Q1. Explain the principle of operation of synchronous Motors with a simple sketch. Where are synchronous motor used onboard? (16)
Q2.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)
Q3. With reference to batteries onboard:
a) Distinguish between ‘Lead acid cell’ and ‘Alkaline cell’ (6)
b) Describe how a battery of alkaline cells may be tested for its usefulness, after a long storage and if found deficient, how it can be remedied? (6)
c) Explain how the ambient temperature is taken into account when determining the condition of the battery (4)
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)
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