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 620KW and the power factor 0.80? (8)
Q5. Explain with the help of a neat diagram the operation of a brushless alternator. What would likely happen if one of the rotating Diode fails and becomes: (16)
a) An open circuit?
b) A short circuit?
Q6. With Reference to 3-phase Transformers:
a) Discuss the essential and desirable conditions to be fulfil for operating two three-phase transformers in parallel. (5)
b) What are the advantages of transformer bank of three 1-phase transformers over a unit three phase transformer of the same kVA rating? (5)
c) In a 25 kW, 3300/233V, 1-phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency at half load 0.8 P. F (6)
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