WO2008028593A1 - Electrical contact arrangement, in particular for medium-voltage installations, as well as a method for its production - Google Patents

Abstract

The invention relates to an electrical contact arrangement, in particular for medium-voltage installations, in which contact elements (1, 2) can be connected to one another, and to a method for producing a contact arrangement such as this. In order in this case to considerably improve the process of making contact, the invention proposes that, of the two contact elements (1, 2) which can be connected to one another, one contact element (2) is composed of a relatively soft material, and the other contact element (1) is composed of a harder material, relative to one another.

Description

 Electrical contact arrangement, in particular for medium-voltage installations, as well

Process for producing the same.

The invention relates to an electrical contact arrangement, in particular for medium-voltage installations, and to a method for producing the same, according to the preamble of patent claims 1 and 7.

Low-voltage, medium-voltage or high-voltage switchgear whose continuous current path is formed by means of fixed contacts, e.g. Screws and / or movable contacts, e.g. Sliding or roller contacts, is formed. This also includes the switching devices, such as circuit breakers, switch disconnectors, contactors and disconnectors.

In known electrical switchgear the current path is formed by a juxtaposition of contacts. If these contacts are movable, the flow path can be opened and closed without any problems.

A closed current path usually has the task of conducting short-circuit and load currents. Furthermore, there is the demand for high compactness of the switchgear. This small-scale, possibly still under hermetic conclusion, u. a. In the case of gas-insulated switchgear, it is necessary to keep the resistance of the current path as small as possible in order to minimize the power loss.

Furthermore, a good thermal conductivity of the current path is required to dissipate the heat loss occurring inside the switchgear to the outside, without exceeding certain temperature limits. This results in a variety of disadvantages. Screw connections or screw contacts only have small electrical resistances and good thermal conductivity if the two screw surfaces are cleanly and completely connected to one another. Industrially manufactured and machined surfaces often do not meet this requirement. The reason for this are microscopic surface irregularities, which can be smoothed or eliminated only with great effort.

Such a simple screw connection according to the prior art is shown in FIG. Two surfaces are pressed against each other by a screw connection. The two contact surfaces are microscopically not conclusive superimposed. This leads to increased electrical contact resistance and poor heat transfer. Increased power losses lead in addition to a difficult derivation of the resulting heat loss to the environment. The permissible limit temperatures can be exceeded in the worst case. This usually requires costly measures, such as more generous size of the switchgear, larger conductor cross-sections and additional heat sinks to improve convection, radiation and conduction. This can only be avoided if the power loss is minimized from the outset and the thermal conductivity is maximized.

In case of a possible pouring of the contact point into a solid insulating material, e.g. Epoxy resin, in addition to note that potting compound can penetrate into a possible gap between the contact surfaces, which can lead to a further reduction in electrical and thermal conductivity.

Furthermore, in outdoor applications, in a gap between the contacts, e.g. Water penetrate and promote corrosion.

The invention has for its object to achieve the largest possible and complete connection of the Verschraubflächen, with a defined completion of the contact surface to the outside. The stated object is achieved according to the invention in an electrical contact arrangement of the generic type by the characterizing features of claim 1.

With regard to a method for producing an electrical contact arrangement, the stated object is achieved by the characterizing features of claim 7.

Advantageous embodiments of the arrangement and the method are specified in the remaining claims.

Core of the device according to the invention is that of the two contact elements to be joined together in relation to each other, a contact element of a softer and the other contact element consists of a harder material. This causes the contact elements have a significantly lower electrical contact resistance and also have a good thermal conductivity, moreover. By tightening the fasteners, the softer contact element nestles against the surface of the hardened contact element much better, with a slight deformation of the softer contact element is wanted.

In a further advantageous embodiment, it is indicated that the two contact elements are shaped so that the contact surfaces or contact contours complement each other after completion of mechanical and electrical contacting at least partially complementary form and are deformed at least near the surface for this purpose.

With regard to design options, one is that the two contact elements have a partially invading pyramidal shape. This is promoted in a reproducible and thus manufacturing technology reasonable way by the deformation of the softer contact piece. Another embodiment is that one of the contact elements has a cup-shaped opening whose edges are preformed beaded, and deform there when creating the contact connection. Upon penetration of the harder contact element in the softer contact element, this bead is deformed and thus leads to an intimate contact with low electrical contact resistance.

In a further advantageous embodiment, it is stated that the contact surfaces result in a complementary cone fit after connection.

A last advantageous embodiment consists in that of the contact elements to be connected, one contact element has a cup-shaped recess and the other contact element has a molding to be introduced there, and that the recess and the molding have different geometric cross-sections.

The core of the inventive method is that of the two contact elements to be joined together in relation to each other, a contact element of a softer and the other contact element consists of a harder material and are joined such that deforms at least the softer contact element. This ensures optimum conformance of the contact-forming surfaces.

This is concretized in a further advantageous embodiment in that the two contact elements are preformed such that the contact surfaces or contact contours complement each other after completion of mechanical and electrical contacting at least partially complementary form and are deformed at least near the surface for this purpose.

In a further advantageous embodiment, it is provided that at least one of the two contact elements is coated with a gold, silver or similar coating before joining.

This can be done by inserting a gold, silver or similar foil between the two contact elements before the components are connected to one another become. The film can only be inserted into the connection at the front but also all-encompassing.

The invention is made clear with reference to several design examples and described in more detail below.

It shows:

Figure 1: First embodiment

Figure 2: State of the art

FIG. 3: Exemplary embodiment with press fit

Figure 4: embodiment with collar-shaped interference fit

Figure 5: embodiment with conical interference fit

Figure 6: Ausgestaltungsbeispiel with a cross-sectionally elliptical contact element

Figure 7: exemplary embodiment with a square in cross-section

contact element

Fig. 1 shows a first embodiment. Shown in the harder contact element in the upper part of the picture, a small depression is introduced in the area around the hole for the screw. The softer contact element, shown below with internal thread, is substantially cylindrically shaped.

When tightening the screw is the softer contact element, shown below with internal thread, initially annular on the outer edge. Upon further tightening of the screw, this support is first compressed so that forms a high pressure on this annular surface. Microscopic surface irregularities become so partially balanced, and the effective footprint increases. The electrical and the thermal resistance decrease.

At the same time a sealing of the contact point against the penetration of potting compound or water can be effected.

If the screw is tightened, then the area around the thread of the softer contact element lifts so far until this area forms an annular surface high mechanical pressure. Fig. 1, below, shows a cross section through these two annular contact areas, which are highlighted by black bars in the figure.

The recess in the harder (upper) contact element can now be introduced in such a way that also in the area between the two rings of high contact pressure, a contact of the two contact surfaces sets when the screw has been closed.

The above-mentioned embodiment, in which a foil of gold, silver or copper, or an alloy of good electrical conductivity is interposed between them before the joining of the contact elements, leads to a further considerable reduction of contact contact resistances.

Films or coatings of the contact pieces with these noble or semi-precious metals can be used in all embodiments shown.

As already described above, FIG. 2 shows the state of the art, as already explained in the introduction.

A further embodiment, which can also be combined with those previously described, is shown in FIG. Here, in addition to the stimiform contact surface, there is additionally an enclosure of the softer, cylindrical part of the contact element through a corresponding bore in the harder contact element - an additional contact surface with high pressure force is provided by the provided press fit. In some cases, the application of the forces required for the pressing can not be done by the screw connection and also not by external forces.

Then, an embodiment of FIG. 4 is possible in which the interference fit is formed only over a limited part of the enclosure. By this measure, the force required for pressing can be reduced and adjusted. Also in these embodiments, a seal of the contact point against the penetration of potting compound or water can be formed.

Another way to reduce the insertion force is a coating of one or both components, e.g. with a silver or similar coating or the heating of the outer and / or the cooling of the inner contact element, so that the thermal expansion of the overlap of the diameter, ie the tightness of the interference fit, can be reduced or canceled for the time of installation.

A further embodiment is a conical fit according to FIG. 5. The lateral contact surface can also be formed here as in FIG. 5 such that the contact of the lateral surfaces takes place only over a limited part of the enclosure in order to be able to influence the press-in force , The embodiments of Figs. 3, 4 and 5 can be combined with the embodiments of Figs. 1 and 2 to optimize the resistance of the contact.

Further embodiments of FIG. 6 see a non-cylindrical softer

Contact element in front. 6 shows a softer contact element with an elliptical cross section (left-hand part of the figure), while FIG. 6 shows in the right-hand part of the picture a softer contact element with a square cross-section and rounded corners.

The elliptical cross section of the softer contact element touches the harder

Contact element in two zones (Fig. 6), while in the square cross section this contact takes place in four zones. There are also other cross-sections conceivable that realize a touch in three or more than four zones. As a result of this measure, the press-in force is reduced and adjustable in comparison with the embodiment according to FIG. 3, similar to FIG. 4.

A further embodiment is described in FIG. 7. Here, both the cross section of the softer contact element and the reduction of the harder contact element are elliptical.

Both parts, i. Both cooperating contact elements can first be placed on each other with their end faces, without the additional contact surface on the circumference of the softer contact element is engaged. After biasing the screw with reduced torque both parts can be rotated by 90 ° from each other, so that a press fit of both contact elements with correspondingly low electrical and thermal contact resistance arises. Finally, the screw is tightened with nominal torque.

In addition to elliptical cross sections, other cross sections can be used which lead to more than two contact zones on the circumference (similar to FIG. 8).

The embodiment according to FIG. 7 can be combined with the embodiments according to FIGS. 1 and 4.

Claims

claims 1. Electrical contact arrangement, in particular for medium-voltage installations, in which contact elements are connected to each other, characterized in that of the two contact elements to be interconnected in relation to each other, a contact element of a softer and the other contact element consists of a harder material. 2. Electrical contact arrangement according to claim 1, characterized in that the two contact elements are shaped so that the contact surfaces or contact contours complement each other after completion of mechanical and electrical contacting at least partially complementary and are deformed at least near the surface for this purpose. 3. Electrical contact arrangement according to claim 2, characterized in that the two contact elements partially penetrating one another Pyramidal form have. 4. Electrical contact arrangement according to claim 2, characterized in that one of the contact elements has a cup-shaped opening whose Edges are beaded preformed, and deform when creating the contact connection there. 5. Electrical contact arrangement according to claim 2, characterized in that the contact surfaces after the connection result in a complementary cone fit. 6. An electrical contact arrangement according to claim 2, characterized in that of the contact elements to be connected, a contact element has a cup-shaped recess and the other contact element has a Anformung there to be introduced, and that recess and Anformung have different geometric cross-sections. 7. A method for producing a transition resistance-reduced contact between two contact elements, in particular in a medium-voltage system, characterized in that of the two contact elements to be interconnected in relation to each other, a contact element of a softer and the other contact element consists of a harder material and are joined such that deforms at least the softer contact element. 8. The method according to claim 7, characterized in that the two contact elements are preformed such that the contact surfaces or contact contours complement each other after completion of mechanical and electrical contacting at least partially complementary form and are deformed at least near the surface for this purpose. 9. The method according to claim 7, characterized in that at least one of the two contact elements is coated with a gold, silver or similar coating before joining. 10. The method according to claim 7, characterized in that between the two contact elements a gold, silver or similar film is inserted before the components are connected together.