Explain the role of carbon brushes in motor work

Motors are divided into brush motors and brushless motors. As the name suggests, the difference is whether there are carbon brushes or not. Today, let's briefly introduce the role of carbon brushes in the motor.

　　 During the operation of the motor, the carbon brushes mainly have the following functions:

    1. The external current (excitation current) is applied to the rotating rotor through the carbon brush (input current)

　　2. Lead the static charge on the main shaft into the earth through the carbon brush (ground carbon brush) (output current)

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

　　 4. Change the direction of the current (in the commutator motor, the brush also plays a role in commutation)

　　 The commutator consists of a brush and a commutating ring, and a carbon brush is a kind of brush. Due to the rotation of the rotor, the brush always rubs against the commutation ring, and spark erosion occurs at the moment of commutation, so the brush is a vulnerable part in the DC motor.

　　 In order to improve the service life and operational stability of the DC motor and reduce the noise and electromagnetic interference of the DC motor, the brushless DC motor is gradually replacing the brushed motor.

　　 Generally, AC motors do not need a constant magnetic field, so no commutator is needed, and no brushes are needed; however, AC motors are generally larger in size. The motors used in household appliances are generally AC motors, such as electric fans, washing machines, refrigerators, air conditioners, etc., do not have carbon brushes, but there are also DC motors, such as many electric shavers, small kitchen appliances, and electric bicycles. Brushes are DC motors (excluding brushless ones). The motors that use dry batteries are all DC motors.

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