DieselShip's Online Content Library

Q9. A wooden ring having a mean diameter of 200 mm and a cross-sectional area of 400 mm2 is wound uniformly with a coil of 300 turns. If the current passed through the coil is 5 A calculate the value of flux produced in the coil. (16)

Q9. (a) Explain about non-linear resistors with some examples and illustration on how they differ from linear resistor. (6)

(b) A half-wave rectifier is used to supply 50V d.c. to a resistive load of 800Ω. The diode has a resistance of 25 Ω. Calculate a.c. voltage required. (10)

Q7. (a) Define Density, Relative Density (6)

(b) A bilge holding tank of 5 m length, 3 m width and 1.8 m depth has water of density 1.020 t/m3 up to a sounding of 1.3 m and oil of density 0.86 t/ m3 is floating on top of water up to an ullage of 0.3 m. Calculate the mass of water and oil in the tank. (10)

Q8. (a) Derive the formula for Admiralty Coefficient. (6)

(b) A ship travels 900 nautical miles at a speed of 12.5 knots and burns 150t of fuel over the voyage. Estimate the distance the ship could travel at a speed of 13.5 knots on 250t of fuel. (10)

Q4. a) What is a commutator? Discuss its rectifying action in detail. (6)
(b) Determine the line current taken by a 440 V, three-phase, star-connected motor having an output of 45 Kw at 0.88 (lagging) power factor and an efficiency of 93 per cent. (10)

Q6. a) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature reactance. (6)

b) Two earth lamps at 120 V, 15 W are used on a 110 V distribution circuit. Due to damage to a motor, the resistance of the positive line is reduced to 10 ohm and that of the negative line to 5 ohm. Find the voltage across each lamp and the extra load on the generator due to the fault. (10)

Q5. With Reference to different types of transformers used onboard.

a) Discuss the basic principle of operation of a transformer (5)

b) Enumerate the different types of transformers used onboard also state their functions for which they are used. (5)

c) A 440/110 V single phase transformer supplies a load of 5kW at 0.8 power factor load. Calculate the primary and secondary currents. (Ignoring transformer power losses)? (6)

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.

Q5. A three-phase transformer has 900 turns in primary and 104 turns in secondary winding respectively. The primary winding is connected with power supply of 6600 Volt from HV switch board. Calculate the secondary line voltage when transformer is connected in A) Star-Delta B) Delta-Star

Q9. 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? B. The primary and secondary windings of a 500 Kva transformer have resistance of 0.42 and 0.0019 respectively. The primary and secondary voltages are 11 000 V and 415 V respectively and the core loss is 2.9 Kw, assuming the power factor of the load to be 0.8. Calculate the efficiency on (i) Full load; (ii) Half load;

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.