what is the role of a commutator in a DC motor?
reverses current in armature as the shaft turns so that torque is always in the same direction.
http://electronics.howstuffworks.com/motor5.htm
That link is to the commutator page. Go back one page in the link to see why the current in the armature electromagnet must be reversed every half turn.
The commutator in a DC motor plays a crucial role in its operation. It is a small cylindrical device that is typically located on the shaft of the motor and is connected to the armature windings. The primary function of the commutator is to enable the motor to convert electrical energy into mechanical energy.
To understand the role of the commutator, it's important to first understand the basic principles of a DC motor. A DC motor consists of two essential components: the stator (fixed part) and the rotor (rotating part). The stator contains the field windings, which produce a magnetic field, while the rotor houses the armature windings, which carry the electric current.
When an electric current is passed through the armature windings, a magnetic field is generated within the rotor. This magnetic field interacts with the magnetic field produced by the stator, causing the rotor to rotate.
Now, here is where the commutator comes into play. The commutator is responsible for maintaining the direction of the current flowing through the armature windings. It achieves this through a series of conducting segments (usually made of copper) and brushes (typically carbon-based). The brushes make physical contact with the commutator segments as it rotates.
As the rotor turns, the commutator reverses the direction of current flow within the armature windings at specific intervals. This reversal is essential for maintaining a constant direction of rotation in the motor. By changing the polarity of the current through the armature windings, the commutator ensures that the interaction between the rotor's magnetic field and the stator's magnetic field continues to produce torque and consistent rotation.
In summary, the commutator in a DC motor serves as a mechanical switch, regularly reversing the direction of the electrical current within the armature windings. This process allows for the continuous and controlled movement of the rotor, enabling the motor to convert electrical power into mechanical motion.