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95MET-4
Sr. No. 3
EXAMINATION OF MARINE ENGINEER OFFICER
Function: Electrical, Electronic & Control Engineering at Operational Level
MARINE ELECTROTECHNOLOGY
India (2003)
M.E.O. Class IV
(Time allowed - 3hours)
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. Explain the meaning of the following terms with reference to automatic control system : (a) Control loop
(b) Transmitter
(c) Controller
(d) Desired value.
2. (a) State why front switch boards are required for A.C system having voltage to earth greater than 55V
(b) Explain how section of an electrical system aboard ship can be isolated for maintenance work
(c) Describe, with reference to electrical connections, the procedure to replace a 3-phase induction motor
with spare motor
3. Describe the action of a diode valve and give an example of its use.
4. Which of the following statements represents the main difference between a relay and a contactor?
(A) Contactors control current and relays control voltage.
(B) A relay is series connected and a contactor is parallel connected.
(C) Contactors can handle heavier loads than relays.
(D) Contactors are made from silver and relays a remade from copper.
Briefly Justify your Answer
5. The most common source of excitation for synchronous motors is a/an _____________.
(A) low voltage battery
(B) motor attenuator set
(C) DC exciter generator
(D) AC supply
Briefly Justify your Answer
SECTION - 2
6. A 6600/440-volt single-phase transformer is rated at 125 kVA and works on a 50 cycle per sec. supply.
There are 80 turns on the secondary winding. Calculate the primary and secondary currents, the number
of turns on the primary winding and the maximum flux in the core.
7. A thin rectangular plate 350mm by 250mm is totally covered on both sides with nickel 0.12mm thick
in 8.25h.The current required would, if supplied to a voltmeter, cause 0.0805kg of silver to be deposited
in 1h.If the E.C.E of nickel is 30410-9 kg/C,calculate the density of nickel in kg/m3 , if the E>C>E> of
silver is taken as 111810-9 kg/C.
8. A coil of resistance 10 Ohms and inductance 0-1 H is connected in series with capacitor of capacitance
150µF, across a 200V, 50Hz supply. Calculate (a) the inductive reactance, (b) the capacitive reactance (c)
the circuit impedance (d) the circuit current (e) the circuit power factor (f) the voltage drop across the coil
(g) the voltage drop across the capacitor.
9. The curve of induced e.m.f. against excitation current for a separately-excited generator when run on
no load at 1200 rev/min is given by:
E.m.f. (v)
15
88
146
196
226
244
254
Excitation Current (A)
0
0.4
0.8
1.2
1.6
2.0
2.4
Deduce the voltage to which the machine would self-excite if the shunt-field resistance was set at 90
and the machine was run at 900 rev/min.
10. A marine shunt motor is used for driving a ‘fresh water’ pump and is found to take an armature
current of 25A at 220V, when running on full load. The speed is measured to be 725 rev/min and the
armature resistance is 0.2. If the field strength is reduced by 10 percent by means of the speed regulator
and the torque remains unchanged, determine the steady speed ultimately attained and the armature
current.
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