Electrical Engineering XYZ MCQs
In DC machines, the armature windings are placed on the rotor because of the necessity for:
- Commutation
- Electromechanical energy conversion
- Development of torque
- Generation of voltage
Correct answer: 1. Commutation
Explanation: In DC (direct current) machines, the armature windings are placed on the rotor to facilitate the process of commutation. Commutation is a crucial aspect of DC machines, especially in DC motors and generators.
Communatation is the process by which the current in the armature winding is reversed at the appropriate moment as the rotor (armature) turns within the magnetic field. This reversal of current direction is essential to maintain the torque (rotational force) in the desired direction in a DC motor and to ensure the proper generation of voltage in a DC generator.
The armature windings, being located on the rotor, rotate through the magnetic field produced by the stator (field winding or magnets). As the rotor turns, the commutator, which is a rotary switch, reverses the current direction in the armature coils at the precise moment when the rotor poles are aligned with the stator poles. This reversal of current direction ensures that the torque is consistently produced in the same direction in a DC motor and that the generated voltage has the correct polarity in a DC generator.
Therefore, the placement of armature windings on the rotor is primarily for the purpose of achieving proper commutation, which is essential for the reliable operation of DC machines.