Download examination of marine engineer officer

78ET-2
Sr. No. 3
EXAMINATION OF MARINE ENGINEER OFFICER
ELECTRO TECHNOLOGY
CLASS II
(Time allowed - 3 hours)
Total Marks 100
INDIA
N.B. -
Morning Paper
(1) Attempt SIX questions only with minimum of ONE question from each part.
(2) All questions carry equal marks.
(3) Neatness in handwriting and clarity in expression carries weightage
Section A
1. Define magnetic flux
The air gap in a certain magnetic circuit is 0.15 cms. long and 25 cm2 in cross-section.
Calculate (a) The reluctance of the gap,
(b) The ampere turns required to send a flux of 800  Wb across the gap, and
(c) The magnetizing force in the gap.
2. Two coil of 20  and 10  resistance, 0.01272H and 0.2544H inductance and two capacitors of 200
 F and 400  F capacitance are connected in series. If the circuit is fed from 250 V 50 c/s supply,
calculate (a) The impedance of the system,
(b) The current taken
(c) The overall power factor, and
(d) The kVA supplied and kW absorbed in the resistors
3.
A 220V shunt motor takes 10.25A on full load. The armature resistance is 0.8 and the field
resistance is 880. The losses due to friction, windage and the iron amount to 150W. Find the output
power and the efficiency of the motor on full load.
4.
In a brake-test on a motor, the effective load on the brake-drum was 222.7N, the effective diameter
of the drum 0.5m and the motor speed 960 rev/min. Under these conditions the input to the motor was
30A at 230V. Calculate the output of the motor and its efficiency.
5.
The current vectors of an unsymmetrical three-phase, three-conductor system are represented by [A]
= 14.0 + jl.5, [B] = - 4.0 – j8.0, [C] = -10.0 + j6.5. Determine the positive and negative phasesequence components, both in actual magnitude and in symbolic form. Calculate also the phase angle
between the positive and negative phase-sequence components of phase A.
6.
Describe the construction and action of a high-tension magneto used for starting emergency
equipment on board ships. What is the function of the capacitor, and what effect does it have on the
safety spark gap?
Section B
7.
Discuss the suitability and limitations of the following insulating materials for use on board ships
and state suitable application in each case. Particular reference should be made to the influence of
environment, and its effect, on deterioration in service : (a) Pure rubber
(b) Paper
(c) Mica
(d) Asbestos
(e) Porcelain
(f) Ebonite
8.
With reference to electrical equipment in areas aboard ship having potentially flammable atmospheres:
(a) Explain the hazards involved.
(b) State the design features that render the equipment safe.
(c) Explain the precautions necessary when maintenance work is being carried out.
9.
Describe the effects of reduction in the applied voltage connected to a standard a.c. squirrel cage
motor with respect to:
(a) Temperature of windings:
(b) Starting current.
(c) Starting torque.
(d) Speed.
-------------------------------X------------------------------