A commutator is made of which of the following?

Explanation:

Construction of Starter motors in automobiles:

• In automobiles, the series wound type is generally used. In this, the field and armature coils are connected in series.
• This enables the motor to produce a high starting torque.
• The armature windings (1) are fixed in slots and their ends are soldered to the commutator segments (2).
• The function of a commutator in a DC generator is to collect the current generated in armature conductors.
• A commutator consists of a set of copper segments that are insulated from each other.
• The number of segments is equal to the number of armature coils.
• Each segment is connected to an armature coil and the commutator is keyed to the shaft.
• The pole shoes (3), two or four in number, are screwed to the yoke (4) and they have field windings (5).
• These windings help to produce the magnetic field.
• The insulation pieces are placed between the pole shoes (3) and the metal yoke (4).
• Copper segments are provided with mica insulation in between the commutator brushes (6).
• These brushes (6) slide in the brush holders and are kept in contact with the commutator with the help of small springs (8).
• The brushes (6) are given a curvature at the bottom to have more contact with the commutator (2).
• The armature is supported either on bushes or coil.