(1) Natural graphite
Natural graphite is the main raw material of this type of carbon brush. The binder is made of pitch or resin, baked or sintered at 1000 degrees. This type of motor has good lubrication performance and current collection performance. Most of them are used in the slip ring of small and medium-sized DC motors and high-speed turbo-generators that run smoothly.
(2) Electrochemical graphite
The main components are carbon black, coke, graphite and other carbon powder materials, which are treated at 2500 degrees to convert them into microcrystalline artificial graphite. This type of carbon brush has excellent commutation and self-lubricating properties, and is widely used in various AC and DC motors, not only has a long life, but also has little wear on the commutator.
(3) Metal graphite
The main materials of this type of carbon brush are electrolytic copper and graphite. Sometimes silver powder (used in precision instruments, very expensive), aluminum powder, lead powder and other metals are sometimes used according to the needs of use. These carbon brushes are divided into containing and non-binding agents. This type of carbon brush has both the friction characteristics of graphite and the high conductivity of metal. Therefore, it is suitable for low-voltage motors with high loads and low commutation requirements (such as automobile starter motors, etc.). Its peripheral speed does not exceed 30 meters per second.