DieselShip's Online Content Library

Q8. (a) Explain what is meant by 'assigned summer freeboard' (6)

(b) A box-shaped vessel 60m long, 10m beam, and 6m deep, is floating in salt water at drafts 4m Forward and 4.4 m. Aft. Find how far forward of amidships a weight of 30 tonnes must be loaded if the draft aft is to remain at 4.4m. (10)

Q6. (a) Sketch an arrangement showing the principal of a proportional plus Integral (P + I) control loop. (6)

(b) Compare the series and parallel resonance circuits. Find the frequency at which the following circuit resonates. (10)

Q5. a) Describe the no-load saturation characteristics of a D.C. generator. (6)

b) A D.C. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 Ω. The machine has six poles and the armature is lap- connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate (10)

i) The speed

ii) The gross torque developed by the armature.

Q5. a) Describe the different type of losses occurring in the Power Transformers. (4)

b) A single-phase power transformer supplied a load of 20 KVA at a P.F of 0.81 (lagging). The iron loss of the transformer is 200 W and the copper loss at this load is 180 W. Calculate

(i) The efficiency

(ii) If the load is now changed to 30 KVA at a p.f of 0.91 (lagging). Calculate the new efficiency

Q9. A) Describe the stability requirements of a ship for dry-docking. (6)

B) The ½ ordinates of a waterplane 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 waterplane about a transverse axis through the centre of flotation. (10)

Q8. a) Show how the power that is transferred across the air gap of the three-phase induction motor is represented. Explain the terms. What portion of this is useful power? (6)

b) A 440 V load of 400 kW at 0.8 (lagging) power factor is jointly supplied by two alternators A and B. The kW load on A is 150 kW and the KVAr load on B is 150 KVAr (lagging). Determine the kW load on B, the KVAr load on A, the power factor of operation on each machine and the current loading of each machine. (10)

Q6. A. With the aid of delta and star connection diagrams, state the basic equation from which   delta – star – delta conversion equation can be derived.

B. Three batteries A, B and C have their negative terminals connected together, between the positive terminals of A and B there is a resistor of 0.5 ohm and between B and C three is a resistor of 0.3 ohm,

i. Battery A 105 V, Internal resistance 0.25 ohm’

ii. Battery B 100 V, Internal resistance 0.2 ohm

iii. Battery C 95 V, Internal resistance 0.25 ohm

Determine the current values in the two resistors and the power dissipated by them.

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)

Q8. A. What is meant by the Admiralty Coefficient and the Fuel Coefficient? (6)

B. A ship 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. (10)

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)