Brush is widely used in various ac and dc generators, synchronous motors, battery dc motor, crane motor collector ring, various types of welding machines and so on. Good commutation performance and long service life. Brush is used in the motor commutator or slip ring, as the sliding contact of the current, it has good electrical, thermal and lubrication properties, and has a certain mechanical strength and commutative spark instinct. Almost all motors use brush, which is an important component of the motor. Widely used in various ac and dc generators, synchronous motors, battery dc motor, crane motor collector ring, various types of welding machines and so on. With the development of science and technology, the types of motors and operating conditions are becoming more and more diversified.

1. Apply the external current (excitation current) through the carbon brush to the rotating rotor (input current);

2. Introduce the static charge on the main shaft through the carbon brush to the ground (grounding carbon brush)(output current);

3. Lead the large shaft (ground) to the protection device for rotor grounding protection and measure the rotor positive and negative ground voltage;

4. Change the direction of the current (in commutator motors, the brush also ACTS as a commutator).