WO2013069485A1 - Film capacitor, capacitor module, and power converter - Google Patents

Abstract

Thermal resistance is improved in a film capacitor that is provided with a wound dielectric resin film, first and second counter electrodes mutually opposite and sandwiching the dielectric resin film, and a terminal electrode electrically connected to each of the counter electrodes. Dielectric resin films (3, 4) are constructed from heat-hardened resin with a resin component having a glass transition point of at least 130°C. The substance used has a residue weight from thermal decomposition at 500°C of no more than 40 wt% when the rate of change of the thermogravity of the resin component is measured with a temperature increase rate of 10°C/minute in nitrogen, and has a surface roughness Ra from 3 nm to 1000 nm. Consequently, during dielectric breakdown, the breakdown portion of the dielectric resin film can easily become gas, the decomposition gas readily scatters from inside of the film capacitor, a self-healing function acts, and the film capacitor is able to withstand continuous use above 125°C, for example.

Description

Film capacitor, capacitor module, and power converter

The present invention relates to a film capacitor and a capacitor module and a power conversion device constituted by using the film capacitor, and more particularly to an improvement for improving the heat resistance of the film capacitor.

As a film capacitor that is of interest to the present invention, there is a film capacitor using a metal-deposited polypropylene film described in, for example, JP-A-7-45466 (Patent Document 1). This film capacitor has a fuse pattern portion obtained by dividing the internal electrode, and by setting the shape of the fuse pattern portion to be appropriate, the fuse functions and sets a current value range leading to disconnection. As a result, this film capacitor is said to have both heat resistance and a self-healing function while the maximum allowable temperature is set to 100 ° C. to 150 ° C.

However, the film capacitor has the following problems to be solved.

Although the fuse pattern part is provided, if dielectric breakdown frequently occurs, the decomposition gas of the dielectric resin film generated by the dielectric breakdown may be accumulated inside the film capacitor. When the cracked gas is accumulated in this way, the cracked gas can become a conductive carbide. Since this conductive carbide brings an energized state inside the film capacitor, the insulation is not restored, and as a result, the self-healing function does not work.

Although the maximum allowable temperature is set to 100 ° C to 150 ° C, it is continuous at 100 ° C to 150 ° C as long as it uses a thermoplastic resin such as polypropylene and a relatively low glass transition point. The use is impossible, and it is fully considered that the film is deformed or the electric characteristics are deteriorated.

By the way, the reliability of film capacitors deteriorates due to moisture absorption. In order to suppress moisture absorption into the film capacitor, it is desirable to use at a temperature as high as possible, for example, a temperature of 100 ° C. or higher, which is the boiling point of water. However, the film capacitor described in Patent Document 1 cannot be used continuously at 100 ° C. to 150 ° C. as described above. Therefore, when a system using a film capacitor is constructed, it is necessary to set the ambient temperature of the film capacitor to less than 100 ° C. at the highest. Therefore, in the film capacitor, moisture absorption is promoted, and only a system with low reliability can be realized from the viewpoint of moisture resistance.

Japanese Patent Laid-Open No. 7-45466

Therefore, an object of the present invention is to provide a film capacitor that can solve the above-described problems, that is, has excellent heat resistance.

Another object of the present invention is to provide a capacitor module configured using the film capacitor described above.

Still another object of the present invention is to provide a power conversion device configured using the film capacitor described above.

The present invention relates to a dielectric resin film formed in an overlapping manner, first and second counter electrodes disposed so as to face each other across the dielectric resin film, and first and second counter electrodes. A film capacitor is first directed to the first and second terminal electrodes, each electrically connected.

In order to solve the technical problems described above, the film capacitor according to the present invention has a surface roughness Ra of at least one main surface as the dielectric resin film of 3 nm or more and 1000 nm or less, and a glass transition as a resin component. It is composed of a thermosetting resin having a point of 130 ° C. or higher, and the thermal decomposition residue weight at 500 ° C. when the thermogravimetric change rate of the resin component is measured in nitrogen at a heating rate of 10 ° C./min is 40% by weight. The following is used.

As described above, since the amount of pyrolysis residue at 500 ° C. in a nitrogen atmosphere is small and the thermal decomposability is good, the breakdown portion of the dielectric resin film can be easily gasified during dielectric breakdown. In addition, since the surface of the dielectric resin film is provided with irregularities that give a predetermined surface roughness Ra, the dielectric resin film may be wound or laminated to overlap each other even between overlapping dielectric resin film portions. Since a slight gap is formed, the decomposition gas is likely to be scattered from the inside of the film capacitor, so that the self-healing function works well. In addition, since a thermosetting resin having a glass transition point of 130 ° C. or higher is used for the dielectric resin film, it has heat resistance that can withstand continuous use at a high temperature of, for example, 125 ° C. or higher.

The present invention is particularly advantageously applied to a wound film capacitor. In this case, the dielectric resin film is wound to form a wound body, the first and second counter electrodes are disposed inside the wound body, and the first and second terminal electrodes are It is formed on each end face of the wound body.

The dielectric resin film preferably contains a resin component obtained by mixing two or more organic materials and cross-linking them. According to this configuration, since the resin has a three-dimensional network structure, the glass transition point can be set to a high temperature, and the vibration of the molecular chain is suppressed even at a high temperature, so that deterioration of electrical characteristics and physical properties is suppressed. For the same reason, the long-term reliability of the film capacitor at a high temperature can be increased.

It is preferable that the convex part which gives the surface roughness of the dielectric resin film is made of the same kind of resin component as the main body part other than the convex part of the dielectric resin film. According to this structure, it can suppress that the dielectric breakdown strength falls for the formation of a convex part.

The present invention is also directed to a capacitor module configured using the film capacitor, that is, a capacitor module including a plurality of film capacitors and a terminal conductor connected to the terminal electrode of the film capacitor.

The present invention is further directed to a power conversion device that includes the film capacitor and a switching element, and is set so that the maximum temperature reached by the film capacitor during operation can be 100 ° C. or higher.

According to the present invention, it is possible to obtain a film capacitor that can be continuously used at a temperature of 125 ° C. or higher and further has a self-healing function.

The reliability of film capacitors decreases due to moisture absorption, but by increasing the ambient temperature, the moisture absorbed by the film capacitors can be efficiently discharged, and high reliability can be maintained. Furthermore, by setting the ambient temperature to 100 ° C. or more, which is the boiling point of water, it is possible to more quickly advance the discharge of moisture from the film capacitor. For example, even if water droplets are formed on the surface of the film capacitor due to dew condensation, it can be evaporated in a short time and the moisture inside the film capacitor can be discharged in a short time.

From the above, if the film capacitor according to the present invention is applied to a power conversion device, the heat generated unavoidably in the power change device can contribute to the evaporation of moisture as described above. The fall of property can be prevented. In addition, since the film capacitor itself has high heat resistance, the cooling mechanism required for the power converter can be simplified, and power that operates at high temperature and high frequency, such as SiC and GaN. It can be combined with a switching element composed of a semiconductor without any problem. From these, it is possible to realize a power converter having a small size, low cost, high performance and high reliability.

1 is a longitudinal sectional view showing a film capacitor 1 according to a first embodiment of the present invention. It is a figure which expand | deploys and shows the 1st and 2nd dielectric resin films 3 and 4 with which the film capacitor | condenser 1 shown in FIG. 1 is equipped. FIG. 5 is a diagram illustrating a film capacitor according to a second embodiment of the present invention, in which first and second dielectric resin films 3 and 4 are developed and shown. It is a perspective view showing one embodiment of a capacitor module constituted using a film capacitor concerning this invention. It is a circuit diagram showing one embodiment of a power converter constituted using a film capacitor concerning this invention. It is a figure which shows the time-dependent change of the capacity | capacitance in the high temperature state of the film capacitor which concerns on the sample 1 produced in the experiment example. It is a figure which shows the impedance (| Z |) -frequency characteristic and equivalent series resistance (ESR) -frequency characteristic of the film capacitor which concerns on the sample 1 produced in the experiment example. It is a perspective view which shows the capacitor module integrated in the power converter device produced in the experiment example, Comprising: The temperature measured about each part of a capacitor module is shown. It is a figure which shows the impedance-frequency characteristic of the capacitor | condenser module integrated in the power converter device produced in the experiment example. It is a figure which shows the equivalent series resistance (ESR) -frequency characteristic of the capacitor | condenser module incorporated in the power converter device produced in the experiment example.

A film capacitor 1 according to a first embodiment of the present invention will be described with reference to FIG. 1 and FIG.

A film capacitor 1 shown in FIG. 1 is of a winding type, and includes first and second dielectric resin films 3 and 4 wound around a winding shaft 2 and first or second dielectric resin films 3 and 4. First and second counter electrodes 5 and 6 that face each other across the dielectric resin film 3 or 4 and are electrically connected to the first and second counter electrodes 5 and 6 respectively. And second terminal electrodes 7 and 8.

As well shown in FIG. 2A, the first counter electrode 5 is formed on the first dielectric resin film 3, and the second counter electrode 6 is formed on the second dielectric resin film 4. Is formed. At this time, the first counter electrode 5 is formed so as to reach the first side edge of the first dielectric resin film 3 but not to the opposite second side edge. On the other hand, as well shown in FIG. 2B, the second counter electrode 6 is formed on the first side edge of the second dielectric resin film 4 on the same side as the first side edge. It is formed so that it does not reach the opposite side edge, but is formed so as to reach the opposite second side edge.

The first and second dielectric resin films 3 and 4 are wound around the winding shaft 2 so as to overlap each other. At this time, as can be seen from FIG. 1, the end of the first counter electrode 5 on the side reaching the side edge of the first dielectric resin film 3 and the second dielectric in the second counter electrode 6. The first dielectric resin film 3 and the second dielectric resin film 4 are shifted from each other in the width direction so that both end portions reaching the side edges of the resin film 4 are exposed. Then, the first and second dielectric resin films 3 and 4 are wound around the winding shaft 2 as described above, whereby a substantially cylindrical wound body 9 is obtained.

In the film capacitor 1 shown in FIG. 1, the first and second dielectric resin films 3 and 4 are arranged so that the second dielectric resin film 4 is outside the first dielectric resin film 3. Each of the first and second counter electrodes 5 and 6 is wound so as to face inward, but the arrangement and orientation of the first and second dielectric resin films 3 and 4 are changed. May be.

The first and second terminal electrodes 7 and 8 are formed by spraying, for example, zinc on each end face of the substantially cylindrical wound body 9 obtained as described above. The first terminal electrode 7 is in contact with the exposed end portion of the first counter electrode 5, thereby being electrically connected to the first counter electrode 5. On the other hand, the second terminal electrode 8 is in contact with the exposed end of the second counter electrode 6, thereby being electrically connected to the second counter electrode 6.

The present invention can be applied not only to the wound film capacitor 1 as shown in FIG. 1, but also to a laminated film capacitor formed by laminating a plurality of planar dielectric resin films. The form in which the dielectric resin films overlap each other is provided by winding the first and second dielectric resin films 3 and 4 in the wound film capacitor 1 shown in FIG. This film capacitor is provided by laminating a plurality of dielectric resin films.

The dielectric resin films 3 and 4 provided in the film capacitor 1 are composed of a thermosetting resin having a glass transition point of 130 ° C. or higher as a resin component, and the rate of change in thermogravimetricity of the resin component in nitrogen is 10 ° C. The weight of pyrolysis residue at 500 ° C. when measured at / min is 40% by weight or less, and the surface roughness Ra of at least one main surface of the dielectric resin films 3 and 4 is 3 nm or more and 1000 nm or less. .

The dielectric resin films 3 and 4 may contain an insulating inorganic filler in addition to the resin component.

As described above, the dielectric resin films 3 and 4 have a small amount of thermal decomposition residue at 500 ° C. in a nitrogen atmosphere and good thermal decomposability. Gasification can be facilitated. Moreover, since the unevenness | corrugation which gives predetermined surface roughness Ra is formed in the surface of the dielectric resin films 3 and 4, even when the dielectric resin films 3 and 4 are wound or laminated | stacked, the dielectric resin film part which overlaps Since a slight gap is formed between them, the decomposition gas is easily scattered from the inside of the film capacitor 1, and the self-healing function works well. In addition, since the dielectric resin films 3 and 4 are made of a thermosetting resin having a glass transition point of 130 ° C. or higher, the dielectric resin films 3 and 4 have heat resistance that can withstand continuous use at a high temperature of 125 ° C. or higher.

Such resin components of dielectric resin films 3 and 4 were obtained by mixing two or more organic materials and cross-linking each other, for example, by mixing polyvinyl acetoacetal and tolylene diisocyanate. It is preferable that a resin component is included. According to this configuration, since the resin has a three-dimensional network structure, the glass transition point can be set to a high temperature, and the vibration of the molecular chain is suppressed even at a high temperature, so that deterioration of electrical characteristics and physical properties is suppressed. For the same reason, the long-term reliability of the film capacitor 1 at a high temperature can be made high.

As a resin component, as long as the above-described urethane-based material such as a mixture of polyvinyl acetoacetal and tolylene diisocyanate is satisfied, the thermal decomposition residue weight at 500 ° C. in nitrogen is 40% by weight or less. For example, polyvinyl acetal, polyvinyl butyral, cellulose, acrylic resin, epoxy resin, or the like may be used. In particular, the resin preferably contains a carbon, oxygen, hydrogen, or nitrogen element in the bridging portion or side chain and is composed of an element that easily becomes a decomposition gas.

In the experimental examples to be described later, the convex portions that give the predetermined surface roughness Ra to the dielectric resin films 3 and 4 were formed by blending silica as a filler into the resin. A solid filler made of the same kind of resin as the resin constituting the resin films 3 and 4 is blended, whereby the convex part is made of the same kind of material as the main body part other than the convex parts of the dielectric resin films 3 and 4. The If the dielectric constant and / or volume resistivity of the filler is made close to the dielectric constant and volume resistivity of the resin constituting the dielectric resin films 3 and 4, it is possible to suppress a decrease in dielectric breakdown strength.

As a method for imparting a predetermined surface roughness Ra to the dielectric resin films 3 and 4, there are the following methods.

First, there is a method of imparting a predetermined surface roughness Ra by pressing a base material having irregularities on the surface against the resin films to be the dielectric resin films 3 and 4.

Secondly, there is a method of obtaining dielectric resin films 3 and 4 having a predetermined surface roughness Ra by applying an uncured resin solution to a substrate having irregularities formed on the surface. Here, for example, a carrier film having irregularities formed on the surface, a coating drum having irregularities formed on the surface, or the like can be used as the substrate.

Thirdly, by preparing a dielectric resin film having a smooth surface, preparing a resin solution of the same type as the resin constituting the dielectric resin film, and spraying the resin solution on the dielectric resin film There is a method for obtaining dielectric resin films 3 and 4 having a predetermined surface roughness Ra.

The first and second counter electrodes 5 and 6 formed on the first and second dielectric resin films 3 and 4, respectively, are changed to patterns as shown in FIGS. 3A and 3B, respectively. Also good. FIGS. 3A and 3B are views for explaining a film capacitor according to a second embodiment of the present invention, in which the first and second dielectric resin films 3 and 4 are developed and shown. is there.

As shown in FIG. 3A, the first counter electrode 5a includes a main body portion 10 divided into a plurality of portions distributed in the length direction of the first dielectric resin film 3, and a first dielectric material. It has the drawer part 11 extended along the 1st side edge of the resin film 3, and each divided part of the main-body part 10 and the drawer part 11 are connected by the narrow connection part 12. FIG. On the other hand, as well shown in FIG. 3B, the second counter electrode 6a has a similar pattern, and the main body 13 divided into a plurality of portions and the first side. The second dielectric resin film 4 on the opposite side of the edge has a lead portion 14 extending along the second side edge, and the divided portions of the main body portion 13 and the lead portion 14 are: They are connected by a narrow connecting portion 15.

According to the film capacitor including the counter electrodes 5a and 6a shown in FIG. 3, when the dielectric breakdown occurs between the counter electrodes 5a and 6a and a current exceeding the allowable value flows, the narrow width is generated by the Joule heat generated by the current. Disconnection occurs preferentially in the connecting portion 12 or 15, so that the fuse function can be made to work more reliably. Then, only the main body part 10 or 13 connected to the connection part 12 or 15 in which the disconnection has occurred stops functioning, but the other main body parts 10 and 13 continue to function thereafter.

The film capacitor according to the present invention is often put into practical use in the form of a capacitor module 20 as shown in FIG.

4, the capacitor module 20 includes three film capacitors 21, 22, and 23. In this embodiment, each of the film capacitors 21 to 23 has an elliptical or oval cross-sectional shape instead of a perfect circle. The three film capacitors 21 to 23 are arranged in parallel to each other and arranged in a row, and first and second terminal electrodes (see FIG. 5) formed on the mutually opposing end surfaces of the film capacitors 21 to 23, respectively. (Not shown) are connected to the first and second terminal conductors 24 and 25, respectively, whereby the three film capacitors 21 to 23 are connected in parallel.

The terminal conductors 24 and 25 are obtained by bending a metal plate having a predetermined shape. The first terminal conductor 24 includes a flat plate portion 26 commonly connecting the first terminal electrodes of the film capacitors 21 to 23 and two lead portions 27 drawn from the flat plate portion 26 in two opposite directions. And 28. The second terminal conductor 25 includes a flat plate portion 29 commonly connecting the second terminal electrodes of the film capacitors 21 to 23, and two lead portions 30 drawn from the flat plate portion 29 in two opposite directions. And 31. As can be seen from FIG. 4, the lead portion 27 of the first terminal conductor 24 and the lead portion 30 of the second terminal conductor 25 are located adjacent to each other, and the lead portion 28 of the first terminal conductor 24 and the second portion 28 The lead conductor 31 of the terminal conductor 25 is located adjacent to the lead conductor 31.

Since the film capacitor according to the present invention has high heat resistance as described above, the cooling mechanism can be simplified when incorporated in a power converter such as a DC-DC converter or an inverter. In addition, not only for switching elements composed of Si power semiconductors that are widely used at present, but also at temperatures exceeding 150 ° C, the maximum operating temperature generally set for Si power semiconductors. For example, the film capacitor according to the present invention can be used in combination with no problem even for a switching element made of a power semiconductor made of SiC, SiN, GaN or the like.

In order to achieve miniaturization of power converters such as inverters, it is necessary to miniaturize passive components such as inductors and capacitors. In order to realize miniaturization of passive components, it is considered that the switching frequency of power semiconductor modules will become a future trend. On the other hand, miniaturization of power conversion devices such as inverters causes an increase in power density, and the operating environment of each component becomes higher. Since the film capacitor according to the present invention has high heat resistance as described above, it can advantageously cope with downsizing of such a power converter.

FIG. 5 shows a circuit diagram of a three-phase inverter 41 as an embodiment of a power converter configured using the film capacitor according to the present invention.

The three-phase inverter 41 includes a power module 43 including three sets of six switching elements 42. The DC power supply 44 is connected to the smoothing capacitor 45 and the power module 43. Three-phase alternating current is extracted from the power module 43 and output to a load 46 such as a motor.

For example, the capacitor module 20 shown in FIG. 4 is advantageously used as the smoothing capacitor 45 described above. In this case, for example, the lead portions 28 and 31 of the capacitor module 20 are connected to the DC power supply 44, and the lead portions 27 and 30 are connected to the power module 43.

When the capacitor module 20 is incorporated in the three-phase inverter 41 so that the connection state as described above is obtained, the heat of the power module 43 is mainly transmitted to the film capacitors 21 to 23 through the terminal conductors 24 and 25. At this time, among the film capacitors 21 to 23, the film capacitor 21 is disposed at a position closest to the power module 43. Therefore, the maximum temperature of the film capacitor 21 is, for example, about 120 ° C. However, the film capacitor 21 can sufficiently withstand the temperature for a long time. Of course, the same applies to the other film capacitors 22 and 23.

The capacitor module 20 can be advantageously applied to other power converters configured by combining components including a switching element and a capacitor, such as a two-phase inverter and a DC-DC converter.

Further, depending on the application of the capacitor module 20, not only all of the film capacitors 21 to 23 reach 100 ° C. or more, but at least one of the film capacitors 21 to 23 may reach 100 ° C. or more.

Also, the temperature of 100 ° C. or higher is not limited to being applied during continuous operation, but may be applied only for a limited time such as when the system is started up or when it is shut down.

Next, experimental examples carried out to confirm the effects of the present invention will be described.

[Experimental Example 1]
At least two kinds of organic materials were mixed so that the composition shown in the column of “Film Composition” in Table 1 was obtained. In the column of “Film Composition”, “PVAA” indicates polyvinyl acetoacetal, “TDI” indicates tolylene diisocyanate, “PVP” indicates polyvinyl phenol, “TAC” indicates triacetyl cellulose, and “NDI” indicates naphthalene diisocyanate. . The “TDI prepolymer body” indicates a TMP (trimethylpropanol) adduct type TDI prepolymer body.

For example, sample 1 will be described in more detail. The PVAA resin powder was mixed and stirred in a mixed solvent of toluene and methyl ethyl ketone to prepare a solution having a PVAA resin concentration of 7% by weight. This resin solution was passed through a high-pressure disperser and filtered.

Next, the above-mentioned PVAA resin solution and a solution in which a TMP adduct type TDI prepolymer body is dissolved in ethyl acetate so as to have a concentration of 75% by weight are combined in a solid compound ratio of PVAA and TDI. The solid content concentration was adjusted and mixed so that the weight ratio of the minute became “4/6”, and the mixed resin solution was stirred so as to be homogeneous. The obtained mixed resin solution was filtered.

For other samples, the same procedure was followed to obtain a mixed resin solution, and the obtained mixed resin solution was filtered.

On the other hand, for samples 1 to 12, 14 and 15 excluding sample 13, silica (average particle diameter D50 is about 0.3 μm) was mixed with a dispersant and a dispersion medium using a ball mill to prepare a silica slurry.

Next, the silica slurry was blended in the above-mentioned mixed resin solution so as to have the amount shown in “Silica blending amount” in Table 1, and stirred to be homogeneous to obtain a mixed resin solution blended with silica. .

Next, the mixed resin solution containing the above silica was coated on a PET (polyethylene terephthalate) substrate using a coater and dried to form a film having a thickness of 4 μm.

On the other hand, as for Sample 13, no silica was blended, as can be seen from the fact that the “silica blending amount” in Table 1 is “0”. Instead, a PET base material with a surface roughness Ra of 100 nm is prepared as a carrier film, and the above-mentioned mixed resin solution is applied onto the carrier film and dried to form a film having a thickness of 4 μm. Molded.

Next, after the film was cured by heat treatment at a temperature of 180 ° C. for 1 hour, aluminum to be a counter electrode was deposited on the film surface so as to have a thickness of 20 nm, and the film was peeled off from the PET base material. A modified film was obtained.

In the column of “Surface roughness Ra” in Table 1, the surface roughness Ra of the peeled metallized film measured by a non-contact three-dimensional surface shape / roughness measuring machine (New View 2000 manufactured by Zygo) is shown. . For samples 1 to 12, 14, and 15, the surface roughness Ra of the metallized main surface side of the metallized film is shown, and for sample 13, the surface roughness of the metallized film on the PET substrate side Ra is shown.

Next, the peeled metallized film was cut with a predetermined width and then wound with a winding machine. After the obtained cylindrical wound body was pressed to have an elliptical cross section, a terminal electrode was formed by metal spraying zinc on the end face, and the film was made conductive with the counter electrode to produce a film capacitor.

Next, after attaching a terminal conductor to the terminal electrode, the wound body was resin-sealed to complete a sample for measuring electrical characteristics.

In the column of “Glass transition point” in Table 1, the glass transition point of the above-mentioned film after thermosetting, measured by DMA (dynamic viscoelasticity measuring apparatus, RSA-III manufactured by TA Instruments) is shown. . The measurement conditions are as follows: the temperature is raised from room temperature to 250 ° C. at a rate of temperature rise of 10 ° C./min, the measurement frequency is 10 rad / sec, the strain is 0.1%, and the temperature at which the loss tangent (tan δ) exhibits the maximum peak value is obtained. It was.

In addition, “the amount of thermal decomposition residue” in Table 1 indicates that only the resin component in the heat-cured film is heated to 800 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere to cause thermal decomposition, The amount of the residue at the time of 500 ° C. was measured by TG-DTA (differential thermogravimetric simultaneous measurement device).

Next, DC 1500V was applied to each sample at 125 ° C. to obtain a voltage waveform, the failure state was examined, and whether or not it had a self-healing function was evaluated. The result is shown in the column of “Self healing function” in Table 1. Here, even if the dielectric breakdown occurs and the applied voltage drops instantaneously, if it returns to the original applied voltage, it is determined that it has a self-healing function, and this is indicated by “◯” in Table 1. On the other hand, if the voltage does not recover after entering the energized state, it is determined that the self-healing function is not provided, and this is indicated by “x” in Table 1.

In Table 1, the sample number is marked with * for a sample that is a comparative example outside the scope of the present invention.

In the sample 9 as a comparative example, the “thermal decomposition residue amount” exceeded 40% by weight, and therefore the “self-healing function” was “x”.

Also, in the sample 10 as a comparative example, the “surface roughness Ra” was less than 3 nm, and thus the “self-healing function” was “x”.

Further, in the sample 15 as a comparative example, the “surface roughness Ra” exceeded 1000 nm. For this reason, the gap between the films of the wound body became too large, and the capacitance was lowered. In addition, the dielectric loss becomes too large, and the electrical characteristics as a capacitor are deteriorated.

On the other hand, Sample 1 having a “thermal decomposition residue amount” of 40% by weight or less, a “surface roughness Ra” of 3 nm or more and 1000 nm or less, and a “glass transition point” of 130 ° C. or more. According to -8 and 11-14, the “self-healing function” was “◯”.

[Experiment 2]
In Experimental Example 2, among the samples prepared in Experimental Example 1, the film capacitor according to Sample 1 was evaluated for reliability in a high temperature state, in particular, the state of capacity reduction.

More specifically, a DC voltage of 760 V was applied to the film capacitor according to sample 1 at a temperature of 125 ° C. in the atmosphere, and the wear state of the capacitor element (capacity reduction state) was evaluated. The result is shown in FIG.

As can be seen from FIG. 6, even after 1500 hours from the start of the test, the capacity decrease was only about 2%. It is determined that this is not a fault condition within an allowable range for the film capacitor.

On the other hand, when a film capacitor using PP (polypropylene) was tested in the same manner, destruction occurred immediately after the start of the test, and the capacity instantaneously became −100%. This is presumably because the PP film could not withstand a temperature of 125 ° C. as a material property.

[Experiment 3]
In Experimental Example 3, a capacitor module as shown in FIG. 4 was manufactured using the three film capacitors according to Sample 1 manufactured in Experimental Example 1. Then, using this capacitor module as a smoothing capacitor, a three-phase inverter as shown in FIG. 5 was constructed, and the heat resistance of the film capacitor was evaluated. In the capacitor module, the terminal conductor was made of copper.

First, the electrical characteristics of the film capacitor used were as shown in FIG. FIG. 7 shows the impedance (| Z |) -frequency characteristic and the equivalent series resistance (ESR) -frequency characteristic of the film capacitor.

Next, the temperature of each part of the capacitor module as a smoothing capacitor when the three-phase inverter as shown in FIG. 5 was configured and operated was measured. The result is entered in FIG. FIG. 8 corresponds to FIG. 4, and the reference numerals shown in FIG. 4 are also displayed in FIG. Referring to FIG. 8, the lead portions 28 and 31 of the capacitor module 20 are connected to the DC power supply 44, and the lead portions 27 and 30 are connected to the power module 43. Therefore, as shown in FIG. 8, the temperature of the drawer portions 27 and 30 reached 151 ° C., and the film capacitor 21 closest to the power module 43 reached 121 ° C.

In order to evaluate the electrical characteristics of the capacitor module 20 under the high temperature conditions as described above, the capacitor module 20 was installed in a thermostat set at 125 ° C., and the electrical characteristics were measured. FIG. 9 shows impedance-frequency characteristics, and FIG. 10 shows equivalent series resistance-frequency characteristics. As can be seen from FIGS. 9 and 10, not only the switching frequency range of several kHz to several tens of kilohertz used in the power semiconductor module composed of Si, but also power composed of SiC, SiN, etc. It was confirmed that good impedance characteristics and ESR characteristics can be obtained even in the switching frequency range of several tens kHz to several tens kHz used in semiconductor modules.

1, 21 to 23 Film capacitor 3, 4 Dielectric resin film 5, 6, 5a, 6a Counter electrode 7, 8 Terminal electrode 9 Winding body 20 Capacitor module 24, 25 Terminal conductor 41 Three-phase inverter 42 Switching element 43 Power module 44 DC power supply 45 Smoothing capacitor 46 Load

Claims (6)

1. Dielectric resin films in a form of overlapping each other;
   First and second opposing electrodes arranged to face each other across the dielectric resin film;
   First and second terminal electrodes electrically connected to the first and second counter electrodes, respectively,
   The dielectric resin film has a surface roughness Ra of at least one main surface of 3 nm or more and 1000 nm or less, and is composed of a thermosetting resin having a glass transition point of 130 ° C. or more as a resin component. A film capacitor having a pyrolysis residue weight of not more than 40% by weight at 500 ° C. when the rate of change in thermogravimetricity is measured in nitrogen at a heating rate of 10 ° C./min.
2. The dielectric resin film is wound to form a wound body, the first and second counter electrodes are disposed inside the wound body, and the first and second terminal electrodes are The film capacitor according to claim 1, wherein the film capacitor is formed on each end face of the wound body.
3. The film capacitor according to claim 1 or 2, wherein the dielectric resin film includes a resin component obtained by mixing two or more organic materials and cross-linking them.
4. 4. The film capacitor according to claim 1, wherein the convex portion that gives the surface roughness of the dielectric resin film is made of the same resin component as the main body portion other than the convex portion of the dielectric resin film. 5. .
5. A capacitor module comprising a plurality of film capacitors according to any one of claims 1 to 4 and a terminal conductor connected to the terminal electrode of the film capacitor.
6. A power conversion device comprising the film capacitor according to any one of claims 1 to 4 and a switching element, wherein the maximum temperature reached by the film capacitor during operation is set to be 100 ° C or higher.

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