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Function of commutator in DC generator

Short answer

The commutator converts alternating coil emf to unidirectional output by reversing connections at the instant of emf reversal. It also collects current via brushes, connects coils in series for additive emf, and with many segments reduces ripple.

Explain the functions of commutator segments in dc generator.

The commutator is a cylinder of hard-drawn copper segments, insulated from one another by mica, fixed on the armature shaft. Armature coil ends are soldered to the segments and stationary carbon brushes rest on it.

The emf induced in an armature conductor is alternating, since each conductor moves alternately under N and S poles. The commutator converts this into DC at the terminals.

Functions

  1. Mechanical rectifier: at the instant the emf in a coil reverses, the coil's connection to the brushes is also reversed, so the brushes always see emf of one polarity. The output current is unidirectional.
  2. Current collection: together with the brushes, it provides a sliding contact between the rotating armature and the stationary external circuit.
  3. Series addition of coil emfs: segments join the coils so that their emfs add between brushes in each parallel path (lap or wave).
  4. Smooth output: with many coils and segments, the rectified emf has very little ripple.
 Coil emf (AC)        Brush output (DC)
   /\                   /\    /\
  /  \                 /  \  /  \
 /    \    /          /    \/    \
       \  /
        \/

✓ Answer checked by Claude Opus 5.5 (high effort)

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