Marine Electrotechnology. Test 1

Choose the group of electrical power supplies that best fits the identification of 'Emergency'

Shaft generator and emergency diesel
Batteries and No 1 diesel
Emergency diesel and batteries
No 1 diesel and No 2 diesel

When a blackout occurs: what should be your first reaction?

Cancel audible alarms
Investigate the cause of the blackout
Inform the Chief Engineer
Inform the bridge about the reason for blackout, and expected time to restart.

An electrical power emergency source in a ship is required because:

The ship's total load can be shared between main and emergency generators
It satisfies the SOLAS requirements for ship safety
The main diesel generator(s) can be taken out of service for overhaul or repair
It satisfies the need to be environmentally 'friendly'

Check-synchroniser equipment is often installed to:

Allow auto-synchronising to take place
Prevent manual synchronising outside permitted limits
Permit faster paralleling
Ensure fair equal sharing between generators

Due to failure of one of the carbon brushes the excitation voltage is lost on one alternator that is operating in parallel. Will that alternator then:

Continue to share the active load (kW) but have very high reactive load (kVAR)
Completely loose its share of the load causing the auxiliary engine to speed up
Try to take all the load and so trip the main circuit breaker
Overload due to reduced voltage output and increased current

A 10% reduction in generator speed occurs due to a faulty governor. The likely consequence for each motor powered from this generator is to:

Reduce motor volt drop by about 10%
Increase motor speed by about 10%
Increase motor power by about 10%
Reduce motor speed by about 10%

'Protective discrimination' means the progressive grading of sizes/tripping times of:

Generators and motors.
Line fuses and overcurrent relays
Magnetic and thermal current transformers.
440 V and 220 V transformers.

The insulation resistance (IR) to earth of a new galley hot-plate is measured to be 30 Mohm. When three identical hot-plates are tested together their combined IR will be:

10 Mohm
30 Mohm
3 Mohm
90 Mohm

The earth lamps in a 3-phase system indicate as follows: Red= bright Yellow= dark Blue= dim

hard earth - light earth - no fault
light earth - hard earth - no fault
light earth - no fault - hard earth
no fault - hard earth - light earth

Review Answers

Marine Electrotechnology. Test 1

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