FAQ

Q. Why is carbon used as a contact material?
A. Due to the particular material characteristics of carbon and graphite sliding contacts in form of carbon brushes are an important component for current transmission in electrical machines.
These include good electrical and thermal conductivity, low mechanical friction and high resistance to elevated temperature. Carbon has no melting point. Therefore, when switching sparks and arcing occur, the formation of beads of molten material is prevented.

Carbon materials form protecting films on every contact material. By means of different raw materials, different processes and different designs the production of products, which match nearly every demand, is possible.

Q. Why do my brushes have high brush wear?
A. Carbon brushes are indicating instruments for the machine status. A high wear rate of the carbon brushes is not mecessarily a sign of a bad brush material. Parameters like electrical load, temperature, humidity, status of the commutator /slip ring, faulty windings, surroundings, influence of dust or chemicals etc. have an important influence on the brush performance. High brush wear might indicate, that any of these parameters is not within standard limits.

Q. Which life time of carbon brushes can I expect?
A. A guarantee for a certain life time of carbon brushes cannot be given. There are many parameters influencing the brush performance which cannot be controlled by a brush supplier such as load conditions, vibrations, oil or chemicals, brush pressure, commutating poles, out-of roundness of commutator or slip ring, high bars, too high or too low surface temperature are only some of these parameters. All these parameters are given by the machine itself. Nevertheless some guide line values for the wear rate are possible like stationery machines 2-7mm/1000hrs, traction motors 2-4mm/10000km. With optimum conditions values at the lower limits or even better are possible.