Jan-2023
SECTION-I
1. Discuss the criteria of the classification of marine high voltage for A.C. and D.C. Systems. Sketch a Ships high voltage distribution system and explain its features. 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.
2.
What are the conditions for producing sustained oscillations? Classify
oscillations with respect to frequency range, principle involved, etc. It is
possible to produce oscillations with RC networks in phase shift oscillator.
Discuss in detail.
3.
Which of the following devices will prevent a DC generator from becoming
motorized?
a) Over current relay, b) Motorization trip, c) Reverse power relay, d) Reverse current relay. Why the remaining options were not considered.
SECTION
II
4.
a) What design factor limits the maximum torque of a d-c motor?
b) A shunt motor runs on no load at 700 r/min off a 440 V supply. The
resistance of the shunt circuit is 2400. The following table gives the
relationship between the flux and the shunt current: 0.5 0.75
Shunt
current (A) 1.5 1.75 1.0 1.25 1.5 1.75 2.0
Flux
per pole (mWb) 6.0 8.0
94 10.2 108 11.2
115
Calculate the additional resistance required in the shunt circuit to raise the no-load speed to 1000 r/min
5. a) On what factors does the capacitance of a parallel-plate capacitor depend?
5.b)
A tuned circuit consisting of a coll having an inductance of 200 H and a
resistance of 20Ω in parallel with a variable capacitor is connected in series
with a resistor of 8000Ω across a 60 V supply having a frequency of 1 MHz
Calculate:
a)
The value of C to give resonance.
The
dynamic impedance and the Q factor of the tuned circuit.
c)
The current in each branch
6.)
The capacitor-start Induction run motor has a much higher starting torque than
the resistance split phase motor. Explain.
6.b) An eight-pole armature is wound with 480 conductors. The magnetic flux and the sp are such that the average om generated in each conductor is 2.2 V, and each conductor is capable of carrying a full load current of 100 A Calculate the terminal voltage on no load, the output current on full load and the total power generated on full load when the armature is
(i) lap connected.
(ii) Wave connected.
SECTION-III
7. If a small amount of oil is spilled during
bunkering and causes a sheen upon the water, state what should be the procedure
adopted for pollution control information to authorities and subsequent
bunkering practice
8.
(a) al Make a detailed sketch of a non-portable 136-liter foam fire
extinguisher
(b)
Briefly explain how to operate the foam
extinguisher
(c)
State the two constituents used, which enable stable foam to be produced.
(d)
State for what approximate length of
time the extinguisher should generate foam.
(e) l Where on board ship would you expect such an extinguisher to be located?
9.
With reference to the 1978 SOLAS protocol which outlines mandatory requirements
for steering gear tests and drills:
(a
) Describe the test procedure to be carried out within the 12 hours before
departure on a sea voyage
(b)
Describe the emergency steering drills that mirst take place at least every 3
months
(c) State how often the tests in (a) and the drill in jbl should be carried out for ships which regularly engaged on voyages of short duration
Feb-2023
SECTION- I
1. With reference to the provision of a shore
electrical supply to a ship:
a).
Sketch an arrangement for taking A.C. shore supply and checks to be carried out
prior Taking shore connection?
b) Describe the method of safely connecting the arrangement sketched in (a) to the shore Supply?
2.
(a) Sketch a circuit diagram of a push button direct on line contactor starter
for a three phase Incorporating overload and short circult protection.
b).
Indicate, on a sketch of the typical characteristic curves of current and
torque against Speed, disadvantages of a direct online start squirrel cage
induction motor.
SECTION
II
4.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 w. Calculate the efficiency at half-full load 0.8
power factor
5
(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?
(b)
The low-voltage release of an a c. motor starter consists of a solenoid into
which an iron plunger is drawn against a spring. The resistance of the solenoid
is 35 ohm. When connected to a 220 V, 50 Hz, ac supply the current taken is at
first 2 A, and when the plunger is drawn into the "full-in" position
the current falls to 0.7 A. Calculate the inductance of the solenoid for both
positions of
the plunger, and the maximum value of flux-linkages in weber turns for the "full in" position of the plunger.
6.
(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
(b)
The batteries A, B, and C have their
negative terminals connected together. Between the positive terminals of A and
B there is a resistor of 0.5 ohm and between B and C there is a resistor of 0.3
chm
Specifications
of the three batteries are given below
Battery
A 105 V, Internal resistance 0.25 ohm
Battery
B 100 V ,, ,, ,, 0.2 ohm
Battery
C 95 V ,, ,,
,, 0.25 ohm
Determine the current values in the two
resistors and the power dissipated by them.
SECTION-II
7.(a)
As per annex II of MARPOL. Describe categories in which substances are divided.
(b). Give conditions under which they can be discharged outside special areas?
8.
With reference to "ISM Code" write short notes on.
(a).
Management Review
(b)
Advantage of drills and procedure
(c)
Master overriding authority.
(d) Advantage of
internal audit
9.
(a) Sketch and describe a total flooding CO2 gas system suitable for the protection
of machinery spaces.
(b).
State, with reasons, which valve should be operated first in the system shown
in
(c) State the periodic maintenance required on the system.
Mar-2023
SECTION-I
1.
(a) Describe the circuit breaker for an a.c. generator using a sketch to show
how arcing is Controlled.
(b)
Explain the sequence of events that might occur if the breaker opens on a short
circuit and state the check you would require following such event; Give a safe
procedure to follow should a main circuit breaker fail to open under fault
Condition.
3.
(a) In a.c. generators, voltage dip occurs in two stages.
i.
Sketch a voltage-time graph showing the pattern of voltage dip. II. Referring
to this graph, state with reasons the effect on the electrical system of a
small power installation when a large load is suddenly switched on.
SECTION
II
4.
a) Why is a synchronous motor not self-starting? What are the various ways in
which it can be started?
b) Differentiate Ge and Si diode characteristics. The reverse bias saturation current for a P-N junction diode is 1.0 µA at 300 K. Determine its AC resistance at 150 mV forward bias.
(5.b) 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 characteristic 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 0.1 1.25
1.5
Open-circuit voltage 220 398 515 598 638 662
Neglect the effects of armature reaction.
6. (a) What is back emf Derive the relation
for the back emf and the supplied voltage in terms of armature reactance.
(6.b) Two earth lamps at 120 V, 15 W are used on a 110 V distribution circuit. Due to damage to a motor, the resistance of the positive line is reduced to 10 ohm and that of the negative line to 5 ohm. Find the voltage across each lamp and the extra load on the generatör due to the fault.
SECTION-III
7. With reference to Annex V of MARPOL 73/78
that deals with the prevention of pollution of the sea by garbage from ships-a)
Define the following terms.
i) Garbage ii) Nearest land iii) Special
areas
(b) State the regulations governing the disposal of garbage outside special areas.
8.
With reference to oil monitoring of bilge and tanker ballast discharges.
a)
Describe with a sketch, the general arrangement of an oil monitoring system
b)
State the inputs that are recorded
(c) Explain the difficulties encountered with the efficient operation of the oil monitoring system.
9.
Explain the principle of port State control and give in detail the verification
the Port State Control Officer may carry out with reference to the following:
a)
Emergency generator
b)
Auxiliary steering gear
c)
Lifeboat engine
d)
Bilge pump
e) SOPEP
Apr- 2023
SECTION
I
1.A.
Under what conditions, can you produce sustained oscillations?
B.
Classify oscillations with respect to frequency range, principal involved, etc.
C. It is possible to produce oscillations with RC networks in phase shift oscillator. Discuss in detail.
3. With reference to the provision of a shore
electrical supply to a ship:
a) Sketch an arrangement for taking A.C.
shore supply and checks to be carried out prior Taking shore connection?
b) Describe the method of safely connecting the arrangement sketched in (A) to the shore Supply?
SECTION
II
4. A )Explain the significance of the root mean square value of an alternating current or voltage waveform. Define the form factor of such a wave form.
4.b) A total load of 8000 kW at 0.8 power
factor is supplied by two alternators in parallel. One alternator supplies
6000kW at 0.9 power factor. Find the KVA rating of the other alternator and the
power factor.
5. A) Sketch an arrangement showing the
principal of a proportional plus Integral (P + 1) control loop.
(5.b) Compare the series and parallel resonance circuits. Find the frequency at which the following circuit resonates.
6 A)
Explain the potential hazards if liquid-cooled transformers are used.
(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) the UMS
monitoring, and control system of your ship has recently started to give false
alarms and incorrect data printouts. State, with reasons, possible causes if
the false alarms and reading are:
i. Localized to a particular area of engine operation; ii. General to the engine room.
7.b) State, with reasons, the action you, as Electrical Engineer, would take to ensure continued safe operation of the vessel if the defects were general to the engine room.
7.c) Explain the
procedure you, as Second Engineer, would adopt in order to locate and rectify a
general fault in the UMS system.
8.a)
Describe information which is available in the record which is attached as a
supplement to the IOPP Certificate, for a bulk carriers and oil tanker.
b)
What are the provisions for engine room under MARPOL 73/78 Annex-1, for large
ocean going vessel?
c)What is IBC Code and what Certificates are issued under the Code and to which ship?
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
1.
Explain
the effect of reduced voltage on standard squirrel cage motors with respect to EACH of the following:
(a) Burn outs.
(b)
Starting current.
(c) Stating torque.
(d) Speed.
2.a)
In a.c. generators, voltage dip occurs in two stages.
(i)
Sketch a voltage-time graph showing the pattern of voltage dip.
(ii)
Referring to this graph, state with reasons the effect on the electrical system
of a small power installation when a large load is suddenly switched on.
(b)
Explain EACH of the following categories of voltage control:
(i) Error operated. (ii) Functional
3.
With reference to the provision of a shore electrical supply to a ship:
a)
Sketch an arrangement for taking A.C. shore supply and checks to be carried out
prior Taking shore. connection?
b) Describe the method of safely connecting the arrangement sketched in (A) to the shore Supply?
4 .A) What are the characteristics of PN junction diode? Point out its specifications. Also point out the significance of dynamic and static resistances.4.b) Draw the circuit of Half-wave rectifier and its output waveform. A diode whose internal resistance is 202 is to supply power to 1000 2 load from 110 V (RMS) source Calculate (a) peak load current, (b) DC load current, (c) AC load current.
5.a. Describe the no-load saturation
characteristic of a d.c. generator.
5.b.) A. d.c. motor takes an armature current of
110 A at 480 V. The resistance of the armature circuit is 0.22. The machine has
six poles and the armature is lap-connected with 864 conductors. The flux per
pole is 0.05 Wb. Calculate
(i) The speed.
(ii) The gross torque developed by the armature.
6.A. What is
back emf? Derive the relation for the back emf and the supplied voltage in
terms of armature resistance.
6.b) A
three-phase induction motor is wound for four poles and is supplied from a 50
Hz system. Calculate:
1. The
synchronous speed.
2. The speed
of the rotor when the slip is 4 %
3. The rotor frequency when the speed of the rotor is 600 r/min.
7.a.
With reference to SOLAS 74 amendments 2000, maintenance plan is to be kept
on-board ship for firefighting system, Enumerate the list of fire protection
system and fire-fighting system sand appliances, which will be required to be
included in the maintenance plan.
b)
Training manual as required by SOLAS 74 amendments 2000, Chapter 11-2 contains
Instructions and information with respect to fire fighting. List the same and
their significance.
8. A) Sketch
and describe a total flooding CO2 gas system suitable for the protection of
machinery spaces.
b). State, with reasons, which valve should be operated first in the system shown in .
9.
A) Describe a vacuum sewage system.
b)
With reference to the system described in (a)-
i.
State advantages of the system,
ii.
State why a holding tank may burequired to be fitted to the system.
iii.
State the problems resulting from the retention of untreated sewage in a
holding tank
iv. State the periodic maintenance required on the system.
JUL- 2023
SECTION-I
1.
Direct online starting for large induction motors such as those for bow thrust
units, may not be viable.
a)
State the reasons for this.
b)
Sketch a starting system that may be used for such motors.
c)Describe the starting method sketched in (a,b).
2. What is a marine High Voltage System? Sketch and describe a
Shipboard high voltage switch board and its protective devices.
3. What is soft starting of an Induction Motor? Describe with a circuit using thyristors used for soft starting. Discuss its advantages and disadvantages.
4.a) Explain the potential hazards if liquid-cooled transformers
are used.
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.
5.b) The low-voltage release of an a.c. motor-starter consists of
a solenoid into which an iron plunger is drawn against a spring. The resistance
of the solenoid is 35 ohm. When connected to a 220 V, 50 Hz, a.c. supply the
current taken is at first 2 A, and when the plunger is drawn into the
"full-in" position the current falls to 0.7 A. Calculate the
inductance of the solenoid for both positions of the plunger, and the maximum
value of flux-linkages in weber-turns for the Full-in" position of the
plunger.
6.b)
Three batteries A, B, and C have their negative terminals connected together.
Between the positive terminals of A and B there is a resistor of 0.5 ohm and
between B and C there is a resistor of 0.3 ohm.
Specifications
of the three batteries are given below:
Battery
A 105 V. Internal resistance 0.25 ohm
Battery
B 100 V. Internal resistance 0.2 ohm
Battery
C 95 V. Internal resistance 0.25 ohm
C.) Determine the current values in the two resistors and the power dissipated by them.
7.With reference to oil monitoring of bilge and
tanker ballast discharges:
a)
Describe with the aid of a sketch, the
general arrangement of an oil monitoring system.
b) State the inputs that are recorded.
c) Explain the difficulties encountered with the efficient operation of the oil monitoring system.
8
a.i) With respect to the hazardous areas of tankers, explain the term
flameproof for electrical equipment.
ii)
State the type of electrical equipment that would be protected in this way.
b) List likely defects of flameproof equipment.
9.
With reference to an emergency fire pump state-
a)
The regulations that influence its location, capacity, and power.
b)
How the power supply to emergency pump is ensured?
c)Why
a relief valve is necessary on the deck main?
d)Requirement of isolation valve in fire main line
SECTION-I
1.With reference to alkaline batteries used
on board ship.
a) Describe the operation of a battery cell
and state the material used.
b) Describe how the cells are mounted to form
a battery.
c) State the advantages and disadvantages compared with lead-acid batteries.
2. With reference to a 3 speed a.c. cage
motor driven cargo winch:
a) Sketch a circuit diagram for a pole change
motor.
b) Describe how speed change and braking are
achieved
3.With reference to electronic control
systems
a) Draw a simple block diagram for
temperature control
b) Describe each component shown in the diagram in (a.
4.b) A transistor amplifier stage comprises a transistor of parameters hie = 8002 hfe = 50 and hoe = 20µ 5, and bias components and coupling capacitors of negligible effect. The input signal consists of an e.m.f. of 60 mV from a source of internal resistance 2.2 kn, and the total load on the stage output is 4 kr. Determine the current, voltage and power gains of the amplifier stage
5.a.) Explain how the efficiency and
regulation of a transformer can be
assessed by open circuit and
short circuit tests
5.B) A turned circuit consists of a coil having an inductance of 20mh and a resistance of 20Ω in parallel with a variable capacitor is connected in series with a resistor of 8000Ω across a 60v supply having frequency of Imhz calculate a) capacitance b) dynamic Impedance a Q factor c) current in each branch
6.b) an eight pole armature is wound with 480
conductor the magnetic flux the speed are such that the avg emf generated in each conductor is 2.2v and each
conductor is capable of carrying a full load current of 100A calculate the
terminal vtg on no load o/p current on full load total power generated on full
load when
(a) lap connected
(b) wave connected
7.
Fire control plan is on of the requirements to be carried on board ship
state the international convention under which the plan is made mandatory with reference
to this plan explain
I) info available in the plan ii) location if is towed and the reason.
8.A)
Explain the purpose of interpoles and state their magnetic polarity relative to
the main poles of both generators and motors
B) A 200v, long-shunt compound wound generator has a full-load output of 20kw. The various resistances are as follows armature (including brush contact) 0.15 ohm, series field 0.025ohm interpole field 0.028ohm shunt field (including the field-regulator resistances 115ohm.The iron losses at full load are 780W, and the friction and windage losses 590W Calculate the efficiency at full load
9. with reference to the maritime labour
convention (MLC) 2006 discuss the requirements for seafarers regarding
A) minimum
age to work onboard
B) seafarers
employment agreements.
C) Hours of work and hours of rest.
Sep-2023
SECTION-I
1.
Compare methods of obtaining speed regulation of three-phase induction motor
generally used in tankers by means of:
a)
Rotor resistance.
b)
Cascade system.
c)
Pole-changing.
Give examples where each system may be employed with advantage.
2.a)
State the necessary conditions required prior to the synchronizing of
electrical alternators.
b)
Describe the type of cumulative damage that may be caused when alternators are
incorrectly synchronized
c)Explain
how the damage referred to in
b)
can be avoided / reduced.
d)
For two alternators operating in parallel state the consequences of
(i)
Reduced torque from the prime mover of one machine.
(ii)Reduced excitation on one machine.
3. With respect to the High Voltage power systems installation, explain the different types of circuit breaker that are used, comparing them on merits and de-merits. Describe the theory of arc phenomenon and the mechanism fitted to mitigare the arc.
SECTION
II
4.a) Sketch
an arrangement showing the principal of proportional plus integral (P+I)
control loop.
b) Compare the series and parallel resonance circuits. Find the frequency at which the following Circuit resonates.
5.a) Explain the potential hazards of liquid-cooled
transformers are used.
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 w. Calculate the efficiency at half-full load 0.8 power factor.
6.a) Compare the effectiveness of a current
limiting circuit breaker with that of a HRC fuse.
b) A 440V shunt motor takes an armature current of 30A at 700 rev/min. The armature resistance is 0. 7ohm if the flux is suddenly reduced 20 per cent, to what value will the armature current rise momentarily ? Assuming unchanged resisting torque to motion, what will be the new steady values of speed and armature current?.
SECTION
– III
7.
With respect to MARPOL 73/78, Annex - II, Noxious liquid chemicals are divided
into categories;
a). State the number of categories, and what
does each category signify.
b) State the requirement of Procedures and Arrangements Manual, and what information is available.
8.
With reference to free fall lifeboat of an ocean going ships:
a)
Periodical maintenance, tests and checks on lifeboat and releasing gear.
b)
Secondary means of lowering.
c) Lifeboat Drills.
9.
Briefly discuss the following with respect to safety of navigation:
a)
Bridge Navigation Watchkeeping Alarm System (BNWAS)
b)
Long Range Identification and Tracking of ships (LRIT)
c) Voyage Simplified Voyage Recorder (VDR/S-VDR)
SECTION- I
1.What
are semiconductor devices What are in advantages over thermionic devices? With
respect to semiconductor devices describe working principle and application of
the following:
(a)
Zener Diode
(b)Transistor
(c)
Photocell for
(d)Thyristor
2.
Tank liquid level sensors are an integral part of ships, Describe with the aid
of suitable sketches the working principle of
(a)
Capacitive type level sensor
(b)
Ultrasonic level sensor
(c)Float
3.The
direct on line start of squirrel cage motor is wide for most electrical drives
on a c. powered ships Describe with sketches as necessary one method of
overcoming each of the following problems:
(a)High
starting current
(b)Low starting torque
SECTION
II
4.a) Explain the significance of the root mean square value of an alternating current or voltage waveform Deline the form factor of such a war form
4.b) A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000kW at 0.9 power factor. Find the KVA rating of the other alternator and the power factor.
b) A battery charging circuit is shown below in 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 1.0 A
6.a)
What is back emf? Derive the relation for the back emf and the supplied voltage
in terms of armature resistance.
6.
b)A three-phase induction motor is wound for four poles and is supplied from a
50 Hz system. Calculate:
(
i) The synchronous speed
(ii)
The speed of the rotor when the slip is 4 per cent
(iii) The rotor frequency when the speed of the rotor is 600 r/min.
7.
Name various statutory Certificates and Documents to be carried on board Gas
Tankers giving a reference to the conventions and justify for their
requirement. 8. With Reference to the Maritime Labour Convention (MLC) 2006,
discuss the requirements for seafarers regarding:
a)
Young Seafarers onboard ships
b)Repatriation,
c)Seafarers Wages.
8.
With Reference to the Maritime Labour Convention (MLC) 2006, discuss the
requirements for seafarers regarding:
a)
Young Seafarers onboard ships
b)Repatriation,
c)Seafarers
Wages.
9.
With reference to an oil/water separator:
a)
Sketch such a device,
(ii)
Describe the passage of oil/water mixture from the delivery of pump to the
outlets of the separator.
b)
State how oil density and temperature affect the case of separation of oil from
water.
c) State how the movement of oil on board ship or its discharge and the discharge of oily bilge or hallast water overboard is recorded.
NOV - 2023
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. 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.
3.
With reference to electronic control systems:
a)
Draw a simple block diagram for temperature control
b)
Describe each component shown in the diagram in (a).
4.
(a) Describe how protection against short circuit is provided.
5.b) What are the losses in transformers? Mention the various factors which affect these lossės. In a 25 KVA, 3300/233 V, single phase transformer, the iron and full-load Cu. losses are respectively 350 and 400 w. Calculate the efficiency at half-full load 0.8 power factor.
Q.7
With reference to MARPOL Annex IV
a)
Draw a biological sewage treatment plant and explain the principal of
operation.
b) Periodical maintenance and checks and tests required to be done to verify the effectiveness of the above system.
8.
a)(i) discuss the various hazards and problems which are associated with
electric cable Insulation in the event of fire II) Suggest remedies for these
problems.
b)
State how the spread of fire may be reduced by the method used for installing
electric cables.
9.With reference to "ISM
Code" write short notes on:
a) Masters Review
b) Requirement and Advantages of
Familiarization of seafarer onboard
c). Designated Person Ashore (DPA)
d) Functional requirements for a Safety Management System.
DEC-2023
Section I
Q 1. a) Compare methods of obtaining speed regulation of three-phase induction motor generally used in tankers by means of i Rotor resistance; ii Cascade system, iii Pole-changing Give examples where each system may be employed with advantage.
Q
2 Tank liquid level sensors are an
integral part of ships. Describe with the aid of suitable sketches the working
principle of:
(a)
Capacitive type level sensor
(b)
Ultrasonic level sensor
(c) Float
(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:
Section II
Q4
(a) Explain the significance of the root mean square value of an alternating
current or voltage wave from: Define the from factor of such a wave form.
(b) A 72 kVA transformer supplies a heating and lighting load of 12 kW at unity power factor and a motor load of 70 kVA at 0.766 ( lagging ) power factor. Calculate the minimum rating of the power- factor improvement capacitors which must be connected in the circuit to ensure that the transformer does not become overloaded.
Q5 (a) show how the power that is transferred
across the air gap of the three-phase induction motor is represented. Explain
the terms. What portion of this is useful power
(b) A 440V shunt motor takes an armature current of 30A at 700 rev/min. The armature resistance is 0.7ohm. If the flux is suddenly reduced 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged resisting torque to motion, what will be the new steady values of speed and armature current? Sketch graphs showing Armature current and speed as functions of time during the transition from initial to final, steady-state conditions.
Q6 (a) What are the factors which determine the synchronous speed of a motor?
(6.b)
A three-phase induction motor is wound for four poles and is supplied from a 50
Hz system. Calculate
(i)The
synchronous speed
(ii)The
speed of the rotor when the slip is 4 per cent
(iii)The rotor frequency when the speed of the rotor is 600 r/min
Section III
Q7.
With reference to the Maritime Labour Convention (MLC) 2006, discuss the
requirements for seafarers regarding-
(a)
Minimum age to work onboard vessels
(b)
Seafarers Employment agreements
(c) Houn of work and hours of rest
Q8.
With reference to entry into enclosed spaces onboard:
(a)
Define "Enclosed space" and give example 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.
Q9.
With reference to free fall lifeboat of an ocean-going ships:
(a)
Periodical maintenance, tests and checks on lifeboat and releasing gear.
(b)
Secondary means of lowering
(c) Lifeboat Drills.
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