Short Answer
The commutator in a DC machine is used to convert the alternating current produced in the armature into direct current. It ensures that the current flowing in the external circuit remains in one direction only.
It also helps in reversing the current in the armature conductors at the correct time. This makes sure that the torque produced in a DC motor is always in the same direction, resulting in smooth and continuous rotation.
Detailed Explanation:
Function of a commutator
Conversion of AC to DC
The commutator plays a very important role in converting alternating current into direct current. In a DC generator, the current induced in the armature winding is naturally alternating. However, most electrical devices require direct current for proper operation.
The commutator solves this problem by reversing the connection of the armature winding after every half rotation. Due to this action, the current that comes out of the machine becomes unidirectional. This process is continuous, so the output appears as smooth direct current.
Reversal of current in motor
In a DC motor, the commutator helps in maintaining continuous rotation. When current flows through the armature conductors in the presence of a magnetic field, a force is produced that causes rotation.
After half a turn, if the current direction is not changed, the direction of force will also change, and the motor will stop or reverse. The commutator prevents this by reversing the current direction at the correct time. This keeps the torque in the same direction and allows smooth rotation of the motor.
Connection between rotating and stationary parts
Another important function of the commutator is to provide a connection between the rotating armature and the stationary external circuit. Since the armature rotates, direct connection is not possible.
The commutator, along with brushes, provides a sliding contact. Brushes remain stationary, while the commutator rotates. This arrangement allows current to flow continuously without interruption.
Smooth operation and reduced sparking
The commutator also helps in improving the performance of the DC machine. By ensuring proper timing of current reversal, it reduces sparking at the brushes. Smooth contact between commutator segments and brushes is very important for efficient operation.
Proper maintenance of the commutator surface is necessary. If the surface becomes rough or dirty, it can lead to energy losses and damage to the machine.
Construction features supporting function
The commutator is made up of copper segments because copper has good electrical conductivity. These segments are separated by insulating material such as mica to prevent short circuits.
The cylindrical shape of the commutator helps in smooth rotation and uniform contact with the brushes. Its design ensures that the switching action takes place quickly and efficiently.
Conclusion
The commutator is a key component of a DC machine. It converts alternating current into direct current, reverses current in the motor, and provides a connection between rotating and stationary parts. Without it, proper operation of a DC machine would not be possible.