Subject wise written questions-ETO
Basic Electrical Engineering
1. (a) What has
the greater equivalent resistance: two equal capacitors in series or in
parallel? Explain with reasons?
(b) A circuit has
a resistance of 3 ohms and an inductance of 0.01 H. The voltage across its ends
is 60V and the frequency is 50Hz. Calculate (a) the impedance
(b) the power
factor (c) the power absorbed. (16 marks)
2. A coil having
a resistance of 10Ω and an inductance of 0.15H is connected in series with a capacitor
across a 100V, 50Hz supply. If the current and the voltage are in phase what
will be the value of the current in the circuit and the voltage drop across the
coil?
3. Explain the significance of the Root Mean Square (RMS) value of an alternating current or voltage waveform. Define the form factor of such a waveform.
DC machine
1. Two 220V D.C.
generators each having linear external characteristics operated in parallel.
One machine has a terminal voltage of 270 V on no-load and 220V at a load
current of 35 A, while the other has a voltage of 280V at no-load and 220 V at
50A. Calculate the output current of each machine and the bus bar voltage when
the total load is 60A. What is the kW output of each machine under this condition?
(16 marks )
2. A shunt generator has an induced e.m.f of 254V. When the generator is loaded, the
terminal voltage is 240V. Neglecting armature reaction, find the load current
if the armature resistance is 0.04ohm and field resistance is 24ohms.
3. Draw the diagram
of a three-point starter and identify the various parts.
4. Two DC shunt
generators are connected in parallel and supply a load to a DC shunt motor
taking current of 150A. One generates an e.m.f of 250V and has an armature
resistance of 0.2ohm and the other generates 255V and has an armature
resistance of 0.3ohm. What are the motor output voltage and power output of each
generator? (Neglect field current)
5. A 220V shunt
motor takes 5A at No load. The armature resistance is 0.25ohm and field resistance
is 200ohm. Calculate.
(i) Efficiency,
when taking full load current of 50A.
(ii) Percentage
change in speed between no-load to full-load.
Three-phase induction motors
1. Write a short
note on the principle of operation of induction motors. (8 marks)
- What is slip for an induction motor? (4 marks)
- If a 6- pole motor is supplied at 60Hz and runs with a slip of 5%, what is the actual rotor speed? or If a 4-pole motor is supplied at 60Hz and runs with a slip of 5%, what is the actual rotor speed?(4 marks)
- Draw a simple ladder logic diagram of star-delta starting of an induction motor.
2. (a) Draw the circuit diagram and explain the working of the star/delta starter.
b) Explain with a diagram of how the direction of the single-phase induction motor is reversed.
3. Explain the
construction and working of three-phase induction motor.
4. A 3-phase
induction motor which is wound for 4-Poles, when running full load develops a
useful torque of 100Nm; also the rotor e.m.f is observed to make
120-cycles/min. It is known that the torque lost on account of friction &
core loss is 7Nm. Calculate the shaft power output, rotor copper loss, motor
input, and motor efficiency.
5. Describe the step-by-step method of overhauling 10kW, 50Hz, 440V, 3-Phase Squirrel induction
motor.
6. The shaft
output of a 3-phase, 60Hz, induction motor is 80KW. The friction and windage
losses are 920W, the stator core loss is 4300W and stator copper loss is 2690W.
The rotor current and rotor resistance referred to stator are 110A and 0.15
respectively. If the slip is 3.8%, what is the percent efficiency?
7. A 400V,
4-pole, 50Hz, 3-phase, 10HP, star-connected induction motor has no load slip of
1% and full load slip of 4%. Find the following:
i) Synchronous speed ii)
No-load speed iii) full-load speed iv) frequency of rotor current at full-load
v) full load torque.
8. Write a short
note on the principle of operation of induction motors. (4 marks)
a. Explain the phenomenon of crawling and cogging in a three-phase induction motor? (4 marks)
b. Difference
between squirrel cage & wound rotor 3-phase induction motor
c. What is the condition
to be satisfied for achieving maximum running torque in an induction motor?
d. The output of
an induction motor running at 20% slip is 36.775kW and the friction and windage
losses are 1500W. Find the rotor copper loss motor efficiency if stator losses
are 3kW. (8 marks)
9. A 4-Pole,
3-phase, Induction motor operates from a supply whose frequency is 50Hz.
Calculate.
i) The speed at which
the magnetic field of the stator is rotating.
ii) Speed of the
rotor, when the slip is 4%
iii) The
frequency of the rotor when the slip is 3%
10. Describe the
following starters:
(i) Three-point
starter
(ii) Star-Delta
starter
11. What is the soft
starting of an induction motor? Describe with a circuit using thyristors used
for soft starting. Discuss its advantages and disadvantages.
12. With reference to 3-phase induction motors:
a. Explain the phenomenon of crawling and cogging in these motors.
b. A 3-phase induction motor is wound for four poles and is supplied from a 50Hz system calculate:
i) The synchronous speed;
ii) The speed of the rotor when the slip is 4 percent;
iii) The rotor frequency when the speed of the rotor is 600r/min.
13. a) Difference between squirrel cage and wound rotor 3-phase induction motor.
b) The output of an induction motor running at 4% slip is 36.775kW and windage losses are 1500W. Find the rotor copper loss and motor efficiency if stator losses are 3kW. (8 marks).
Single-phase motor
1. With reference
to single phase induction motor
(a) Using double
field revolving field theory, explain why single phase induction motor is not
self-starting.
(b) Draw a
torque-speed characteristics of a single-phase induction motor on the basis of
double field revolving field theory.
(c) Write short
notes on the following motors:
i) Split phase
induction motor
ii) Capacitor
motor
iii) Shaded pole motor
iv) Universal
motor
Transformers
1.
With reference to different types of transformers used onboard.
a. Discuss
the basic principle of operation of a transformer (5marks)
b. Enumerate
the different types of transformers used onboard also state their functions for
which they are used (5 marks)
c. A
440/110V single phase transformer supplies a load of 5KW at 0.8 power factor
load. Calculate the primary and secondary currents (Ignoring transformer power losses)?
(6 marks)
or
d. A 440/220V single phase transformer supplies a load of 5kW at 0.8 power factor load. Calculate the primary and secondary currents (ignoring transformer power losses)? (6 marks)
2. In a container
ship, a 3-phase delta/delta connected 6600/440 V, 60Hz transformer is feeding
AMP supply from shore to 440 Volts switchboard. The transformer primary current
takes a line current of 100AMP when secondary load p.f 0.8 lagging p.f is
connected. Determine each coil- current and KW output of the transformer.
3. A 100KVA,
2400/240V, 50Hz, Single phase transformer has the no-load current of 0.64A and a
core loss of 700W when its HV side is energized at rated voltage &
frequency. Calculate the two components of no-load current. If this transformer
supplies a load current of 40A at 0.8laging p.f. at its low voltage side,
determine the primary current and its power factor. Ignore the leakage impedance
drop.
4. What are the
advantages of the transformer bank of three 1-phase transformers over a unit three-phase transformer of the same kVA rating?
a) What are the
losses in the transformer? Mention the various factors which affect these losses.
b) In a 25kW,
3300/233V, 1-phase transformer the iron and full load copper losses are 350
watts and 400 watts respectively. Calculate the efficiency at half load, 0.8
p.f.
5. A 440V/110V,
single-phase transformer takes a no-load current of 5A at power factor 0.25
lagging. On load, the transformer supplies 7.5kVA at p.f. 0.8 lagging.
Calculate.
i) The
transformer secondary current
ii) The
transformer primary current and primary p.f.
6. A 3-phase the transformer has 900 turns in primary and 104 turns in secondary winding
respectively. The primary winding is connected with the power supply of 66000V from
HV switchboard. Calculate the secondary line voltage when the transformer is
connected in
i) Star-delta
connection ii) delta-Star connection
7. (a) Discuss
the essential and desirable conditions to be fulfilled for operating two
three-phase transformers in parallel.
(b) Two single
phase transformers share a load of 400kVA at p.f. of 0.8 lagging. Their
equivalent impedances referred to secondary winding are (1+2.5j) Ω and (1.5+3j)
Ω respectively. Calculate the load shared by the transformers.
8. With reference to 3-phase Transformers:
a) Discuss the essential and desirable conditions to be fulfill for operating two three-phase transformers in parallel.
b) What are the advantages of transformer bank of three single- phase transformers over a unit three phase transformer of the same kVA rating.
c) In a 25KW, 3300/233V, 1-Phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency at half load, 0.8 p.f.
9. With reference to 3-phase Transformers:
a) Describe the different types of losses occurring in power transformers
b) A single power transformer supplied a load of 20kVA at a p.f. of 0.81(lagging). The iron loss of the transformer is 200kW and the copper loss at this load is 180kW. Calculate
i) Efficiency
ii) if the load is now changed to 30kVA at a p.f. of 0.91(lagging), calculate new efficiency.
AC Machine (Three-phase synchronous Machines
& AC Generators or Alternator)
1. Explain with
the help of a neat diagram the operation of a brushless alternator. What would
likely happen if one of the rotating Diodes fails and become:
(a) An open circuit?
(b) A short circuit? ( 16 marks )
2. An alternator
does not build up any voltage after the start. Describe step by step procedure to
solve the problem for all reasons.
a) Describe any
two methods of determining the voltage regulation of a 3-phase alternator.
b) Two
alternators are connected in parallel with what happens when we increase the
excitation of one machine.
3. (i) What
precaution must be taken when testing the insulation of generator cables and
wiring connected to an AVR unit?
ii) How could you
monitor the correct instant for synchronizing if the synchroscope and
synchronizing lamps are not working?
iii) How the
air-gap of an alternator is measured and why the air-gap of an alternator to be
checked periodically.
4. With respect
to (w.r.t.) paralleling of alternators:
a) If the
synchroscope is malfunctioning, which instrument is the most essential to
parallel an alternator with bulbar? Justify your answer.
b) Why it is
desirable to operate paralleled alternators at the same power factor (p.f.).
c) Why it is
necessary that incoming alternator frequency is more than busbar?
d) What are the
likely consequences of attempting to close the incomer’s circuit breaker when
the generator voltages are not in synchronism?
e) How could you
monitor the correct instant for synchronizing without the aid of a synchroscope
and synchronizing lamps?
5. The following
loads are supplied by two alternators running in parallel:
i) 1400kW @ p.f.
0.86 lagging ii) 900kW @ p.f. 0.8 lagging
iii) 800kW @ p.f.
unity IV) 500kW @ p.f. 0.8 leading
If the load on
one machine is adjusted to 2100kW @ p.f. of 0.92. Find the load and power
factor (p.f.) of the other machine.
6. With reference
to diesel engine driven Alternators:
a. Explain the
Automatic Voltage Regulator (AVR) to control the terminal voltage of the generator.
(6 marks)
b. Two generators
rated 2000kW and 4000kW operating in parallel. The droop settings of their
governor are 4% and 5% respectively from no load to full load. Assuming that
the generators are operating at 50Hz at no load, how would a load of 6000kW be
will share between them? What will be the system frequency at this speed?
Assuming free governor operation. (10 marks)
7. Two
alternators running in parallel with Alternator-1 having 2000kW capacity with
4% speed drop and alternator-2 having 1000kW capacity with 4% speed drop. The
no-load frequency is 62Hz. How much kW load shared by each alternator if the total
load is 1200kW?
8. A total load
of 8000kW at p.f. of 0.8 lagging is supplied by two alternators in parallel.
One alternator supplies 6000kW at p.f. 0.9 lagging. Find the kVA rating of the
other alternator and the p.f.
9. State the
applications of the synchronous motors. Discuss how a synchronous motor can
function as a synchronous capacitor. Compare synchronous motors with induction
motor drives.
10. With respect
to alternators onboard:
a. Briefly
explain True Power, Apparent Power, and Power Factor?
b. The alternator
is rated for 750kVA at 0.85 p.f. What is the maximum load (Kilowatt) that can
be put on it? Would you be overloading the alternator if the Kilowatt reading
were now 620kW and the power factor 0.80?
11. Sketch and
describe the main engine shaft driven generator arrangement with an electronic
system for frequency correction.
12. Explain the principle of operation of Synchronous Motor with a simple sketch. Where are synchronous motors used onboard?
13. Draw and explain the working of a Synchroscope. How could you monitor the correct instant for synchronizing without the aid of a synchroscope?
Power system (Including switchgear &
Protection)
1. Explain three
methods of overcurrent protection for electrical circuits. Explain with the aid of a diagram, the meaning of
the inverse current time characteristic.
2. With respect
to insulated and earthed neutral systems used onboard:
a) Discuss the
advantages and disadvantages of both the insulated and earthed systems used
onboard. (8 marks)
b) Discuss the
consequences of earth fault in an earthed distribution system. (4 marks)
c) What would be the
ohmic value of the NER to limit the earth fault to the full load rating of a 2
MW, 0.8pf, and 3.3KV 3Phase A.C generator? (4 marks)
d) What is earth fault and how do you identify earth fault in 440v system onboard? (4 marks)
3. With respect
to Generators and Main circuit breakers and their protection devices:
What are safeties
incorporated in Air Circuit Breaker (ACB) of ships generator and prime mover? (10
marks)
Write a short note
on negative phase sequence relay (6 marks)
Explain the
procedure to test reverse power relay?
4. (a) A 440 v 10
KW 0.8 PF 3 phase loaded supplied as shown. Calculate short circuit fault
current at the load and at the main switchboard (8 marks)
b) What are the
safety produce procedures if any work has to be carried out in leaves MSB bus-bar?
(8 marks)
5. (a) What is
the significance of earth fault in an isolated neutral system? Explain with a
suitable diagram.
b) List the
advantages and disadvantages of an electric propulsion system.
6. With respect to
Circuit breakers compare the effectiveness of a current limiting circuit a breaker with that of an HRC fuse.
7. a) Explain briefly about checks and calibration of a thermostat which is used to stop an air compressor, when cooling water temperature goes to high?
b) What is the significance of earth fault in an isolated neutral system? Explain with a suitable diagram.
8. With respect to a three phase shipboard electrical distribution system:
- a. Enumerate the advantages of an insulated neutral system.
- b. Enumerate disadvantages of an insulated neutral system.
- c. Describe how the Earth Neutral System is earthed.
- d. Compare the use of an insulated neutral system as opposed to the use of an earthed neutral system with regard to the risk of electric shock from either system.
9. a) Discuss the criteria of the classification of marine high voltage for AC and DC system.
b) Sketch a ships HV distribution system and explain its features.
c) Discuss the various methods of testing the insulation of HV system. Mention the significance of PI Test; Why 3-terminals insulation testers are used in HV insulation measurements?
ELECTRICAL
PROPULSION
1. Diesel-electric propulsion is now being chosen as the power plant for an increasingly wide variety of vessels.
a) Sketch a simple layout of such an installation
b) Explain the
advantages of selecting such a plant.
2. List out the
advantages and disadvantages of the electric propulsion system.
3. With reference
to an emergency source of electrical power in cargo ships:-
a) Describe a
typical power source
b) Give a typical
list of essential services, which must be supplied simultaneously.
c) Explain how the
emergency installation can be periodically tested.
Batteries, Electronics, Instrumentation & Control
1. (a) Draw and
explain the block diagram of PLC?
(b) What are the
equipment where the PLCs are used onboard?
(c) What are the
advantages of PLC CONTROLLERS over other types of controllers?
2. (a)
Explain why 3 wire RTD is perfect for accurate measurement of
temperature? (8 marks)
(b) Explain with a diagram how the boiler water level
is measured (8 marks)
3. (a) How to
check and calibrate a thermostat which is used to stop an air compressor when the cooling tower goes to high.
(b) Describe 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 cooling system.
(c) What is the
basic circuit behind an engine room crane? Explain the operation with a
suitable diagram.
4. (a) Explain
with the aid of a diagram, a controller utilizing proportional plus integral
action.
(b) Explain
briefly what you know about “Pulse width Modulation” and how it can be applied
for propulsion control.
5. (a) Describe
the working of a single-phase full-wave rectifier with a resistive load. Draw
the load voltage and current waveforms.
(b) Diode
half-wave rectifier supply a resistive load of 100Ω from a 100V ac r.m.s
voltage source. The diode is a resistance of 5Ω during the conduction state.
Calculate
i) The DC output
voltage ii) DC avg. load current
6. What is
Zener diode and how does it regulate the voltage? What happens to the series
current, load current, and Zener current when the dc input voltage of a Zener
regulator increases? Draw a neat diagram of the Zener regulator and explain.
7. What is
semiconductor devices? What are its advantages over thermionic devices? With
respect to semiconductor devices describe the working principle and application of
the following:
a. Zener diode
b. Transistor
c. Photocell
d. Thyristor
8. a) Explain
the construction & principle of operation of permanent magnet moving coil
(PMMC) type instrument.
b) A PMMC type the instrument has a coil of dimension 15mmX12mm. The flux density in the air gap
is 1.8x10-3 Wb/m 2 and the spring constant is 0.4x10-6 Nm/rad. Determine the
No. of turns required to produce an angular deflection of 90*when a current of
5mA is flowing through the coil.
9. (a) Explain the working of fuel oil leak off alarm system of Main Engine.
(b) Explain the
operation of the Main Engine RRM Indication system.
10. (a) Draw
& explain the basic flow and control diagram of the refrigeration system onboard ship.
(b) Write down
the function of the following components:
(i) Thermo
Couples (ii) DP Transmitter (iii) IP Converter (iv) IGBT
11. Briefly explain the Principle of Variable Frequency Drives (VFD). Discuss the advantages and disadvantages of VFDs onboard merchant vessels?
12. With reference to batteries onboard:
a) Distinguish between Lead-acid cell and Alkaline Cell
b) Describe how a battery of alkaline cells may be tested for its usefulness, after a long storage and if found deficient, how it can be remedied?
c) Explain how the ambient temperature is taken into account when determining the condition of the battery.
13. i) Sketch and describe hydraulic circuit of steering gear incorporating automatic isolation system.
ii) Explain emergency steering
ii) Describe the routine tests of steering gear as per SOLAS requirement.
14. a) By means of a schematic ckt. diagram illustrates the peak rectifier. If the supply voltage is v(t)= VmSinwt, what is the voltage across the load resistor?
b) A battery-charging ckt. As shown below fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1A.
Safeties
1. (a) Describe
the routine tests required for self-contained breathing apparatus sets.
(b) Describe the
procedure to be adopted to find missing personnel in a smoke-filled Accommodation
area.
2. With Reference
to entry into enclosed spaces
(a) Define enclosed
space and give examples of enclosed spaces onboard. (4 marks)
(b) Describe
hazards relating to entry into enclosed spaces on board
(c) Describe the
checks done for testing the atmosphere inside such enclosed spaces. (4 marks)
(d) Explain
safety precaution is taken prior to entry into enclosed spaces onboard vessels. (8 marks)
3. With respect
to the hazardous areas of tankers:
(i) Explain the
term flameproof (Ext.) for electrical equipment.
(ii) State the
type of electrical equipment that would be protected in this way.
(iii) List likely
defects of flameproof equipment.
4. With reference
to electrical safety onboard a vessel
(a) Write short
note on “electric shock “(6 marks)
(b) Enumerate the
relation between shock current levels, the applied voltage, and the body Resistance.
(5marks)
(c) How do you
treat a person who has suffered an electric shock on board from an AC supply? (5
marks)
5. How will you
fight a fire in a purifier room? How will you at least restrict the fire if you
are the first person to sight the fire in the purifier room?
6. How will you
fight a fire in a galley? How will you at least restrict the fire if you are
the first person to sight the fire in the galley?
7. With respect
to MARPOL Annex-IV:
(a) Draw a
biological sewage treatment plant and explain the principle of operation.
(b) Periodical maintenance
and checks/tests required to be done to verify the effectiveness of the system.
8. With respect
to MARPOL Annex-V
(a) Please
explain the regulations stipulated for disposal of garbage under annex 5 MARPOL
73/78
(b) Please state
the special area notified under Annex-V MARPOL73/78
(c) Also state
what precaution you will take during of waste from an electrical workshop
9. With the aid
of suitable line diagrams where ever required sketch and Describe a suitable Marine
growth protection system (MGPS) installed on the vessel to prevent fouling of
internal Sea Water system mention the important precautions if any while
handling the system.t the minimum LSA to be carried out by passenger ship.
10. With
reference to the fixed CO2 flooding system for firefighting on board ships, explain
the following:
(a) Advantages
and disadvantages of CO2as a fire fighting medium.
(b) The purpose
of providing time delay with a suitable block and line diagram
(c) What are the
job pertaining to the five-year maintenance routines on the system.
11. (a) Describe
CO2fixed firefighting system for machinery spaces and cargo spaces of the bulk carrier. or CO2 it to be released in engine room in case of fire. Briefly describe steps taken before it can be released.
b) Explain the safety
precautions taken prior to the release of CO2to the engine room.
12. Which all
matrix, checklists, and permits will you fill-up? Before commencing the work and
who will authorize the work permits?
13. (a) You are
working onboard the Deck Cargo crane. What are the hazards associated with working
at height?
(b) What risk
mitigation measures will you take to mitigate the hazards identified by you
while working at heights?
(c) Which all risk
assessment checklists, work checklist and work permits will you fill up before commencing
the work and who will authorize the work permits?
14. (a) What are
the safety incorporated in ACB of ship’s generator and Prime mover? (10 marks)
b) What are the
safety produce procedures if any work have to be carried out in leaves MSB? Bus-bar
(8marks)
15. (a) List the
items which are contained in the training manual pertaining to life-saving
appliances.
(b) Describe the
frequency of abandon ship drills and fire drills and how they should be
conducted.
(c) State the
regulation regarding the maintenance of life boat falls.
(d) List the
minimum LSA to be carried out by the passenger ship.
16. (a) Explain
working of galley CO2 firefighting control system
b) Explain
working of electrical oven fitted in galley range with circuit diagram.
17. With reference to MARPOL Annex1:
a) Draw a 15ppm Oily water separator and Explain the Principle of operation.
b) Periodical maintenance & checks/tests required to be done to verify the effectiveness of the above system.
Numerical questions and answers
Please comments! We do take time and effort to answer these questions; if not, what is the point?
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9 Comments
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