JPH0213807B2 - - Google Patents

Description

[Detailed description of the invention]

Currently, capacitors commonly used include metallized paper deposited with zinc or aluminum and non-deposited polyethylene terephthalate film (hereinafter referred to as
Capacitor elements were made by winding thin dielectric materials such as PET film (hereinafter referred to as PET film) or polypropylene film (hereinafter referred to as PP film), which were impregnated with synthetic insulating oil such as polybutene or alkylbenzene. The insulating oil, paper, and film used are flammable substances and have a low flash point, so there is a significant risk of a fire if a problem occurs in the capacitor. In addition, for the purpose of flame retardancy, we added an impregnating agent called polydimethylsiloxane (hereinafter referred to as silicone oil) to capacitors that use conventional thin dielectric materials made of paper and plastic film.
Even when the oil was changed to , the withstand voltage performance was significantly lower than that of conventionally used synthetic insulating oils such as polybutene and alkylbenzene, which had the major drawback of deteriorating quality. Therefore, in view of the above points, the present inventors have developed a method for impregnating a capacitor with a flame-retardant silicone oil having a high flash point to make the capacitor flame-retardant and maintain its electrical characteristics. As a result of repeated experiments on the configuration of various thin dielectrics, electrode margin widths, and voltage resistance, we found that voltage resistance and reliability were significantly improved. That is, the metallized plastic film capacitor is characterized in that a capacitor element is formed by overlapping and winding a metallized polyethylene terephthalate film and a plurality of polyethylene terephthalate films, and the element is impregnated with silicone oil. In this case, the optimum viscosity of the silicone oil is in the range of 50 to 300 cSt (at a temperature of 25°C). Compared to other general mineral insulating oils and synthetic insulating oils, silicone oil has very little viscosity change due to temperature.
Other electrical properties also show consistent performance over a wide temperature range. However, when the viscosity is 50 cSt or more, it has a high flash point of 300°C or more, and when it exceeds 300 cSt, the impregnating property becomes poor. Furthermore, the metallized polyethylene terephthalate film capacitor is characterized in that the ratio between the rated voltage and the electrode margin width is within the range of 0.2 to 0.4 KVDC/mm. The present invention will be described in further detail below. Table 1 shows typical insulation oil properties for polybutene, alkylbenzene and silicone oils. The dielectric breakdown voltage value, which is particularly noteworthy, also showed no significant difference.

[Table] However, compared to conventional polybutene (symbol c in the figure) and alkylbenzene (symbol b in the figure), in terms of the breakdown number-breakdown voltage characteristics shown in Figure 1,
In the case of silicone oil (symbol a in the figure), the breakdown voltage value decreases significantly with each repetition. Also the second
According to the hydrogen gas absorption characteristic diagram shown in the figure using the insulation committee test method (50℃, 8KV, _H2 gas), conventional polybutene (symbol c in the figure) and alkylbenzene (symbol b in the figure) are gas absorption types. On the other hand, silicone oil (symbol a in the figure) is a gas-generating type. Therefore, due to silicone oil's lower withstand voltage performance and hydrogen gas absorption properties compared to conventionally used polybutenes and alkylbenzenes, the quality of silicone oil-impregnated capacitors will be lower than conventional products if no measures are taken. This will result in a significant decline. 3A and 3B are arrangement diagrams of the thin dielectric material of the capacitor, where 1 is the metallized thin dielectric material, 2 is the non-evaporated thin dielectric material, 3 is the electrode margin portion, and 4 is the metallicon portion. Table 2 shows the flash point and viscosity of silicone oil.
JIS C 2321 nonflammable insulating oil flammability test results are shown below.

[Table] When silicone oils are tested using this method, low-flammability silicone oils will burn, but oils with a viscosity of 50 cSt or higher will not start burning immediately. Therefore the viscosity
It can be said that all oils other than 50 cSt or less are fairly flame retardant. Further, there is a close relationship between the impregnating property of the capacitor and the viscosity of the insulating oil used, and the lower the viscosity, the better the impregnating property. Therefore, the above capacitor has a viscosity of 50, 200, 300,
Impregnating with 500 cSt silicone oil under the same processing conditions as conventional insulating oil, decomposing samples of each viscosity,
A visual inspection was conducted. When the viscosity reached approximately 50-200-300 cSt by visual judgment, sufficient infiltration of silicone oil was observed, indicating good impregnating properties. However, in the case of a viscosity of 500 cSt, although infiltration was observed at the end face of the element, there was insufficient wetting between the thin dielectric layers. In addition, in considering the viscosity characteristics of conventional polybutene and alkylbenzene insulating oils, when adopting silicone oil, a viscosity of 50 cSt to 300 cSt is optimal (at a temperature of 25°C) in terms of flame retardancy, impregnability, and compatibility with manufacturing equipment conditions. It is judged that. Table 3 shows the conditions and test results for manufacturing metallized film capacitors using the thin dielectric arrangement shown in Figure 3 and varying the ratio of insulating oil, thin dielectric material, and rated voltage to electrode margin width. .

[Table] The rated capacitance of the samples in Table 3 is 8 μF, and 20 samples were manufactured for each sample. Among sample group symbols, symbol A
and E are samples according to the present invention, with symbols B, C,
D, F and G are samples for comparison. In addition, MPET described in the thin dielectric column indicates metalized polyethylene terephthalate, PET indicates polyethylene terephthalate, MP indicates metalized capacitor paper, and CP indicates capacitor paper. Figure 4 shows the ratio of the DC corona initiation (annihilation) voltage to the electrode margin width (KVDC/mm) measured by changing the temperature range of the above sample.
Comparing sample groups B and F or sample groups A and G, by changing the insulating oil to silicone oil,
At the DC corona onset voltage (hereinafter referred to as DC-CSV) [or DC corona extinction voltage (hereinafter referred to as DC-CCV)] per 1 mm electrode margin width, sample group B
is reduced to nearly 60% compared to sample group F. Moreover, sample group A shows a result that is several percent lower than sample group G. On the other hand, sample group A according to the present invention, which was constructed using MPET film and PET film and impregnated with silicone oil, exhibited superior properties equivalent to or better than sample group F, which corresponds to conventional products. Ta. Also, when comparing sample groups B and D, by increasing the number of thin dielectric layers,
DC-CSV, (or DC-CCV) has been improved. Figure 5 shows the rated voltage per 1 mm electrode margin width (KVDC/mm) and the DC-CSV against the rated voltage.
(or DC-CCV) voltage ratio. In the figure, curve d is a thin dielectric material impregnated with silicone oil in the same manner as in FIG. Increasing the electrode margin width leads to an improvement in DC-CSV or DC-CCV, but when considering manufacturing conditions, durability, and economic efficiency, the ratio of rated voltage to electrode margin width is 0.2 to 0.4 KVDC/ The optimum configuration is within the mm range. In order to confirm this reliability life, a DC VT test was conducted and the results are shown in FIG. When comparing sample groups B and F, sample B impregnated with silicone oil has a slightly shorter lifespan. This can be assumed to be due to the amount of DC corona and the durability of the paper dielectric. However, it was demonstrated that the sample group A according to the present invention described above exhibits extremely superior durability compared to the conventional product (sample group F). Moreover, the present invention shows good durability with no major difference from Sample Group G using alkylbenzene, which is a conventional insulating oil, and has superior quality and reliability in addition to being flame retardant compared to conventional products. It has now become possible to manufacture a capacitor that has both of these functions. As mentioned above, the metallized film capacitor of the present invention can achieve flame retardancy, which has been strongly required since the ban on the use of PCB oil, contribute to the safety of capacitors, and have industrial and practical value. It is a big thing.

[Brief explanation of drawings]

Figure 1 is a breakdown voltage characteristic diagram of various insulating oils, Figure 2 is a gas absorption characteristic diagram of the same insulating oils, Figure 3 A and B are layout diagrams of thin dielectrics in metallized film capacitors, and Figure 4 is DC corona starting voltage-temperature characteristic diagram,
Figure 5 is a DC corona starting voltage vs. rated voltage characteristic diagram.
FIG. 6 is a DC VT test characteristic diagram. 1: metallized thin dielectric, 2: non-evaporated thin dielectric, 3: electrode margin.

Claims (1)

[Claims] 1. A capacitor element is formed by overlapping and winding a metalized polyethylene terephthalate film and a plurality of polyethylene terephthalate films,
A metallized plastic film capacitor characterized in that the element is impregnated with polydimethylsiloxane. 2 The viscosity of the above polydimethylsiloxane is
A metallized plastic film capacitor according to claim 1, characterized in that the metallized plastic film capacitor has a temperature of 50 to 300 cSt at ℃. 3. Claim 1 or 2, characterized in that the ratio of the rated voltage to the electrode margin width of the metallized polyethylene terephthalate film capacitor is within the range of 0.2 to 0.4 KVDC/mm. metallized plastic film capacitor.