DieselShip's Online Content Library

Q1. Describe with the aid of a simple sketch the arrangement of the three-phase winding of an alternator showing the neutral point. Explain why for most ships the neutral point is insulated. Explain why in some installation the neutral point in earthed. (16)

Q2. Diesel electric propulsion is now being chosen as the power plant for an increasingly wide variety of vessels. (16)
a) Sketch a simple layout of such an installation.
b) Explain the advantages of selecting such a plant.

Q1. What are semiconductor devices? What are its advantages over thermionic devices? With respect to semiconductor devices describe working principle and application of the following: (16)

(a) Zener Diode

(b) Transistor

(c) Photocell

(d) Thyristor

Q4. A 4-pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A, and the flux per pole is 0.3Wb, armature resistance 0.2Ω. Calculate the full load speed of the motor to maintain rated terminal voltage at the full load. (16)

Q5. a) Which has the greater equivalent resistance; two equal capacitors in series or in parallel? Explain with reasons? (6)

b) A circuit has a resistance of 3Ω inductance of 0.01H. The voltage across its end is 60V and the frequency is 50Hz. Calculate

a) the impedance

b) the power factor

c) the power absorbed. (10)

Q4. With respect to Alternators onboard:

a) Briefly explain true power, Apparent power and power factor? (8)

b) The alternator is rated for 750 KVA at 0.85 PF, what is the maximum load (Kilo Watt) that can be put on it? Would you be overloading the alternator if the kilowatt reading were now 620 KW and the power factor 0.80? (8)

Q7. With reference to entry into enclosed spaces onboard:
a) Define “Enclosed space” and give example of enclosed spaces onboard (6)
b) Describe the checks done for testing the atmosphere inside such enclosed spaces. (5)

c) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel. (5)

Q9. With respect to the hazardous areas of tankers.
(a) Explain the term flameproof (Ex d) for electrical equipment. (6)
(b) State the type of electrical equipment that would be protected in this way. (5)
(c) List likely defects of flameproof equipment. (5)

Q9. Briefly discuss the following with respect to safety of navigation:

a) Bridge Navigation Watchkeeping Alarm System (BNWAS) (6)

b) Long Range Identification and Tracking of ships (LRIT). (5)

c) Voyage Simplified Voyage Recorder (VDR/S-VDR) (5)