JPH06310368A - Metallized film capacitor - Google Patents

Abstract

PURPOSE:To provide a metallized film capacitor wherein a metallized film is improved in self-recovery properties through a fuse effect and which is kept high in reliability to dielectric breakdown and least lessened in capacity due to a fuse action. CONSTITUTION:A metallized surface is split into unit capacitors 3a by cross- shaped slits 2b on which no metal is deposited, and the unit capacitors 3a are connected together in parallel through fuses 3b formed of small metallized part located between the cross-shaped slits 2b. The split unit capacitor 3a is so set as to be 10 to 1000mm<2> in deposition area, 130V/mum to 350Vmum in potential gradient (rated charge voltage/nominal thickness of plastic film), and less than 0.03J in storage energy obtained based on its area, resultant dielectric constant of dielectric, and rated charge voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC filter capacitor using a metallized plastic film having a safety mechanism (hereinafter referred to as a metallized film), a charging / discharging capacitor, or the like. The present invention relates to a DC capacitor in a broad sense (including a charge / discharge capacitor with high repetition rate).

[0002]

2. Description of the Related Art A DC filter capacitor is used to selectively filter an AC component contained in DC to obtain a voltage close to pure DC. Further, the charging / discharging capacitor generates a large current by the sharp discharge of the charged energy. These are widely and commonly used as capacitors for industrial equipment.

Conventionally, the dielectric of the capacitor in this field is
Paper that uses aluminum foil electrodes, plastic film, or a combination of these has been adopted. In some fields, vapor-deposited capacitors using metallized films are also used.

[0004]

By the way, recently, even in the field of capacitors for industrial equipment of this kind, the size of the device itself has been reduced.
With the progress of weight reduction, the demand for smaller and lighter capacitors is also increasing.

Generally, the amount of energy storage (hereinafter referred to as energy density) per unit volume of a dielectric material stored in a capacitor is given by the following equation. _{W / S · d = ε O} ε S (E / d) 2/2 = ε O ε S (G 2/2 [J / ^{m 3]} W: stored energy (J) S: electrode area ^{[m 2]}
d: Dielectric thickness [m] ε _O : Vacuum permittivity ε _S : Relative permittivity
G: Potential gradient [V / m]

That is, the energy density of a capacitor is
It is proportional to the relative permittivity of the dielectric material and proportional to the square of the potential gradient. The relative permittivity is a value peculiar to the material, which can be adopted within a certain narrow range, and it can be considered that the energy density of the capacitor depends on the potential gradient.

In the conventional aluminum electrode foil capacitor, the set potential gradient has an upper limit of 130 V / μm at most. On the other hand, metalized film capacitors, which have been widely adopted recently, are characterized by their self-healing effect (evaporated metal around the insulation defect part evaporates due to energy due to momentary short circuit).
By improving the reliability against dielectric breakdown due to scattering and disconnection from the functional part of the capacitor and recovery of the function of the capacitor), it becomes possible to set a higher potential gradient and to design up to about 180 V / μm. ing. However, in order to enhance the self-recovery property, there is a limit to the examination mainly on the material of the vapor-deposited metal, the thickness of the thin film, etc., and the demand for further size reduction and weight reduction cannot be met.

[0008] As described above, in the case of increasing the electric potential gradient in the ordinary metal vapor-deposited film, the limit was recognized mainly from the reliability against the dielectric breakdown of the capacitor.
Focusing on the capacitor with a safety function for AC applications which is adopted in JIS C 4901 (1984) low voltage phase advance capacitor and JIS C 4908 (1988) capacitor for electric equipment, the structure applying this to a DC capacitor is examined. As a result, the self-healing action of the vapor-deposited film is enhanced by the fuse effect, the reliability against dielectric breakdown is secured, and the metallized film capacitor capable of minimizing the capacitance reduction due to the fuse operation or the like can be realized.

[0009]

That is, the metallized film capacitor according to claim 1 comprises a pair of two plastic films having metal vapor deposition on one surface, or a plastic film and metal having metal vapor deposition on both surfaces. Wrap a pair of plastic films without vapor deposition,
At least one of the pair of two vapor deposition surfaces is subdivided into unit capacitors by a grid-shaped slit without metal vapor deposition, and unit capacitors are connected in parallel by a fuse portion formed between the slits and each subdivided. The vapor deposition area of the unit capacitor is 10 to 1000 mm ² , and the potential gradient of the plastic film is 35 V at 130 V / μm or more.
The feature is that the voltage is set to 0 V / μm or less.

The metallized film capacitor according to claim 2 is characterized in that the energy stored in each unit capacitor at the rated voltage charging is 0.03 J or less.

Furthermore, the metallized film capacitor according to claim 3 is characterized in that the capacitor used is for a DC filter or for charging and discharging.

The metallized film capacitor according to claim 4 is
The size of the fuse portion connecting each unit capacitor is characterized by being 0.1 mm or more and 1.5 mm or less in the narrowest portion.

Conventionally, there are many cases in which a slit forming a segment is provided only in one direction of the film width, such as the one disclosed in Japanese Patent Laid-Open No. 4-359416. In such a slit, the unit capacitor (hereinafter referred to as a segment) required for the performance of the capacitor of this application is divided into 10 to 1000 mm ² , and particularly 50
With a film width of mm or more, there are many practical problems due to the following reasons. The first is that the width between the slits becomes extremely narrow and the restrictions on the processing technology increase, and the second is that the capacity decreases due to the increase in the slits. On the other hand, the lattice-shaped slits in the present application have less of these restrictions and can form arbitrarily segmented segments.

The area of the segment is 10 to 10
00 mm ² is suitable. When it is less than 10 mm ² , the capacitance loss of the slit portion is large and the economical efficiency of the processing technology including the fuse portion is difficult, which is not a good idea. 1000 mm
If it exceeds ² , the electrostatic capacity that decreases at the time of one fuse operation increases, and the potential gradient is restricted by the electrostatic capacity life of the capacitor, which is not a good idea.

The potential gradient of the film, that is, the potential gradient obtained by dividing the normal operating voltage (rated voltage) by the film thickness is 13
It is suitable to set it to 0 to 350 V / μm. 130
If it is less than V / μm, there is no advantage over the conventional ordinary capacitor, and there is no point in adopting this method. 350V / μ
If m is exceeded, the film will be in the original withstand voltage region, the frequency of fuse operations will increase rapidly, and the function will be lost due to the decrease in the capacitance of the capacitor, making it unusable for practical use.

The relationship between the area of the segment and the rated charging voltage is that the stored energy W per segment is 0.03.
J or less is suitable. The W per segment is
It shall be calculated by the following formula. W = ^CE 2/2 [J] C = Sε _S (/1.13×10 ¹¹ d [F] W: stored energy (J) C: 1 capacitance segment (F) d: dielectric thickness [m S: Area of one segment [m ² ] ε _S (: relative permittivity E: charging voltage [V] If it exceeds 0.03 J, proper fuse setting becomes difficult and damage to the dielectric material occurs to prevent dielectric breakdown. The reliability is reduced, and the capacity reduction rate is also increased.

Further, it is appropriate that the size of the fuse portion connecting between the segments is 0.1 to 1.5 mm at the narrowest portion.
If it is less than 0.1 mm, there are many malfunctions due to normal current, and the stability of the electrostatic capacity is lost. If it exceeds 1.5 mm, the sensitivity of the fuse is poor, the dielectric is damaged, and the reliability of dielectric breakdown is lost.

With this configuration, it is possible to achieve a significant reduction in size and weight as compared with the conventional capacitor.

[0019]

Next, specific examples of the metallized film capacitor of the present invention will be described in detail with reference to the drawings.

[0020]

[Embodiment 1] FIG. 1 shows a metal-evaporated film capacitor according to an embodiment of the present invention. FIG. 1 (1) is an exploded perspective view thereof, and FIG. 2 (2) is a sectional view of a pair of metal-evaporated films. Is. In the figure, reference numeral 1 is a first metal vapor deposition film, and an electrode coating 3 is formed on the surface of a first dielectric film 2 such as a polypropylene film by metal vapor deposition. 2a is a margin portion, and the electrode coating 3 is not formed on this portion. 2b is a lattice-shaped slit portion,
No electrode coating 3 is formed on this portion either. Reference numerals 3b denote fuse portions, respectively, and the segments 3a, which are subdivided unit capacitors, are connected in parallel. Reference numeral 4 is a second metal vapor deposition film, which is the same as the name of each part of the first metal vapor deposition film, 5 is a second dielectric film, 5a is a margin portion, 5b is a slit portion, 6 is an electrode coating (split electrode). ), 6a is a segment part, and 6b is a fuse part.
Reference numerals 7 and 8 denote metal spraying portions for pulling out the leads. Figure 1
W1 in (4) is the size of the narrowest part of the fuse, as shown in FIG.
The w2 and w3 in (3) indicate the segment size, respectively.

Next, the specifications of the test capacitor of this structure manufactured for the test are shown below. Specifications of test capacitor ・ Type of metal evaporated film Zinc evaporated polypropylene film ・ Coating resistance value 5Ω / □ ・ Dimension 100mm width Margin 3.0mm
Thickness 12 μm Segment area 400 mm ² Fuse narrowest part 0.6 m
m Slit widths are all the same ・ Application DC filter capacitor ・ Capacitor rated voltage 2500 VDC Capacity 30 μF ・ Impregnant vegetable oil (rapeseed oil) impregnation ・ Exterior square tin case storage ・ 10 samples (10 for conventional products without slits for comparison) ) The test results are shown in Table 1.

[0022]

[Table 1]

The test method is called a step-up withstand voltage test, and the test capacitor is put in a hot air circulation type constant temperature bath set at 80 ° C. and 180 V / μm (216
DC voltage corresponding to 0 V is applied for 10 ⁵ seconds (27.8 Hr
s) Apply. After applying the voltage, the temperature is kept at room temperature and various characteristics such as the capacitance of the capacitor are measured. Next, a voltage corresponding to 200 V / μm is applied in the same manner, application and measurement are repeated in sequence, and the applied voltage is continuously increased until dielectric breakdown of the capacitor occurs or there is almost no capacity.

From the above test results, the following was found. That is, in contrast to the conventional capacitors, which were all subject to dielectric breakdown before and after the rated set voltage, the capacitor of the present invention did not cause dielectric breakdown and withstands the voltage of the original withstand voltage region of the film without a large decrease in capacitance, Dielectric breakdown does not occur even when almost disappears. As described above, it was confirmed that the fuse effect against the DC voltage was achieved together with the high capacity stability.

Although the polypropylene film is used as the dielectric film in the above embodiment, other types of films such as polyethylene terephthalate film may be used. Further, although zinc is used as the vapor deposition metal in the above-mentioned embodiment, it is not limited to zinc, and other metals such as aluminum or a zinc / aluminum mixture may be used. This time, it was carried out with a vegetable oil-immersed condenser, but the impregnating agent / filler is not limited to this. Further, it can be applied to both oil immersion type and dry type. In FIG. 1 (1), the slit direction is an example of a direction parallel to and perpendicular to the longitudinal direction of the film, but the invention is not limited to this, and the split electrodes (segments) are formed by diagonally intersecting slits. But of course it's good. In this example, the vapor deposition surfaces of both the pair of surfaces are the divided electrodes, but one of them may be an ordinary vapor deposition film in which the divided electrodes are not formed.

[0026]

[Embodiment 2] With the construction shown in FIG. 1 of Embodiment 1, five kinds of zinc vapor-deposited polypropylene films having a segment area of 4 to 2000 mm ² are manufactured by changing the segment size w2 and w3 (FIG. 1 (3)). A test capacitor with the following specifications was manufactured. Specifications of capacitor under test ・ Type of metal evaporated film Zinc evaporated polypropylene film ・ Coating resistance value 7Ω / □ ・ Dimensions 100mm width 3.0mm margin
Thickness 8 μm Segment area 4 to 2000 mm, 5 types for checking, Narrowest fuse part 0.6 mm ・ Application DC filter capacitor ・ Capacitor rated voltage 1600VDC capacity 60 μF ・ Exterior epoxy resin encapsulation dry type ・ 10 samples each

The test results are shown in FIG. The test method is
(1) With respect to the initial capacitance value of a normal capacitor having no slit portion, how the capacitance loss rate at the initial stage due to the provision of the slit changes depending on the segment area is determined by capacitance measurement. (2) At a temperature of 80 ° C., a DC voltage 1.3 times the rated voltage is continuously applied for 2000 Hrs to obtain the capacity reduction rate with respect to the initial value.

From the above results, the following was found. First, if the segment area becomes smaller, the initial capacity will decrease due to the increase in the non-electrode part, but conversely, if the segment area becomes larger, the capacity decrease rate in the life test will increase. Area is 10-1
In the range of 000 mm ² , both contradictory items can be satisfied.

It was also confirmed that even if the type and thickness of the film, the vapor deposition metal and the resistance value, the presence or absence of impregnation, etc. were changed, both performances were satisfied within this range.

[0030]

[Embodiment 3] With the structure shown in FIG. 1 of Embodiment 1, as the metal vapor deposition film, there are two kinds of films, that is, polypropylene film and polyethylene terephthalate, and the thickness of the film is in the range of 5 to 20 μm, and the segment area is arbitrary. A capacitor element with the rated voltage set was manufactured. This element was housed in a tin case and vacuum impregnated with an impregnating agent, which was a mixture of petroleum wax and polybutene oil, was used as a test capacitor. There are six types of film, but the segment area was changed to make a total of 13 types of test capacitors.

Test method Test 1 DC continuous current test: A DC voltage 1.2 times the rated set voltage was applied for 2000H in a hot air circulation type constant temperature bath at 70 ° C.
rs is continuously applied. At this time, it was judged whether or not dielectric breakdown occurred during the test and whether or not the rate of change in capacitance after the test was completed was within 10%. When the number of samples was 10, and even one dielectric breakdown occurred, x was determined, and when the average value of the capacitance change rate was 10% or more, x was determined. Test 2 Charge / discharge test: In a hot air circulation type constant temperature bath at 70 ° C,
Charge / discharge at the rated voltage was performed 10,000,000 times under the conditions of a voltage reversal rate of about 10%, a discharge pulse width of 100 to 300 μsec, and a charge / discharge frequency of 2 to 3 PPS. The criteria for judgment are the same as in Test 1. The test results are shown in Table 2.

[0032]

[Table 2]

From the above results, the following was found. The larger the energy per segment (the larger the rated charging voltage, the larger the area of one segment,
The energy increases as the relative permittivity increases), and the reliability against dielectric breakdown and capacity reduction decreases in both the DC continuous current test and the charge / discharge test. To provide proper performance, the energy for charging the rated voltage per segment needs to be 0.03 J or less.

[0034]

As described above, according to the present invention, the capacitor of one element is made into an assembly of a large number of divided capacitors, each unit capacitor is provided with a fuse, and the minimum capacity reduction is achieved without dielectric breakdown in the event of an abnormality. The function of the capacitor is to ensure the function of the capacitor, and the conditions under which the capacitor works properly at this time are specified. By adopting the present invention, a small and lightweight capacitor with high insulation performance compared to conventional capacitors It has become possible to provide.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of a capacitor element of the present invention.

FIG. 2 is a diagram showing a relationship between a segment area and capacitance performance.

[Explanation of symbols]

 1 1st metal vapor deposition film 2 1st dielectric film 2a margin part 2b slit part 3 electrode film (split electrode) 3a segment part 3b fuse part 4 2nd metal deposition film 5 2nd dielectric film 5a margin part 5b Slit part 6 Electrode coating (divided electrode) 6a Segment part 6b Fuse part 7 Lead lead part 8 Lead lead part w1 Narrowest part size of fuse part w2 Segment part size w3 Segment part size

Claims (4)

[Claims] 1. A pair of plastic films having metal vapor deposition on one side thereof, or a pair of plastic films having metal vapor deposition on both sides and a plastic film not having metal vapor deposition on both sides, and the pair of two At least one of the vapor-deposited surfaces is subdivided into unit capacitors by a lattice-shaped slit without metal vapor deposition, and unit capacitors are connected in parallel by a fuse portion formed between the slits, and each subdivided unit capacitor is Deposition area is 10
A metallized film capacitor having a thickness of 1000 mm ² and a plastic film potential gradient of 130 V / μm or more and 350 V / μm or less. 2. The metallized film capacitor according to claim 1, wherein the stored energy of each unit capacitor at the time of charging the rated voltage is 0.03 J or less. 3. The metallized film capacitor according to claim 1, wherein the use of the capacitor used is for a DC filter or for charging / discharging. 4. The size of the fuse portion connecting each unit capacitor is 0.1 mm or more and 1.5 mm or less at the narrowest portion, according to claim 1. Metallized film capacitor.