Electrical Distribution

Question 1

What voltage and frequency is used in U.S. Navy shipboard electrical systems?

Answer 1

450 VAC, 3-phase, 60 Hz.

Question 2

Why is the shipboard electrical system ungrounded?

Answer 2

For reliability; at least two faults are needed to cause system failure.

Question 3

What is selective tripping?

Answer 3

Isolating faults as close to the fault as possible, protecting other parts of the system.

Question 4

List two requirements for paralleling generators.

Answer 4

Matching phase rotation
Having the same output voltage
Oncoming machine at a slightly higher frequency

Question 5

What component automatically switches to an alternate power source when voltage is lost?

Answer 5

Automatic Bus Transfer (ABT).

Question 6

Name two types of generators used in ship service.

Answer 6

Ship Service Turbine Generator (SSTG)
Gas Turbine Generator (GTG)
Emergency Diesel Generator (EDG)