the current sensor CT (step S101). The detected current is acquired as an analog signal by the A / D conversion unit 116 of the acquisition unit 111. Then, the A / D conversion unit 116 digitizes the acquired signal by A / D conversion (step S102).

[0030] Next, the current conversion unit 117 converts the signal digitized by the A / D conversion unit 116 into a current dimension signal (step S103). The offset corrector 118 corrects the offset of the acquired current for two phases (step S104). The offset corrector 118 corrects the offset by, for example, adjusting the detection value when no current is flowing to 0 A.

[0031] Next, the gain corrector 119 corrects the gains of the acquired currents for two phases (step S105). The gain corrector 119 corrects the gain by, for example, correcting one of the acquired currents for two phases to make the amplitude equal to that of the other current.

[0032] Next, the phase difference determination unit 120 determines whether the phase difference between the two phase currents output from the acquisition unit 111 is smaller than the phase difference when the two current sensors CT are attached in the same direction (step S106). The phase difference determination unit 120 calculates, for example, zero cross points where the two phase currents output from the acquisition unit 111 change polarity, and calculates the phase difference from the zero cross points.

[0033] If the phase difference determination unit 120 determines that the phase difference between the two phases of current output from the acquisition unit 111 is smaller than the phase difference when the two current sensors CT are installed in the same direction (YES in step S106), the polarity correction unit 121 corrects the positive / negative polarity of one of the two phases of current output from the acquisition unit 111 (step S107). The polarity correction unit 121 corrects the positive / negative polarity by, for example, multiplying the one phase of current of the two phases of current output from the acquisition unit 111 by −1. On the other hand, if the phase difference determination unit 120 determines that the phase difference between the two phases of current output from the acquisition unit 111 is not smaller than the phase difference when the two current sensors CT are installed in the same direction (NO in step S106), the processing proceeds to step S108.

[0034] Next, the calculation unit 113 calculates the current for the remaining one phase (step S108). The calculation unit 113 calculates the current for the remaining one phase using the currents for two phases output from the correction unit 112. When the two current sensors CT are installed in alternate directions, the calculation unit 113 calculates the current for the remaining one phase from the currents for two phases corrected by the polarity correction unit 121.

[0035] Next, the diagnosing unit 114 diagnoses the deterioration of the equipment including the motor 30 using information including at least the current for the remaining one phase calculated by the calculating unit 113 (step S109).

[0036] For example, the diagnosis unit 114 calculates a current vector and determines the degree of bearing wear of the motor 30 based on the calculated current vector. The relationship between the current vector and the degree of bearing wear is predetermined, for example, based on experiments or simulations. The diagnosis unit 114 determines the degree of bearing wear of the motor 30 based on the calculated current vector and the predetermined relationship between the current vector and the degree of bearing wear. Furthermore, for example, a threshold value of a current vector that allows determination of whether an abnormality has occurred in the device from experiments or simulations may be defined in advance, and the output unit 115 may determine whether an abnormality has occurred in the device.

[0037] Next, the output unit 115 outputs information relating to the deterioration of the equipment including the motor 30 (step S110). The information relating to the deterioration of the equipment includes information indicating the degree of deterioration, such as the degree of wear on the bearings of the motor 30 and the degree of increase in friction fluctuations of the bearings of the motor 30.

[0038] In the present embodiment, the offset correction unit 118 and the gain correction unit 119 correct the offset and gain of the current for two phases after conversion by the A / D conversion unit 116 and the current conversion unit 117, respectively, but this is not limiting. For example, the offset correction unit 118 and the gain correction unit 119 may be configured to correct the offset and gain of the current for two phases after conversion by the A / D conversion unit 116.

[0039] 5, the phase difference determining unit 120 may determine the phase difference from the amplitude of a composite wave obtained by combining currents for two phases output from the obtaining unit 111. 6A and 6B are diagrams showing the waveform of a composite wave obtained by combining currents for two phases output from the acquisition unit 111, where (a) shows the waveform of the composite wave when two current sensors CT are installed in the same direction, and (b) shows the waveform of the composite wave when two current sensors CT are installed in alternating directions. In Fig. 6, the horizontal axis shows time and the vertical axis shows amplitude, with half the current period set to 1 on the horizontal axis and the amplitude of the current waveform of the phase current output from the acquisition unit 111 set to 1 on the vertical axis.

[0040] The waveforms of the two phases of current output from the acquisition unit 111 are as shown in Figures 3(a) and (b), and Figure 6(a) shows the waveform of the composite wave obtained by combining the two phases of current shown in Figure 3(a), and Figure 6(b) shows the waveform of the composite wave obtained by combining the two phases of current shown in Figure 3(b). When two current sensors CT are attached in the same direction, the amplitude of the composite wave is equal to the amplitude of the current (see FIG. 3(a)) output from the acquisition unit 111, as shown in FIG. 6(a). When two current sensors CT are attached in alternate directions, the amplitude of the composite wave is √3 times the amplitude of the current (see FIG. 3(b)) output from the acquisition unit 111, as shown in FIG. 6(b).

[0041] From the above, when the amplitude of the composite wave of the two phases of current output from the acquisition unit 111 becomes larger than the amplitude of the current output from the acquisition unit 111, the phase difference determination unit 120 can determine that the phase difference is smaller than when the two current sensors CT are installed in the same direction.

[0042] 5, the diagnosing unit 114 may calculate a negative-sequence current vector of the three-phase current flowing through the electric wire 21 from the currents of the three phases, and diagnose the deterioration of the equipment using the calculated negative-sequence current vector. TIFF2025153019000002.tif7138, where a is the vector operator, The file is TIFF2025153019000003.tif12140. Furthermore, the diagnosing unit 114 may diagnose the deterioration of the device using only the current for the remaining one phase calculated by the calculating unit 113.

[0043] <Effects> The monitoring device 100 of the present disclosure is a monitoring device 100 for equipment equipped with a motor 30, the motor 30 is connected to three-phase AC, and is equipped with two current sensors CT that pass through an electric wire 21 through which the three-phase AC is supplied to acquire current for one phase of the three-phase AC, and is equipped with: an acquisition unit 111 that acquires current for two phases from the two current sensors CT; a correction unit 112 that corrects the positive and negative polarity of one phase of the acquired current for two phases when the phase difference of the current for two phases output from the acquisition unit 111 is smaller than the phase difference when the two current sensors CT are installed in the same direction; a calculation unit 113 that calculates the current for the remaining one phase from the current for the two phases corrected by the correction unit 112; and an output unit 115 that outputs information regarding deterioration of the equipment using information including at least the current for the remaining one phase calculated by the calculation unit 113. In this case, for an equipment equipped with a motor 30 connected to three-phase AC, when the current for two phases is acquired using two current sensors CT and the current for the remaining phase is calculated, and the deterioration of the equipment is diagnosed using the calculated current for the remaining phase, the diagnosis can be made more accurately than when the deterioration of the equipment is diagnosed without making any correction for the installation direction of the current sensors CT for the two phases. Furthermore, the monitoring device 100 of the present disclosure outputs information regarding deterioration of the device using the currents for the two phases corrected by the corrector 112 and the current for the remaining one phase calculated by the calculator 113. In this case, it is possible to perform a diagnosis more accurately than when a deterioration diagnosis is performed from the current for one phase. Here, the acquisition unit 111 includes an offset correction unit 118 that corrects the offsets of the currents for two phases acquired from the current sensors CT, respectively. In this case, the phase difference between the acquired currents for two phases can be accurately calculated. Furthermore, when the amplitude of the composite wave of the currents for the two phases output from the acquisition unit 111 becomes larger than the amplitude of the currents output from the acquisition unit 111, the correction unit 112 determines that the phase difference between the currents for the two phases output from the acquisition unit 111 is smaller than the phase difference when the two current sensors CT are installed in the same direction. In this case, it is possible to determine whether the phase difference between the acquired currents for the two phases is smaller than the phase difference when the two current sensors CT are installed in the same direction without calculating the phase difference. The acquisition unit 111 also includes a gain correction unit 119 that corrects the gain of at least one of the two phases of current acquired from the current sensor CT. In this case, a composite wave of the acquired two phases of current can be accurately calculated.

[0044] Although the embodiments have been described above, the technical scope of the present disclosure is not limited to the scope of the above-described embodiments. It is clear from the claims that combinations of two or more of the above-described embodiments, and various modifications or improvements to the above-described embodiments, are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0045] 10... inverter device, 21... electric wire, 30... motor, 100... monitoring device, 111... acquisition unit, 112... correction unit, 113... calculation unit, 114... diagnosis unit, 115... output unit, CT... current sensor

Claims

1. A monitoring device for a motor-equipped device, The motor is connected to a three-phase AC current; two current detectors that acquire a current for one phase of the three-phase AC and that pass through a line through which the three-phase AC is supplied; an acquisition unit that acquires currents for two phases from the two current detectors; a correction unit that corrects the positive or negative polarity of one of the acquired two-phase currents when the phase difference between the two-phase currents output from the acquisition unit is smaller than the phase difference when the two current detectors are installed in the same direction; and a calculation unit that calculates a current for one remaining phase from the currents for the two phases corrected by the correction unit; an output unit that outputs information about deterioration of the device using information including at least the current for the remaining one phase calculated by the calculation unit; A monitoring device comprising:

2. The monitoring device according to claim 1 , wherein the monitoring device outputs information relating to deterioration of the equipment using the currents for the two phases corrected by the corrector and the current for the remaining one phase calculated by the calculator.

3. The monitoring device according to claim 1 , wherein the acquisition unit includes an offset correction unit that corrects offsets of currents for two phases acquired from the current detectors.

4. 3. The monitoring device according to claim 1, wherein the correction unit determines that the phase difference between the two phases of current output from the acquisition unit is smaller than the phase difference when the two current detectors are installed in the same direction when the amplitude of the composite wave of the two phases of current output from the acquisition unit is larger than the amplitude of the current output from the acquisition unit.

5. The monitoring device according to claim 4 , wherein the acquisition unit includes a gain correction unit that corrects a gain of at least one of the two phases of current acquired from the current detector.

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