DieselShip's Online Content Library

Q4. a) Sketch and describe a star-delta starter for starting an induction motor (10)

b) Three similar coils, each having a resistance of 10 ohms and an inductance of 0.02 H are connected in

i) Star

ii) Delta to a 3-phase, 50-Hz supply with 500V

Calculate the total power absorbed and the line current in each case. (6)

Q7. (a) Describe the function of the stern frame. (6)

(b) A ship displacing 10000 tonne and travelling at 16 knots has a fuel consumption of 41 tonne per day. Calculate the consumption per day if the displacement is increased to 13750 tonne and the speed is increased to 17 knots. Within this speed range, fuel consumption per day varies as (speed)3/8 (10)

Q8. (a) What are the effects of adding mass to draught and trim of a ship? (6)

(b) The half ordinates of the waterplane area of a ship of 8200 t displacement, 90 m long are 0, 2.61, 3,68, 4.74, 5.84, 7.00, 7.30, 6.47, 5.35, 4.26, 3.16, 1.88 and o m respectively. It floats in sea water of 1.024 t/m3. Calculate the change in mean draught when moving into water of 1.005 t/m3 (10)

Q10. (A). Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse.

(B) An AC Voltage Of 24 V is connected in series with the silicon diode and load resistance 500 Ohm having forward resistance 1O Ohms. Calculate the peak output voltage.

Q 7. With reference to Synchronous Motors.

A. Draw and explain the principle of operation Synchronous Motors.

B. Find the synchronous impedance reactance of an alternator in which a given field current produces an armature current of 200 A on short circuit and a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm. To what induced voltage must the alternator be excited if it is to deliver a load of 100A at a p.f of 0.8 lagging, with a terminal voltage of 200 V.

Q3. What would be value of Neutral Earthing Resister in a high voltage ship of three phase alternators to limit the earth fault current to the full load of rating of a 4 MW having 0.8 power factor generating 6600 volts?

Q8. A. What is silicon controlled rectifier (SCR)? How is the break over voltage of the SCR defined?  B. A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 . The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate - (i) The speed; (ii) The gross torque developed by the armature

Q8: A. What is meant by the Admiralty Coefficient and the Fuel Coefficient?

B. A slip of 14900 tonne displacement has a shaft power of 4460 Kw at 14.55 knots. The shaft power is reduced to 4120 kW and the fuel consumption at the same displacement is 541 kg/h. Calculate the fuel coefficient for the ship.

Q7. A. Describe the stability requirements of a ship for dry-docking.

(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.

Q6. (a) Describe the relationship between frictional resistance and

(i) Ship’s speed;

(ii) the wetted area;

(iii) surface roughness;

(iv) The length of the vessel.

b) A ship 150m long and 8.5m draught has a rudder whose area is one sixtieth of the middle-line plane and diameter of stock 320mm. Calculate the maximum speed at which the vessel may travel if the maximum allowable stress is 70 MN/m? the centre of stock 0.9m from the centre of effort and the maximum rudder angle is 35 degrees. (10)

Q6. The force acting normal to the centerline plane of a rudder is given by the expression:

Fn = 15.5 A v2 α newtons

Where, A = Rudder area (m2)

v = Ship speed (m/s)

α = Rudder helm angle (degrees)

A ship travelling at a speed of 20 knots has a rudder configuration as shown in Fig Q4. The center of effort for areas A1 and A2 are 32% of the width from their respective leading edges. The rudder angle is limited to 35º from the ship's centerline.

Calculate EACH of the following:

(a) The diameter of the rudder stock required for a maximum allowable stress of 77 MN/m2;

(b) The drag component of the rudder force when the rudder is put hard over at full speed.

Q9. (a) Describe the effects on centre of gravity of slack tanks. (b) A box-shaped vessel 100-meter-long x 20 meters wide X 12 meters deep is floating in salt water on an even keel at 6 meters’ draft. A forward compartment is 10 meters long, 12 meters wide and extends from the outer bottom to a watertight flat, 4 meters long 12 meters wide and extends from the outer bottom to a watertight flat, 4 meters above the keel. the compartment contains cargo of permeability 25%. find the new draft if this compartment is bilged.