DieselShip's Online Content Library

Q1. (a) Compare methods of obtaining speed regulation of three-phase induction motor generally used in tankers by means of: (16)
i. Rotor resistance.
ii. Cascade system.
iii. Pole-changing.

Give examples where each system may be employed with advantage.

Q2. a) State the necessary conditions required prior to the synchronizing of electrical alternators. (4)

b) Describe the type of cumulative damage that may be caused when alternators are incorrectly synchronized. (4)

c) Explain how the damage referred to in (b) can be avoided / reduced. (4)

d) For two alternators operating in parallel state the consequences of: (4)

(i) Reduced torque from the prime mover of one machine.

(ii) Reduced excitation on one machine.

Q1. With respect to the High Voltage power systems installation, explain the different types of circuit breaker that are used, comparing them on merits and de-merits. Describe the theory of arc phenomenon and the mechanism fitted to mitigate the arc. (16)

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)

Q4. A) Explain the potential hazards if liquid-cooled transformers are used. (6)
b) What are the losses in transformers? Mention the various factors which affect these losses. In a 25 KVA, 3300/233 V, single phase transformer, the iron and full-load Cu. Losses are respectively 350 and 400 w. Calculate the efficiency at half-full load 0.8 power factor. (10)

Q6. a) Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse.

b) A 440 V shunt motor takes an armature current of 30 A at 700 rev/min. The armature resistance is 0.7 ohm. If the flux is suddenly reduced 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged torque to motion, what will be the new steady values of speed and armature current? Sketch graphs showing armature current and speed as functions of time during the transition from initial to final, steady-state conditions.   (10)

Q9. With respect to MARPOL 73/78, Annex-ll, Noxious liquid chemicals are divided into categories.

a) State the number of categories, and what does each category signify. (8)

b) State the requirement of procedures and Arrangements Manual, and what information is available. (8)

Q9. With reference to free fall lifeboat of an ocean-going ships:
a) Periodical maintenance, tests and checks on lifeboat and releasing gear. (6)
b) Secondary means of lowering. (5)
c) Lifeboat Drills. (5)

Q8. Briefly discuss the following with respect to safety of navigation:

a) Bridge Navigation Watchkeeping Alarm System (BNWAS) (6)

b) Long Range Identification and Tracking of ships (LRIT). (5)

c) Voyage Simplified Voyage Recorder (VDR/S-VDR) (5)