Function of brush

Brush and commutator are used together. It is mainly used to connect the circuit of magnetic field winding and armature winding, and keep the electromagnetic torque on the armature shaft in a fixed direction.
Brush is an important component of motor, which is responsible for conducting current between rotating parts and stationary parts. It is also called carbon brush because it is mostly made of graphite.
The brush material is mostly made of graphite. In order to increase the conductivity, it is also made of copper-containing graphite. The graphite has good conductivity, soft texture and wear resistance. The brush can be used for DC motor or AC commutator motor, such as general electric tools, such as hand drill and angle grinder.

In practical use, a slip ring is usually equipped with at least two brushes to avoid open circuit due to poor contact of a single brush.
The functions of the brush are as follows:
1. Apply the external current (excitation current) to the rotating rotor (input current) through the brush;
2. Lead the static charge on the main shaft to the ground (grounding brush) (output current) through the brush;
3. Change the current direction (in the commutator motor, the brush also plays the role of commutation);
4. Lead the large shaft (ground) to the protection device for rotor grounding protection and measurement of rotor positive and negative voltage to ground.
The brush device is the conductive part that rotates the motor. A device for connecting circuits and fixed parts such as commutators and slip rings. In the DC motor, the brush connects the rotating armature with the external circuit, so that the current can be input into or output from the armature through the brush. Excitation current is input to rotor coil through brush and slip ring in synchronous motor. The wound induction motor also uses the brush to connect the resistance in the rotor circuit. The brush device is composed of brush, brush holder, brush rod, brush rod base, bus bar, etc. The brush is placed in the brush box of the brush holder and pressed on the commutator with a spring to maintain a certain pressure. Electric brush is often made of graphite, so it is also called carbon brush.

The brush device generally consists of brush, brush holder, brush rod, brush rod base and other parts. The brush is made of graphite with good conductivity and wear resistance. It is placed in the brush holder, and a spring is pressed on it to maintain a certain contact pressure between the brush and the commutator surface when the armature rotates. The brush holder is fixed on the brush rod, and the brush rod is installed on the brush rod base, which is insulated from each other. The brush rod base is installed on the end cover, which can move and adjust the position of the brush. The brush is connected with the brush rod by copper braid wire, and then led out by wire. The role of the brush holder is to fix the brush device (brush holder) to the connecting piece of the motor. The brush holder is the connecting piece between the brush holder and the brush holder. The brush holder is composed of the brush box, spring, pressure finger and other parts.