Question

Explain the function of the following parts of an electric motor
(A) Armature
(B) Brushes
(C) Split ring

Answer 1

Armature is the major component of the rotor which hosts the windings of the rotor also termed as the armature windings. Brushes are used in electric motors to transfer power between the rotating armature coils and the stationary wires to the rotor. Split rings are used to supply unidirectional current to the rotor coils so that they generate a torque rotating in the same direction.

Complete Answer:
The armature in an electric motor provides housing and support to the armature winding. In electrical machines, the magnetic field is generated by a permanent magnet or electromagnet. Now the armature winding interacts with the magnetic field present in the air gap. An armature, used in an electric motor is used to communicate between two magnetic fluxes. In an electric motor, due to the relative motion between the flux produced by the field winding and the flux produced by the armature winding, an electromotive force is induced which causes current to flow in the armature windings on the rotor. This electric current on interaction with the magnetic field present inside the air gap and the rotor creates a force which in-turn creates a torque. This torque is responsible for rotating the rotor.
A brush is used to serve as an electrical contact between stationary points and moving surfaces. They are generally used to transfer power from rotating shafts to stationary wires. The majority of brushes are made of carbon.
Split rings are used in direct current machines to reverse the direction of currents flowing in the rotor. Since the rotor is always moving, we need brushes to keep contact with the rotor wires for constant power transfer. These brushes are used to conduct electric current to the rotor wires. The direction of this current needs to be reversed after every half cycle to keep the armature rotating in the same direction. Thus split rings are used with the conducting parts separated by insulating sheets of mica.

Note:
The mica sheets used in commutators erode at a rate lesser than that of the metals used in split rings. This causes a very small portion of mica sheets to slip over some part of the adjoining section of the commutator. This unwanted covering of the insulator (mica) over the conductors may cause sparking. However, this happens only after major erosion and degradation of the metal in the commutator.