DieselShip's Online Content Library

Q1. Explain the effect of reduced voltage on standard squirrel cage motors with respect to EACH of the following:

a) Burn outs (4)

b) Starting current (4)

c) Starting torque (4)

d) Speed (4)

Q2. a) In A.C. generators, voltage dip occurs in two stages.

i) Sketch a voltages-time graph showing the pattern of voltage dip. (4)

ii) Referring to this graph, state the reasons the effect on the electrical system of a small power installation when a large load is suddenly switched on. (4)

b) Explain EACH of the following categories of voltage control:

i) Error operated (4)

ii) Functional (4)

Q3. With reference to the provision of a shore electrical supply to a ship:

a) Sketch an arrangement for taking A.C. Shore supply and checks to be carried out prior taking shore connection? (8)

b) Describe the methods of safely connecting the arrangement sketched in (A) to the shore supply? (8)

Q4. a) What are the characteristics of PN junction diode? Point out its specifications. Also point out the significance of dynamic and static resistances. (6)

b) Draw the circuit of half-wave rectifier and its output waveform. A diode whose internal resistance is 20 Ω is to supply power of 1000 Ω load from 110 V (RMS) source. Calculate

(a) Peak load current

(b) DC load current

(c) AC load current. (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.

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

b) A three-phase induction motor is wound for four poles and is supplied from a 50 HZ system.

Calculate:

(i) The synchronous speed

(ii) The speed of the rotor when the slip is 4 percent

(iii) The rotor frequency when the speed of the rotor is 600 r/min. (10)

Q7. a) With reference to SOLAS 74 amendments 2000, maintenance plan is to be kept on-board ship for firefighting system,

a) Enumerate the list of fire protection system and fire-fighting systems and appliances which will be required to be included in the maintenance plan. (8)

b) Training manual as required by SOLAS 74 amendments 2000, chapter II -2 contains instructions and information with respect to fire fighting. List the same and their significance. (8)

Q8. a) Sketch and describe a total flooding CO2 gas system suitable for the protection of machinery spaces. (8)

b) State, with reasons, which valve should be operated first in the system shown in (a).  (8)

Q9. a) Describe a vacuum sewage system. (8)

b) With reference to the system described in (a)

i) State advantages of the system. (2)

ii) State why a holding tank may be required to be fitted to the system. (2)

iii) State the problems resulting from the retention of untreated sewage in a holding tank. (2)

iv) State the periodic maintenance required on the system. (2)