DieselShip's Online Content Library

Q1.a) Explain the meaning of the term power factor correction (4)

b) State advantages of power factor correction (4)

c) Explain, with the aid of a circuit diagram, how power factor correction can be effected in a three phase circuit using capacitors. (4)

d) Explain one method other than the use of capacitors by means of which power factor correction may be effected. (4)

Q2. Describe how the starting torque of electric induction motors may be improved by using EACH of the following:

(a) Wound rotor; (5)

(b) Double cage. (5)

Q3. a) Describe, with the aid of a sketch, an electronic soft starting system that may be used for large a.c. induction motors. (8)

b) Discuss the advantages and disadvantages of soft starting system. (8)

Q4. A) With reference to voltage variation profiles caused by load changes imposed on alternating current generators when starting large motors online:

a) Sketch a voltage dip, showing an acceptable recovery time. (2)

b) State salient factors that cause the variation in part (a) (3)

c) Outline salient factors that assist recovery from the deviation shown in part (3)

B) A three-phase induction motor is wound for four poles and is supplied from a 50 Hz System calculate:

a) The synchronous speed

b) The speed of rotor when the slip is 4 per cent.

c) The rotor frequency when the speed of the rotor is 600 r/min (8)

Q5. A) With reference to large electrical transformers on board ships:

a) State where these transformers may be used (2)

b) State a typical efficiency range for a transformer (2)

c) State the protective devices that are fitted (2)

d) Describe the maintenance requirements (2)

B) What are the losses in transformers? Mention the various factors which affect these losses. In a 25KVA, 3300/223 V, Single phase transformer, the iron and full load Cu. Losses are respectively 350 and 400 watts. Calculate the efficiency at half-full load, 0.8 power factor (8)

Q6. A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000kW at 0.9 power factor. Find the kVA rating of the other alternator and the power factor. (16)

Q7.a) With reference to shipboard sewage treatment plants, describe the principle of operation of each of the following:

(i) Biological

(ii) Physical (8)

b) Explain why sewage systems involving aerobic action are to be preferred to those with aerobic action (4)

c) Explain the meaning and significance of biological oxygen demand (4)

Q7.  With reference to the Maritime Labour Convention (MLC) 2006. Discuss the requirements for seafarers regarding: -
a) Minimum age to work onboard vessels (5)
b) Seafarers Employment agreements (5)
c) Hours of work and hours of rest. (6)

Q9. With reference to “ISM Code” write short notes on:
a) Masters Review (4)
b) Requirement and Advantages of Familiarization of seafarer onboard (4)
c) Designated Person Ashore (DPA) (4)
d) Functional requirements for a Safety Management System. (4)