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 protective function?
- ✓ Low-voltage protection, preventing the motor from restarting automatically after a power interruptionCorrect
- B. Low-voltage release, allowing the motor to restart automatically when voltage is restored
- C. Ground-fault protection by isolating the control circuit from the power circuit
- D. Overload protection by sensing sustained excess current through thermal heaters
Why A is correct
Per NEETS Mod. 3 §3-2, 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 until the start button is pressed again. Low-voltage release, by contrast, allows automatic restart.
Cited:NEETS Mod. 3 §3-2