Q1. Discuss the criteria of the classification of marine high voltage for A.C. and D.C. Systems. Sketch a Ships high voltage distribution system and explain its features. Discuss the various methods of testing the insulation of HV system, Mention the significance of PI test, why 3 terminals insulation testers are used in HV insulation measurements. (16)
Q2. What are the condition for producing sustained oscillations? Classify oscillations with respect to frequency range, principle involved, etc. It is possible to produce oscillations with RC networks in phase shift oscillator. Discuss in detail. (16)
Q3. Which of the following devices will prevent a DC generator from becoming motorized?
a) Over current relay
b) Motorization trip
c) Reverse power relay
d) Reverse current relay.
why the remaining options were not considered. (16)
Q4. a) What design factor limits the maximum torque of a d.c. motor? (6)
(b) A shunt motor runs on no load at 700 r/min off a 440 V supply. The resistance of the shunt circuit is 240Ω. The following table gives the relationship between the flux and the shunt current:
Shunt current (A): 0.5 0.75 1.0 1.25 1.5 1.75 2.0
Flux per pole (mWb): 6.0 8.0 9.4 10.2 10.8 11.2 11.5
Calculate the additional resistance required in the shunt circuit to raise the no-load speed to 1000r/min (10)
Q5. (a) On what factors does the capacitance of a parallel-plate capacitor depend? (6)
(b) A tuned circuit consisting of a coil having an inductance of 200µH and a resistance of 20Ω in parallel with a variable capacitor is connected in series with a resistor of 8000Ω across a 60 V supply having a frequency of 1 MHz. Calculate: (10)
(a) The value of C to give resonance.
(b) The dynamic impedance and the Q factor of the tuned circuit.
(c) The current in each branch
Q6. (a) The capacitor-start induction run motor has a much higher starting torque than the resistance split-phase motor. Explain (6)
(b) An eight-pole armature is wound with 480 conductors. The magnetic flux and the speed are such that the average e.m.f. generated in each conductor is 2.2 V, and each conductor is capable of carrying a full load current of 100 A. Calculate the terminal voltage on no load, the output current on full load and the total power generated on full load when the armature is:
(i) Lap connected
(ii) Wave connected (10)
Q7. If a small amount of oil is spilled during bunkering and causes a sheen upon the water, state what should be the procedure adopted for pollution control, information to authorities and subsequent bunkering practice (16)
Q8. (a) Make a detailed sketch of a non-portable 136-liter foam fire extinguisher. (4)
(b) Briefly explain how to operate the foam extinguisher. (3)
(c) State the two constituents used, which enable stable foam to be produced. (3)
(d) State for what approximate length of time, the extinguisher should generate foam. (3)
(e) Where on board ship would you expect such an extinguisher to be located? (3)
Q9. with reference to the 1978 SOLAS protocol which outlines mandatory requirements for steering gear tests and drills:
(a) Describe the test procedure to be carried out within the 12 hours before departure on a sea voyage. (6)
(b) Describe the emergency steering drills that must take place at least every 3 months. (5)
(c) State how often the tests in (a) and the drill in (b) should be carried out for ships which regularly engaged on voyages of short duration (5)
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