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Carbon brushes in the automotive industry

This current transmission technology is over a century old, but in no way obsolete. Carbon brushes establish electrical contact to the rotating component of a machine via sliding rings or collectors. They can still be found in almost all electrical motors in automobiles, motors in starters, wipers, window regulators, interior fans, radiator fans or petrol pumps, to mention a few.

The automotive industry sets high demands in this respect. Carbon brushes for starters are not only required today to withstand approx. 40,000 start cycles, but also pass comprehensive additional tests, such as salt water spray tests or heat and cold testing. Requirements regarding the minimisation of noise development and carbon brush spark suppression are increasing. Each company has its own tests in this respect, these being in part also standardised test procedures. Extreme everyday conditions are simulated to ensure the reliable function of the electric motor under practical conditions.

A lot of know-how is therefore invested in the materials used, these being tailored to suit the type of motor and specification involved. In addition to pure carbon and graphite materials, impregnated variants and compounds of graphite and different metals (e.g. copper) are frequently used. Layered carbon brushes are optimally suited to special applications.

Commentators made of graphite materials are also used in modern fuel pumps. In addition to favourable electrical characteristics, the enhancement of service life through lubrication of the components running in the fuel is of interest.

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