JP3362638B2 - Method and apparatus for measuring insulation resistance of array type capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring insulation resistance of array type capacitors.

[0002]

2. Description of the Related Art Generally, an insulation resistance value is measured in order to judge the quality of a capacitor. When measuring this insulation resistance value, the insulation resistance cannot be correctly measured due to the capacity of the capacitor when the capacitor is not charged. Therefore, a method of measuring the insulation resistance of the capacitor is generally used by first applying a DC voltage to the capacitor to precharge it and then measuring the leakage current (charging current). Of course, good products have less leakage current.

There is known an array type capacitor 1 in which a plurality of capacitor elements C1 to C4 are arranged in parallel as shown in FIGS. The array type capacitor 1 is provided with internal electrodes 5a to 5h facing each other between a plurality of dielectric layers 2 to 4, and after all layers 2 to 4 are laminated and integrated, they are electrically connected to the internal electrodes 5a to 5h. External electrodes 6a to 6h are provided. In addition, in FIG. 1, in order to simplify the explanation,
Although the number of dielectric layers is three, it may be four or more. Also, the number of capacitor elements is not limited to four, but two or three.
Of course, the number may be five or more.

There are the following three modes as the defective modes of the insulation resistance of such an array type capacitor. Mode 1: Insulation failure of the capacitor elements C1 to C4 itself Mode 2: Internal electrodes 5a to 5 of adjacent capacitor elements
Insulation failure mode 3 between h: external electrodes 6a to 6 of adjacent capacitor elements
Insulation failure between h

In order to detect insulation failure in the above three modes, conventionally, the wiring of the insulation resistance measuring circuit has been rearranged as shown in FIG. That is, FIG. 3A shows mode 1
Is a measuring circuit of the measuring terminal 10,
By making 11 contact, and measuring the current in the 1) direction, the insulation resistance of the capacitor elements C1 to C4 itself is detected. In the figure, 12 is a DC power supply, 13 is an AC power supply for contact detection, 14 is a changeover switch, 15 is a current limiting resistor,
16 is an ammeter. Although only one element measuring circuit is shown in FIG. 3, the measuring circuits may be provided in parallel according to the number of elements and the insulation resistances of all the elements C1 to C4 may be simultaneously measured. FIG. 3B shows a measurement circuit for mode 2, in which the internal electrodes 5a to 5h are measured by measuring the current 2) flowing diagonally in the adjacent capacitor elements C1 to C4.
Insulation failure between is detected. FIG. 3C shows mode 3
Of the external electrode 6a by measuring the current 3) flowing between the adjacent capacitor elements C1 to C4.
Insulation failure during ~ 6h is detected.

[0006]

However, in order to measure the insulation resistance with the above measuring circuit, it is necessary to change the wiring of the measuring circuit for each of the failure modes 1 to 3, and the measurement efficiency is very poor. Further, it is necessary to detect the contact between the measurement terminals 10 and 11 before measuring the insulation resistance. Therefore, the switch 14 is switched to the AC power supply 13 side to detect the current flowing through the circuit. Since the detection needs to be performed before the measurement in each mode, the measurement work becomes more troublesome. Moreover, in Modes 2 and 3, since the insulation failure of the adjacent inner and outer electrodes is measured, there is a problem that contact detection cannot be effectively performed because there is only a small capacitance (for example, several pF or less) such as stray capacitance.

Therefore, an object of the present invention is to wire the measuring circuit.
Detection of insulation failure in modes 1 to 3 without changing
Another object of the present invention is to provide a method and an apparatus for measuring the insulation resistance of an array type capacitor that can efficiently measure the insulation resistance of each capacitor element .

[0008]

In order to achieve the above object, the invention according to claim 1 applies a DC voltage to an array type capacitor in which a plurality of capacitor elements are arranged in parallel, and insulates the insulation resistance from the leakage current. in the insulation resistance measurement method for measuring the external electrode of the all capacitor element
A first step of bringing the measuring terminals into contact with each other, and a second step of simultaneously applying a DC voltage of the same polarity to all the capacitor elements via the measuring terminals and detecting the leakage currents thereof, respectively .
Outside the process, all of the capacitor element, the measuring terminal
Simultaneously applying a reverse polarity of the DC voltage to each capacitor elements adjacent remain in contact with the part electrode, the leakage current that
From the third step of detecting each and the leakage current obtained from the second step, the insulation failure of each capacitor element or the insulation failure between the internal electrodes of the adjacent capacitor elements is detected.
Then, from the leakage current obtained in the third step,
It detects the insulation failure of the capacitor element or the insulation failure between the external electrodes of the adjacent capacitor elements, and detects any insulation failure.
If not obtained, obtained from the second step or the third step
Measure the insulation resistance of each capacitor element from the leakage current.
4 steps are included.

First, the measurement terminals of all capacitor elements are
The leak current is detected by contacting the external electrodes and applying a DC voltage of the same polarity to all the capacitor elements. This leakage current includes the current 1) of mode 1 and the current 2) of mode 2. Next, a DC voltage of opposite polarity is applied to all the capacitor elements for each adjacent capacitor element, and the leak current is detected. This leakage current includes the current 1) of mode 1 and the current 3) of mode 3. 2 obtained as above
If any one of the currents of a large type has a very large current value, it means that there is a defective insulation in any one of modes 1 to 3, and it is understood that this array type capacitor is a defective product. On the other hand, if the two types of current decreases to draw a predetermined time curve, mode 1 to mode no insulation failure 3, this means that the array capacitor is good, the second step or the The insulation resistance of the capacitor element is obtained from the leakage current obtained from the process of 3 .
Of course, either the second step or the third step may be performed first.

In the second step and the third step, the measuring terminal and the external electrode of the array type capacitor are brought into contact with each other. However, if this contact is insufficient, the measured current value will be incorrect. Will be things. Therefore, it is desirable to apply an AC voltage to each capacitor element and perform contact detection from the flowing current before the second step or the third step. When the contact is insufficient, the flowing current is small, and thus the contact failure can be easily identified. Further, in the measurement of Mode 2 or Mode 3 alone, it is difficult to detect the contact because there is only a small capacitance such as a stray capacitance. However, in the present invention, Mode 2 and Mode 1 are used simultaneously, or Mode 3 and Mode 1 are used. Since they are detected at the same time, the capacitance value is large, and contact detection can be reliably performed. The second step and the third step, when carried out in a separate measuring circuit includes a second step and it is necessary to perform the respective front contact detection of the third step, as in the present invention When the second step and the third step are performed by a common circuit having a changeover switch, the second step and the third step can be continuously performed, so that the contact detection can be performed in the second step. All you have to do is before.

In the above measuring method, mode 1 and mode 2 are used.
Are simultaneously detected, and mode 1 and mode 3 are simultaneously detected, so it is difficult to accurately measure only the insulation resistance of the capacitor element alone. That is, a combined value of the two modes is measured as the measured current value. Therefore, in order to measure the insulation resistance of a single capacitor element, the step of applying a DC voltage to each capacitor element at different timing for each adjacent capacitor element is added.
It is desirable to install it in As the timing, for example, a DC voltage may be applied while scanning the capacitor elements arranged in parallel, or a DC voltage may be applied every other element. In this case, it is possible to accurately measure the value that is not influenced by the adjacent capacitor element, that is, the insulation resistance of the single capacitor element.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 4 and 5 show the premise of the present invention.
An example of the insulation resistance measuring device will be described. In this example , the measurement of modes 1 and 2 and the measurement of modes 1 and 3 are performed by separate circuits. The array type capacitor 1, which is the object to be measured, has four capacitor elements C as in FIGS.
Those containing 1 to C4 were used. FIG. 4 shows a first measurement circuit 20 for performing the measurement in Mode 1 and Mode 2, and includes eight measurement terminals 21a to 21h, a DC power supply 22 and a contact detection circuit, which are in contact with the external electrodes 6a to 6h of the array type capacitor 1, respectively. AC power supply 23, power supply selector switch 24, four current limiting resistors 25a to 25d, and four ammeters 26a to
26d, and four switches 27a to 27d.
The current limiting resistors 25a to 25d and ammeters 26a to 26
d and the switches 27a to 27d are connected in parallel with each other. Further, FIG. 5 shows a second measurement circuit 30 for performing the measurement in the mode 1 and the mode 3, in which eight measurement terminals 31a to 31h, which are respectively in contact with the external electrodes 6a to 6h of the array type capacitor 1, a DC power supply 32, An AC power supply 33 for contact detection, a power supply switching switch 34, four current limiting resistors 35a to 35d, four ammeters 36a to 36d, and four switches 37a to 37d are provided.

First, a method of measuring the mode 1 and the mode 2 using the first measuring circuit 20 will be described. After bringing the measurement terminals 21a to 21h into contact with the external electrodes 6a to 6h, first, the switch 24 is switched to the AC power source 23 side, and all the switches 27a to 27d are turned on to apply an AC signal to the capacitor elements C1 to C4. And the ammeter 26
Contact detection is performed from the detection values of a to 26d. When it is determined that the contact is good, all the switches 27a to
27d is turned off and the switch 24 is switched to the DC power supply 22 side. After that, the switches 27a to 27d
Is turned on to apply a DC voltage to the capacitor elements C1 to C4, and the leakage current is measured by the ammeters 26a to 26d.
At this time, since current flows in the same direction in each of the capacitor elements C1 to C4, the ammeters 26a to 26d indicate that the current flowing through the capacitor element 1) and the adjacent capacitor elements C1 to C4.
4 and the current flowing between the internal electrodes 2) will be measured. If there is insulation failure in either mode 1 or 2,
Since this current value is extremely large, it is possible to easily detect insulation failure. On the other hand, when this current draws a curve for a predetermined time and decreases, the insulation resistance of the capacitor element can be known from the leakage current value after a predetermined time. It should be noted that this leakage current value is determined by the adjacent capacitor elements C1 to C.
The current 2) flowing between the internal electrodes of No. 4 is also included, but this current is very small if the insulation between the internal electrodes is not bad, so it can be almost ignored.

In the above case, the sum of the current values of 1) and 2) is measured by the ammeters 26a to 26d, and the insulation resistance of the capacitor elements C1 to C4 is analogized from the measured value.
It is also possible to measure only the current value of 1) by using the following method to accurately know the insulation resistance of each capacitor element C1 to C4. That is, the contact detection ends, and the switch 2
4 is switched to the DC power source 22 side, and then switches 27a to
A method of switching with the switches 27a to 27d is used so that the DC voltage is applied to the adjacent capacitor elements at different timings instead of simultaneously turning on the 27d. Specifically, for example, from the switch 27a to the switch 2
Switching in order over 7d, capacitor elements C1-C
4 in order to apply the DC voltage, or to switch to apply the DC voltage to every other capacitor element (for example, when the switches 27a and 27c are turned on, the switch 2
7b and 27d are turned off).

Next, a method of measuring the mode 1 and the mode 3 using the second measuring circuit 30 will be described. After bringing the measurement terminals 31a to 31h into contact with the external electrodes 6a to 6h, first, the switch 34 is switched to the AC power supply 33 side, and all the switches 37a to 37d are turned on to apply an AC signal to the capacitor elements C1 to C4. And ammeter 36
Contact detection is performed from the detection values of a to 36d. When it is determined that the contact is good, all the switches 37a to
37d is turned off and the switch 34 is switched to the DC power source 32 side. After that, the switches 37a to 37d
Is turned on to apply a DC voltage to the capacitor elements C1 to C4, and the leak current is measured by the ammeters 36a to 36d.
At this time, since a reverse current flows through each of the adjacent capacitor elements C1 to C4, the ammeters 36a, 36
c measures the sum of the current 1) flowing through the capacitor element and the current 3) flowing between the external electrodes of the adjacent capacitor elements C1 to C4, and the ammeters 36b and 36d indicate that the current 1) ′ flowing through the capacitor element. And the current 3) flowing between the external electrodes of the adjacent capacitor elements C1 to C4 are to be measured. Similar to the case of the first measurement circuit 20, if there is an insulation failure in either mode 1 or 3, the current value becomes very large, and the insulation failure can be easily detected.
On the other hand, when this current drops along a curve for a predetermined time, it means that there is no insulation failure in modes 1 and 3, so the insulation resistance of the capacitor elements C1 to C4 can be calculated from the leakage current value after a predetermined time. I can know. The insulation resistance of the capacitor elements C1 to C4 is determined by the measurement circuit 20 described above.
Since the measurement has already been performed in (see FIG. 4), it is not necessary to perform the measurement again, and it suffices only to confirm that there is no insulation failure in mode 3.

Also in the measuring circuit 30, when measuring the insulation resistance of the individual capacitor elements C1 to C4, the switch 37 is used as described in the description of the measuring circuit 20.
Do not turn on a to 37d at the same time, and apply a DC voltage at different timing for each adjacent capacitor element,
You may switch with switch 37a-37d.

FIG. 6 shows an insulation resistance measuring apparatus according to the present invention.
A first embodiment will be described. This embodiment is an example in which the measurement of modes 1 to 3 is performed by a single circuit. As the array type capacitor 1 as the object to be measured, one including four capacitor elements C1 to C4 was used as in FIGS. This measuring circuit 40 is provided with the external electrodes 6a to 6a of the array type capacitor 1.
Eight measuring terminals 41a to 41h which respectively contact h,
DC power supply 42, AC power supply 43 for contact detection, power supply changeover switch 44, six current limiting resistors 45a to 45f, six ammeters 46a to 46f, and four switches 47a to 47.
d.

Next, mode 1 using the measuring circuit 40
The measurement methods 3 to 3 will be described with reference to the flowchart of FIG. 7. First, the measurement terminals 41a to 41h are connected to the external electrode 6
a to 6h (step S1), the switch 44 is switched to the AC power source 43 side (step S1).
2) All the switches 47a to 47d are set to the solid line positions (step S3), and the AC signals are transferred to the capacitor elements C1 to C.
4 is applied. Then, contact detection is performed from the detection values of the ammeters 46a to 46d (step S4). When it is determined that the contact is good, the switch 44 is switched to the DC power supply 42 side while keeping the switches 47a to 47d in the solid line position (step S5). As a result, the DC voltage is applied to the capacitor elements C1 to C4, and the leak current is measured by the ammeters 46a to 46d. At this time, since current flows in the same direction in each of the capacitor elements C1 to C4, the ammeters 46a to 46d indicate that the currents flowing in the capacitor elements 1).
And the current 2) flowing between the internal electrodes of the adjacent capacitor elements C1 to C4 are to be measured. That is, it is possible to perform the measurement in modes 1 and 2 (step S
6). After the measurement of Modes 1 and 2 is completed, switch 44
With the DC power source 42 side, the switches 47a to 47d
To the broken line position (step S7). As a result, a direct current flows in the capacitor elements C1 and C3 in the 1) direction,
The capacitor elements C2 and C4 flow in the 1) 'direction, and a current flows in the opposite direction for each adjacent element. At the same time, also between the external electrodes of the adjacent capacitor elements C1 to C4.
3) Current flows in the direction. Therefore, the ammeters 46a, 4
6c, 46e, and 46f are currents 1) and 1) ′ flowing through the capacitor elements C1 to C4, and adjacent capacitor elements C1 to C4.
The sum of this and the current that flows between the external electrodes 3) will be measured. That is, the measurements in modes 1 and 3 can be performed (step S8). From the above measurement results, the insulation resistance of the capacitor elements C1 to C4, the insulation failure between the internal electrodes, and the insulation failure between the external electrodes can be detected. The specific method is shown in FIG.
Since it is as described in the example of FIG. 5 , redundant description will be omitted. Further, in the above description, the case where the switches 47a to 47d are switched at the same time has been described, but as described in the examples of FIGS. 4 and 5, by switching the switches 47a to 47d while scanning or switching every other switch. Alternatively, the DC voltage may be applied at different timings for each adjacent capacitor element. By this, 1),
Only the current value of 1) 'can be measured, and the insulation resistance of the single capacitor element can be known accurately.

FIG. 8 shows an insulation resistance measuring apparatus according to the present invention.
A second embodiment will be described. This embodiment is a modification of the first embodiment , and the number of ammeters is reduced to four as compared with the first embodiment . The same parts as those in FIG. 6 are designated by the same reference numerals, and duplicate description will be omitted. In the case of this measurement circuit 50, the contact on the solid line side of the switch 47a and the contact on the broken line side of the switch 47b are connected by a wiring 51, and the switch 47a is connected.
The wiring 52 connects the contact on the solid line side of c and the contact on the broken line side of the switch 47d. Therefore, the capacitor element C
Ammeter 4 for currents 1), 1) 'flowing in two directions C2 and C4
6b and 46d can measure both, and ammeter 46 in FIG.
e and 46f could be omitted.

The ammeter used in the present invention is not limited to an analog type measuring instrument, and after being amplified by an OP amplifier or the like, A
It is also possible to perform D / D conversion and measure the current value with a digital signal. As a method of measuring the insulation resistance of the capacitor element, generally, a method of measuring the insulation resistance of the capacitor element from a leakage current value after a predetermined pre-charging (for example, 60 seconds) according to JIS standard is used. Not limited to the method, a method of predicting the current value at the end of charging from the current value at the beginning of charging or any other method may be used. Also, this time, we used the method to switch between AC power supply (for contact detection) and DC power supply (for insulation resistance measurement), but by switching AC voltage on DC voltage, there is no switching between contact detection and insulation resistance measurement. It is also possible to do this.

[0021]

As is apparent from the above description, according to the present invention, a DC voltage of the same polarity is applied to all the capacitor elements of the array type capacitor to detect the leakage current thereof, and all the capacitor elements are detected. A leak current is detected by applying a DC voltage of opposite polarity to each of the capacitor elements adjacent to each other, and from these two types of current, insulation failure of each capacitor element, insulation failure between the internal electrodes of adjacent capacitor elements, and Detects the insulation failure between the external electrodes of the adjacent capacitor elements, and if there is no insulation failure, check each capacitor.
Since the insulation resistance of the capacitor element is measured , it is not necessary to rearrange the wiring of the measurement circuit for each failure mode,
The measurement efficiency is improved. Further, in the present invention, since the mode 2 and the mode 1 are detected simultaneously, or the mode 3 and the mode 1 are detected at the same time, the respective capacitance values are large, and contact detection between the measurement terminal and the external electrode of the array type capacitor can be performed. It can be done reliably. Furthermore, the above two types of leaks
Current can be measured with the measuring terminal in contact with the external electrode.
Contact detection is performed each time each leak current is measured.
It is not necessary to improve the measurement efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of an array type capacitor.

FIG. 2 is an exploded perspective view of the array type capacitor shown in FIG.

FIG. 3 is a circuit diagram showing a method for measuring insulation resistance of a conventional array type capacitor.

FIG. 4 is a circuit diagram of a first measurement circuit of an insulation resistance measuring device which is a premise of the present invention.

FIG. 5 is a circuit diagram of a second measurement circuit of the insulation resistance measuring device which is a premise of the present invention.

FIG. 6 is a circuit diagram of a first embodiment of an insulation resistance measuring device according to the present invention.

FIG. 7 is a flow chart for explaining the operation of the insulation resistance measuring device of FIG.

FIG. 8 is a circuit diagram of a second embodiment of the insulation resistance measuring device according to the present invention.

[Explanation of symbols]

1 array type capacitors C1 to C4 capacitor elements 40, 50 measuring circuits 41a to 41h measuring terminals 42 DC power source 43 AC power source 44 power source changeover switches 45a to 45d current limiting resistors 46a to 46f ammeters 47a to 47d switches

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 31/00 G01R 27/02 G01R 31/02 H01G 13/00 361

Claims (7)

(57) [Claims] 1. A DC voltage applied to the plurality of capacitor elements in the array type capacitors placed in parallel, the insulation resistance measuring method for measuring the insulation resistance from the leakage current, the
Measuring terminals on the external electrodes of all capacitor elements
The first step of contact, and the above for all capacitor elements
Via the measurement terminal by applying a DC voltage of the same polarity at the same time, a second step of detecting the leakage current, respectively, to all co <br/> capacitor element, are brought into contact with the measuring terminal to the external electrode
The opposite polarity of the DC voltage to each capacitor elements adjacent remain
Simultaneously applied, a third step of detecting the leakage current, respectively, from the leakage current obtained from the second step, the
The insulation failure or the capacitor element detects insulation failure between the internal electrodes of adjacent capacitor elements, obtained from the third step
Insulation failure of each capacitor element
Does not detect insulation failure between the external electrodes of adjacent capacitor elements.
The second work if no insulation failure is detected.
Or the leakage current obtained from the third step
And a fourth step of measuring the insulation resistance of the sensor element . 2. Before the second step or the third step,
It is preferable that the method includes a step of applying an AC voltage to each capacitor element through the measurement terminal and performing contact detection between the measurement terminal and the external electrode from the flowing current simultaneously with the second step or the third step. The method for measuring insulation resistance of an array type capacitor according to claim 1. To wherein said each capacitor element, a DC voltage is applied at different timings for each adjacent capacitor element,
Calculate the insulation resistance of each capacitor element from the leakage current
The method for measuring insulation resistance of an array type capacitor according to claim 1 , further comprising a step . 4. A first capacitor element (C1, C3) and a first capacitor element (C1, C3)
A second capacitor element (C 2, C4) DC voltage is applied to the array type capacitors placed in parallel, the insulation resistance tester for measuring the insulation resistance from the leakage current, straight
Current source (42) and the external power source of the first capacitor element.
A pair of first measuring terminals (41a, 41a) that contact the poles.
b, 41e, 41f) and the second capacitor element
A pair of second measuring terminals (41c, 41c,
41d, 41g, 41h) and the second measuring terminal respectively.
Connected to each other and switchable in synchronization with the first and second positions.
Number switch means (47a, 47b, 47c, 47d)
And connect the first measurement terminal and the DC power supply,
From the DC power supply through the first measurement terminal to the first capacitor
Applying a DC voltage to the device in the first direction,
The first ammeter (46a, 46c) that detects the leakage current
1 measuring circuit, the second measuring terminal, and the DC power supply
Is connected via the switch means in the first position,
From the above DC power supply to the second measuring terminal through the second measuring terminal.
DC voltage is applied to the sensor element in the first direction,
Leakage current is detected by the second ammeter (46b, 46d)
Second measurement circuit, second measurement terminal, and DC power supply
And via the switch means in the second position
Then, from the above DC power supply to the second measuring terminal through the second measuring terminal.
DC voltage is applied to the capacitor element in the opposite direction to the first direction.
The leakage current is applied to the third ammeter (46e, 46e).
An insulation resistance measuring device for an array capacitor, comprising: a third measuring circuit for detecting in f) . 5. A first capacitor element (C1, C3) and a first capacitor element (C1, C3)
2 of the capacitor element and (C2, C4) a DC voltage is applied to the array type capacitors placed in parallel, the insulation resistance tester for measuring the insulation resistance from the leakage current, straight
Current source (42) and the external power source of the first capacitor element.
A pair of first measuring terminals (41a, 41a) that contact the poles.
b, 41e, 41f) and the second capacitor element
A pair of second measuring terminals (41c, 41c,
41d, 41g, 41h) and the second measuring terminal respectively.
Connected to each other and switchable in synchronization with the first and second positions.
Number switch means (47a, 47b, 47c, 47d)
And connect the first measurement terminal and the DC power supply,
From the DC power supply through the first measurement terminal to the first capacitor
Applying a DC voltage to the device in the first direction,
The first ammeter (46a, 46c) that detects the leakage current
1 measuring circuit, the second measuring terminal, and the DC power supply
Is connected via the switch means in the first position,
From the above DC power supply to the second measuring terminal through the second measuring terminal.
DC voltage is applied to the sensor element in the first direction,
Leakage current is detected by the second ammeter (46b, 46d)
Second measurement circuit, second measurement terminal, and DC power supply
And via the switch means in the second position
Then, from the above DC power supply to the second measuring terminal through the second measuring terminal.
DC voltage is applied to the capacitor element in the opposite direction to the first direction.
Applied, and the leak current is applied to the second ammeter (46b, 4b).
An insulation resistance measuring device for an array-type capacitor, comprising: a third measuring circuit for detecting in 6d) . 6. The array type according to claim 4, wherein an AC power source is provided in parallel with the DC power source, and a switch means for selectively switching between the DC power source and the AC power source is provided. Capacitor insulation resistance measuring device. 7. The switch device according to claim 4, wherein each capacitor element is provided with a switch means for switching a circuit so that a DC voltage is applied to each adjacent capacitor element at different timings. Insulation resistance measuring device for array type capacitors.