DE2108988A1 - Process for the manufacture of electrolytic capacitors - Google Patents

Description

February 22, 1971

Attachment to
Patent application

EOBERT BOSCH GMBH, 7 Stuttgart (Germany) Process for the production of electrical capacitors

The invention has a method of making electrical Capacitors on the subject with a dielectric made of at least a paper tape impregnated with an additional dielectric and of at least one plastic strip that shrinks under the action of heat and / or swells under the action of the impregnating agent. The capacitor coverings can consist of vapor-deposited, burn-out metal layers or of metal foils.

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l \ UötJöö - 2 -

Robert Bosch GmbH E. 235

Stuttgart

It is known in such capacitors, the cavities in the paper and the gaps between the paper and plastic layers after winding or layering the capacitor elements and after prior drying and degassing with an impregnating agent to be filled in to increase the dielectric strength of the paper and to avoid electrical discharges in columns and To prevent cavities in the capacitor elements.

The condenser elements are dried and degassed in a vacuum ( <10 "Torr) carried out at temperatures of about 100-135 ° ^ · Gases and vapors occur essentially in parallel to the surfaces of the insulating strips and capacitor coverings from the capacitor elements, i.e. in the same way which the impregnating agent must penetrate into the gaps and cavities between the layers of the capacitor elements.

This penetration of the impregnating agent can be made more difficult or even prevented by the fact that there are in the capacitor element Plastic straps at the drying temperature increased to 100 - 135 ° ^ shrink in their longitudinal direction, thereby narrowing the gap between the plastic and paper layers in the capacitor element and both the escape of gases and vapors and the penetration of the impregnating agent are made more difficult. Additional to that, that when the plastic film comes into contact with an impregnating agent which causes the film to swell from its edge, another Narrowing of the gap at the end faces of the capacitor elements occurs, which long before the impregnation becomes a tight one Completion of the gaps and spaces between the layers of the Capacitor elements can lead. Measures that can prevent this, such as cooling down the capacitor elements and the Impregnating agent to a temperature at which the swelling of the plastic takes place slowly enough, and the layering of the condenser bands at lower than usual contact pressure, are time consuming and costly and not always applicable.

209838/0213 - 3 -

210898b - 3 -

Robert Bosch GMBH . R. 235

Stuttgart

Another way - the action of heat and impregnating agent on shrinkable and swellable plastic tapes and impregnated To avoid paper tapes containing capacitor elements is, according to a new method, that according to the invention the paper strips to be worked into the capacitor elements are impregnated before the capacitor elements are layered or wound will. This pre-impregnation can be carried out on metallized or metal-free, and on wound or unwound paper tapes.

The layering or winding of capacitor elements made from pre-impregnated Paper and swellable plastic tapes are then applied with the highest possible contact pressure. This will complete the filling of cavities still present inside the capacitor elements by excess impregnating agent from the pre-impregnated Paper and favored by swollen plastic film. After this In layers or coils, the capacitor elements are heated in a vacuum to remove any gas inclusions before they are closed remove the gaps and cavities and, if swellable foils are used, carry out the swelling. Used for pre-impregnation of the paper an impregnation agent (hard wax) which is solid at room temperature is used, it may be useful to add the layered or wound capacitor elements with an impregnating agent (mineral oil) that is liquid at room temperature re-impregnate in a vacuum and the heating of the capacitor elements to be carried out only after re-impregnation. For the tempering of the completely impregnated capacitor elements is one temperature above their later operating temperature. ■.

Comparative tests were carried out with 60 mm wide capacitor windings, which consist of two 8 Ai thick, zinc-vaporized paper mandrels and 6 Ai lying between the paper tapes

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BATH

Robert Bosch GmbH R. 235

Stuttgart

thick "polypropylene tape and a diameter of 30 mm.

Such capacitor winding impregnated in hergebrachter V / ice and after erfindungsgenäßen method hard wax (dropping point 95 ° C) and with a petroleum jelly (dropping point 52 ⁰ C) re-impregnated.

To carry out the method according to the invention, the metallized Pspier tapes were first wound individually on rolls, dried in a known manner and impregnated at II5 C with hard wax. After they had cooled down, they were pre-impregnated Paper ribbons processed on a conventional capacitor winding machine together with polypropylene ribbons to form capacitor windings and contact bridges are sprayed onto their end faces using the Schoop metal spraying process. After spraying the capacitor bridge was a part of the capacitor winding at 105 ° C for 24 hours in a vacuum and another part for 15 hours tempered in circulating air.

Another group of capacitor coils were produced from similar metallized, but not pre-impregnated paper tapes and polypropylene tapes and dried by known methods and impregnated with the same impregnating agents. The impregnation of the capacitor winding with hard wax (dropping point 95 ° ^C), for example, after 24 hours of drying and degassing of the winding in a vacuum (<_ 10 "Torr) at 115 ° C, carried out and the post-impregnation with vaseline at 70 ⁰ C.

When measuring the dielectric strength (dss is that ' Voltage at which self-healing drifts in the capacitor windings occur) of the two groups of capacitor windings treated differently, it was found that the dielectric strength of the

209838/0213 - 5 -

Robert Bosch GmbH R. 235

Stuttgart

impregnated metallized paper tapes and polypropylene tapes The capacitor winding produced is more than twice as large as the dielectric strength of the capacitor windings made from non-pre-impregnated paper tapes.

An examination of the capacitor waves carried out after the measurement showed that the conventionally treated capacitor windings only in the area of their end faces up to approx / a 20% of their volume were completely impregnated and therefore had a large number of breakdowns inside, while the Capacitor windings with pre-impregnated paper tapes only a small number, evenly distributed over the entire Vickel width Breakthroughs was found.

The method described is suitable not only for the production of capacitors, but also for the production of insulation for other electrical purposes.

209 8 38/0213

BAD OBtGINAL

Claims (4)

Robert Bosch GmbH R. 235 Ba / Kf Stuttgart February 22, 1971 Expectations Process for the production of electrical capacitors, the at least one impregnated with an impregnating agent Paper layer and at least one layer of one which shrinks under the action of heat and / or under the action of the impregnating agent contain swelling plastic, characterized in that the impregnation of the paper before Layering of the capacitor elements takes place and that this may be carried out under vacuum after the layering Subject to heat treatment, which causes the shrinkage and / or swelling processes in the plastic layers. 2. The method according to claim 1, characterized in that the stratification takes place by winding up ribbons. 3. Method according to claim 1 or 2, characterized in that the paper is in the form of loosely wound tapes is impregnated. 4. Process according to Claims 1 to 3, characterized in that that it is used to produce insulation against electrical voltages. 209838/0213. BAD ORKSiNAi <r