DieselShip's Online Content Library

Q1. (a) Draw circuit diagram and explain working of Star – Delta starter.  (8)

(b) Explain with diagram how direction of single phase induction motor is reversed. (8)

Q2. Briefly explain the principle of operation of Variable Frequency Drives (VFD). Discuss the

advantages and disadvantages of VFDs onboard merchant vessels? (16)

Q1.a) Explain three methods of overcurrent protection for electrical circuit. (8)

b) Explain with aid of diagram, the meaning of the term inverse current time characteristic (8)

Q4. (a) Explain the principle of a Transformer? Discuss the various types of transformers used onboard? (8)

(b) In a container ship, a 3-ph, delta/delta connected 6600/440 V, 60 Hz transformer is feeding AMP supply from shore to 440 Volt switchboard. Transformer primary current takes a line current of 100 amp, when secondary load of 0.8 lagging p.f. is connected. Determine each coil-current and KW output of transformer. (8)

Q5. A circuit has a resistance of 3Ω and an inductance of 0.01H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate

a) The impedance (6)

b) The power factor (5)

c) The power absorbed. (5)

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. (a) With reference to working onboard the Deck Cargo crane, elaborate the hazards associated with working at heights? (5)

(b) What risk mitigation measures will you take to mitigate the hazards identified by you while working at heights? (6)

(c) Which all risk assessment checklists, work checklists and work Permits will you fill up before commencing the work and who will authorize the work permits? (5)

Q7. With Reference to Electrical Safety onboard a vessel:

a) Write Short note on “Electric Shock” (6)

b) Enumerate the relation between Shock Current Levels, the Applied Voltage and the Body resistance. (5)

c) How do you treat a person who has suffered an electric shock onboard from a AC supply? (5)

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)