The role of carbon brushes in motors

The role of carbon brushes in motors

Carbon brushes are used between the stationary and rotating parts of motors, generators or other rotating machinery and become one of its important components. As a sliding contact, carbon brushes are widely used in many electrical equipment. Product materials are mainly electrochemical graphite, greased graphite, metal (including copper, silver) graphite. The shape is rectangular, and the metal wire is installed in the spring. The carbon brush is a sliding contact part, so it is easy to wear and needs to be replaced and cleaned regularly.

The role of the carbon brush is to introduce the rotor current required by the motor operation into the rotor coil through the connecting piece on the slip ring. The fit and smoothness of the carbon brush and the connecting piece, and the size of the contact surface affect its life and reliability. In a DC motor, it also undertakes the task of commutating (rectifying) the alternating electromotive force induced in the armature winding.

The commutator is composed of brushes and commutation rings, and carbon brushes are one type of brushes. Due to the rotation of the rotor, the brushes are always rubbed with the commutation ring, and spark erosion will occur at the moment of commutation, so the brushes are the wearing parts in the DC motor.