Power Sources and Distribution Flashcards
7 cards from real GROL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Power Sources and Distribution flashcards as text
What is the primary purpose of a Ground Fault Circuit Interrupter (GFCI) in a marine AC electrical system?
Answer: To detect a small current imbalance between line and neutral that may indicate current flowing through a person or water
A GFCI monitors line-to-neutral current balance and trips within milliseconds when a mismatch as small as 5 milliamps is detected, indicating a shock hazard path.
What is 'stray current corrosion' in the context of marine electrical systems?
Answer: Accelerated electrochemical corrosion caused by DC current leaking from the vessel's wiring into the surrounding water
Stray currents leak from DC systems into the water and return through underwater metal fittings, creating an electrolytic cell that rapidly dissolves metal.
According to ABYC standards, what is the maximum permissible voltage drop in a shore power supply cable to a vessel?
Answer: 3% of the nominal supply voltage
ABYC E-11 limits shore power cable voltage drop to 3% of nominal supply voltage to ensure proper operation of all connected equipment.
What is the primary purpose of the bonding system in a marine electrical installation?
Answer: Electrically connecting all non-current-carrying metal parts to eliminate voltage differences that could cause shock or accelerate corrosion
Bonding interconnects all non-current-carrying metal parts of the vessel to prevent voltage potential differences, reducing shock hazard and protecting against stray current corrosion.
What does galvanic isolation accomplish when using shore power aboard a vessel?
Answer: It electrically separates the shore power grounding conductor from the vessel's DC negative, breaking a potential corrosion current path through the water
An isolation transformer or galvanic isolator breaks the conductive path between shore power ground and the vessel's DC negative, eliminating corrosion-driving currents through the water.
What is the function of the main shore power circuit breaker in a vessel's AC distribution panel?
Answer: To provide overcurrent protection for the entire vessel AC system and serve as the principal means of disconnecting shore power
The main shore power breaker provides overcurrent protection for all downstream circuits and serves as the principal means of isolating shore power from the vessel.
According to ABYC E-11, what color identifies the AC ungrounded (hot) conductor in a single-phase 120V North American marine circuit?
Answer: Black (ungrounded hot conductor color)
ABYC E-11 specifies black as the color of the AC ungrounded (hot) conductor in single-phase 120V North American marine circuits.