JP2586005B2 - Oil impregnated capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oil-impregnated capacitor using a polypropylene film (hereinafter referred to as a PP film) impregnated with insulating oil as a dielectric layer.

In recent years, a plastic film has been used as a dielectric layer of a capacitor. However, an oil-impregnated capacitor is no exception, and a PP film is often used because of its excellent electrical properties.

However, unlike an unimpregnated capacitor, an oil-impregnated capacitor generally uses a roughened film due to problems such as impregnation of insulating oil and compatibility of the film.

However, in conventional capacitors, increasing the oil impregnating property increases the swelling of the film, hinders the fluidity of the oil between the film layers due to the increase in thickness, and tends to cause insulation deterioration due to the concentration of electric field, which significantly reduces the life of the capacitor. Had.

[Object of the invention]

The inventors of the present invention have made intensive studies in view of the above points, and as a result, have sought to provide an oil-impregnated capacitor having a dielectric layer having a sufficient inter-layer oil layer and excellent capacitor life.

[Configuration of the invention]

In order to achieve the above object, the present invention provides an oil-impregnated capacitor provided with the following structure: an electrode, a dielectric layer, and an insulating oil, wherein all or a part of the derivative layer contains 96% by weight or more of isotactic. A biaxially oriented polypropylene film having a crystal size of 150 ° or less is used, and the film has an oil amount in the film of 5 × 10 ^{−2 to} 20 × 10 ⁻² g /
cm ³ is an oil-impregnated condenser characterized by having a diameter of ³ cm ³ .

In the present invention, the biaxially stretched polypropylene film is a stretched polypropylene film, and has a degree of isotacticity (hereinafter abbreviated as II) of 96% by weight or more, preferably
Must be 98-99.6% by weight. If the content is less than 96% by weight, the pressure resistance is drastically reduced due to an increase in elution to insulating oil and swelling of the film, and the life of the capacitor is greatly reduced. The rate of increase in the thickness of the film is preferably 10% or less. The crystal size of this film is 150 ° or less, preferably 145 ° or less. If it exceeds 150 °, the segment density of the amorphous portion in the film is reduced, and the molecular chain length is shortened, so that the dielectric strength is reduced and the life is shortened.
The surface of the film may have a roughened surface. The amount of insulating oil in the film is 5 × 10 ^{-2 to} 20 × 10 ^-2 g / cm ^3.
And preferably 7 × 10 ⁻² to 15 × 10 ⁻² g / cm ³ . If the amount of oil is less than 5 × 10 ⁻² g / cm ³ , unimpregnated portions are apt to be formed in the microvoids in the film as the derivative layer, and degradation due to partial discharge or the like progresses and leads to dielectric breakdown.
On the other hand, if it exceeds 20 × 10 ^-2 g / cm ³ , the dielectric strength decreases due to a change in crystal structure.

The film of the present invention may contain other components that do not impair the properties of the present invention.

The electrode and insulating oil in the present invention are not particularly limited as long as they are known as a capacitor. Further, the dielectric layer is preferably formed of the above film, but another film or the like may be laminated on the above film.

Next, an example of the method for producing the oil-impregnated capacitor of the present invention will be described. However, it is not limited to this. First, polypropylene with II of 95.6-99.6% by weight
Using a extruder heated to 240-270 ° C, extrude the polymer melted from the T-die into a sheet equivalent to 400-800μ,
After cooling the molten sheet by contacting it with a chill roll of 30 to 75 ° C for 3 to 8 seconds, re-heat it with a roll heated to 100 to 120 ° C for 6 to 12 seconds, and then lengthwise at a temperature of 145 to 155 ° C. To 4.
The film is stretched from 0 to 5.3 times, and then stretched in a direction perpendicular to the film at a temperature of 155 to 165 ° C at a temperature of from 7 to 11.0 times to obtain a biaxially stretched film.

The film formed as described above is vapor-deposited with a metal to form a well-known metallized film.
Alternatively, a metal foil is overlaid on the above film and wound to form a capacitor.

Then, the condenser of the present invention can be obtained by putting the above-mentioned condenser in a container and putting a well-known insulating oil, preferably monoisopropyl biphenyl or diallyl alkane, in a vacuum chamber.

〔The invention's effect〕

As described above, the capacitor of the present invention uses a film of polypropylene having II of 96% by weight or more, a crystal size of 150 ° or less, and a lubrication amount of 5 × 10 ^{-2 to} 20 × 10 ^-2 g / cm ³ as a dielectric. Since the layers were formed, the following excellent effects could be obtained.

In other words, an improvement of about 20% in the durability characteristic in the accelerated test can be expected due to the improvement of the withstand voltage as compared with the conventional product. The effects of the present invention were evaluated based on the following criteria.

The life characteristics are as follows. Three films of 100mm width and 15μ thickness are stacked on top of each other to make a 0.2μF capacitor using 80mm width and 8μ thickness Al foil as electrodes, and a 3.0KV AC (applied voltage 1.5 times the potential gradient 45V / μ) ) Was applied at a high temperature of 80 ° C. for 400 hours, and then a capacitor breakdown test was performed with a DC voltage, and the life index was determined from the following table according to the capacitor breakdown state. The life index refers to the sum of the indices for the six elements obtained by performing a capacitor breakdown test on six elements, obtaining an index from the table below for each element. DC breakdown voltage indicates the degree of deterioration of the structure during AC power application.

(1) Measurement of oil content in film A. Preparation of standard sample (a) Cut a film into a size of 10 cm × 30 cm.

(B) After sufficiently removing the static electricity from the film with an ion gun (manufactured by Zerastal UK), the weight is measured with a balance that can read up to 10 ^-4 g.

(C) The film is immersed in a heated insulating oil (diallyl alkane, "Nisseki Oil S") at 80 ° C to 100 ° C and taken out at different times so that the amount of impregnated oil is different.

(D) Kimwipe (TYPES200) of Jujo Kimberly Co., Ltd.
Wipe off the oil on the surface of the film completely with a normal wipe 5 times.

(E) Weigh precisely as in (b).

B. Preparation of calibration Using the sample of item (e) above, a Hitachi diffraction grating infrared spectrophotometer (EP-1-G3 type, manufactured by Hitachi, Ltd.) was used to increase the chart speed to 700 cm ¹ at a chart speed of FAST-2. Use the outgoing peak. Let the scan (Scan) to 750cm ^-1 ~650cm ^-1 as measured at that time. Sample size is 4cm wide x 7 long
cm.

C. Area Measurement In the waveform processing, a baseline M is drawn on the waveform W as shown in FIGS. Next, a perpendicular line is drawn from the vertex P of the waveform, and the intersection with the baseline M is defined as Q. Also, P, Q
A line N that is a middle point between the two and is perpendicular to a perpendicular line from the vertex P is drawn, and intersections of the line N and the waveform W are denoted by R and S, respectively.

In the above-described waveform processing, a peak (Peak) height a is set between P and Q, and a half width b is set between R and S. The half width b is measured using a scope of about 50 times and read to 10 μm.

The peak area is represented by a × bmm ² . The calibration line plots the unit oil amount (g / cm ² ) against the peak area.

D. Determination of oil amount Take out the film in the condenser used for the aluminum foil winding, determine the peak area under the same conditions as above, and calculate the oil amount (g / g) from the calibration curve.
cm ²⁾ is measured. TESA Tronic
The thickness to the first decimal place was determined using TTD-20 (manufactured by Switzerland) and divided by the film thickness to define the amount of oil in the film (g / cm ³ ).

(2) Measurement of Thickness Increase Rate The film thickness before and after oil immersion was measured using the same sample using TTD-20 manufactured by TESA Tronic.

Thickness increase rate (%) = [(BA) / A] x 100 A: Film thickness before oil immersion B: Film thickness after oil immersion Oil impregnation treatment is PXE immersion at 80 ° C for 24 hours.

(3) Measurement of crystal size Applied voltage 35KV-15M by wide angle X-ray diffraction (reflection method)
A.Scan Speed 1 ゜ / min Time CONST 2SeC FS 8000cps SL
The iT DS.SS1 ゜ RS0.3 mm filter was measured using nickel under the above conditions, and was determined by the following equation, and the measured value of the (110) plane was defined as the crystal size.

Crystal size (Å) = (K · λ) / (β · cos θ) K: Scherrer constant, where K = 1 here λ: 1.5418 β: Half width θ: Peak angle [Example] The details of the present invention will be described based on this.

Example 1 Table 1 from a T-die with an extrusion temperature of 250 ° C and a width of 600 mm and an interval of 1.2 mm.
Extruded and melted different raw materials of II, contacted with styrene cooled to 35 ° C for 3 seconds, and then pressed with a metal roll heated to 120 ° C.
After heating for 0 seconds, the film is stretched 5.0 times in the length direction with a temperature of 153 ° C and an infrared heater (10KW), and then stretched 8.5 times in a perpendicular direction at a temperature of 160 ° C to obtain a biaxially stretched film. Are stacked on each other to form a dielectric layer, and an electrode is made of 8 μm thick Al foil.
A 0.2 μF capacitor was manufactured and impregnated with insulating oil such as diallyl alkane for 10 hours at 80 ° C. and then heat-treated at 80 ° C. for 65 hours to obtain an oil immersion capacitor in which the dielectric layer film was impregnated with insulating oil. 3.0KV at 80 ℃ using the capacitor
AC was applied for 400 hours to compare the life of the capacitors. As shown in Table 1, the thickness increase rate was 10% or less when II was 96.5% or more and the crystal size was 150 ° or less, and the withstand voltage was improved.

Example 2 A film and a capacitor were prepared in the same manner as in Example 1 and were impregnated with insulating oil at 80 ° C. for 10 hours.
Investigation of the relationship between the oil absorption of the dielectric layer and the life characteristics of the capacitor obtained by combining the time at 70 to 105 ° C for 24 to 65 hours clearly showed that the oil amount in the film was as shown in Table 2. It can be seen that the life of the condenser is greatly affected.

[Brief description of the drawings]

1 to 3 are diagrams showing an example of a waveform processing method in measuring the amount of oil in a film according to the present invention.

Claims (1)

(57) [Claims] 1. An oil-impregnated capacitor comprising an electrode, a dielectric layer and an insulating oil, wherein all or part of the dielectric layer has an isotacticity of 96% by weight or more and a crystal size of 150 ° or less. An axially stretched polypropylene film is used, and the film has an oil content of 5 × 10 ^-2.
An oil-impregnated condenser characterized by having a weight of ~ 20 × 10 ^-2 g / cm ³ .