What is a DC motor?

What is a direct current motor?

A Direct Current (DC) motor is a motor that turns energy from a direct current and turns this into mechanical energy. 

The first DC motor was developed around the 1830’s-1840s. They were commercially unsuccessful, because these motors were battry powered and batteries were still very expensive and bad in quality. When the electrical grid was created and possibilities to build rechargeable batteries were invented in the late 1800s, the first commercially viable DC motors entered the market. This type of motor has been improved continiously, but other types of motors, like the BLDC motor, have been developed in the mean time too.  As a result, the use of brushed DC motors in several applications is limeted today. Some examples of applications in which they are still used are: 

The stator and rotor as used in a drilling machine

•   Cranes
•   Conveyors
•   Pumps
•   Fans
•   Machine tools
•   Air compressors
•   Toys
•   Motor starters in cars

 
How a dc motor actually works

There are four types of DC motors:

  • Permanent Magnet DC motor
  • Series motor
  • Shunt motor
  • Compound motor

All four types work in roughly the same way, as a DC motor always consists of two main parts: a rotor and a stator.  dddd

The rotor is normally located on the inside of the motor, while the stator is located on the outside.  The rotor contains coil windings that are powered by the DC current and the stator contains either permanent magnets or electromagnetic windings.  When the motor is powered by DC current, a magnetic field is created within the stator, attracting and repelling the magnets on the rotor. This causes the rotor to start rotating.

To keep the rotor rotating, the motor has a commutator.  When the rotor aligns with the magnetic field, it would stop spinning, but in this case the commutator would reverse the current through the stator and this way reverse the magnetic field. This way the rotor can keep spinning. How the DC motor works is also displayed schematically on the right of this page.