Q2. Briefly explain the principle of operation of Variable Frequency Drives (VFD). Discuss the
advantages and disadvantages of VFDs onboard merchant vessels? (16)
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. 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)
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)
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