JPH03269268A - Diagnostic apparatus of deterioration of capacitor - Google Patents

Abstract

PURPOSE:To make an apparatus conduct a stable operation at all times by measuring a discharge characteristic of a predetermined section on the basis of an output of a voltage detecting circuit when an input power source is broken, and by judging a capacitor to be deteriorated when the characteristic is outside the range of a predetermined value. CONSTITUTION:When an input power source 1 of a capacitor 3 is broken, a discharge characteristic in a predetermined section is measured on the basis of an output of a voltage detecting circuit 9. When the discharge characteristic is outside the range of a predetermined value, a computer 7 judges the capacitor 3 to be deteriorated. This deterioration abnormality is stored in a storage circuit 8 and simultaneously a signal is outputted from an arithmetic control element to the microcomputer 7 so as to control a base circuit 11 through an inverter device 12. Then the inverter device 12 and a load are separated from each other electrically and a charging circuit of the capacitor 3 turns to be the one proper to the inverter 12. Thereby a stable operation can be conducted at all times without being affected by the load, and the general-purpose property is increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a capacitor deterioration diagnosis device, and in particular to a smoothing capacitor used for smoothing the DC power supply voltage of a main circuit or a control circuit such as an inverter device. This relates to the diagnosis of deterioration.

[Prior Art] A conventional technique for diagnosing deterioration of smoothing capacitors used in this type of inverter device is disclosed in Japanese Patent Laid-Open No. 60-2
There is No. 16792.

In this conventional example, when the load motor changes between power operation and regeneration operation, there is a non-operation period in which the power converter and the regeneration converter stop operating at the same time, so the voltage across the smoothing capacitor changes at this time. was compared with a predetermined set value, and if it exceeded the set value, it was determined that the smoothing capacitor had deteriorated.

[Problems to be Solved by the Invention] In the above conventional example, in order to detect the voltage change of the smoothing capacitor, it is necessary that both the power converter and the regenerative converter have a non-operating period. Depending on the type, both power and regeneration operation modes may not occur, so it could not be applied to those that do not have such non-operating periods.

In addition, the regenerative energy changes depending on the type or condition of the load, and as a result, the voltage change of the smoothing capacitor that occurs during the above-mentioned non-operation period is affected by the load, so loads such as general-purpose inverters are especially It cannot be applied to things that have not been decided yet.

The present invention solves the above-mentioned problems and provides a highly versatile capacitor deterioration diagnostic device that does not utilize the above-mentioned non-operating time period and always operates stably without being affected by load. This is how it was done.

[Means for Solving the Problems] In order to solve the above-mentioned problems of the conventional technology, when the input power to the capacitor is cut off, the discharge characteristics when the charge of the capacitor is discharged through a predetermined circuit are measured. This is how it was done.

As a means for this purpose, a voltage detection means for the capacitor is provided, and in a predetermined voltage section of the capacitor,
Alternatively, the capacitor is provided with means for measuring the discharge characteristics in a time interval, and means for diagnosing that the capacitor has deteriorated when the discharge characteristics deviate from a predetermined range. Furthermore, it is provided with means for issuing an alarm or means for handling an abnormality as necessary.

Another method is to measure the charging characteristics when input power to the capacitor is turned on.

The means for this purpose includes a current detection means for measuring the charging current to the capacitor, and a means for integrating the charging current of the capacitor in a predetermined voltage section of the capacitor, and this integrated value is a predetermined value. The capacitor is equipped with means for diagnosing that the capacitor has deteriorated if the capacitor falls outside of the specified range. Furthermore, it is provided with means for issuing an alarm or means for handling an abnormality as necessary.

[Operation: When the input power to the capacitor is cut off, the voltage detected by the voltage detection means has a discharge characteristic measured by the discharge characteristic measuring means, and this measured value is compared with a predetermined range, If the value is outside this range, it is diagnosed that the capacitor has deteriorated. If necessary, an alarm means or an abnormality processing means can be provided to issue an alarm or handle an abnormality.

Furthermore, when the input power to the capacitor is turned on, the current value measured by the current detecting means is time-integrated and compared with a predetermined range, and if it is out of this range, it is diagnosed that the capacitor has deteriorated. . If necessary, an alarm means or an abnormality processing means can be provided to issue an alarm or handle an abnormality.

[Example 1] Hereinafter, a first embodiment of a method of diagnosing capacitor deterioration based on the discharge characteristics of a capacitor when input power is cut off will be described.
This will be explained with reference to FIG. 4.

FIG. 1 shows an embodiment of the present invention, and shows an inverter device for driving an AC motor.

An AC power source 1, a forward converter 2 connected to the AC power source 1 and converting the AC power of the AC power source 1 into DC power, and an inverse converter 2 that converts the DC power into AC having arbitrary variable voltage and variable frequency. 5, a smoothing capacitor 3 connected between the forward converter 2 and the inverse converter 5 and serving to smooth the output of the forward converter 2, and a discharge circuit 4 for discharging the charge of the capacitor 3. A microcomputer 7 (hereinafter referred to as microcomma) that controls the inverter main circuit and the inverter device 12, a storage circuit 8 that stores software or various data of the microcomma, a detection circuit 9 that measures each current, voltage, etc. of the inverter device 12, Inverter device 1
Display circuit or signal output circuit 1 that displays and outputs the state of 2.
0 shows an inverter device 12 equipped with a control device for a base circuit 11 that drives an inverter 5. Further, 20 indicates a voltage signal of the capacitor 3.

Here, the smoothing capacitor 3 is the subject of deterioration diagnosis in the present invention.

FIG. 2 shows the voltage (VD) of the capacitor 3 and the state of time (1). In particular, in region (2), it is assumed that the input to the inverter device 12 is cut off and the operation of the inverter 5 is stopped.

In this region, the capacitor 3 is discharged only by the discharge circuit 4, and the normal discharge time (△td) from the predetermined voltage v1 to the voltage V2 is determined by the capacitance of the capacitor 3 and the constant of the discharge circuit 4. It can be calculated from , and it can also be actually measured using an inverter device with a normal capacitor.

When the discharge circuit 4 has only a resistor with a resistance value R, the capacitor 3
When the capacitance of is C, the discharge time (Δt) is expressed by the following formula.

Δt=-CRIn(v2/V1)・・・・・・・・・(
1) If the discharge circuit has a resistor with a resistance value R, a power supply circuit with power consumption W, etc., the following equation is obtained.

1 △t=-CRIn ((V22+RtJ)/(V□2+
RtJ)) (2) From equations (1) and (2), it can be seen that the capacitance C of the capacitor 3 and the discharge time (Δt) are proportional. Therefore, when the capacitor capacitance C decreases, which is one manifestation of capacitor deterioration, the discharge time (Δtd) becomes shorter by the proportion of the decrease, 1 2 .

FIG. 3 shows a flowchart of the operation. Confirm that the voltage VD of capacitor 3 is the predetermined voltage □ (
Step 201) L/, the timer counter is started from zero (step 202). Thereafter, when the voltage VD reaches a predetermined voltage V2 (step 203), it is determined whether the timer counter is within a predetermined value range for determining deterioration of the capacitor 3 (step 204). If it is outside the range, it is assumed that the capacitor 3 has deteriorated, and the deterioration abnormality of the capacitor 3 is stored in the memory circuit 8 (step 205). At the same time, an alarm signal is output (step 206) to notify the abnormality.

Note that the "value determined for deterioration determination" described in step 204 above may be a predetermined absolute value, or it may be the same value as above when the power is first turned on or shut off to the inverter device. It may be a value determined using the initial value of the capacitor capacitance measured by the method described above.

The method of actually operating the inverter device and measuring the initial value can absorb the capacitance IL error of the capacitor and the resistance value error of the discharge circuit, so it has the advantage of being more accurate than that obtained by calculation.

Further, in the above description, deterioration is diagnosed by measuring the time required for a prescribed voltage change, but deterioration may be diagnosed by measuring the voltage change for a prescribed time. In this case, in the operation flowchart of FIG. 3, the processing content of step 203 is set to "determine when the timer counter reaches the specified time ΔL", and step 204
``Determine whether ■□−■2' is within the range''
You should do it. However, V2' is the specified time Δt.

is the capacitor voltage at the time of .

FIG. 4 shows an example of the voltage detection circuit 9 for the capacitor 3.

The voltage signal 20 of the capacitor 3 is divided by the resistors R1 and R2, and the reference voltage created by the resistors R3 and R4 and the comparison circuit I
The signals are compared at C and converted into an 0N10FF signal 21, which is input to the microcomma.

As an example of a circuit in which the microcomputer 7 changes the reference voltage of the comparator circuit IC, the signal 22 operates the element Ql and the resistor R
This becomes possible by adding 5 to the circuit. As a result, the voltage level V used in steps 201 and 203 above,
and V2 can be easily realized.

The above is a case where the input is cut off after the inverter stops operating, but if the connection with the AC power supply 1 is cut off while the inverter is in operation (within the range shown in Figure 2) or for some other reason, the voltage of the AC power supply 1 For example, even if OV drops, the capacitor voltage VD suddenly decreases and the inverter detects a voltage abnormality and cuts off the output (stops the inverter's operation) as soon as it reaches the limit value VT that satisfies the performance of the inverter. Therefore, the subsequent region is the same as the discharge region described so far, and the capacitor 3
It becomes possible to diagnose the deterioration of

By the way, when the input power to the inverter device 12 is cut off,
This corresponds to a case where the power supply for the control circuit of the inverter device is about to run out, and therefore, if the inverter device stops operating after that, an abnormality alarm will not be issued, but the deterioration abnormality of the capacitor 3 has already been stored in the memory circuit 8 in step 205. Therefore, the abnormality can be notified the next time the control power is turned on.

On the other hand, if the power supply system is designed to shut off power to the main circuit and control circuit separately, and only the main circuit is shut off, even if the inverter is stopped, the control device alone will not notify you of an abnormality. can. Note that a discharge resistor is often connected to the discharge circuit 4 to prevent electric shock while the inverter is stopped, but if a discharge circuit is formed in place of this, the discharge resistor is not necessarily necessary.

As described above, the method for determining the deterioration of the capacitor 3 based on the discharge region of the capacitor 3 when the inverter is stopped and the input power is cut off is that the inverter device and the load are electrically disconnected, and the discharge circuit of the capacitor 3 is connected to the inverter. Since it is unique to the device, it is not affected by the load. Moreover, unlike conventional inverter devices, this can be realized without using special non-operating time periods.

Next, an embodiment of the present invention for determining capacitor deterioration due to charging current to the capacitor 3 will be described with reference to FIGS. 56 to 7.

In Figure 5, the same numbers as those in Figure 1 should be entered.

13 is a limiting resistor that prevents rush current to capacitor 3;
14 is a circuit that short-circuits the limiting resistor 13, 30 is a detection circuit that detects the charging current to the capacitor 3, and 31 is a detection circuit 3.
Indicates a 0 signal.

FIG. 6 shows the charging current 1c and the voltage of the capacitor 3 during charging of the capacitor 3 when the input power of the inverter device is turned on.

shows the change over time. (When the power is turned on, the inverter 5 has not started operating yet, so the capacitor 3 and the load 6 are electrically disconnected. Therefore, it is not affected by the load.) Change in voltage VD of the capacitor 3 ΔVo When the capacitance of the capacitor 3 is C, the charging current IC is expressed as follows.

Transforming this equation results in the following equation.

Therefore, the voltage VD of capacitor 3 changes from V3 to V4 (■3
, v4 is a predetermined voltage), the capacitance of the capacitor 3 can be calculated as (4 ), and if it is out of a predetermined range, it can be diagnosed as deterioration of the capacitor 3, and an alarm signal can be issued to notify of the abnormality.

FIG. 7 shows a flowchart of the operation.

Confirm that the capacitor voltage VD becomes the voltage V during the charging operation (step 301) L/, clear the register ΣIc that stores the time integral of the charging current to zero (step 302)
)do. Then the voltage V. becomes V4 (step 30
Up to 4), at every sampling time (△1.), the multiplication value of this time (△1.) and the charging current ■ averaged during this time is added to the register ΣIc (step 303
) continue to do. Charging current l stored in this register ΣIc. The time integral value of is compared with a predetermined value (step 305), and if it is outside the range, it is diagnosed as deterioration of the capacitor 3 and the abnormality is stored in the memory circuit (step 306), and an alarm signal is output (step 306). Step 307)L
/, it is possible to notify the abnormality of the capacitor 3.

Note that the current detector 30 may be attached to the connection line to the smoothing capacitor 3 so as to directly detect the current of the smoothing capacitor 3, but in the case of the present invention, the inverter 5 is not operating when the inverter device is initially powered on. Since the current is measured at times, the current of the smoothing capacitor 3 can be detected by installing it as shown in FIG. This current detector can also be used as a current detector conventionally used for overcurrent protection. Therefore, there is no need to newly provide a current detector.

In addition, in order to measure the charging characteristics, the current-time product was determined in the examples shown in Figures 5 to 7, but as is clear from Figure 6, this was done by rectifying the AC power supply 1 with the forward converter 2. This is because the voltage and current are pulsating, so charging characteristics cannot be measured only by the voltage or current value. If the AC power source 1 is directly connected to a flat DC power source instead of being rectified by the forward converter 2, charging characteristics can be measured using only the voltage or current value. In this case, it is possible to measure the charging characteristics, such as the time during which the capacitor voltage passes through a predetermined voltage section, or the change in the content 1 voltage during a predetermined time.

As described above, when the input power of the inverter device is turned on, the capacitor 3
The method of determining deterioration by measuring the charging characteristics of a capacitor is to
Since the charging circuit is unique to the inverter device, it is not affected by the load. Moreover, unlike conventional inverter devices, this can be realized without using special non-operating time periods.

Although the method of the present invention has been described above as being built into an inverter device, the above method can be easily assembled as a detection device externally, and can be applied to existing inverter devices that do not have the above diagnostic function. can be easily added or used.

Furthermore, the deterioration diagnosis method according to the present invention can also be applied to a control power supply voltage smoothing capacitor that supplies control power to a control circuit board such as an inverter device. Since the control circuit is a constant load, deterioration of the capacitor can be diagnosed by similarly measuring the charging and discharging characteristics when the input power is turned on and off.

Although the embodiment described above uses a microcomputer, it goes without saying that it can be constructed using hardware having similar functions.

[Effects of the Invention] As described above, the method for determining the deterioration of the capacitor 3 in the discharge region of the capacitor 3 when the inverter is stopped and the input power is cut off is such that the inverter device and the load are electrically separated and the capacitor 3 is Since the discharge circuit is unique to the inverter device, it is not affected by the load. Moreover, unlike conventional inverter devices, this can be realized without using special non-operating time periods.

Also, when the input power of the inverter device is turned on, the capacitor 3
The method of determining deterioration by measuring the charging characteristics of a capacitor is to
Since the charging circuit is unique to the inverter device, it is not affected by the load. Moreover, unlike conventional inverter devices, this can be realized without using special non-operating time periods.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram explaining the time course of capacitor voltage, Fig. 3 is an operation flowchart, and Fig. 4 is an embodiment of the voltage detection circuit. 5 is a block diagram of one embodiment, FIG. 6 is a diagram explaining the time course of capacitor voltage and current, and FIG. 7 is an operation flowchart. Explanation of symbols 1... AC power supply, 2...
・・・Forward converter, 3・・・・・・・・・Capacitor,
4... Song/discharge circuit 5... Inverse converter, 6... AC machine, 7...
...Microphone computer 8...Memory circuit 9...Old detection circuit 10...
Sub-bulb for display circuit and alarm signal output circuit. 11......L\-S circuit 2...Inverter device 3...Inrush current limiting resistor 4...
...Short circuit 15...Current detector 0...Capacitor voltage signal 1...
...0N10F signal 2... Drive signal of element Q1 0...
... Current detector 1 ... Output signal 3 of current detector 30

Claims (1)

[Claims] 1. In a control device equipped with a capacitor for smoothing a DC power supply, the voltage detection means of the capacitor; , an arithmetic control that measures discharge characteristics in a predetermined interval, determines that the capacitor has deteriorated when the discharge characteristics are outside a predetermined value range, and stores and outputs a signal; A deterioration diagnostic device characterized by comprising: a. 2. The deterioration diagnosing device according to claim 1, wherein the measurement of the discharge characteristics includes: measuring the discharge time in a predetermined voltage section based on the output of the voltage detection means. 3. The deterioration diagnosing device according to claim 1, wherein the measurement of the discharge characteristics includes: measuring a discharge voltage value in a predetermined time interval based on the output of the voltage detection means. 4. A forward conversion circuit for converting AC power into DC power; a capacitor connected to the output section of the forward conversion circuit to smooth the DC voltage at the output section; and a capacitor connected to the output section of the forward conversion circuit for smoothing the DC voltage. An inverter device comprising an inverse conversion circuit that converts a power source into a variable frequency power source to supply power to a load, and a control device that variably controls the output frequency of the inverse conversion circuit, comprising: a voltage detection means for the capacitor; When the power supply is cut off, the discharge characteristics of the capacitor are measured in a predetermined period based on the output of the voltage detection means, and if the discharge characteristics are outside the predetermined value range, the capacitor is discharged. An inverter device comprising: an arithmetic control section that determines that the inverter has deteriorated and outputs or stores a signal. 5. The inverter device according to claim 4, wherein the measurement of the discharge characteristics includes measuring the discharge time in a predetermined voltage section based on the output of the voltage detection means. 6. The inverter device according to claim 4, wherein the measurement of the discharge characteristics includes measuring a discharge voltage value in a predetermined time interval based on the output of the voltage detection means. 7. In a control device equipped with a capacitor for smoothing a DC power supply, the voltage detection means of the capacitor, the current detection means of the capacitor, and the output of the voltage detection means and the output of the current detection means are inputted and the The present invention is characterized by comprising an arithmetic control unit that measures the charging characteristics of the capacitor when the input power is turned on, and determines that the capacitor has deteriorated and outputs a signal if the charging characteristics of the capacitor deviate from a predetermined charging characteristic range of the capacitor. Deterioration diagnosis device. 8. The measurement of the charging characteristic according to claim 7 is performed when the input power to the capacitor is turned on and the voltage of the capacitor increases, the output of the voltage detection means is the lower limit of a predetermined reference voltage range. When the output of the current detection means reaches the upper limit of a predetermined reference voltage range, the time integration of the output of the current detection means is stopped. 8. The deterioration diagnosing device according to claim 7, wherein the current and time integral value from the starting point to the ending point are determined. 9. A forward conversion circuit for converting AC power into DC power; a capacitor connected to the output section of the forward conversion circuit to smooth the DC voltage of the output section; and a capacitor connected to the output section of the forward conversion circuit for smoothing the DC voltage. An inverter device comprising an inverse conversion circuit that converts a power source into a variable frequency power source, and a control device that variably controls the output frequency of the inverse conversion circuit, comprising: a voltage detection means for the capacitor; a current detection means for the capacitor; The output of the voltage detection means and the output of the current detection means are input to measure the charging characteristics of the capacitor when the input power is turned on, and if the charging characteristics of the capacitor are out of a predetermined charging characteristic range, it is determined that the capacitor has deteriorated. An inverter device comprising an arithmetic control unit that diagnoses. 10. The measurement of the charging characteristic according to claim 9 is carried out when the voltage of the capacitor increases when the input power of the inverter device is turned on, and the output of the voltage detection means reaches the lower limit value of a predetermined reference voltage range. When the voltage reaches the upper limit of a predetermined reference voltage range, the time integration of the output of the current detection means is started, and when the output of the voltage detection means reaches the upper limit of a predetermined reference voltage range, the time integration of the output of the current detection means is ended. 10. The inverter device according to claim 9, wherein the current and time integral value from the start point to the end point are determined. 11. Claims 4 to 4 further include an alarm means for issuing an alarm based on the output of the arithmetic control unit that has diagnosed that the capacitor has deteriorated, or for issuing an alarm based on information stored by the deterioration diagnosing means. 6. The inverter device according to any one of claims 9 and 10. 12. The device according to any one of claims 1 to 3, claim 7, and claim 8, further comprising an alarm means for issuing an alarm based on the output of the arithmetic and control unit that has diagnosed that the capacitor has deteriorated. Deterioration diagnosis device. 13. Claims 4 to 6 include a calculation control unit that performs abnormality processing so as to stop the operation of the inverter device based on the output of the calculation control unit that diagnoses that the capacitor has deteriorated. The inverter device according to any one of claims 9 to 11. 14. Claims 1 to 3, further comprising a calculation control unit that performs abnormality processing so as to stop the operation of the control device based on the output of the calculation control unit that diagnoses that the capacitor has deteriorated. The deterioration diagnosis device according to any one of claims 7, 8, and 12.