JPS59208710A - Contacor for load tap selector of on-load tap changing transformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a contact device for use in a load tap selector of an on-load tap-changing transformer, as defined in the generic part of claim 1. Such a contact device is known from West German patent DE 2910161C2.

In a load tap selector of an on-load tap-changing transformer, it is required that the contacts of the load tap selector operate with only a small overall contact resistance. This is required in the low current and low voltage conditioning and testing carried out during the final manufacturing process of transformer windings in order to obtain transformer characteristic curves.

load tap selector contacts integrated into the transformer, since the low voltages or small currents used for measurements are often insufficient to pass through the foreign layer formed in the load tap selector contacts The measurement results may be significantly altered due to contact resistance. However, in normal operation of the transformer, the contact resistance of the load tap selector contacts, e.g. Flows through.

A solution to this problem can be implemented by silver plating or magnetic recording on all contact areas. However, this solution is an expensive method. It is also conceivable to apply a relatively thin recording layer to the contact portion of the contact device that is involved in the contact action, but on the other hand, this method has the disadvantage that electroplating of silver is not possible in a limited manner to the desired area. . Furthermore, the contact parts of the contact devices involved in the contact action must also switch large load currents, so that silver as contact material is known to be unsuitable.

It is an object of the present invention to improve the contact device described at the outset in such a way that the load tap selector has an extremely low contact resistance without the need for the typical silver plating or coating that requires the use of silver over the entire contact. It is to be.

This problem is solved by the configuration described in the characterizing part of claim 1.

The advantages obtained by the invention are, first of all, that the large expense of electrolytic silver plating, for example of the entire contact arrangement, is no longer required; A very small transient resistance is achieved by the silver layer. Here, it is important to use silver in order to achieve extremely low contact mechanical resistance only in the area of the contact member of the load tap selector that is actually in contact, and not in other areas. This advantage not only saves on silver costs, but also means that the switching part that actually switches the load current can be made of something other than silver. The silver used sparingly in the switching region is used only during short switching times, and the contacts act as a combination of known materials suitable for switching power.

On the other hand, the contacts switched by bee loads have very thin magnetic recording layers, but because they are rolling contacts, mechanical wear is substantially less. Also, the extremely thin partial change coating applied does not wear out.

Partially coating the contact member with silver is done by electrical discharge machining (Fu).
This is advantageously carried out according to the principle of ``nkenerodierens''). In this case, the electrode made of silver constituting the positive electrode is guided vibratingly in layers over the contact element, so that a surface of the desired size and a layer of the desired thickness of 5 to 50 μm is formed in a simple manner. .

No special processing work is required to equalize the mismatched single layer thickness. Layer thicknesses of 5 to 50 .mu.m, which are found to be particularly advantageous here, can also be carried out in electrolytic silver plating and are also perfect for the function of the contacts. However, it is also advantageous to reduce the total layer thickness beyond the above-mentioned values if the layer thickness is less than or equal to that required for plating.

The invention will now be disclosed with reference to the accompanying drawings, in which examples are shown.

A cylindrical contact roller 2 guided on a movable contact carrier 1 is disposed so as to be displaceable according to a displacing path B on a substantially flat surface of a fixed contact part 3. This cylindrical contact roll 2 has thin annular cover portions 4 and 5 at both end portions of its side surfaces. This magnetic recording main part 4.5 is small compared to all sides, and is, for example, a small part about the size of one throat at most. In a similar manner, partial change coatings 7 and 8 are applied to the surface of the fixed contact part B at the center of the rolling path of the annular magnetic recording layer parts 4 and 5 of the contact roll 2, respectively. 3, these come into contact in the operating position of the contact roll 2.

The correspondence of reference symbols in the figure is as follows.

1: Movable contact carrier 2: Contact roll 3: Fixed contact portion 4.5: Annular silver coating 6; Rolling path 7, 8
：Silver layer agent Hikaru Esaki Favorable agent Hikaru Esaki

Claims (1)

Claims: 1) A substantially copper or (prepared metal) contact carrier having at least one movable contact carrier that guides a transferable cylindrical contact roll on a transfer path of a substantially flat fixed contact surface. In this contact device for a load tap selector of an on-load tap-changing transformer, the side surface of the contact roll (2) is provided with at least one thin annular silver nucleus in a small proportion compared to the side surface. A layer (4,5') is formed on the surface of the fixed contact part (3) at the transfer path site where the annular silver nucleus layer (4,5'l is the center) of the contact roll, A partially thin silver core layer (7°8) is formed, and when the contact device is at rest, the annular silver core layer of the contact roll is located on a partial recording layer on the surface of the fixed contact part. 2. A contacting device according to claim 1, characterized in that the silver core layers have a thickness of about 5 to 50 μm. 2. A contacting device according to claim 1, comprising: a contact roll (2). are formed with nub-shaped silver coatings (4, 5) at both ends of their side surfaces, and fixed contact portions (3).
Two partial silver coatings (7, 8') are formed accordingly.