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Q6. A. Describe the effect of the following loads on power factor: -

(i) Induction motors; (ii) Transformers; (iii) Partly loaded motors; (iv) Cage type motors.

B. In a 50-Kav, star-connected, 440-V, 3-phase, 50-Hz alternator, the effective armature resistance is 0.25 ohm per phase. The synchronous reactance is 3.2 ohm per phase and leakage reactance is 0.5 ohm phase. Determine at rated load and unity power factor:

(a) Internal e.m.f Ea (b) no-load e.m.f E0 (c) percentage regulation on full-load (d) value of synchronous reactance which replaces armature reaction.

Q9. A. Sketch a graph of starting current, and torque against the speed of rotation for a single cage motor. (6)

B. A 230 V motor, which normally develops 10kW at 1000 rev/min with an efficiency of 85%, is to be used as a generator. The armature resistance is 0.15 Ohm and the shunt field resistance is 220 Ohm. If it is driven at 1080 rev/min and the field current is adjusted to 1.1A by means of the shunt regulator what output in kW could be expected as a generator, if the armature copper loss was kept down to that when running as a motor. (10)

Q7. A. Describe stability requirement for dry-docking.

B. A ship of 8000 tonne displacement floats upright in seawater. KG = 7.6m and GM = 0.5m. A tank, KG is 0.6m above the keel and 3.5m from the centre line, contains 100 tonne of water ballast. Neglecting the free surface effect, calculate the angle which the ship will heel, when the ballast water is pumped out.

Q7. (a) Describe how bulkheads are tested. (6)

(b) A double bottom tank containing seawater is 6m long, 12m wide and 1m deep. The inlet pipe from the pump has its center 75mm above the outer bottom. The pump has a pressure of 70 kN/m² and is left running indefinitely. calculate the load on the tank top:

 (i) If there is no outlet.

(ii) If the overflow pipe extends 5m above the tank top. (10)

Q10. A) Describe the stability requirements of a ship for dry-docking. (6)

B) A ship 130m long displaces 14000 tonne when floating at draughts of 7.5m forward and 8.10m aft. GML – 125m, TPC – 18, LCF-3m aft of midships. Calculate the final draughts when a mass of 180 tonne lying 40m aft of midships is removed from the ship. (10)

Q8. A. Explain the reasons for fitting bulbous bow. B. When a ship is 800 nautical miles from port its speed is reduced by 20%, thereby reducing the daily fuel consumption by 42 tonne and arriving in port with 50 tonne on board. If the fuel consumption in t/h is given by the expression (0.136+0.001 V3) where V is the speed in knots, estimate: (i) The reduced consumption per day; (ii) The amount of fuel on board when the speed was reduced; (iii) The percentage decrease in consumption for the latter part of the voyage;

(iv) The percentage increases in time for this latter period.

Q6. Describe the movement of a ship with negative metacentric height B. A ship of 8000 tonne displacement has its centre of gravity 4.5m above the keel and transverse metacenter 5.0m above the keel when a rectangular tank 7.5m long and 15m wide contains seawater. A mass of 10 tonne is moved 12m across the deck. Calculate the angle of heel i. If there is free surface of water ii. If the water doesn’t completely fill the tank.

Q10. A. Explain the considerations which govern the size and shape of a rudder. B. A ship of 12000 tonne displacement has a rudder 15m2 in area, whose centre is 5m below the waterline.  The metacentric height of the ship is 0.3m and the centre of buoyancy is 3.3m below the waterline.  When travelling at 20 knots the rudder is turned through 30 .  Find the initial angle of heel if the force Fn perpendicular to the plane of the rudder is given by: Fa=577 Av2 sin  N, Allow 20% for the race effect.

Q8. A. Describe the ways in which an unstable ship can be made stable. B. When a mass of 25 tonnes is shifted 15m transversely across the deck of a ship of 8,000 tonnes displacement, it causes a deflection of 20cms in a plumb line 4m long. If the KM=7 m, calculate the KG

Q10. A) Describe measures which may be taken to improve the stability or trim of a damaged ship. (6)

B) A watertight bulkhead is 8m high and is supported by vertical stiffeners 700mm apart, connected at the tank top by brackets having 10 rivets 20mm diameter. The bulkhead is flooded to its top edge with sea water. Determine:

(a) Shearing force at top of stiffeners,

(b) Shear stress in the rivets,

(c) Position of zero shear. (10)

Q6. A ship 90 m long displaces 5200 tonne and floats at draughts of 4.95m forward and 5.35 m aft when in sea water of 1023 kg/m3. The water plane area is 1100m2, GML 95m, LCB 0.6m forward of midships and LCF 2.2m aft of midships. Calculate the new draughts when the vessel moves into fresh water of 1002 kg/m3

Q6. A. Describe the effect of cavitation’s on the propeller blades.

b) A ship has a constant cross-section in the form of a triangle which floats apex down in sea water. The ship is 85 m tong, 12 m wide at the deck and has a depth from keel to deck of 9 m. Draw the displacement curve using 1.25 m Intervals of draught from the keel to the 7 .5m waterline. From this curve obtain the Displacement in fresh water at a draught of 6.50 m. (10)