How do brushed DC motors work? The need for regular maintenance explained

DC motors are electric motors that are powered by direct current. Features include the ability to run at high speeds, and high starting torque. They can broadly be divided into two groups. This page provides a simple introduction to the brushed DC motor and how they work.

Electric motors can be divided into a number of different types based on their structure and how they are driven. AC motors are driven by alternating current, stepper motors rotate in fixed steps each time a pulse of electric power is input, and DC motors are driven by direct current. Compared to the other types, the benefits of DC motors include being able to operate at high speeds and delivering high starting torque.

DC motors can be further divided into brushed DC motors and brushless DC motors. The operation of brushed DC motors is based on the mechanical linkage between their commutator and brushes. Brushless DC motors, on the other hand, do not have a commutator and brushes, and instead are electronically controlled with a drive circuit. The main features of DC motors are as follows.

A feature specific to the brushed DC motor described here, is that they do not require a drive circuit in applications where speed control is not needed.

The following link provides more details about the differences between brushed and brushless DC motors:

What are the differences between brushed and brushless DC motors?

Brushed DC motors are further divided into two types based on the type of magnet they use.

The choice of motor type is determined by the application and required motor size.

As explained above, brushed DC motors deliver high starting torque and can operate at high speeds despite their simple structure. They are also easy to use, being able to operate without a drive circuit if speed control is not needed. However, brushed DC motors have the following disadvantages.

The brushes and commutator in a brushed DC motor are in continual contact with one another as the motor rotates. This is what causes the electrical and acoustic noise.

The short life of these motors is another important consideration. The continual contact between brushes and commutator as the motor rotates causes these parts to gradually deteriorate by friction-induced wear. As the metal brushes wear down, their contact with the commutator diminish, and no longer do a good job of conducting electric power. As a result, the motor will no longer work properly. This explains why the brushes and commutator are consumable parts, requiring maintenance in the form of regular inspection or replacement.

DC motors are divided into brushed DC motors and brushless DC motors. Brushed DC motors work by having the coil rotate inside the surrounding magnets. The rotation of the coil causes the contact between commutator and brush to alternate, therefore switching the current flow through the coil. As a result, the brushed DC motor can operate.

Despite its simple structure, the continual contact between the brushes and commutator as the motor rotates causes wear, and this creates a need for regular maintenance to replace worn parts.