Jan -2022
SECTION - I
2. Briefly explain the Principle of Operation of Variable Frequency Drives (VFD). Discuss the advantages and disadvantages of VFDs onboard merchant vessels?
3
. Explain three methods of overcurrent protection for electrical circuit.
Explain with aid of diagram, the meaning of the term inverse current time characteristic.
SECTION - II
4.
(a) Explain the Principle of a Transformer? Discuss the various types of
transformers used onboard?
(b) In a container ship, a 3-ph, delta/ delta connected 6600/440 V, 60 Hz transformer is feeding AMP supply from shore to 440 Volt switchboard. Transformer primary current takes a line current of 100 amp, when secondary Load of 0.8 Lagging p.f. is connected. Determine each coil- current and KW output of transformer.
5.
A circuit has a resistance of 3Ω and an inductance of 0.01H. The voltage across
its ends is 60V and the frequency is 50Hz. Calculate
(a)
the impedance
(b)
the power factor
(C)the power absorbed.
6. With respect to Alternators onboard:
(a)
Briefly explain True Power, Apparent Power and Power Factor?
(b) The alternator is rated for 750 KVA at 0.85 PF. What is the maximin load (Kilo Watt) that can be put on it? Would you be overloading the alternator if the Kilowatt reading were now 620 KW and the power factor 0.80?
(Dec 20218, Feb, Aug, Oct , Nov ,Dec 2019, Jan 2020, Feb, Apr, Jul 2021, Sept 2024 )
SECTION - III
7.
(a) With reference to working onboard the Deck Cargo crane, elaborate the
hazards associated with working at heights.?
(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 checklists and work Permits will you fill up before commencing the work and who will authorize the work permits?
8.
With Reference to Electrical Safety onboard a vessel:
(a)
Write Short Note on "Electric Shock"
(b)
Enumerate the relation between Shock Current Levels, the Applied Voltage and
the Body resistance.
(c)How do you treat a person who has suffered an electric shock onboard from a AC supply?
9.
With Reference to entry into enclosed spaces onboard.
(a)
Define "Enclosed Space" and give examples of enclosed spaces onboard.
(b)
Describe the checks done for testing the atmosphere inside such enclosed spaces
(C) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel.
Feb - 2022
SECTION-I
1.
With Respect to PLC's used onboard ships:
(a)
Draw and Explain the block diagram of a PLC?
(b)
Name the onboard ship equipment where PLCs are used.
(c) What are the advantages of PLC controllers over other type of controllers.
2.
(a)Briefly explain Intrinsically safe circuit and Explosion proof circuit.
(b)What
is EXD and EX1? Where they are used onboard ship.
(c)What
all Intrinsically safe equipment used on Deck. Explain how they are
intrinsically safe
(d) What is Zener Barrier? How flame and explosion contained inside the enclosure.
3. (a) Explain why it is necessary to have reverse power protection for alternators intended for operation.
(b) Sketch a reverse power trip and explain briefly the principle on which the operation of this reverse power trip is based and how tripping is activated.
SECTION-II
4.
(a) Compare the effectiveness of a current limiting circuit breaker with that
of a HRC fuse.
(b)A coil having a resistance of 10 ohm and an inductance of 0.15 His connected in series with a capacitor across a 100 V, 50 Hz 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?
5.
With reference to adjoining circuit calculate following.
(a)
Current in each branch of circuit
(b) Total current
(i)Calculate
the two components of no-load current.
(ii) If this transformer supplies a load current of 40 amp at 0.8 lagging power factor at its low voltage side, determine the primary current and its power factor. Ignore leakage impedance drop.
SECTION - III
7.
(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.
8.(a)
Describe CO₂ fixed fire fighting system for machinery spaces and cargo spaces
of a bulk carrier.
(b)
Explain safety precautions taken prior to release of CO₂ to the engine room.
9.
With Reference to entry into enclosed spaces onboard:
(a)
Define "Enclosed Space" and give examples of enclosed spaces onboard.
(b)
Describe the checks done for testing the atmosphere inside such enclosed spaces
(c) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel.
1.(a)
What precaution must be taken when testing the insulation of generator cables
and wiring connected to an AVR unit?
(b)Flow
could you monitor the correct instant for synchronising, if synchroscope and
synchronising lamps are not working?
(C) How the air gap of an alternator is measured and why the air gap of in alternator to be checked periodically?
2.
With Respect to Insulated and Earthed Neutral Systems used on board:
a)
Discuss the Advantages and Disadvantages of both the Insulated and earthed
systems used onboard.
(b)
Discuss the consequences of Earth fault in an earthed distribution system.
(C) What would be the Ohmic Value of the NER to limit the earth fault to the full load rating of a 2 MW, 0.8 pl, 3.3KV, 3 Phase A.C. generator?
3.(a) Explain with the aid of a diagram, a controller utilizing proportional plus integral action,(b)List
out the advantages and disadvantages of electric propulsion system
(c) Explain briefly what you know about "Pulse Width Modulation "and how it can be applied for propulsion control.
4. (a) Explain the construction and principle of operation of permanent magnet moving coil instrument.
(b) A permanent magnet moving coil instrument has a coil of dimension 15 mm x 12 mm. The flux density in the air gap is 1.8 × 10 wb/m² and the spring constant is 0.4 x 10 Nm / rad. Determine the number of turns required to produce an angular deflection of 90° when a current of 5 mA is flowing through the coil.
5.(A) 400V, 4-polc, 50 Hz, 3-phase. 10 hp, star connected induction motor has a no load slip of 1% and full load slip of 4%, find the following: (i) Syn. speed (ii) no-load speed (iii) full- load speed. (iv) frequency of rotor current at full- load(v) full-load torque.
6. With reference to Diesel Engine driven Alternators:
(a) Explain the significance of the term "Speed droop" during the parallel operation of alternators. Assuming two alternators are running in parallel. outline the frequency vs load characteristics of the alternators while load sharing.
(b)Two 3 alternators operate in parallel. The rating of A is 1000kw and B is 800 kw. The droop setting of each generators is 4%. If the load to be shared by both the generators is 1000 kw, Calculate the load sharing by generators A and B, if the original frequency at no-load is 62Hz.
SECTION-lll
7.
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.
8. With reference to an automatic water sprinkler, fire detecting, alarm and extinguishing system for accommodation spaces:
(a)Sketch
a typical system and describe the operation of this system
(b)Describe
the sprinkler head and its operation;
(c)
State how the temperature rating of the sprinkler head is determined
9.With Respect to MARPOL Annex V;
(a)Explain
the regulations stipulated for disposal of garbage under annex V of MARPOL
73/78.
(b)State
the Special areas notified under annex V of Marpol 73/78.
(C) State what precautions you will take during disposal of waste from Electrical Workshop.
Apr- 2022
SECTION-I
1. Describe with the aid of a simple sketch the arrangement of the three-phase winding of an alternator showing the neutral point. Explain why for most ships the neutral point is insulated. Explain why in some installation the neutral point is earthed.
2.
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.
3. What are semiconductor devices? What are its advantages over thermionic devices? With respect to semiconductor devices describe working principle and application of the following:
(a)
Zener Diode,
(b)
Transistor,
(c)
Photocell,
(d) Thyristor.
4. A 4-pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A, and the flux per pole is 0.3wb. Armature resistance 0.2 2. Calculate the full load speed of the motor to maintain rated terminal voltage at the full load.
5. Which has the greater equivalent resistance; two equal capacitors in series or in parallel? Explain with reasons? A circuit has a resistance of 32 and an inductance of 0.01H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate (a) the impedance (b) the power factor (c) the power absorbed.
6. With respect to Alternators onboard:
(a)
Briefly explain True Power, Apparent Power and Power Factor?
(b) The alternator is rated for 750 KVA at 0.85 PF. What is the maximum load (Kilo Watt) that can be put on it? Would you be overloading the alternator if the Kilowatt reading were now 620 KW and the power factor 0.80?
7. With Reference to entry into enclosed spaces onboard:
(a)
Define "Enclosed Space" and give examples of enclosed spaces onboard.
(b)
Describe the checks done for testing the atmosphere inside such enclosed spaces
(c) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel.
8. With respect to the hazardous areas of tankers:
(a)Explain
the term flameproof (Exd) for electrical equipment.
(b)State
the type of electrical equipment that would be protected in this way.
(c)List likely defects of flameproof equipment.
9.
Briefly discuss the following with respect to safety of navigation:
(a)
Bridge Navigational Watch keeping Alarm System (BNWAS).
(b)
Long range identification and tracking of ships (LRIT)
(c) Voyage Data Recorder (VDR) and Simplified Voyage Data Recorder (S-VDR)
Jun- 2022
1. With respect to Generators and Main Circuit Breakers and their protection devices:
(a)
What are safeties incorporated in Air Circuit Breaker (ACB) of ship's generator
and prime mover?
(b) Write Short Note on Negative Phase Sequence Relay.
2. Explain three methods of overcurrent protection for electrical circuit.
.Explain with aid of diagram, the meaning of the term inverse current time characteristic. Jan - 2022
3. What are semiconductor devices? What are its advantages over thermionic devices? With respect to semiconductor devices describe working principle and application of the following: -
(a) Zener Diode,
(b) Transistor,
(c) Photocell,
(d) Thyristor.
4. (a) Which has the greater equivalent resistance: two equal capacitors in series or in parallel? Explain with reasons?
(b)A
circuit has a resistance of 32 and an inductance of 0.011. The voltage across
its ends is 60V and the frequency is 501 Iz. Calculate
(a) the impedance
(b) the power factor
(c) the power absorbed.
5.
b) A single-phase power transformer supplied a load of 20 KVA at a P.F. of 0.81
(lagging). The iron loss of the transformer is 200 kw and the copper loss at
this load is 180kw. Calculate 3
(i)
the efficiency
(ii)If the load is now changed to 30 KVA at a p.f of 0.91 (lagging), calcine the new efficiency.
6.With respect to Alternators onboard:
(a)
Briefly explain True Power, Apparent Power and Power Factor?
6.b) The alternator is rated for 750 KVA at 0.85 PF. What is the maximum load (Kilo Watt) that can be put on it? Would you be overloading the alternator if the Kilowatt reading were now 620 KW and the power factor 0.80?
a)
Define "Enclosed Space" and give examples of enclosed spices onboard.
(b)
Describe the cheeks done for testing the atmosphere inside sueli enclosed
spaces.
(c) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel.
(a)Write
Short Note on "Electric Shock"
(b)
Enumerate the relation between Shock Current Levels, the Applied Voltage and
the Body resistance.
(c) How do you treat a person who has suffered an electric shock onboard from a AC supply?
(a)
Bridge Navigational Watch keeping Alarm System (BNWAS)
(b)
Long range identification and tracking of ships (1 RIT).
(c) Voyage simplified voyage recorder (VDR/S-VDR)
Jul 2022
1.
Briefly explain the Principle of Operation of Induction Motors.
(a)
What is Slip for an induction motor?
(b) Draw a simple ladder logic diagram of star delta starting of an Induction motor.
(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.
3. What is Zener diode and how does it regulate the voltage ? What happens to the series current, load current and Zener Current when the d.c. input voltage of a Zener regulator increases? Draw a neat diagram of zener regulator and explain.
4. With Respect to Insulated and Earthed Neutral Systems used on board:
a.
Discuss the Advantages and Disadvantages of both the Insulated and earthed
systems used onboard.
b.
Discuss the consequences of Earth fault in an earthed distribution system.
c. What would be the Ohmic Value of the NER to limit the earth fault to the full load rating of a 2 MW, 0.8 pf, 3.3KV, 3 Phase A.C. generator?
a)
Discuss the basic principle of operation of a transformer,
(b)Enumerate
the different types of transformers used onboard also state their functions for
which they are used.
(C) A 440/110 V single phase transformer supplies a load of SKW at 0.8 power factor load, Calculate the primary and secondary currents. (Ignoring transformer power losses)?
7. 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?
8.With
reference 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 above system.
(A) Explain the term flameproof (Exd) for
electrical equipment.
(B)
State the type of electrical equipment that would be protected in this way
(C) List likely defects of flameproof equipment.
b)
State advantages of power factor correction.
c)
Explain, with the aid of a circuit diagram, how power factor correction can be
effected in a three phase circuit using capacitors.
d) Explain one method other than the use of capacitors by means of which power factor correction may be effected.
2.
Describe how the starting torque of electric induction motors may be improved
by using each of the following:
(a)
wound rotor
(b) double cage
3.
a) Describe, with the aid of a sketch, an electronic soft starting system that
may be used for large a.c. induction motors.
b) Discuss the advantages and disadvantages of soft starting system.
4. a) With reference to voltage variation profiles caused by load changes imposed on alternating current generators when starting large motors online:
(a)
sketch a voltage dip, showing an acceptable recovery time
(b) state salient factors that cause the variation in part
(c) outline salient factors that assist recovery from the deviation shown in part
a)
The synchronous speed;
b)
The speed of the rotor when the slip is 4 per cent;
c)The rotor frequency when the speed of the rotor is 600 r/min
5. A) With reference to large electrical transformers on board ships:
(a)
state where these transformers may be used
(b)
state a typical efficiency range for a transformer
(c)
state the protective devices that are fitted
(d)escribe the maintenance requirements
5.B) What are the losses in transformers? Mention the various factors which affect these losses. In a 25 KVA, 3300/233 V, single phase transformer, the iron and full-load Cu. losses are respectively 350 and 400 watts. Calculate the efficiency at half-full load, 0.8 power factor.
7.a) With reference to shipboard sewage treatment plants, describe the principle of operation of each of the following:
(i)
Biological (ii) Physical
(b)
Explain why sewage systems involving aerobic action are to be preferred to
those with anaerobic action.
(c) Explain the meaning and significance of biological oxygen demand
8. With Reference to the Maritime Labour Convention (MLC) 2006, discuss the requirements for seafarers regarding: -
a)
Minimum age to work on board vessels;
b)
Seafarers' Employment Agreements
c) Hours of work and hours of rest.
9.
With reference to "ISM Code" write short notes on:
a)
Masters Review
b)
Requirement and Advantages of Familiarization of seafarer on board
c)
Designated Person Ashore (DPA)
d) Functional requirements for a safety Management system
(i)
Rectifier circuit
(ii)
Amplifier circuit
(iii) Oscillator circuit.
2.a) Sketch a circuit for a basic d.c. voltage stabilising circuit using a Zener diode and a series resistor.
b)
Sketch& describe the reverse current characteristic for a typical Zener
diode.
c)
List the factors which determine the value of the series resistor in the
circuit.
d) List the factors which determine the power rating of the chosen Zener diode.
b)
A heater unit of inductance has a resistance of 6.5 ohms and is intended for
use with 100V mains. For 50Hz what voltage would it be suitable when placed in
series with an external apparatus, of negligible resistance, having an
inductance of 0.01H? If the frequency rises by 5
per cent and this voltage remains constant, what would be the resulting change of voltage at the heater terminals?
5.b)In
a full-wave rectifier without filter, the load resistance is 4 k 2. Each diode
has a forward resistance of 0.8 ΚΩ. If the peak voltage applied to each diode
is 120 V at 50 Hz, calculate
(i)
The average value of current
(ii)
Efficiency and
(iii) Regulation at a load current of 10 mA
6.b) A 3000 KVA, 6-pole alternator runs at 1000 r.p.m. in parallel with other machines on 3300 V bus-bars. The synchronous reactance is 25%. Calculate the synchronizing power for one mechanical degree of displacement and the corresponding synchronizing torque.
7.
With reference to oil discharge monitoring of bilges and slopes from an oil
tanker:
a)
Describe with the aid of a sketch, the general arrangement of an oil discharge
monitoring and control system,
b)
State the inputs that are recorded,
c)Explain the difficulties encountered with the efficient operation of the oil monitoring system
8.
With reference to an automatic water sprinkler, fire detecting, alarm and
extinguishing system for accommodation spaces:
a)
(i) Sketch a typical system
(ii)Describe
the operation of this system
b)
State the sources of water available
c)
Describe the sprinkler head and its operation.
d)State
how the temperature rating of the sprinkler head is determined
Q.9 April,2023
b) What is critical dilution in flammability
diagram?
c)
How does inert gas reduce flammability range
d)
Describe purging and gas freeing operation of cargo tank in Crude Oil Tanker.
Oct – 2022
1. (a) Draw a circuit diagram of a transistor connected as a common emitter amplifier including bias resistors, coupling, and decoupling capacitors.
(b) Explain the operation of the circuit components
3. a) Sketch a main engine shaft-driven generator arrangement with an electronic system for frequency correction.
b) Describe the operation of the generator arrangement sketched in (a).
4.a)
List the factors that determine the starting torque of the three-phase
induction motor. How does this torque generally compare with the value of the
rated torque
4.b) An 18.65 KW,6 pole, 50 Hz, 3 phase slip ring induction motor runs at 960 rpm on full load with a rotor current per phase of 35 A allowing 1 KW for mechanical losses, find the resistance/phase of three-phase Winding.
5.a) With the aid of delta and star connection diagrams, state the basic equation from which the delta-star and star-delta conversion equation can be derived
5.b) A 230/115 V, single phase transformer is supplied with a load of 5A at p.f 0.86 lagging, the no-load current is 0.2 A at p.f 0.208 lagging. Calculate the primary current and p.f.
6. A 3000 KVA, 6 poles, 3 phase, star connected alternator runs at 1000 r.p.m in parallel with other machines on 3300 V bus-bars. The synchronous reactance is 25%. Calculate the synchronizing power for one mechanical degree of displacement and the corresponding synchronizing torque.
SECTION - III
7.
Describe the pumping of machinery space bilges and disposal of oil/sludge
residues of your ship using the following guidelines;
a)
When outside the twelve-mile limit and not in a special area; b) Inside the
twelve mile limit and in special areas;
c)
For logging the discharges;
d) The disposal of oily residues for vessels with no incinerator.
8. With reference to the pump room of an oil tanker describe the following with particular emphasis on safety aspects: -
a)
Ventilation system.
b)
Procedure to be followed for pump room entry.
c)Lighting
system.
b) Procedure to Be Followed for Pump Room Entry:
1.a)
Explain why it is necessary to have reverse power protection for alternators
intended for operation.
b)(i)
Sketch a reverse power trip.
(ii) Briefly explain the principle on which the operation of this power trip is based and how tripping is activated.
2. List at least two factors that cause deterioration of the frequency response of a transistor amplifier. Explain how each factor affects the performance of the amplifier. and the portion of the frequency range where it is effective.
3.a)
What are the causes of overheating of an induction motor
b)
What preventive measures are provided against damage to an induction motor in
installed condition.
c)What
is the purpose of "fuse back up protection" provided to an induction
motor.
d)
How does an induction motor develop torque?
e) What is the condition to be satisfied for achieving maximum running torque in an induction motor?
5.b) The following results were obtained on a 50 kVA transformer: open circuit test-primary voltage, 3300 V; secondary voltage, 415 V; primary power, 430 W. Short circuit test - primary voltage, 124V; primary current, 15.3 A; primary power, 525 W; secondary current, to be assumed at full load value. Calculate:
(i)The
efficiencies at full load and at half load for 0.7 power factor.
(ii)
The voltage regulations for power factor 0.7 (i) lagging, (ii) leading
(iii) The secondary terminal voltages corresponding to (i) and (ii).
6.a) What is a silicon-controlled rectifier (SCR)? How is the breakover voltage of the SCR defined?
6.b)A.d.c.
motor takes an armature current of 110 A at 480 V. The resistance of the
armature circuit is 0.2 Ω. The machine has six poles and the armature is
lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate
(a)
The speed;
(b) The gross torque developed by the armature.
7.a)
State the hazards which may be encountered when entering an enclosed space and the
precautions that should be taken.
b)
Sketch and describe an oxygen analyser which can be used to sample the
atmosphere in void or closed spaces.
c) Instruction given to junior as per the ISM procedures.
a)
Effectiveness of foam is directly related to its degree of effervescence and
surface tension
b)
Low expansion foam is best suited for use against localized fire, whilst high
expansion foam is most effective in with major conflagrations,
c)In the absence of foam appliances, water jets can be effectively used against oil fires.
9.
With reference to MARPOL Annex 1:
a).
Draw a 15 ppm Oily water separator and explain the principle of operation.
b). Periodical maintenance and checks tests required to be done to verify the effectiveness of the above system.
b) Describe the operation of the generator arrangement sketched in (A).
2. It is proposed to operate a bow thrusters' unit from a 3.3 KV electrical supply outline suitable option for the design of installation under each of the following heading.
A.
Protection of main switch board;
B.
Overload of a bow thrusters motor;
C. Cable protection.
3. Explain the matching of an induction electric motor to a pump required for main circulating duty, with the aid of pump characteristic and torque/ship diagrams.
SECTION II
4. b) A shunt motor supplied at 230 V runs at 900 rpm. When the armature current is 30 A, the resistance of the armature circuit is 0.4 Ω calculate the resistance required in series with the armature circuit to reduce the speed to 500 rpm. Assume that the armature current is 25 Amps.
5.a) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance
5. b) The earth-lamps on a main switchboard comprise two 240V 60W lamps connected in the usual manner. The potential difference at the busbars is 220V.Damage by sea water occurs to a distribution cable so that the insulation resistance to the earth is reduced to 16 ohms and 6 ohms for +ve and -ve cables respectively. Find by calculation (a) which of the two lamps burns the brighter; and (b) the additional load on the generators occasioned by the fault. The resistance of the cables and the ship's structure may be neglected, and that of the lamps taken as constant at the value corresponding to the 60W rating.
b) A 3000 KVA, 6-pole alternator runs at 1000 r.p.m. in parallel with other machines on 3300 V busbars. The synchronous reactance is 25%. Calculate the synchronizing power for one mechanical degree of displacement and the corresponding synchronizing torque.
7.
Explain the following terms/statement:
a).
SEEMP.
b).
Special Areas as defines in MARPOL 73/78.
C)EEDI/EEOI
8. With reference to the Maritime Labour Convention (MLC) 2006, discuss the requirements for seafarers regarding.
a).
Seafarer employment agreements
b).
Repatriation.
c). Seafarers Wages.
A.
Centrifugal brake,
B. Dead man's handle;
C. Davit limit switch.
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