Power Sources and Distribution Flashcards

What is the minimum duration that SOLAS regulations require an emergency generator to supply power aboard a passenger vessel?

Answer: 18 hours minimum to support critical safety systems

SOLAS regulation II-1/43 requires emergency generators on passenger ships to maintain power to critical safety systems for a minimum of 18 hours.

How does a modified sine wave inverter differ from a pure sine wave inverter in marine applications?

Answer: Modified sine wave inverters produce a stepped approximation waveform that may prevent some sensitive electronics from operating correctly

Modified sine wave inverters generate a stepped waveform that approximates a sine wave but can interfere with sensitive electronics, audio equipment, and certain motor-driven appliances.

What is the primary function of an Automatic Transfer Switch (ATS) in a vessel's power distribution system?

Answer: To automatically transfer the electrical load from the failed normal power source to the emergency generator without manual intervention

The ATS continuously monitors normal power quality and automatically transfers connected loads to the emergency source when the primary source fails or degrades below acceptable limits.

Before closing the bus tie circuit breaker to parallel two AC generators aboard a vessel, which combination of parameters must be matched?

Answer: Voltage magnitude, frequency, phase sequence, and phase angle

All four parameters — voltage, frequency, phase sequence, and phase angle — must match before paralleling to prevent destructive circulating currents or mechanical shock to the prime movers.

In shipboard generator control systems, what is 'droop'?

Answer: An intentional decrease in speed or voltage as generator load increases, enabling multiple parallel generators to share load proportionally

Droop is a deliberate control characteristic where frequency or voltage decreases slightly as load increases, allowing paralleled generators to automatically divide load without a master/slave control arrangement.

What is the principal benefit of installing a shore power isolation transformer aboard a vessel?

Answer: It prevents the shore power grounding conductor from connecting to the vessel's underwater hardware, eliminating the galvanic corrosion current path through the water

An isolation transformer breaks the conductive path between shore grounding and the vessel's DC negative, preventing the boat from becoming part of a galvanic corrosion cell via the shore power connection.

What does UPS stand for, and what critical function does it serve in a vessel's communications power system?

Answer: Uninterruptible Power Supply — provides instantaneous battery backup to critical communications equipment so that no interruption occurs during power source transitions

A UPS supplies continuous, conditioned power to communications equipment with zero transfer time, ensuring radio communications are never interrupted during power failures.