Q3. 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) What is earth fault and how do you identify Earth fault in the 440 V system onboard. (4)
c) Discuss the consequences of earth fault in an earthed distribution system. (4)
Q3. a) What are safeties incorporated in ACB of ship’s generator and prime mover? (10)
b) Explain the procedure to test reverse power relay (6)
Q4. a) A 440 V, 10KW 0.8 pf phase load is supplied as shown.
Calculate short circuit fault current at the load and at the main switch board (8)
b) Explain the safe working procedure that you will follow while working in live MSB bus bar. (8)
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. With Reference to different types of transformers used onboard.
a) Discuss the basic principle of operation of a transformer (5)
b) Enumerate the different types of transformers used onboard also state their functions for which they are used. (5)
c) A 440/110 V single phase transformer supplies a load of 5kW at 0.8 power factor load. Calculate the primary and secondary currents. (Ignoring transformer power losses)? (6)
Q6. a) Describe the working of a single-phase full wave rectifier with a resistive load. Draw the load voltage and current waveforms. (8)
b) Diode half wave rectifier supply a resistive load of 100Ω from a 100 V ac r.m.s voltage source. The diode is a resistance of 5Ω during conduction state. Calculate
i) The DC output voltage
ii) DC average load current (8)
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)
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