Correct Answer - Option 3 : mica
The insulating material used between the commutator segments is normally mica as it has a very high dielectric stress of around 1180 kV/cm.
Commutator:
- A commutator is a mechanical converter that converts the alternating voltage generated in the armature winding into a direct voltage across the brushes and vice-versa.
- The commutator is made of copper segments insulated from each other by mica sheets and mounted on the shaft of the machine.
- The armature conductors are soldered to the commutator segments in a suitable manner to give rise to the armature winding.
- Depending upon the orientation of armature winding (Lap or Wave) armature conductors are connected to the commutator segments.
Cause of sparking on Commutator:
- Weak mica between segments of the commutator or damage due to commutator insulation.
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Damage occurs at the commutator segment.
- Rough commutator surface.
- The commutator is not fully round.
- Segments short-circuited by carbon filing.
- Oil and dirt on commutator surface.
Effect of sparking on Commutator:
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Overheat and carbonize the commutator.
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Increased power consumption.
