USCG Exam PracticeMotors and generators
The synchronous speed of a three-phase induction motor is determined by which of the following?
- A. Supply voltage and the number of armature coils
- ✓ Supply frequency and the number of stator polesCorrect
- C. Rotor slip and the full-load current
- D. Field excitation current and rotor resistance
Why B is correct
Per NEETS Mod. 5 §4-1 and DOE-HDBK-1011 Vol.4 §12-1, synchronous speed is given by Ns = 120f / poles, where f is supply frequency and poles is the number of stator poles. Slip, voltage, and rotor resistance do not appear in this formula.