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Q1. 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?

B. Describe the method of safely connecting the arrangement sketched in (A) to the shore Supply?

Q2. With reference to U.M.S. operations:

A. State with reasons the essential requirements for unattended machinery spaces;

B. As second Engineer, describe how you would respond to the irretrievable failure of the Machinery space fire alarm system whilst the ship is on voyage.

Q3. The direct online start of squirrel cage motor is used for most electrical drives on a.c. powered ships. Describe with sketches as necessary one method of overcoming each of the following Problems:

A. High starting current; B. Low starting torque.

Q4. A. In a.c. generators, voltage dip occurs in two stages.

I. Sketch a voltage-time graph showing the pattern of voltage dip.

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

B. Explain EACH of the following categories of voltage control:

(i) Error operated; (ii) Functional.

Q5. A. Which of the following devices will prevent a DC generator from becoming motorized? i. Over current relay; ii. Motorization trip; iii. Reverse power relay;  iv. Reverse current relay. B. Give a detailed explanations as to why other options were not considered.

Q6. A. Describe with the aid of a sketch, an isolator for a 3 phase 440V, 20-amp electric supply List the safety features of the isolator described in the sketch. B. A moving coil ammeter, a thermal ammeter and a rectifier are connected in series with a resistor across a 110 V sinusoidal a.c. supply. The circuit has a resistance of 50 to current in one direction and, due to the rectifier, an infinite resistance to current in the reverse direction. Calculate: (i) The readings on the ammeters; (ii) The form and peak factors of the current wave.

Q7. A. What is leakage flux as it applies to the iron-core transformer? How is it taken into account in the analysis of the transformer?

B. The following results were obtained on a 50KVA transformer: open circuit test-primary voltage, 3300V; secondary voltage, 415 V; primary power, 430 W. Short circuit test primary voltage, 124V; primary current, 15.3 A; primary power, 525 W; secondary current full load value. Calculate: (i) The efficiencies at full load and at half load for 0.7 power factor (ii) The Voltage regulations for power factor 0.7 (i) Lagging, (ii) leading (iii) The secondary terminal voltages corresponding to (i) and (ii)

Q8. A. What is silicon controlled rectifier (SCR)? How is the break over voltage of the SCR defined?  B. A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 . The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate - (i) The speed; (ii) The gross torque developed by the armature

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;

Q10. A 100 Kw, 460 V shunt generator was run as a motor on no load at its rated voltage and speed. The total current taken was 9.8 A, including a shunt current of 2.7 A. The resistance of the armature circuit at normal working temperature was 0.11  Calculate the efficiencies at i. Full load; ii. Half load