Brushed DC motors are the easiest motors since the end of the 19th century. With a DC power or battery supply required for operation, the common brushed DC motor consists of an armature, commutator, field winding and brushes as shown in Figure 1.1.
Figure 1.1 Brushed DC motor construction
The brushes used in the DC motor are mostly made up of carbon and are mounted on commutator that is attached on armature shaft. The close view of brushes is shown in Figure 1.2.
Figure 1.2 Carbon Brushes
1.3 Problems in Early DC Motors
As early brushed DC motors use carbon brushes that gets crashed over time by rubbing with commutator, as shown in Figure 1.3.
Figure 1.3 Sparking in brushed DC motor
By time passing as brushes get rubbed over and over with commutator the sparking gets started that is very dangerous and can even burn the armature or stator winding after short circuiting. More disadvantages of DC brushed motor are:
• Requires more maintenance due to brushes
• It has shorter life
• Torque disturbance at high speed due to brushes
• Has less efficiency due to voltage drop across brushes
• Heat is also produced in air gap due to brushes’ friction that can cause severe effects.