USCG Exam PracticeElectrical basics — generators, motors, and safety
In a DC generator, what is the purpose of the commutator?
- A. To regulate field current and thereby control output voltage
- ✓ To reverse the external circuit connections at the instant the induced voltage would reverse, producing unidirectional outputCorrect
- C. To reduce armature reaction by opposing the distortion of the main magnetic field
- D. To increase the number of armature coils cutting flux simultaneously
Why B is correct
NEETS Mod. 5 §1-1 explains that the commutator is a split ring whose segments, contacted by carbon brushes, reverse the external connections to the loop at the instant the induced voltage would reverse, so the brushes always deliver current in one direction. Field current regulation and armature reaction correction are separate functions.
Cited:NEETS Mod. 5 §1-1