Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
1999-04-02
2001-07-03
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S328000, C361S517000, C361S535000
Reexamination Certificate
active
06256188
ABSTRACT:
The present invention relates to a power capacitor comprising at least one capacitor unit, each capacitor unit comprising at least one winding, having at least two foils of insulating material.
Power capacitors are for example known from the French patent No 2.598.024. The casing surrounds one or more capacitor units and each unit comprises at least one winding, having at least two foils made of insulating material. For the known capacitor, the casing is made of plastic material. However casings made by pressing of aluminum or steel are also known.
A drawback of the steel casings, made by pressing, is that the cutting, folding, assembling, welding and painting of them is a work which takes a lot of time and makes such a manufacturing expensive. Moreover when the casing is manufactured, it is also difficult for integrating therein fixing points, to enable fixing the capacitor components. Moreover, those casings also form a burden for the environment, because their recycling is not obvious. On the other hand, casings made of plastic material are more easy to recycle, but their resistance to high temperature fluctuations is poor and they do not enable a good thermal exchange because the used plastic material is a bad thermal conductor. The casings made by pressing of aluminum are poorly resistant from a mechanical point of view due to their thin walls.
It is an object of the invention to present a power capacitor, having a casing manufactured according to a different manner, which is easier and cheaper to manufacture and which enables a better thermal exchange and resistance.
To that purpose a power capacitor according to the invention is characterized in that the capacitor unit(s) is (are) housed in a casing of which at least the body is made of extruded aluminum, which body surrounds a (the) capacitor unit(s). Extruded aluminum offers the advantage to present a casing which is highly mechanically resistant, even more resistant than pressed steel. Moreover extruded aluminum is easy and cheap to manufacture and it has a good resistance to corrosion without having to apply a paint layer thereon. Its thermal properties are also excellent.
It should be noted that the use of extruded aluminum to fix thereon a capacitor is described in article IBM Technical Disclosure Bulletin vol. 25 n° 7a December 1992, US p. 3419 and called “Technique for mounting bulky discrete components on printed circuit boards”.
However that article does not concern power capacitors. Moreover those capacitors are not cased but simply fixed to a support, made of extruded aluminum. That document therefore does not teach the use of extruded aluminum as casing for storing therein windings of a capacitor, but is limited to a fixing element for fixing a capacitor, which itself is housed in a conventional housing.
The document “Patents abstracts of Japan vol. 15 n° 383 (E-1116)” of Dec. 27, 1991, also describes a casing in extruded aluminum, but does not specify that it is the windings of a power capacitor which are housed in that casing.
A first preferred embodiment of a power capacitor according to the invention is characterized in that said casing is provided with cooling wings obtained upon extruding of the casing. The cooling wings can easily be formed during the extrusion process and they contribute to the good thermal exchange of the casing.
A second preferred embodiment of a power capacitor according to the invention is characterized in that said casing is galvanized. Galvanization of the casing makes the latter more resistant to corrosion and enables to give a more esthetical aspect to the casing.
A third preferred embodiment of a power capacitor according to the invention is characterized in that at least one internal side of the casing is provided with fixing grooves, for fixing capacitor components. Those fixing grooves can be easily integrated during the extrusion itself.
A fourth preferred embodiment of a power capacitor according to the invention is characterized in that at least one internal side of the casing is provided with an earth groove, of which the internal wall is provided with screw thread for applying a screw. This is particularly advantageous for making an earth connection.
Preferably at least one external side of the casing is provided with at least one slide rail. In such a manner several casings can be connected together.
REFERENCES:
patent: Re. 28015 (1974-05-01), Vermilyea et al.
patent: 2535945 (1950-12-01), Menschik et al.
patent: 3321677 (1967-05-01), Mandelcorn et al.
patent: 3331993 (1967-07-01), Brown et al.
patent: 5306887 (1994-04-01), Smith
patent: 002028855 (1982-12-01), None
patent: 03154398 (1991-02-01), None
Bonhomme Henri
Lovkvist Thomas
Monni Cipriano
Asea Brown Boveri Jumet S.A. (ABB)
Dinkins Anthony
Jacobson & Holman PLLC
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