USCG Exam PracticeMotor controllers and remote control
A three-wire start/stop control scheme with a seal-in (holding) contact on a motor controller provides which type of protection?
- A. Overload protection against sustained excess current
- ✓ Low-voltage protection preventing automatic restart after a power lossCorrect
- C. Ground-fault protection against accidental circuit grounds
- D. Short-circuit protection equivalent to a fuse or circuit breaker
Why B is correct
NEETS Mod. 3 §3-2 explains that the three-wire start/stop scheme with a seal-in contact provides low-voltage (no-volt) protection: a momentary loss of power drops out the contactor, and the motor will not restart by itself when power returns until the start button is pressed again. Overload and short-circuit protection are separate functions.
Cited:NEETS Mod. 3 §3-2