Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
1999-12-29
2002-06-18
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S09900B, C174S14900R, C174S168000, C361S612000
Reexamination Certificate
active
06407336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for carrying high currents at a low inductance, in particular for a power converter or the like, with two flat electrical conductors that are spaced apart, roughly parallel to each other and insulated from each other.
2. Background of the Related Art
Such devices are known as bus bar packets and are used to set up inverters with quick-switching power semiconductors. Known bus bar packets have a laminated structure including two copper plates that act as conductors, sandwiched around a plate of film made out of a solid-state insulator. Because the distance between the copper plates is slight, the bus bar packets are suitable for conducting high currents at a low inductance. The solid-state insulator arranged between the copper plates achieves the required dielectric strength of the bus bar packets, e.g., 1 kV.
Due to partial discharges between the copper plates, the solid-state insulator sandwiched between them is subject to aging which diminishes the insulator's dielectric strength. In general, attempts to mitigate this shortcoming by using better and better insulating materials have been made; however, an alternative method of avoiding such aging effects is needed.
SUMMARY OF THE INVENTION
In view of the above problems of the prior art, an object of the present invention is to provide a device for carrying high currents at a low inductance which has a dielectric strength as independent as possible of aging phenomena.
The invention advantageously achieves this object by virtue of the fact that the space between the two conductors has no transition from one of the two conductors to a solid-state insulator, and from there to the other of the two conductors.
According to a first aspect of the present invention, there is no solid-state insulator between the conductors. As a result, no aging phenomena caused by partial discharges can arise in the solid-state insulator. Therefore, a reduction in dielectric strength due to such aging phenomena is also not possible. According to this aspect, the dielectric strength between the conductors is essentially independent of the aging of the materials used. The significant advantage in this is that the device remains finctionally reliable over a longer period of time. Another advantage of this aspect of the invention is that the absence of any solid-state insulator makes it possible to apply significantly higher voltages between the two conductors without this impairing the functional capacity of the device.
It is particularly advantageous for the space between the conductors to contain a non-solid, insulating medium, preferably air. If partial discharges now take place between the conductors of the device, they will not result in damage to the non-solid, insulating medium sandwiched in between them. At the same time, however, the insulating medium achieves the required insulation between the two conductors in a simple manner.
In particular, the use of air as an insulator brings with it the significant advantage that a high dielectric strength can be reached via the appropriate selection of distance between the two conductors on the one hand, and that the outlay and resultant costs for this device are especially low on the other.
According to another aspect of the present invention, the space between the two conductors is formed by the conductor surfaces created by the two conductors, and by the connecting surfaces created between the edges of the two conductors. This ensures that the area impacted by the voltage present between the two conductors contains no material from a solid-state insulator. Instead, this area preferably contains only air. Therefore, no aging phenomena in insulating materials can arise in this endangered area, which produces the already-mentioned advantages.
According to a further aspect of the present invention, the two conductors are held in a mount on their surfaces facing away from each other. Therefore, the mounts are not present in the aforementioned endangered area. As a result, the mounts, which preferably consist of an insulating material, are not subjected to any aging due to partial discharges. The mounts hence exhibit a guaranteed functional reliability over a long period of time to go along with the already-mentioned advantages.
In a further aspect of the present invention, the two conductors are linked together outside the space present between them by two connections. The connections are therefore not arranged in the aforementioned endangered area. Since the insulation clearance of these insulating connections is independent of the distance between the conductors, and hence can be sufficiently large given a low inductance, aging phenomena in the connections owing to partial discharges are essentially precluded.
It is particularly advantageous for the mounts to be secured to the connections. This especially easy and effective step yields a structurally stable and yet inexpensive design of the device.
According to yet another aspect of the present invention, the two conductors are staggered relative to each other. This makes it possible to lengthen the insulation clearances that arise between the two conductors via the mounts and connections. The dielectric strength of the device according to the invention can therefore be further improved without any greater outlay.
According to a still further aspect of the present invention, one of the two conductors is provided with a solid-state insulator on its surface facing the other of the two conductors. This gives rise to a transition between one of the two conductors and the solid-state insulator. Another transition from the solid-state insulator to the other of the two conductors is not present, however. Instead, the non-solid, insulating medium, preferably air, is present there. The solid-state insulator is not used primarily for building up the dielectric strength between the two conductors. This continues to be achieved primarily by the non-solid insulating medium. The solid-state insulator essentially acts only to avoid a short circuit between the two conductors, e.g., if a metal part gets between the conductors. Since the solid-state insulator hence has no influence on dielectric strength, partial discharges in the solid-state insulator also do not have any negative consequences in terms of this dielectric strength. Therefore, the solid-state insulator provides simple and cost-effective protection against a possible short circuit between the two connectors.
According to another aspect of the present invention, the space between the two conductors is enveloped by a protective screen or the like and/or viewable from the outside for inspection purposes. This makes it possible to prevent a short circuit between the two conductors in a particularly easy and cost-effective but yet effective manner.
REFERENCES:
patent: 5923523 (1999-07-01), Herbert
patent: 5936833 (1999-08-01), Grossman et al.
Ehler Hans-Jürgen
Jakob Roland
Pelz Andreas
Rudniski David
Alstom Power Conversion GmbH
Pillsbury & Winthrop LLP
Reichard Dean A.
Walkenhorst W. David
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