FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF INVENTION
A method to improve impregnation of films in the development all film CVT
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Ramakichenan Vaithiyanathan, of Product Technology Centre, CG Global R&D Centre, Crompton Greaves Limited, Kanjur (E), Mumbai 400042, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention

The invention relates to a method to improve impregnation of films in the development all film CVT
Impregnation of all film capacitor elements with oil is not uniform due to different behavior of film and oil interaction during rise and fall in temperature and this non¬uniform impregnation of oil give rise to electrical breakdown of elements at operating condition. In order to ease the impregnation of oil between foil and film and between films, a method is proposed which enhances the oil presence between films and film and foil under various temperature conditions. The prior art Patent US20080151471 discloses the concept of using foils (with no folding at edges) separated with a gap meant for formation of sub-capacitors to increase the voltage level at smaller capacitance value. The comparison of aspects in the prior art with those indicated in the proposed methods indicates that there is pin holes in the film strip due to manufacturing defects which causes breakdown and hence two films are used in the prior art as compared to holes are made in the film at the center of the films in case of proposed invention to enhance oil flow between foil and films and between films and the conducting strips overlap in the prior art and does not in the proposed invention and finally the conducting strips/foils provide sub-capacitors in series in the prior art while the arrangement (film or strips with folded edges) is in parallel in case of proposed invention. Another prior art US4323948 discloses the concept of folded edge foils having advantages in terms of reducing partial discharges and electrical stresses overall and those foils are made narrow and wide to relieve the stress and improve breakdown voltage wherein a high dielectric constant and low resistively insulation materials are provided near the narrow electrode foil and vice
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versa near the wide electrode foil. But in the proposed invention, the folded edge foils are provided to enhance oil flow into the film and foil region and those foil are of equal size against unequal electrode foils mentioned in the prior art. The reference 'Dielectric performances of SF6 impregnated polypropylene film capacitor' ma sen , zhang deshun , li yi department of electric wateriats harbin institude of electrical technology harbin , china, CH2587-4/88/0000-8 1988 IEEE discloses the concept of folded edge foils having advantages in terms of reducing partial discharges and electrical stresses overall and evaluated the performances under SF6 medium. But in the proposed invention, the folded edge foils are provided to increase the space between film and foil and enhance oil flow into the film and foil region.
It is an object of the invention to provide capacitor elements made of dielectric layers and electrode foils and the electrode foils are made of strips of conducting foils over the surface of dielectric layers separated with a gaps between them and all the conducting foil strips are to be connected in parallel which are sandwiched between the dielectrics layers.
It is an object of the invention to provide pin-holes at the centre of the film layers or solid dielectric materials in between the gaps of conducting foil strips.
It is an object of the invention to provide folded edge foil and a mat surface on the folded edge side of the conducting strips.
Another object of the invention is to provide a roughened surface film layers.
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A method to improve impregnation of films in the development of all film CVT s for capacitor elements comprises plurality of folded edge conducting foil strips seperated with gaps and the said folded edge conducting foils strips are connected in parallel to form an electrode terminal of a capacitor element and a similar electrode arrangements are used for the construction of capacitor elements. A plurality of dielectric layers are sandwitched between the said electrode arrangements consists of plurality of insulating films impregnated with oil and the said plurality of films are provided with plurality of perforated holes at the centre of the films at regular intervals.
According to Invention, said plurality of folded edge conducting foils strips are seperated with gaps are meant to prevent sagging due to self weight of other CVT capacitor elements.
According to Invention, said plurality of folded edge conducting foils strips are seperated with gaps to provide path for flow of oil between film and foil and in between films so as to improve impregnation.
According to Invention, said plurality of folded edge conducting foils strips are having mat surface towards the folded edge sides to enhance and retain oil presence during rise and fall in temperature during operating condition.
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According to Invention, said plurality of folded edge conducting foil strips seperated with gaps are connected in parallel.
According to Invention, said plurality of folded edge conducting foil strips forms an electrode arrangement for the construction of capacitor elements.
According to Invention, plurality of dielectric layers is sandwiched between the said electrode arrangements.
According to Invention, plurality of dielectric layers consists of plurality of insulating films impregnated with oil and the said plurality of films are provided with plurality of perforated holes which are located anywhere under the gaps of the folded edge conducting foil strips. This is provided to enhance oil flow between films.
According to Invention, said plurality of films are provided with plurality of perforated holes anywere in the films under the gaps of the folded edge conducting foil strips and almost two film layers of the total dielectric layers between the electrodes should not have any perforated holes. This is to avoid direct breakdown of the oil gaps.
According to Invention, said plurality of film are having roughened surface on both sides to improve impregnation of oil.
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Impregnation of film with the oil is one of the problems in the development of all film cvt. Therefore this invention gives an arrangement of film-foil that will improve the film impregnation. The element of all film cvt contains a plain foil and plain double side roughened film and this is impregnated with oil. Instead of a plain foil, a folded edges foil can improve the flow of oil into the film surface. But the presence of folded edges on the two sides of the foil gives tension to the edges of the film when it is pressed and a sagging of the film exists at the center of the element. In order to avoid sagging and equalize the tension along the film, the same foil is divided into two parts having folded edges and placed on the film with a distance apart. Therefore equal pressure along the film is established and the sagging of film is minimized. This will enhance the presence of oil between foil and film In order to enhance the presence of oil uniformly between the two films, the center of the film is pinned at regular intervals. Because the foils are kept a distance apart, some small portion of the film is left unused. Therefore the pinning of film does not create any problem due to electric stress between the foil. If any electrical problem exists due to the presence of small holes in the center of the film then only one of the two films can have pinned holes. The other benefits are its effective inductance will further come down, increases corona inception voltage and easy to implement right away.
The invention is described in detail herein, plurality of strips of conducting foil seperated with gaps and is having folded edges placed on the dielectric layers on opposite sides and are sandwiched between the dielectric layers. The plurality of dielectric layers made of plurality of films are having a plurality of perforated holes at the centre of the films at
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regular intervals and that exists under the gaps of conducting foil strips for flow of oil between films via holes made in the film and the gaps of conducting foil strips. The provision of folded edges of all the conducting strips give rise to a space between foil and film to improve oil flow and to retain oil between film and foil during rise and fall of temperature. The provision of folded edges also helps to maintain an even mechanical support along the width of the capacitor elements and hence sagging of element structure due to self weight of the other elements is prevented.