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Q1. Differentiate between half and full wave rectification. State where half wave rectification may be used and the purpose for which it is not well adapted. Sketch a bridge connection by which full wave rectification may be obtained. (16)

Q2. a) i. Describe the characteristics of a D.C. motor. (4)

ii Explain the advantages of such a motor for deck machinery. (4)

B. Describe with the aid of a sketch a control system for the motor in (A). (8)

Q3. With reference to preferential tripping in a marine electrical distribution system.
a) With the aid of a sketch, describe a typical arrangement to provide three stages of tripping an instantaneous protection against short circuit. (10)
b) State why this protection is required. (6)

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)

Q5. a) List the factors that determine the starting torque of the three-phase induction motor. How does this torque generally compare with the value of the rated torque? (6)
b) The low-voltage release of an a.c. motor-starter consists of a solenoid into which an iron plunger is drawn against a spring. The resistance of the solenoid is 35 ohm. When connected to a 220 V, 50 Hz, a.c. supply the current taken is at first 2 A, and when the plunger is drawn into the “full-in” position the current falls to 0.7 A. Calculate the inductance of the solenoid for both positions of the plunger, and the maximum value of flux-linkages in weber-turns for the “full-in” position of the plunger. (10)

Q6. A) With the aid of delta and star connection diagrams, state the basic equation from which the delta-star and star- delta conversion equation can be derived. (6)
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 there is a resistor of 0.3 ohm
Specifications of the three batteries are given below.
Battery A 105 V, Internal resistance   0.25 ohm
Battery B 100 V, Internal resistance   0.2 ohm
Battery C   95 V, Internal resistance   0.25 ohm
Determine the current values in the two resistors and the power dissipated by them. (10)

Q7. With reference to Annex V of MARPOL 73/78 that deals with the prevention of pollution of the sea by garbage from ships –

a) Define the following terms.

i) Garbage

ii) Nearest land

iii) Special areas (8)

b) State the regulations governing the disposal of garbage outside special areas. (8)

Q8. Fire protection for the accommodation spaces of passenger vessels incorporates means of detection, fighting and containment to reduce the spread of any fire.

A. Describe the means of detection and firefighting commonly installed. (8)

B. State how the spread of fire is prevented and how the containment is used with the firefighting and detection arrangement to locate the fire. (8)

Q9. With reference to Maritime Labour Convention (MLC) 2006, briefly discuss the following:

a) Minimum requirements for seafarers working on a ship.

b) Conditions of employment.

c) Accommodation and recreational facilities

d) Health protection, welfare, and social security protection. (16)