Q4. With reference to a three-phase shipboard electrical distribution system:
a) Enumerate the advantages of an insulted neutral system. (4)
b) Enumerate the disadvantages of an insulted neutral system. (4)
c) Describe how the Earthed neutral system is earthed. (4)
d) Compare the use of an insulated neutral system as opposed to the use of an Earthed neutral system with regard to the risk of electric shock from either system. (4)
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)
Q6. (a) The capacitor-start induction run motor has a much higher starting torque than the resistance split-phase motor. Explain (6)
(b) 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. (10)
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