Electricity: electrical systems and devices – Electrolytic systems or devices – Liquid electrolytic capacitor
Reexamination Certificate
1999-12-20
2001-10-02
Reichard, Dean A. (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Liquid electrolytic capacitor
C361S518000, C361S511000
Reexamination Certificate
active
06297944
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a capacitor assembly having an aluminum electrolytic capacitor which is installed in a casing that is closed by a cover disc, and two metallic connecting elements disposed in the cover disc for capacitor connections.
Such a capacitor assembly is known, for example, from the Siemens Matsushita Components Datenbuch 1997 “Aluminum Electrolytic Capacitors”, pages 62-68.
There, the connecting elements have an internal thread, with conductors or busbars preferably being attached through the use of screws or threaded pins. In that case the connecting element on the anode side in the cover disc is composed of pure aluminum (Al 99.5 and purer), since it is wetted with electrolyte in the interior of the capacitor and a blocking oxide layer must be formed. The low strength of the soft, pure aluminum only permits low tightening torques when the electrical connections are attached, often leading to the thread being damaged during the fitting process. Furthermore, it is also quite common for connections to become loose again when stressed mechanically, resulting in poor contact.
In addition to the difficulties described above, the length tolerance of the components is a major problem when interconnecting a plurality of capacitors to form capacitor banks. On one hand, in order to dissipate the heat losses well, the base of the capacitor cup should be pressed firmly against the mounting plate. On the other hand, due to the increasing current load, the elements used for interconnection are becoming ever more solid and less flexible. That necessitates special length compensating elements, or interconnecting elements having a complex construction. The boards used for interconnection are generally seated on the upper level of the screw connections, which leads to increased inductance between the screw connections of the connecting elements.
Although it is possible to overcome the problem of low tightening strengths by using larger connecting threads, that in turn results in considerably greater costs for the cover disc. Length compensation through the use of compensating elements or through the use of more or less flexible connecting elements generally leads to unsatisfactory compromises with respect to heat dissipation and inductance, so that the structural configuration options for interconnection are highly constrained.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a capacitor assembly having an aluminum electrolytic capacitor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type so as to ensure problem-free attachment while at the same time compensating for length tolerance of components and ensuring that inductance is as low as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a capacitor assembly, comprising a casing having a cover disc closing the casing; an aluminum electrolytic capacitor installed in the casing; two solid, metallic connecting elements disposed in the cover disc for capacitor connections; external connections; and a radially acting clamping connection connecting the connecting elements to the external connections.
In accordance with another feature of the invention, the external connections are formed by a sandwich board for connecting the capacitor to a plurality of other aluminum electrolytic capacitors to form a capacitor bank.
In accordance with a further feature of the invention, the connecting elements have a round cross section.
In accordance with an added feature of the invention, the connecting elements have a cross section with surfaces.
In accordance with a concomitant feature of the invention, the connecting elements have a quadrilateral or hexagonal cross section with surfaces.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a capacitor assembly having an aluminum electrolytic capacitor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 2623101 (1952-12-01), Kurland et al.
patent: 3091656 (1963-05-01), Lamoureaux, Jr.
patent: 3976922 (1976-08-01), Peck et al.
patent: 4131935 (1978-12-01), Clement
patent: 4514788 (1985-04-01), Klaschka et al.
patent: 5579203 (1996-11-01), Klaschka
patent: 5706166 (1998-01-01), Schweikert et al.
Epcos AG
Greenberg Laurence A.
Lerner Herbert L.
Reichard Dean A.
Stemeer Werner H.
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