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Q6. An alternator having 8 pole driven by 900 rpm Diesel engine supplies power to load of Synchronous motor having 24 poles and Induction motor of 8 poles and 2 % slip. A) Calculate the frequency and speed of Synchronous Motor. B) Calculate the frequency and Speed of Induction Motor

Q10. A 100 kW, 460 V shunt generator was run as a motor on no load at its rated voltage and speed. The total current taken was 9.8 A, including a shunt current of 2.7 A. The resistance of the armature circuit at normal working temperature was 0.11  Calculate the efficiencies at i. Full load; ii. Half load. (16)

Q9. The ½ ordinates of a water plane at 15m intervals, commencing from aft, ar. 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.

Q8. A ship 150 m in length, 24 m breadth, displaces 25000 tonne when floating at a draught of 9 m in sea water of density 1025 kg/m³. The ship’s propeller has a diameter of 5.8 m, a pitch ratio of 0.9 and a blade area ratio of 0.45. With the propeller operating at 2 rev/sec, the following results were recorded:

Apparent slip ratio = 0.06

Thrust power = 3800 kW

Propeller efficiency = 64%

The Taylor wake fraction is given by: WT = 0.5CB - 0.05

Calculate EACH of the following for the above condition:

(a) The ship’s speed

(b) The real slip ratio

(c) The thrust per unit area of blade surface

(d) The torque delivered to the propeller.

Q6. A ship 75m long has semi ordinates at the load water plane commencing from forward as follows: 0, 1, 2, 4, 5, 5, 5,4, 3, 2 and 0 metres respectively.

The spacing between the first three semi-ordinates and the last three semi-ordinates is half of that between the other semi-ordinates. Find the position of the Centre of Flotation relative to amidships.

Q8. A ship consumes an average of 70 tonne of fuel per day on main engines at a speed of 17 knots. The fuel consumption for auxiliary purposes is 8 tonne per day. When 800 nautical miles from port it is found that only 140 tonne of fuel remains on board and this will be insufficient to reach port at the normal speed. Determine, using a graphical solution, the speed at which the ship should travel to complete the voyage with 20 tonne of fuel remaining.

Q8. (a) Define coefficient of fineness of waterplane area, block coefficient and midships coefficient. (b) A box shaped vessel has length 100m and breadth 12m and floats at a range of drafts from 1m to 10m. Produce curves of KB1, BM and KM.

Q8. A. Describe the fundamental principle of a propeller. (6)

B. A propeller 6m diameter has a pitch ratio of 0.9, BAR 0.48 and, when turning at 110 rev/min, has a real slip of 25% and wake faction 0.30. If the propeller delivers a thrust of 300 KN and the propeller efficiency is 0.65. Calculate - i Blade area; ii Ship speed; iii. Thrust power; iv Shaft power v. Torque (10)

Q9. Describe the effect of cavitaion on: i. The thrust and ordque; ii. The propeller blades B. A ship 150m long and 19m beam floats at a draught of 8m and last a block coefficient of 0.68 i) if the admicatry coefficient is 600 calculate the shaft power required at 18 knots; ii) If the speed is now increased to 21 knots, and within this speed range resistance varies as speed find the new shaft power.

Q5. In some circumstances electrical current may be induced into the shafting of rotating machinery.

a) State the problem that may be caused by this current. (6)

b) Explain with aid of sketches, how currents may be avoided or reduced in the following instances:

(i) D.C machines

(ii) Main shafting fitted with a bronze propeller (10)

Q6.a) Define centre of buoyancy and show with the aid of sketches how a vessel which is Stable will return to the upright after being heeled by an external force (6)

b. An oil tanker of 17000 tonne displacement has its centre of gravity 1 m aft of midships and has 250 tonne of oil fuel in its forward deep tank 75 m from midships. This fuel is transferred to the after oil fuel bunker whose centre is 50 m from midships. 200 tonne of fuel from the after bunker is now burned. (10)

Calculate the new position of the centre of gravity:

(a) after the oil has been transferred

(b) after the oil has been used.

Q10. A. What are the factors which determine the synchronous speed of a motor? (6)

B. A twelve-pole, three-phase, delta-connected alternator runs at 600 rev/min and supplies a balanced star-connected load. Each phase of the load is a coil of resistance 35 ohm and inductive reactance 25 ohm. The line terminal voltage of the alternator is 440V. Determine (a) frequency of supply (b) current in each coil (c) current in each phase of the alternator (d) total power supplied to the load. (10)