JPS6363868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved apparatus for testing the tracking resistance of insulating materials.

In parts such as printed circuit boards for electrical equipment, where opposing poles are insulated with a single insulating material, dust accumulates on the surface of the insulating material when voltage is applied between the poles. When moisture in the air condenses, current leaks between different poles through the moist dust. When this leakage current occurs repeatedly, the surface insulation of the insulating material deteriorates, a conductive path (track) is formed, and dielectric breakdown or electric leakage ignition occurs.
This formation process is called insulating material tracking.
The accelerated evaluation test method for this is the International Electrotechnical Standard IEC.
It has been provisionally set at -112. This provisional method has many problems with data dispersion and data applicability, so technical committee TC15 continues to discuss standard revisions year after year.

The present invention makes it possible to evaluate the surface insulation deterioration phenomenon of an insulating material with high precision, high efficiency, and high applicability. In other words, the current IEC method evaluates only dielectric breakdown caused by an increase in leakage current, but the present invention makes it possible to evaluate the ignition phenomenon that occurs before dielectric breakdown, improving evaluation accuracy and applicability. This is intended to improve the quality of life.

First, the principle of a conventional tracking tester will be explained with reference to FIG.

1 is a sample, and 2 is an electrode support on which the sample is placed and which supports a pair of opposing electrodes 3, 3 that are in contact with the surface of the sample. 4 is a dropping nozzle for dropping the dust simulating test liquid, and 5 is a dropping device for supplying the test liquid to the nozzle 4 and causing it to drip. The components of the test liquid, the frequency of dropping, the amount, etc. are determined under certain conditions, and it is stipulated that repeated dropping of 50 drops is equivalent to the accumulation of wet dust over several years.

A constant short-circuit current voltage is applied between the opposing electrodes 3 and 3 from the power source 6, and the test liquid is applied to the dripping device 5 and the nozzle 4.
Adjust the amount and drip repeatedly at a constant frequency (1 drop every 30 seconds). At the same time, the detector 7 detects the current leaking between the opposing electrodes, and the dielectric breakdown condition (leakage current
When the current flow condition is 0.5 A or more for 2 seconds or more), the current breaker 8 operates and the number of drops is displayed on the counter 9.
It is measured in

In this way, for the same insulating material, the number of breakdown drops is determined by supplying power in several stages, and the number of breakdown drops is 50.
Determine the relative voltage of the drop and use this value as the material's Comparative Tracking Index.
shall be.

In this test, the number of dielectric breakdown drops of data,
Tracking resistance index varies significantly depending on material and test power. However, in the past, there were many unknown points about the tracking phenomenon itself, so it was not possible to determine the cause of data dispersion.

As a result of testing a large number of materials at various test powers, the inventors found that the causes of data variations were (a) fluctuations in the dropping conditions of the test liquid (b) fluctuations in the supplied power (c) It was determined that this was caused by an abnormal tracking phenomenon.

Therefore, as a test device, the above (a) and (b) should be excluded to a minimum, and (c) can be determined with high accuracy as a unique characteristic of the material and power supply. Highly accurate evaluation becomes possible.

Based on the results of these studies, an improved test device was proposed. One of them is the patent application 1978-19178.
It is described in. Its main feature is that electrode supports supporting opposing electrodes are arranged circularly on a rotary table.
By intermittently moving the rotary table, the electrode support is positioned directly below the dripping nozzle and the test liquid is dripped.

According to this method, the conditions for dropping the test liquid can be kept constant, and various items can be measured on a large number of samples according to a predetermined program.

However, it was found that the following new inconvenience occurred.

(1) Wind is generated when the electrode support moves, and this affects the micro-tracking phenomenon.

(2) If a minute discharge occurs when the electrode support moves at the connection part of the sliding conductive connector for energizing the counter electrode, this minute discharge and the minute tracking phenomenon between the counter electrodes can be separated. Difficult to detect.

(3) The power that can be supplied to the movable electrode support depends on the characteristics of its sliding connecting parts, making it difficult to increase capacity, increase frequency, and convert to DC. Furthermore, when a heater or the like is provided to heat the sample in order to change the measurement temperature, it is necessary to provide a new large-capacity sliding connecting part, which is subject to various restrictions.

These shortcomings do not pose a problem when conducting IEC standard tests within the scope of current standards, but they become serious shortcomings when it comes to understanding various tracking phenomena with high precision.

The present invention solves the conventional drawbacks, and its basic configuration will be explained with reference to FIG.

In FIG. 2, a sample 1, an electrode support 2, a pair of opposing electrodes 3, 3, a dropping nozzle 4, a dropping device 5,
The power source 6, leakage current detector 7, current breaker 8, and broken drop counter 9 are the same as in the conventional example.

In the present invention, the electrode support 2 is fixed, and the dropping device 5 is mounted on the rotary table 10. The nozzle 4 of the dropping device 5 moves directly above the sample 1 on a predetermined electrode support 2 by the intermittent movement of the rotary table 10, then descends during dropping, and rises immediately after dropping. Signals such as these operation timings and power supply for driving the vertical movement of the nozzle are transmitted by the sliding conductive mechanism 11.

The rotary table 10 is operated by a drive machine 13 in conjunction with a time control cam 12. The operation of this rotating table is to change the horizontal position of the sample and the dripping nozzle, and the positions of the sample and the dripping nozzle are detected by the time control cam 12, and the timing of the vertical movement of the dripping nozzle and the dropping of the test liquid are controlled. Timing is controlled by a time control cam 12.

The time control cams 12 are arranged in a number equal to or more than the number of electrode supports 2, and independently control the dropping of the test liquid for each electrode support, and also control the leakage power supply provided independently for each counter electrode. The inspection timing of the comparison detector 14 is controlled as follows.

FIG. 3 shows the relationship between the elapsed time immediately after dropping the test liquid and the leakage current I.

a indicates the leakage current at the initial stage of dropping the test liquid;
When the test liquid is dropped at time 0, a peak current ip ₁ flows within time t seconds and the liquid evaporates, and almost no leakage current flows until the next drop 30 seconds later.

b is an example where the material has deteriorated to the verge of dielectric breakdown. The current ip ₂ that flows when the test liquid is dropped approaches the dielectric breakdown current of 0.5 A, and a minute ignition current flows after the test liquid evaporates. For example, at time t ₃ The material ignites at a point,
A current i ₃ flows. Then, at the next dropping time t ₄
In some cases, a current larger than IP ₂ will not leak, and _a current smaller than IP ₂ will flow, delaying dielectric breakdown. This is caused by mechanical breakage of the track due to ignition, and in this case, the ignition may ignite and burn the surrounding materials, resulting in decreased resistance and dielectric breakdown due to heating. As described above, the test data differs markedly between circuit breakage due to ignition and ignition, which is one of the causes of data variation.

As a result of the experiment, it was found that the ignition current (i _i ≧0.2A) and the ignition current leakage time (t _i ≧2 seconds) were almost constant, and only the timing of the ignition current generation varied depending on the test conditions.

Therefore, as in the comparison standard example of breaking current shown in c.
If the circuit for detecting the IEC dielectric breakdown standard is used as it is, and the detection sensitivity is adjusted within two steps to detect the ignition standard IGN, the number of ignited droplets can be evaluated at the same time.

Therefore, the detection timing of the ignition current is controlled by the time control cam 12 to control the operation timing of the signal comparator 14, and the two-stage simultaneous evaluation of the IEC dielectric breakdown condition and the ignition condition at the local time in the entire time range is performed in one step. This can be done using an earth leakage breaker 8. Further, the counter 9 is adapted to read one or both of the number of dielectric breakdown drops and the number of ignited drops according to the operation program of the time control cam 12.

Note that the electrode support 2 is provided with a heater 1 for heating the sample.
5 to enable tracking resistance testing during heating.

4 and 5 show examples of the structure of the test apparatus of the present invention. Reference numeral 16 denotes a fixed base, which has a circular cutout in the center, and 12 electrode supports 2 are arranged circularly at equal intervals on its upper surface. On the other hand, the rotary table 10 is fixed to the fixed table 16.
is placed in the center of the The dripping device 5 mounted on the rotating table 10 includes a container 17 containing a test liquid, a dripping pump 18, a support 20 that supports the dripping nozzle 4 connected to the pump 18 with a flexible pipe 19,
The support body 20 is provided with a support 21 and the like to which the support body 20 is attached so as to be movable up and down, and is provided with a roller 23 that slides in contact with a cam plate 22 that rotates in conjunction with the operation of the rotary table 10 to move the support body 20 up and down. It is configured as follows. Reference numeral 24 denotes a fixed plate provided on the lower side of the rotary table 10, and a sliding conductive mechanism 11 is provided between the fixed plate and the rotary table.

In the tracking resistance test device of the present invention, a plurality of electrode supports 2 supporting a pair of opposing electrodes to be brought into contact with a sample are arranged in a circle on a fixed stand, and a device for dropping a test liquid between the opposing electrodes is placed on a rotating stand. Since the rotary table is configured to rotate intermittently, there is no need to interpose a sliding conductive mechanism when supplying power between opposing electrodes or detecting leakage current. Therefore, there is no inconvenience caused by minute discharges that cannot be separated from minute tracking phenomena. In addition, there are no restrictions on the power supplied to the counter electrode or the heater for heating the sample, making it easier to combine various test conditions and expanding the setting control range for high voltage tests, constant temperature tests, etc.

In addition, maintenance of the device becomes easier, and in particular, disturbances in electrical signals in the moving parts hardly affect the test data, making it possible to perform severe continuous tests.

In addition, since the control device shown by the time control cam 12 controls the timing of dropping the test liquid in relation to the operation of the rotary table, it is possible to prevent not only track destruction according to IEC standards but also track ignition. can also be evaluated. By considering track ignition as a type of dielectric breakdown and performing the above two types of evaluation at the same time, it is possible to conduct tracking resistance tests of materials that are accompanied by ignition before dielectric breakdown with relatively high accuracy, which was previously impossible. I can do it.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of a conventional tracking resistance testing device, Fig. 2 is a block diagram showing the principle of the tracking resistance testing device of the present invention, and Fig. 3 is a block diagram showing the principle of a tracking resistance testing device of the present invention.
Figure a shows an example of the time change of initial leakage current, b
is a diagram showing an example of the time change of leakage current during ignition, c
FIG. 3 is a diagram showing an example of a comparison standard for breaking current. Fourth
The figure is a plan view showing an embodiment of the tracking resistance testing device of the present invention, and FIG. 5 is a side view with essential parts thereof cut away. DESCRIPTION OF SYMBOLS 1... Sample, 2... Electrode support, 3... Counter electrode, 4... Dripping nozzle, 5... Dripping device, 6...
Power supply, 7...Earth leakage detector, 8...Earth leakage breaker, 9
. . . Droplet counter, 10 . . . Rotating table, 12 . . . Time control cam, 16 …… Fixed table.

Claims (1)

[Claims] 1. A fixing table on which a plurality of electrode supports supporting a pair of opposing electrodes to be brought into contact with the sample are arranged in a circle;
a rotary table that is equipped with a dripping device that drips a test liquid between the opposing electrodes and rotates intermittently; a device that supplies power between each of the opposing electrodes; a device that detects leakage current between the opposing electrodes; A tracking resistance test device comprising a device that controls the timing of dropping a test liquid of a dropping device and the timing of detecting leakage current in relation to the operation of a rotating table.