Ground contact
Earthing contacts transmit electrical currents safely and specifically to rotating parts by forming a low-resistance bridge. They can often be found in railway technology, where they take over the transmission of electricity to rotating drive axles, for example. The power transmission by means of a low-resistance bridge prevents the flow of power through the bearings, which would otherwise be damaged. In addition to the transmission of drive currents, grounding contacts are also used for signal transmission and lightning protection.
Earthing contacts usually consist of one or more high-metal carbon brush (s) with guide (s) and a rotating disk or a slip ring made of metal, which are conductively connected to the axis. The rotating disc is made of either pure metal or metal coated with electrographite (see patent).
Applications
The main area of application for earthing contacts is railway technology , where they create a circuit across the rotating axes. A distinction is made between different systems depending on the bearing of the axles (inside or outside) and the current to be transmitted. In addition to the transmission of traction current , grounding contacts also carry signals that are used, for example, to determine the location of trains or to secure tracks.
In addition to railway technology, earthing contacts can also be found in wind turbines , electroplating and lightning protection .
Coal-coal grounding contacts
The carbon-carbon grounding contact differs from the conventional grounding contact in that it is a carbon-carbon contact. Instead of the metal-containing carbon brush, electrographite is used here ; the metal contact plate is coated with electrographite. This multiplies the service life of the system. The transmission resistance remains constant over the entire service life, while with conventional systems consisting of a metal-containing carbon brush and metal disc it increases continuously due to a patina that forms . Otherwise the structure corresponds to a conventional earth contact.