Function: Electrical, Electronic & Control Engineering at Management Level

95MET-2 Sr. No. 10 EXAMINATION OF MARINE ENGINEER OFFICER Function: Electrical, Electronic & Control Engineering at Management Level MARINE ELECTROTECHNOLOGY

M.E.O. Class II (Time allowed - 3hours) India (2002) Morning Paper Total Marks 100

NB : (1)Answer SIX Questions : SECTION -ONE :- Answer atleast TWO Questions SECTION -TWO :- 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. 2. (a) 3. 4. 5.

SECTION - 2

6. 7. 8. 9. 10.

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A diode valve, having the following characteristic Ia ( milliamperes ) 0 5.5 13 22 32 42 52 59 63

Va ( volts ) 0 25 50 75 100 125 150 175 200

Is connected in series with a resistor of 10,000 Ohms to a 240 V d.c.supply. If a resistor of 40,000 Ohms is connected between the anode and cathode, determine the current through the diode.

A 400V shunt motor has an armature resistance of 0.3 ohm and a shunt-field circuit resistance of 300 ohm. Calculate the speed attained by the motor when the current taken from the supply is (a) 30A and (b)50A. The open –circuit charcteristic of the machine, when driven as a generator at 1500 rev/min, is given by the following figures: Field current (A) 0.25 0.5 0.75 1.0 1.25 1.5 Open-circuit voltage 220 398 515 598 638 662 Neglect the effects of armature reaction.

A section of a supply cable AB 1km long has a fault to earth such that, when end B is disconnected, the resistance measurement from end A to earth is 5 ohm. When end A is disconnected, the resistance reading from end B to earth is 3 ohm. The length of the cable AB has a resistance of 4 ohm when intact. Find the distance of the fault from end A.

A 175 kVA, 6600 / 440 V, single-phase transformer has an iron loss of 2.75 kW. The primary and secondary windings have resistances of 0.4 Ohm and 0.0015 Ohm respectively. Calculate the efficiency on full load when the power factor is 0.9

State superposition theorem and discuss its limitations. Find the voltage at P to chassis ground for the circuit of figure.

V1 = +10 V

R1 3 

R2 6  V2 = – 5 V

The use of four diodes, in a full-wave bridge rectifier circuit, will ______. (A) provide unidirectional current to the load (B) allow a very high leakage current from the load (C) convert direct current to alternating current (D) offer high opposition to current in two directions Justify your answer stating why the other conditions were not considered

Which of the following statements is true concerning a polyphase synchronous propulsion motor? (A) The motor is started as an induction motor. (B) Resistance is gradually added to the rotor circuit. (C) The starting current is held below the rated current. (D) The field winding is energized for starting purposes only. Justify your answer stating why the other conditions were not considered

With reference to squirrel cage, induction, electric motors: (a) Describe the construction of such a motor; (b) Sketch the torque against speed curve of such a motor; (c) Describe a method employed by a retrofitted device used to improve the part load performance of an induction motor. Sketch a circuit diagram for an automatic voltage regulator illustrating how the A.V.R. utilizes a silicon- controlled rectifier to control the excitation system for an alternator. (b) Describe how the A.V.R. monitors output and controls the excitation system.

With reference to alkaline batteries used on board ship: (a) Describe the operation of a battery cell and state the materials used; (b) Describe how the cells are mounted to form a battery; (c) State the advantages and disadvantages compared with lead-acid batteries.