USCG Exam PracticeElectrical basics — generators, motors, and safety
What is the primary purpose of a commutator in a DC generator?
- A. To regulate field current and 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 distorted magnetic field
- D. To smooth the pulsating DC output by storing charge between pulses
Why B is correct
Per NEETS Mod. 5 §1-1, 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. Armature reaction is addressed by interpoles, not the commutator itself.
Cited:NEETS Mod. 5 §1-1