95MET-4

Sr. No. 6

EXAMINATION OF MARINE ENGINEER OFFICER

Function: Electrical, Electronic & Control Engineering at Operational Level

MARINE ELECTROTECHNOLOGY

M.E.O. Class IV

(Time allowed - 3hours)

India (2004) Morning Paper Total Marks 100

NB : (1)Answer SIX Questions :

SECTION -1 :- Answer atleast TWO Questions

SECTION -2 :- Answer atleast TWO Questions

(2)All Questions carry equal marks

(3)Neatness in handwriting and clarity in expression carries weightage

(4) Illustration of an Answer with clear sketches / diagrams carries weightage.

SECTION - 1

1.(a) Sketch and describe a power (watt) meter for an a.c. switchboard.

(b)State why type of load governs power factor and give examples of power factor for a resistance load and for normal marine operation.

2Describe an automatic control system capable of maintaining the jacket water temperature

within close limits during wide changes in engine load, explain with a simple line sketch of a main engine jacket cooling system.

3.A lead-acid battery is considered fully charged when the ______.

(a)electrolyte gasses are freed

(b)battery charger ammeter indicates a positive reading

(c)terminal voltage reaches a constant value at a given temperature

(d)specific gravity of all cells reaches the correct value and no longer increases over a period of 1 to 4 hours.

Briefly justify your answer and describe the maintenance required for shipboard batteries.

  1. If the motor terminal markings are unknown how would you identify the start, run and common terminal connections.
  1. (a) What is a direct connected alternator

(b) what is the difference between direct connected and direct coupled units.

SECTION - 2

6. A shunt motor has an armature resistance of 0.2 ohms and with an armature current of 120 amperes runs at 750 r.p.m. off a 400-volt supply. Calculate the speed and armature current of the motor if the flux per pole is reduced to 75 per cent of its initial value, the total torque remaining unaltered.

7. 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 6 poles and the armature is lap connected with 864 conductors. The flux per pole is 0.05 wb. Calculate (a) speed, (b) the gross torque developed by the armature.

8. An inductance coil has a resistance of 19.5 and when connected to a 220V, 50Hz supply, the current passing is 10A. Find the inductance of the coil.

9. An air gap of length 3 mm is cut in the iron magnetic circuit of a measuring device. If a flux of 0.05 Wb is required in the air gap, which has an area of 650 mm2, find the ampere-turns required for the air gap to produce the necessary flux.

  1. Local action in a nickel-cadmium battery is offset by ______.

(a)separating the positive and negative plates with plastic spacers

(b)separating the positive and negative plates with resin impregnated spacers

(c)adding a small amount of lithium hydroxide to the electrolyte

(d)trickle charging

Briefly justify your answer

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