DieselShip's Online Content Library

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

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

Q2. a) Briefly explain the principle of Operation of induction Motors (4)

b) What is slip for an induction motor? (4)

c) Draw a simple ladder logic diagram of star delta starting of an induction motor. (8)

Q3. a) What precautions must be taken when testing the insulation of generator cables and wiring connected to an AVR unit? (6)

b) If synchroscope is malfunctioning, which instrument is the most essential to parallel an alternator with the busbar? Justify your answer (6)

c) How the air gap of an alternator is measured and why the air gap of an alternator to be checked periodically? (4)

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)

Q5. A shunt generator has an induced emf of 254 V. When the generator is loaded, the terminal voltage is 240 V, Neglecting armature reaction, find the load current if the armature resistance is 0.04 ohm and the field circuit resistance is 24 ohms. (16)

Q6. A 100 KVA, 2400/240 V, 50 Hz, 1-phase transformer has no- load current of 0.64 A and a core loss of 700 W, when its high voltage side is energized at rated voltage and frequency . calculate the two components of no-load current. If this transformer supplies a load current of 40 amp at 0.8 lagging power factor at its low voltage side, determine the primary current and its power factor. Ignore leakage impedance drop. (16)

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)

Q8. a) Describe CO2 Fixed fire fighting system for machinery spaces and cargo spaces of a bulk carrier. (8)

b) Explain safety precautions taken prior to release of CO2 to the engine room. (8)

Q7.a) Sketch and describe hydraulic circuit of steering gear incorporating automatic isolation system. (8)

b) Explain ‘Emergency steering’ (4)

c) Describe the routine tests of steering gear as per SOLAS requirement. (4)

Q2. With Respect to Insulated and Earthed Neutral Systems used on board:

a) Discuss the Advantages and Disadvantages of both Insulated and Earthed Systems used on board. (8)

b) Discuss the consequences of earth fault in an earthed distribution system. (4)

c) What would be the Ohmic value of the NER to limit the earth fault to the full load rating of a 2 MW, 0.8 pf, 3.3KV, 3Phase A.C. generator? (4)

Q3. a) Explain with the aid of a diagram, a controller utilizing proportional plus integral action. (6)

b) List out the Advantages and Disadvantages of electric propulsion system (5)

c) Explain briefly what you know about “Pulse Width Modulation” and how it can be applied for propulsion control. (5)

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)

Q1. With Respect to PLC’s used onboard ships:

a) Draw and explain the block diagram of a PLC. (8)

b) Name the onboard ship equipment where PLC’s are used. (4)

c) What are the advantages of PLC controllers over other type of controllers? (4)

Q5. A 400V, 4-pole, 50 Hz, 3-phase, 10 hp, star connected induction motor has a no load slip of 1% and full load slip of 4%, find the following:

(i) Syn speed

(ii) No -load speed

(iii) Full load speed

(iv) Frequency of rotor current at full load

(v) Full – load torque (16)

Q6. With reference to Diesel engine driven alternator:

a) Explain the significance of the term “speed droop” during the parallel operation of alternators. Assuming two alternators are running in parallel, outline the frequency vs load characteristics of the alternators while load sharing. (8)

b) Two 3Ø alternators operate in parallel, the rating of A is 1000 kW and B is 800 kW. The droop setting of each generator is 4%, If the load to be shared by both the generators is 1000 kw, calculate the load sharing by generators A and B, if the original frequency at no-load is 62Hz. (8)

Q7. a) Describe the routine tests required for self-contained breathing apparatus sets (8)

b) Describe the procedure to be adopted to find missing personnel in a smoke-filled accommodation area. (8)

Q8. 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 MARPOL, Annex V:

a) Explain the regulations stipulated for disposal of garbage under annex V of MARPOL 73/78. (8)

b) State the special areas notified under annex V of Marpol 73/78 (4)

c) State what precautions you will take during disposal of waste from Electrical workshop (4)