JP5705102B2 - Insulation deterioration diagnosis device - Google Patents

Description

  The present invention relates to a power feeding circuit connected between an inverter device and a load device driven by an inverter, and an apparatus for diagnosing insulation deterioration of the load device.

  Inverter-driven load equipment includes an electric motor, an uninterruptible power supply (UPS), an electromagnetic cooker, and lighting, but all of them cause insulation deterioration due to aging. For example, in an electric motor used for a transporter or the like, with frequent movement of a workbench connected to the electric motor, the conductor cable for supplying power may be rubbed, distorted, expanded and contracted, and the conductor coating may be damaged. In an electric motor used for a processing machine or the like, cutting fluid or oil may splash on the electric motor and erode to an internal insulating material through a shaft shaft or the like.

  In this way, the degree of insulation degradation of load equipment driven by an inverter varies depending on the environment of use and the durability of the components, but leakage current flows through the location where this insulation degradation occurs, causing a risk of electric shock to the human body and interruption of leakage It becomes a factor that the device operates. The earth leakage breaker is installed to prevent electric shock to the human body. Naturally, human life is a matter of course, but once the earth leakage circuit breaker is activated, the equipment and equipment containing the motor will stop, so it will take time to identify the cause and location of the earth leakage and restore it. The operating efficiency will be reduced.

  As a method for diagnosing such insulation deterioration, an insulation resistance meter (Megger) is generally used. The insulation resistance meter measures the current that flows when a high DC voltage is applied to the diagnostic circuit, and calculates the insulation resistance based on Ohm's law.

  Patent Document 1 (FIG. 1) proposes an example in which the principle of an insulation resistance meter is applied to an insulation deterioration diagnosis of an electric motor. By opening and closing a switch, a power supply circuit to the electric motor is changed to a closed circuit including an insulation resistance and a ground. Insulation degradation is diagnosed by switching and measuring the current that flows when a DC voltage is applied to the closed circuit.

  Since the cause and progress of the insulation deterioration vary depending on the usage environment, the diagnosis of the insulation deterioration needs to be performed periodically. For this reason, although the switching method of Patent Document 1 can accurately measure the insulation deterioration, it is necessary to completely stop the electric motor when switching the power feeding circuit. Therefore, the diagnosis time of insulation deterioration is limited before or after driving the motor, and in load equipment that requires long-term continuous operation, insulation deterioration diagnosis cannot be performed until power supply is completely stopped. There is a problem that insulation deterioration cannot be detected in advance.

  Similarly, when an insulation resistance meter is used, it is necessary to stop the power supply to the load or cut off the connection at the time of diagnosis, and the insulation deterioration diagnosis cannot be performed in a live line state. Furthermore, insulation deterioration diagnosis using an insulation resistance meter is often performed manually by humans during periodic inspections. However, when there are many devices subject to periodic inspection, there is a possibility that a high voltage is applied to a circuit of another system due to a human error, resulting in a failure of the load device.

  From this point of view, the zero-phase current transformer used for the earth leakage breaker, the earth leakage protection relay, etc. is effective for the insulation deterioration diagnosis in the live line state.

  In Patent Document 2 (FIG. 2) and Patent Document 3 (FIG. 1), a zero-phase current measurement that measures a differential current component of a forward path and a return path and a zero-phase current of a three-phase AC in the middle of a power feeding circuit to a load device. By arranging a detector (ZCT: Zero-phase Current Transformer) and detecting the zero-phase current, the current leaking from the electric circuit can be obtained. In this case, it is not necessary to cut off the power supply or connection to the load, and the leakage current leaking from the electric circuit in the live line state can be measured. However, a load device driven by an inverter is generally supplied with a current having a frequency of several Hz to several tens of Hz, and a leakage current flows to the ground via a stray capacitance generated between the energized cable and the ground. There is.

  As a countermeasure, when the insulation resistance is calculated from the value of the voltage applied to the circuit and the value of the leakage current, and the insulation deterioration diagnosis is performed, the amount of current that leaks through the stray capacitance is detected from the detection target. Must be excluded. Since the current leaking through the insulation resistance and the current leaking through the stray capacitance are components of R and C, respectively, they can be separated as leakage current vectors having a phase difference of 90 degrees. However, since the zero-phase current transformer detects a combined vector of two leakage current vectors in principle, it cannot separate them.

  In Patent Document 4 (FIGS. 1 and 2), a current that leaks through an insulation resistance by extracting a vector component having the same phase as the voltage applied to the electric circuit from the output waveform of the zero-phase current transformer. Only detecting.

  In Patent Document 5 (FIG. 1), in a three-phase AC circuit, a voltage for insulation deterioration diagnosis is superimposed on the electric circuit via a transformer, and a voltage for insulation deterioration diagnosis is obtained by a zero-phase current transformer provided in the electric circuit. By extracting only the same frequency component under two or more frequency conditions, only the current leaking through the insulation resistance is detected from the leakage current leaking from the three-phase AC circuit.

  In Patent Document 6 (FIG. 1), in the three-phase AC circuit, the waveforms of the currents flowing in the respective phases are 120 degrees different from each other, but the third harmonic components of the current waveforms flowing in the respective phases are all in phase. Focusing on this, only the current leaking through the insulation resistance is detected from the leakage current leaking from the three-phase AC circuit by extracting the in-phase component of the third harmonic voltage and the third harmonic current.

  In Patent Document 7 (FIG. 1), a fundamental wave component and a fifth harmonic component are extracted from a leakage current and a voltage measured by a zero-phase current transformer and a voltage measuring device, and the leakage current in the fundamental wave and the fifth harmonic is extracted. By analyzing according to a predetermined analysis algorithm from the phase relationship between the voltage and the voltage, only the current leaking through the insulation resistance is detected.

JP2007-159289A (FIG. 1) Japanese Patent Laying-Open No. 2003-284235 (FIG. 2) JP-A-4-132969 (FIG. 1) Japanese Patent Laid-Open No. 4-169869 (FIGS. 1 and 2) Japanese Patent Laying-Open No. 2003-2328281 (FIG. 1) JP-A-6-43196 (FIG. 1) Japanese Patent Laying-Open No. 2004-317466 (FIG. 1)

  As described above, a plurality of methods are known for detecting only the current leaking through the insulation resistance in the live line state. However, both methods have problems. For example, in the case of the method using the phase relationship between the voltage and the leakage current, the voltage and the waveform of the leakage current are important signal information, but the zero-phase current transformer that can measure the leakage current with one sensor is a magnetic material. Since a relatively large current flows as a leakage current, the magnetization state of the magnetic material changes, and the output waveform of the zero-phase current device and the leakage current waveform do not match, resulting in phase characteristics. There is a problem that an error occurs.

  On the other hand, it is possible to use a current sensor having no phase shift in principle without using a zero-phase current transformer. However, in order to detect the zero-phase current, it is necessary to provide a current sensor for each phase, which leads to an increase in the size of the device and a complicated sensor output wiring. Further, when an insulation deterioration diagnosis voltage is applied from the outside to the electric circuit via a transformer, the transformer is large and has problems in terms of the size and cost of the apparatus.

  In the method of measuring the third-order harmonic component, since the phases of the three-phase circuit are measured together (synthesized), there is a problem that the phase in which the insulation deterioration has occurred cannot be specified.

  In addition, in the method that can identify the phase in which insulation degradation has occurred from the leakage current and the fundamental wave component and the fifth harmonic component of the voltage, the phase characteristics of the zero-phase current transformer are used because the phase relationship between the voltage and the leakage current is used. There is a problem with the fluctuations. Furthermore, it is a precondition that the fifth harmonic component is included in the voltage signal applied to the electric circuit, and that the signal level is low even if it is included.

  The object of the present invention is to detect only the current leaking through the insulation resistance without using the phase relationship between the leakage current and the voltage, calculate the insulation resistance value of each phase, and determine the phase where the insulation deterioration has occurred. The object is to provide an insulation deterioration diagnosis device that can be identified.

In order to achieve the above object, the present invention provides a three-phase power supply circuit connected between an inverter device and an inverter-driven load device and a device for diagnosing insulation deterioration of the load device,
A zero-phase current measurement unit for measuring the zero-phase current of the three-phase feed circuit,
A harmonic extraction unit for extracting a third-order harmonic component and a 3n-order harmonic component (n is an integer of 2 or more) from the measured zero-phase current;
A calculation unit that calculates an insulation resistance value of the power feeding circuit of each phase based on the extracted third harmonic component and 3n harmonic component ;
The calculation unit calculates the third harmonic component and the 3n-order harmonic component of the applied voltage in the power supply circuit of each phase under each condition in which the load device is driven with voltages of at least three different fundamental frequencies f1, f2, and f3. The third-order harmonic component I _{0_3f} and the 3n-order harmonic component I _{0_3nf} of the ratio s and the zero-phase current I ₀ are acquired, respectively, and leaked via the insulation resistance of the power supply circuit of each phase using the following equation (5) A leakage current value of each phase is calculated by calculating a combined value a of currents to be solved and solving three simultaneous equations obtained for the fundamental frequencies f1, f2, and f3 .

  According to the present invention, when diagnosing insulation degradation, each phase can be obtained without using the phase relationship between leakage current and voltage by using the measured third-order harmonic component and 3n-order harmonic component of the zero-phase current. It is possible to calculate the insulation resistance value of the power feeding circuit. As a result, it is possible to accurately diagnose the insulation deterioration without being affected by the variation in the phase characteristics of the zero-phase current measuring unit.

It is a block diagram which shows the insulation deterioration diagnostic apparatus which concerns on Embodiment 1 of this invention. It is sectional drawing which shows arrangement | positioning of a zero phase current transformer and a three-phase cable wire. FIG. 3A is an explanatory diagram showing a magnetic field vector generated by a current flowing through a three-phase AC circuit. FIG. 3A shows a case where there is no leakage current, and FIG. 3B shows a case where there is a leakage current. FIG. 4A is an explanatory diagram showing a current vector leaking through the insulation resistance of each phase and a current vector leaking through the capacitor of each phase, and FIG. 4A is the same when the insulation resistance and the capacitor are the same in each phase; FIG. 4B shows a case where the insulation resistance and the capacitor are different for each phase. It is explanatory drawing which shows the vector component of the 3rd harmonic component of a zero phase current, and a 3n order harmonic component. It is a block diagram which shows the other example of an insulation degradation diagnostic apparatus. It is a block diagram which shows the further another example of an insulation degradation diagnostic apparatus. It is a block diagram which shows the insulation degradation diagnostic apparatus which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an insulation deterioration diagnosis apparatus 101 according to Embodiment 1 of the present invention. The load device 3 is driven by feeding a phase current from the inverter device 2 via a plurality of cable lines 6a, 6b, and 6c that function as a feeding power path. For example, three cable lines are used for three-phase driving, and two cable lines are used for single-phase driving.

  Examples of the inverter-driven load device 3 include an electric motor, an uninterruptible power supply (UPS), an electromagnetic cooker, and lighting. Insulation resistances 8a, 8b, 8c and capacitors 7a, 7b, 7c representing stray capacitance exist between the cable lines 6a, 6b, 6c and the ground, respectively. Note that the ground terminal of the inverter device 1 and the ground terminal of the load device 3 may be connected by an earth wire.

  The control device 1 has a function of controlling the operation of the inverter device 2, and transmits a control signal such as a waveform, magnitude, and cycle of a three-phase drive current to the inverter device 2 in accordance with the driving method of the load device 3. . The inverter device 2 has a function of modulating a direct current signal input from a preceding converter or the like based on a control signal from the control device 1, and an alternating current signal having a waveform, amplitude, and frequency commanded by the control device 1. Output.

  The insulation deterioration diagnosis apparatus 101 includes a zero-phase current sensor 4, an insulation deterioration detection circuit 90, an information transmission cable 9, a display 11 and the like.

  The information transmission cable 9 includes information on the ratio between the third-order harmonic component and the 3n-order harmonic component (n is an integer of 2 or more) of the voltage applied from the inverter device 2 to the cable wires 6a, 6b, 6c, and The frequency information is transmitted from the control device 1 to the insulation deterioration detection circuit 90. The 3n-order harmonic means a 6th-order harmonic, a 9th-order harmonic, a 12th-order harmonic, and the like.

  The zero-phase current sensor 4 is provided in the middle of the cable lines 6a, 6b, and 6c, and has a function of measuring the zero-phase current of the power feeding circuit. Zero-phase current refers to leakage current that flows from the electric circuit to the ground via an insulation resistance. Here, considering that the signal output from the inverter device 2 is an AC signal, and that the current leaking through the capacitors 7a, 7b, and 7c and the insulation resistors 8a, 8b, and 8c is a minute current, it is zero. As the phase current sensor 4, for example, a zero-phase current transformer (ZCT: Zero-phase Current Transformer) or a zero-phase current transformer to which a fluxgate current sensor is applied is preferably used.

  The insulation deterioration detection circuit 90 includes a filter circuit 5, an insulation resistance calculation circuit 10, and the like.

  The filter circuit 5 has a function of extracting a third-order harmonic component and a 3n-order harmonic component from the output voltage waveform of the zero-phase current sensor 4. The filter circuit 5 may be configured by an analog circuit, but considering that the voltage frequency supplied from the inverter device 2 to the load device 3 is variable and the fundamental frequency fluctuates, a DSP (Digital Signal Processor) or the like The digital circuit is preferably used. In the case of a digital circuit, the output voltage waveform of the zero-phase current sensor 4 is A / D converted, and a discrete Fourier calculation process is performed to extract a harmonic component and the inverter device 2 obtained via the information transmission cable 9 Based on the drive frequency (fundamental frequency), it is possible to extract the third-order harmonic component and the 3n-order harmonic component.

  The insulation resistance calculation circuit 10 performs a predetermined calculation using information obtained via the information transmission cable 9, for example, information about the voltage applied to the cable lines 6 a, 6 b, 6 c and the output value of the filter circuit 5. It has a function of calculating the insulation resistance values of the cable lines 6a, 6b, 6c according to the equation.

  The display 11 displays the result of the insulation deterioration diagnosis. For example, the display 11 is composed of a display or the like, and the insulation deterioration can be visually monitored by periodically displaying the insulation resistance value of each phase. It should be noted that instead of the display device 11, an earth leakage circuit breaker, an earth leakage relay, a warning buzzer, or the like may be used to notify the user of insulation deterioration, and a function desired by the user when insulation deterioration occurs can be added. is there.

  Next, an insulation deterioration detection method will be described. When a zero-phase current transformer is used as the zero-phase current sensor 4, as shown in FIG. 2, all the three-phase cable wires 6a, 6b, 6c are passed through the inside of the annular core 4a of the zero-phase current transformer. The zero-phase current transformer can detect the magnitude of the combined vector of the current vector Iu flowing through the cable line 6a, the current vector Iv flowing through the cable line 6b, and the current vector Iw flowing through the cable line 6c.

In the three-phase AC circuit, the phase of the fundamental voltage of each phase differs by 120 degrees. When there is no current leaking from the electric circuit, as shown in FIG. 3A, the amplitudes of the current values flowing through the cable lines 6a, 6b, and 6c are the same. Therefore, from the cable lines 6a, 6b, and 6c, The generated magnetic field has the same value, the magnitude of the resultant magnetic field vector becomes zero, and zero voltage is output to the zero-phase current transformer. In FIG. 3A, the magnetic field generated from the U-phase cable wire 6a is H _(U) , the magnetic field generated from the V-phase cable wire 6b is H _(V) , and the magnetic field generated from the W-phase cable wire 6c is H _(W). It is said.

  On the other hand, when there is a current leaking from the electric circuit to the ground, for example, as shown in FIG. 3B, the amplitude of the magnetic field generated from each of the cable lines 6a, 6b, and 6c becomes different. The magnitude is not zero, and a value proportional to the magnitude of the resultant vector is obtained as the output of the zero-phase current transformer. In FIG. 3B, the magnitudes of the V-phase and W-phase magnetic fields are smaller than those in FIG. 3A, but the current leaked from the electric circuit is an in-phase component. The fact that the applied voltage and the leakage current are in phase means that the leakage current flows through the resistance component and no leakage current flows through the capacitance component.

As shown in FIG. 1, the cable lines 6a, 6b, and 6c of each phase have stray capacitance between the ground and the capacitors 7a, 7b, and 7c. Therefore, it is necessary to consider not only the current that flows to the ground via the insulation resistors 8a, 8b, and 8c, but also the current that flows to the ground via the capacitors 7a, 7b, and 7c. That is, as shown in FIG. 4A, the zero-phase current transformer has a magnitude of the combined vector of the current I _0R leaking through the insulation resistance of each phase and the current I _0C leaking through the capacitor of each phase. A voltage signal proportional to the height is output. If the values of the capacitors 7a, 7b, and 7c are the same, the magnitude of the combined vector of the current I _0C that leaks through the capacitors is zero. On the other hand, the capacitors 7a, 7b, 7c value, if the insulation resistance 8a, 8b, the value of 8c respectively different example, a synthetic vector _{I 0} as shown in Figure 4 (b).

  In the case of a three-phase AC circuit, the phase of the fundamental wave voltage of each phase differs by 120 degrees, but the third-order and 3n-order harmonic components are in phase. Therefore, for example, when focusing on the third harmonic component, as shown in FIG. 5A, the third harmonic component vector of the current leaking from each phase is added in the same direction.

The insulation resistance values of the insulation resistances 8a, 8b, and 8c for each phase are R _(U) , R _(V) , and R _(W), and the insulation capacitance values of the capacitors 7a, 7b, and 7c for each phase are C _{(U )} , C _(V) , C _(W), and the magnitude of the third harmonic component of the voltage applied to each insulation resistance and each capacitor V _{(U) — 3f} , V _{(V) — 3f} , V _{(W) Assuming} that _{_3f} , the following formulas (1) and (2) are established.

As shown in FIG. 5B, the third-order harmonic component I _{0 — 3f} of the zero-phase current I ₀ has a combined vector magnitude of current leaking through each of the insulation resistors 8a, 8b, and 8c. If the magnitude of the combined vector of currents leaking through the capacitors 7a, 7b, and 7c is b, Equation (3) is established.

  Further, the impedances of the capacitors 7a, 7b, and 7c depend on the frequency f as can be seen from the equation (2). Therefore, as shown in FIG. 5C, when attention is paid to the harmonic component of n times (n: 2, 3, 4,...) Of the third harmonic, Expression (4) is established. Note that s in Equation (4) represents the ratio of the 3n-order harmonic voltage to the 3rd-order harmonic voltage as shown in Equation (4a), and the 3n-order harmonic voltage of each phase is the same.

  From Expression (3) and Expression (4), the magnitude a of the combined vector of currents leaking through the respective insulation resistances 8a, 8b, and 8c is expressed by Expression (5).

  In particular, when the drive voltage waveform of the load device 3 is a rectangular wave, the rectangular wave is expressed by Expression (6) by Fourier expansion.

  In the case of a rectangular wave, the voltage ratio between the 9th harmonic, which is the 3nth order, and the third harmonic is 1/3. When s = 1/3 and n = 3, the magnitude a of the combined vector of currents leaking through the respective insulation resistances 8a, 8b, 8c is expressed by Expression (7).

  That is, by using the values of the zero-phase currents of the third harmonic component and the 3n harmonic component, the magnitude a of the combined vector of currents leaking through the respective insulation resistances 8a, 8b, 8c can be obtained. As a result, the degree of insulation deterioration can be determined. However, the value obtained here is a leakage current flowing through the combined resistance of the insulation resistances 8a, 8b, and 8c, and it cannot be specified through which insulation resistance the current leaks.

Therefore, by applying the frequency variable function that is the basic function of the inverter device 2, the load device 3 is inverter-driven with voltages of at least three different basic frequencies f 1, f 2, and f 3 under the control of the control device 1, and each has different conditions. Measure the zero-phase current below. The obtained zero-phase current is extracted from the zero-phase current values of the third-order harmonic component and the 3n-order harmonic component via the filter circuit 5, and is expressed by equations (8) to (10). Thus, three equations relating to the magnitudes a ₁ , a ₂ , and a ₃ of the combined vector of leakage currents can be obtained. Information such as the value of the third harmonic voltage of each phase and the ratio s between the value of the third harmonic voltage and the value of the 3n harmonic voltage of each phase is transmitted from the control device 1 via the information transmission cable 9. Can be obtained.

In this way, for the three unknowns of the insulation resistance values R _(U) , R _(V) , and R _(W) , three simultaneous equations of Formula (8), Formula (9), and Formula (10) are established. By solving the simultaneous equations, values of R _(U) , R _(V) , and R _(W) can be obtained, and as a result, it is possible to specify the insulation resistance in which the insulation deterioration has occurred. Therefore, it is possible to accurately diagnose the insulation deterioration of the load device 3 and the cable wires 6a, 6b, and 6c using the increase or decrease or change rate of the insulation resistance value for each phase of the U phase, V phase, and W phase as an index. .

  In addition, in the formulas (8) to (10), the value of the third harmonic voltage of each phase is substituted, but as an alternative, the following formulas (11), (12), and (13) are shown. As described above, the simultaneous equation may be calculated as the current leaking through the insulation resistance of each phase, and the insulation deterioration diagnosis may be evaluated by the third harmonic component of the current leaking from each phase through the insulation resistance. . In this case, the information obtained from the control device 1 via the information transmission cable 9 is only information on the fundamental frequency and the ratio between the third harmonic voltage value and the 3n harmonic voltage value of each phase. Information on the values of the 3rd order and 3n order harmonic voltages is not necessary.

  When the load device 3 is an uninterruptible power supply (UPS), an electromagnetic cooker, lighting, or the like, it is relatively easy to drive the load device 3 with voltages of different basic frequencies f1, f2, and f3. However, when the load device 3 is a main shaft motor, it is often driven at a constant rotational speed, so it is considered difficult to measure the zero-phase current under a plurality of frequency conditions. In this case, for example, the drive frequency is gradually changed, and the output waveform of the zero-phase detector obtained during the acceleration period until the rotational speed of the motor reaches a constant speed from a low speed, for example, a short-time Fourier calculation By performing processing or the like, it is possible to extract zero-phase currents corresponding to three or more different fundamental frequencies f1, f2, and f3 from the data being accelerated. Similarly, when the rotational speed of the electric motor is gradually reduced, zero-phase currents corresponding to different basic frequencies f1, f2, and f3 can be extracted.

  As a further alternative, under the situation where the motor is rotating at a constant speed, by changing the frequency of the d-axis current that does not contribute to the torque of the motor, zero-phase currents corresponding to different fundamental frequencies f1, f2, and f3 are obtained. Extraction is possible.

  In the configuration of FIG. 1, information on the voltage value of the third harmonic component and the 3n harmonic component applied to the three-phase AC circuit and the value of the ratio is acquired from the control device 1 via the information transmission cable 9. doing. As an alternative, as shown in FIG. 6, a voltage measuring device 13 such as VT (Voltage Transformer) is installed in the middle of the cable lines 6 a, 6 b, 6 c to measure the phase voltage of each phase, and the filter circuit 14 It is also possible to acquire the voltage values of the second harmonic component and the 3nth harmonic component.

  1 and FIG. 6, the voltage values of the third harmonic component and the 3n harmonic component applied to the cable lines 6a, 6b, 6c are directly provided to the insulation deterioration detection circuits 90, 91. It is configured. As an alternative, as shown in FIG. 7, the voltage waveform applied to each phase from the control device 1 is transmitted to the filter circuit 15 via the information transmission cable 9, and the third harmonic component and It is also possible to acquire the voltage value of the 3n-order harmonic component.

  As the information transmission cable 9, a wired or wireless information communication means can be used. 1, 6, and 7, the insulation deterioration detection circuits 90, 91, and 92 are illustrated separately from the inverter device 2 and the control device 1, but may be disposed in the same casing. Absent.

  In the above description, the zero-phase current sensor 4 is preferably a zero-phase current transformer as shown in the present embodiment. For example, the phase current is measured for all three phases, and the zero-phase current sensor 4 is calculated from the waveform of each phase current. A method for obtaining the current may be used.

As described above, in this embodiment, the insulation resistance values R _(U) , R _(V) , and R _(W) of the respective phases in the cable lines 6a, 6b, and 6c that supply power to the inverter-driven load device 3 are calculated. Can do. Therefore, it is possible to monitor the increase / decrease or change of each insulation resistance value and identify the phase in which the insulation deterioration occurs, so that the diagnosis accuracy of the insulation deterioration can be improved.

Embodiment 2. FIG.
FIG. 8 is a configuration diagram showing an insulation deterioration diagnosis apparatus 104 according to Embodiment 2 of the present invention. The insulation deterioration diagnosis device 104 according to the present embodiment has the same configuration as that of the insulation deterioration diagnosis device 101 according to the first embodiment. However, instead of the information transmission cable 9, the insulation deterioration detection circuit 93 is converted into a frequency-voltage value. A circuit 12 is provided. That is, in the first embodiment, using the information transmission cable 9, the frequency of the voltage applied from the control device 1 to the cable lines 6a, 6b, and 6c, and the voltage values of the third harmonic component and the 3n harmonic component. The information regarding is supplied to the filter circuit 5 and the insulation resistance arithmetic circuit 10. In the present embodiment, functions equivalent to those of the first embodiment are realized without using the information transmission cable 9.

When the capacitors 7a, 7b, and 7c existing in the cable wires 6a, 6b, and 6c of the respective phases have the same value, the magnitude of the combined vector is zero in the fundamental component of the current _I0C that leaks through the capacitors. It is. However, it is considered difficult to match the values of the capacitors 7a, 7b, and 7c due to environmental fluctuations in the manufacture of the electric motor and the wiring construction. In other words, even if the current leaked through the insulation resistors 8a, 8b, and 8c is negligible at the initial stage of manufacture, the output of the zero-phase current sensor 4 is not completely zero, and the output of the zero-phase current sensor 4 A signal component corresponding to the fundamental frequency can be extracted from the voltage waveform.

  Although depending on the signal level of the zero-phase current sensor 4, when performing discrete Fourier arithmetic processing, a peak value clearly appears at a location corresponding to the fundamental frequency. That is, it is possible to estimate the fundamental frequency by performing peak detection.

When the fundamental frequency clearly appears, for example, it is considered that the fundamental wave, third-order, and 3n-order harmonic voltage values can be calculated backward from the fundamental frequency. Therefore, based on the fundamental frequency obtained by the filter circuit 5, a frequency-voltage value conversion circuit 12 for converting the fundamental wave, third-order and 3n-order harmonic voltage values is provided, and the converted voltage value and the filter circuit 5 are obtained. Insulation resistance values R _(U) , R _(V) , and R _(W) can be calculated from the values of the third harmonic component and the value of the 3n harmonic component according to the equations (8) to (10). it can.

  As described above, in the present embodiment, it is based on the output of the zero-phase current sensor 4 without obtaining information on the frequency of the voltage applied to the electric circuit from the control device 1 and the voltage value of the third-order and 3n-order harmonic components. Thus, the insulation resistance value of each phase can be obtained, and as a result, the insulation deterioration diagnosis of each phase can be performed.

1 control device, 2 inverter device, 3 load equipment, 4 zero-phase current sensor,
5 Filter circuit, 6a, 6b, 6c Cable line,
7a, 7b, 7c capacitors, 8a, 8b, 8c insulation resistance,
9 Information transmission cable, 10 Insulation resistance calculation circuit, 11 Display,
12 frequency-voltage conversion circuit, 13 voltage measuring device,
5, 14, 15 filter circuit, 90-93 insulation deterioration detection circuit,
101-104 Insulation deterioration diagnosis device.

Claims (5)

A device for diagnosing the three-phase power supply circuit connected between the inverter device and the load device driven by the inverter and the insulation deterioration of the load device,
A zero-phase current measurement unit for measuring the zero-phase current of the three-phase feed circuit,
A harmonic extraction unit for extracting a third-order harmonic component and a 3n-order harmonic component (n is an integer of 2 or more) from the measured zero-phase current;
A calculation unit that calculates an insulation resistance value of the power feeding circuit of each phase based on the extracted third harmonic component and 3n harmonic component ;
The calculation unit calculates the third harmonic component and the 3n-order harmonic component of the applied voltage in the power supply circuit of each phase under each condition in which the load device is driven with voltages of at least three different fundamental frequencies f1, f2, and f3. The ratio s and the third harmonic component I _{0_3f} and the 3n harmonic component I _{0_3nf} of the zero-phase current I ₀ are acquired, respectively, and leaked through the insulation resistance of the feeding circuit of each phase using the following formula (A1) An insulation deterioration diagnostic apparatus , wherein a leakage current value of each phase is calculated by calculating a combined value a of currents to be calculated and solving three simultaneous equations obtained for the fundamental frequencies f1, f2, and f3 .

The calculation unit calculates the insulation resistance value of the power supply circuit of each phase using the calculated leakage current value of each phase and the third harmonic component and 3n-order harmonic component of the applied voltage in the power supply circuit of each phase. The insulation deterioration diagnosis apparatus according to claim 1 . The inverter device is controlled by a control device,
Operation unit, the control unit of the inverter unit, insulation deterioration diagnostic apparatus according to claim 1, wherein the obtaining the third harmonic component and 3n-order harmonic component of the applied voltage in each phase of the power supply path. The inverter device is controlled by a control device,
The harmonic extraction unit obtains the voltage waveform applied to the power feeding circuit of each phase from the control device of the inverter device, extracts the third harmonic component and the 3n harmonic component of the applied voltage,
Calculation unit, from the harmonic extraction unit, insulation deterioration diagnostic apparatus according to claim 1, wherein the obtaining the third harmonic component and 3n-order harmonic component of the applied voltage in each phase of the power supply path. A voltage measurement unit for measuring each voltage waveform applied to the power supply circuit,
The harmonic extraction unit obtains a voltage waveform from the voltage measurement unit, extracts a third harmonic component and a 3n order harmonic component of the applied voltage,
Calculation unit, from the harmonic extraction unit, insulation deterioration diagnostic apparatus according to claim 1, wherein the obtaining the third harmonic component and 3n-order harmonic component of the applied voltage in each phase of the power supply path.

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