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Q9. A. Describe how the distribution of mass within the ship affects the rolling period;

B) The ½ ordinates of a water plane at 15m intervals, commencing from aft, are 1, 7, 10.5, 11, 11, 10.5, 8, 4 and 0m. Calculate:

(a). TPC;

(b). Distance of the centre of flotation from midships.

(c). Second moment of area of the water plane about a transverse axis through the centre of flotation.

Q9. A. What are the factors which determine the synchronous speed of a motor? (6)

B. A 72 KVA transformer supplies a heating and lighting load of 12 KW at unity power factor and a motor load of 70 kVA at 0.766 (lagging) power factor; Calculate the minimum rating of the power-factor improvement capacitors which must be connected in the circuit the ensure that the transformer does not become overloaded. (10)

Q7. a) Describe how water tightness is maintained where bulkheads are pierced by longitudinal beams or pipes. (6)

b) A ship of 15000 tonne displacement has an Admiralty Coefficient, based on shaft power, of 420. The mechanical efficiency of the machinery is 83%, shaft losses 6%, propeller efficiency 65% and QPC 0.71. At a particular speed the thrust power is 2550 Kw. (10)

Calculate: (i) Indicated power,         (ii) Effective power,           (iii) Ship speed.

Q10. a) Explain the concept of dynamical stability. (6)

b) A ship of length 140m, Breadth of 18.5m, draught of 8.1m and a displacement of 17,025 tonnes in sea water, has a face pitch ratio of 0.673. The diameter of the Propeller is 4.8m. The results of the speed trial show that true slip may be regarded as constant over a range of 9 to 13 knots and is 30%, w = 0.5CB-0.05. If fuel used is 20t/day at 13 knots and fuel consumption/day varies as cube of speed of ship, determine the fuel consumption, when propeller runs at 110 rpm. (10)

Q9. A ship 120 meters long at the waterline has equidistantly spaced half-ordinates commencing from forward as follows 0,3.7,5.9,7.6,7.5,4.6, and 0.1 meters respectively. Find the area of the waterplane using Simpson’s Second rule and the TPC at this draft, Water density is 1.025 t/m3. (16)

Q9. a) Draw a metacentric diagram for a vessel of constant triangle cross-section (6)

b) A block of wood of uniform density has a constant cross-section in the form of a triangle, apex down. The width is 0.5 m and the depth 0.5 m. It floats at a draught of 0.45 m. Calculate the metacentric height (10)

Q7. a) What is the difference between a DC Generator and a DC motor? (6)

b) A 4-pole, 32 conductor, Lap-wound DC shunt generator with terminal voltage of 200 V delivering 12 A to the load has ra = 2 and field circuit resistance of 200 Ω. It is driven at 1000 RPM .

a) Calculate the flux per pole in the machine. (6)

b) If the machine has to be run as a motor with the same terminal voltage and drawing 5 A from mains, maintaining the same magnetic field, find the speed of the machine. (10)

Q6. A coil of resistance 10 ohm and inductance 0.1H is connected in series with a capacitor of capacitance 150pF, across a 200 V, 50 Hz supply.

Calculate:

a) the inductive reactance. (3)

b) the capacitive reactance. (3)

c) the circuit impedance. (2)

d) the circuit current. (2)

e) the circuit power factor. (2)

f) the voltage drop across the coil. (2)

g) the voltage drop across the capacitor. (2)

Q6. (a) What are the different types of DC motors? (6)

(b) A 10 H.P. 230 V shunt motor takes an armature current of 6A from 230 V mains at no load runs at 1200 r.p.m. The armature resistance is 0.25Ω. Determine speed and electromagnetic torque when the armature takes 36 amps with the same flux. (10)

Q8. a) Explain how excitation of the rotor is produced and supplied. (6)

b) A 75-kW, 400-V, 4-pole, 3-phase star connected synchronous motor has a resistance and synchronous reactance per phase of 0.04 Ohm and 0.4 Ohm respectively. Compute for full-load 0.8 p.f. lead the open circuit e.m.f. per phase and mechanical power developed. Assume an efficiency of 92.5%. (10)

Q6. (a) Describe the provisions of additional structural strength to withstand pounding. (6)

(b) A vessel travelling at 17 knots turns with a radius of 450 m when the rudder is put hard over. The centre of gravity is 7 m above the keel, the transverse metacentre 7.45 m above the keel and the centre of buoyancy 4 m above the keel. If the centripetal force is assumed to act at the centre of buoyancy, calculate the angle of heel when turning. The rudder force may be ignored. (10)

Q4. a) Why is it important to maintain high efficiency of operation? And low values of voltages regulation for power transformers? (6)

b) A shunt motor supplied at 230 V runs at 900 rpm. When the armature current is 30 A, the resistance of the armature circuit is 0.4 Ω. Calculate the resistance required in series with the armature circuit to reduce the speed to 500 rpm. Assume that the armature current is 25 Amps. (10)