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95MET-4 Sr. No. 4 EXAMINATION OF MARINE ENGINEER OFFICER Function: Electrical, Electronic & Control Engineering at Operational Level MARINE ELECTROTECHNOLOGY India (2002) M.E.O. Class IV (Time allowed - 3hours) Morning Paper Total Marks 100 NB : (1)All Questions are Compulsory (2)All Questions carry equal marks (3)Neatness in handwriting and clarity in expression carries weightage 1. Describe an electric telegraph system and describe its operation. 2. (a) Draw a simple battery charging circuit showing a battery being charged from a single phase a.c. supply using a transformer and rectifier bridge. (b) Sketch the waveforms of the input and output rectifier voltages and the battery voltages. 3. Describe with the aid of a suitable sketch, an apparatus whereby a small electrical signal can be amplified to operate control devices. 4. The output voltage of a three-phase alternator is regulated by the _____________. (a.) AC voltage to the armature (b.) AC voltage to the field (c.) DC voltage to the armature (d.) DC voltage to the Field Briefly Justify Your Answer 5. The function of a rectifier is similar to that of a _______. (a.) trap (b.) regulating valve (c.) check valve (d.) filter Briefly Justify Your Answer 6. A 440V single-phase motor is rated at 7.5kW and operates at a power factor of 0.8 (lagging) with an efficiency of 88 per cent. Find the current taken from the supply. 7. A battery of 40 cells in series delivers a constant discharging current of 4A for 40 hours, the average p.d. per cell being 1.93V during the process. The battery is then completely recharged by a current of 8A flowing for 24 hours, the average p.d.per cell being 2.2V. Calculate the ampere hour and the watt hour efficiencies for the battery. 8. If 0.5m of manganin resistance wire, 0.1mm diameter, have a resistance of 267.5 Ohms, find the resistivity of the material. 9. A fore-pole, wave wound generator delivers 40kW at 200V. Its armature has 181 turns and a resistance of 0.01 Ohms. The air-gap flux/pole is 0.02Wb. Calculate the speed of the machine, neglecting any voltage drop at the brushes and taking the shunt-field resistance as 50 Ohms. 10. The armature of a four-pole generator rotates at 600 rev/min. The area of each poleface is 0.09m2 and the flux density in the air-gap is 0.92T. Find the average e.m.f. induced in each conductor. If the armature winding is made up of 210 single-turn coils connected so as to provided four parallel paths between the brushes, find the generator terminal voltage. ------------------------------X-------------------------------