DieselShip's Online Content Library

Q1. With respect to generators and main circuit breakers and their protection devices:

a) What are safeties incorporated in Air circuit breaker (ACB) of ship’s generator and prime mover? (10)

b) Write Short Note on Negative phase Sequence Relay. (6)

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. 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

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)

Q5. a) Describe the different type of losses occurring in the Power Transformers. (4)

b) A single-phase power transformer supplied a load of 20 KVA at a P.F of 0.81 (lagging). The iron loss of the transformer is 200 W and the copper loss at this load is 180 W. Calculate

(i) The efficiency

(ii) If the load is now changed to 30 KVA at a p.f of 0.91 (lagging). Calculate the new efficiency

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)

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)

Q8. 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)