What is a carbon brush

The main component of a carbon brush is carbon. When it works, it operates like a brush on a rotating part, hence the name carbon brush. Its main material is graphite. What is graphite? First, let's understand the main material of carbon brushes, graphite. Graphite is a natural element, and its main component is carbon. It is black in color, opaque, and has a semi-metallic luster. Its hardness is not high. Both graphite and diamond are composed of carbon, but their properties are quite different, which is caused by the different arrangement structures of carbon atoms.

Although graphite is composed of carbon, it is a high-temperature resistant material with a melting point of 3652℃. By taking advantage of this high-temperature resistance, graphite can be processed into high-temperature resistant chemical weapon crucibles. Graphite has excellent electrical conductivity, surpassing that of many metals, so it is made into conductive components such as electrodes and carbon brushes. The internal structure of graphite determines that it has excellent lubricity. We often put pencil dust or graphite in rusty door locks, making it much easier to open the door. This should be the lubricating effect played by graphite.

Don't think that graphite can only be used to make basic products like pencil leads. Now, the new material graphene extracted from graphite, you must have heard of it, right? It has become the most sought-after new technology material in the world.

Brushed motor

Brushed motors are composed of electronics and rotors. In DC motors, to make the rotor rotate, the direction of the current needs to be constantly changed; otherwise, the rotor can only rotate half a circle. This is similar to pedading a bicycle pedal with one foot, where one foot can only pedal half a circle. Therefore, in DC motors, the current in the rotor needs to be changed, that is, the direction of the current-carrying conductor needs to be reversed when it is necessary. The commutator is composed of two semi-circular sections, separated by insulating materials at the connection points. The two ends of the commutator rotate and are respectively connected to the carbon brushes. The carbon brushes will repeatedly connect to the section of the commutator that meets the driving force, and thus the motor starts to rotate repeatedly.

Brushed motors use mechanical commutation. The external magnetic poles remain stationary while the internal magnetic coils move. When the motor is in operation, the commutator and the coils rotate together, while the carbon brushes and the magnetic steel remain stationary. As a result, friction occurs between the commutator and the carbon brushes, completing the direction switching of the current. In brushed motors, each group of coils is arranged in a circular ring and separated from each other by insulating materials to form a cylindrical shape that is integrated with the motor shaft. The power supply passes through two carbon brushes and is pressed against the coils under the pressure of a spring. When each group of coils rotates under the carbon brushes, electricity is supplied to this group of coils.

As the motor rotates, electricity is applied to different coils or two different stages of the same coil to generate a magnetic field. The two poles of the coil form an Angle with the two poles close to the stator of the permanent magnet. Through the repulsion between the two poles and the attraction between opposite poles, a force is produced to drive the motor to rotate.

Carbon brushes play a very important role in DC motors. They transfer current between the moving parts of the motor. This transfer is a sliding conduction that can transfer current from the fixed end to the rotating parts of the generator or motor. Several carbon brushes form a carbon frame, so this transfer method also causes the carbon brushes to be prone to wear. Carbon brushes can also change the direction of the current. That is the function of reversing.

Carbon brushes are also used in AC electrical equipment. The shape and material of carbon brushes in AC motors are the same as those in DC motors. In AC motors, the rotor is wound and speed change is required, which is why carbon brushes are needed. For example, the hand drills and polishing machines we commonly use also need to have their carbon brushes replaced frequently. Their role is also very important.