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MET oral KUNDRA





1. What is special about steering gear safety.
It has got overload alarm at 150% and short circuit trip.

2. Maintenance of alternator what all to do.
(a) Clean the felt/ air filters.
(b) Remove dust/ dirt from the rotor.
(c) Clean the connections and put some petroleum jelly.
(d) Check the air gap with the plastic feeler gauge.
(e) Check the lub oil level in bearing.
(f) Insulation resistance to take with megger.
(g) Check condition of winding.
(h) Carry out continuity test.

3. Purpose of air gap and how checked.
To avoid the mechanical contact between the stator & rotor and to determine the condition of the bearing. Measured with the help of feeler gauge.


4. Trips on air circuit breaker with values

5. conditions for paralleling alternators
(a) Frequency
(b) Phase
(c) Voltage

6. How to parallel alternators
There are three methods of Paralleling alternators:-
(i) Dark lamp method
(ii) Bright lamp Method
(iii) Synchorscope

7. Why megger is used to test insulation and not multi meter
Megger is used to test insulation because it has higher range say upto 500V.

8. Suppose a motor is not starting what checks u will make
Electrical Checks:
a. Check the connections.
b. Check, if has tripped, then reset and try to start.
c. Check supply is coming from MSB or not.
d. Check single-phasing has not occurred.
Mechanical :
Check the coupling between the motor and driven part is not too tight.

9. Suppose a motor is running hot what checks.
a. Single-phasing
b. Fan is working or not.
c. Overload is occurring.
d. Check condition of bearing.

10. Why insulation resistance checked and how?
A measurement of the insulation resistance gives the best guide to the state of health of the electrical equipment.
a. Disconnect the electrical supply.
b. Refer to the electrical circuit & manufacturer’s instruction before testing.
c. Measure the insulation of the windings to the earth and as soon as possible when the machine is just hot after it has stopped. The minimum value should be
1 MW.

11. Why motor insulation deteriorates
a. Moisture – results in decrease in the measured value of insulation resistance.
b. Dust & dirt deposits – reduces insulation resistance & failure of insulation due to oxidation.
c. Oil & Grease – prevents heat dissipation & causes dirt and dust to settle on the insulation.
d. Ageing – over the period of time the insulation deteriorates due to it getting affected by temperature variation, mechanical stresses, vibrations, moisture and some varnish tend to become hard with age & crack during the operation.
e. Temperature – Excessive temperature dehydrates and oxidizes the insulation, making it brittle & disintegrate under vibration & shock.

12. If water goes to motor what you do.
a. Disconnect the electrical supply.
b. Put MEN AT WORK tag.
c. Remove the coupling bolts.
d. Now, lift the motor using lifting gear & put it on a clean place.
e. remove the cover & fan.
f. Take out bearing & the shaft.
g. The salt contamination must be removed by thoroughly washing with clean fresh water (preferably warm) or if possible , distilled water.
h. De-greasants must be used if it is found that there was ingress of oil.
i. Spirits or alcohol may be used to clean contacts.
j. Dry the motor with dry air & then switch on its heaters or use powerful lamps. During this process , keep its inspection covers open to permits moisture to escape.
k. Put the varnish on the winding & let it dry.
l. Check the insulation resistance. If it is ok then assemble it back & put it for use.
m. The motor must be started on less load & its current monitored for few hours to confirm its satisfactory operation.

13. How do you test that Megger is working Ok

14. What are portable electrical testing instruments used in ER
a. Clampmeter
b. Megger
c. Multimeter
d. Tester



15. What is harm if reverse power flow?
Motoring effect will take place & can damage the prime mover.

16. Why preferential trip provided Purpose?
Preferential trip is provided to safe guard the machineries which are important for safety of ship & safety of personnel onboard.
Preferential trips are designed to disconnect the non-essential services i.e., Breakers controlling Air Conditioning, Galley power, blowers, refrigeration) in the event of partial overload or partial failure of the supply, with the aim of preventing operation of the main breaker trip & loss of power to essential services.

17. How do you test emergency generator?
a. Regular or weekly testing of the emergency generator should include simulation of the loss of normal power.
b. The start up equipment may be provide a push button to interrupt the normal voltage supply to the panel which then triggers the start sequence.
c. Loss of main power supply can easily be simulated by pulling a fuse in the auto-start panel which supplies the under voltage or under frequency relay.
d. This no load running checks should, when practicable, be supplemented occasionally by a proper load test. This requires the disconnection of the normal mains power while the emergency generator is loaded upto near its rated value.

18. How do you check press and temp alarms. What equipment used for same

19. If you get earth fault alarm what you do?
a. Accept the alarm.
b. First of start isolate the breakers one by one.
c. Then, check where the alarm has came & should be eliminated when located.
d. Damaged conductor insulation must be repaired.
e. Dampness or moisture in insulation must be dried out by gentle heat & precautions should be taken to prevent future ingress of moisture.
f. If dirt is the cause, then a thorough cleaning with electro cleaner solvent should be applied & clean.

20. If on starting Generator you find that voltage is not building up what you do?
Residual magnetism is lost. So supply power from outside by connecting battery.

21. What equipment emergency generator supplies.
(a) For a period of 3 Hrs at Emergency lighting at every muster & embarkation station.
(b) For a period of 18 hrs at:-
(i) In all service & accommodation alleyways, stairways & exits, personal lift cars & personnel lift trunks.
(ii) In the machinery spaces & main generating stations including their control positions.
(iii) In all control stations, machinery control rooms, and at each main & emergency switchboard.
(iv) At all stowage positions.
(v) At the steering gear.
(vi) At the fire pump & in all cargo pump rooms.
(vii) The navigational lights.
(viii) VHF & MF Radio installation.
(ix) The ship earth radio station.
(x) At all internal communication equipment
(xi) The fire detection & fire alarm system.
(xii) Intermittent operation of the daylight signalling lamp & all integral signals that are required in an emergency.


22. What is diff between AC and DC?
The difference between AC and DC is that AC is an alternating current (the amount of electrons) that flows in both directions and DC is direct current that flows in only one direction;
The wires outside of our house are connected at two ends to AC generators. DC is found in batteries and solar cells.
alternating current varies with time, sinusoidally... where as DC remains steady.

23. What is rms value?
The RMS value of an alternating current is also known as its heating value, as it is a voltage which is equivalent to the direct current value that would be required to get the same heating effect.

24. What maintenance carried out on Lead acid batteries.
a. Connection to be checked for tightness.
b. Casing surface to be kept clean.
c. Terminals are protected with petroleum jelly or Vaseline.
d. Specific gravity to be check with hydrometer.
1.21 Charged Condition
1.18 Discharged Condition
e. Batteries to be topped up with distilled water.
f. Check & clear vents to ensure H2 gas produced is vented.S

Safeties to be observed while operation & maintenance.
i. Use hand gloves & safety goggles while adding distilled water, shifting of battery, or checking sp. Gravity.
ii. Use insulated spanners to tighten terminals (No Sparking, short-circuiting should take place)
iii. Use plastic bottle or jar to add distilled water.
iv. Should not be left in discharged condition for long period.
v. If adding acid, then first put little Acid, then add water & do the same process.
vi. No naked lights to be taken inside.
vii. No smoking inside battery room.

25. What precautions you will take before entering battery room.
a.Inform the bridge & the engine control room
b.Check the oxygen content.
c. Should be ventilated properly.
d. All PPE to be donned properly & rubber hand gloves to be used.
e. No Naked lamps to be taken inside.
f. .


26. What is meaning of power factor. What is best value. What is normal value onboard. How do you improve?
Power Factor :- The power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power and is a dimensionless number between 0 and 1

The best value is 0.85. The normal value onboard varies in between 0.8 to 0.9.
Power factor can be improved by connecting a Capacitor in parallel.

27. What is meaning of saying current and voltages are in phase

28.What happens to resistance of conductor when temp rises.
Resistance is directly proportional to temperature.
So, resistance will increase if temperature rises.

29. Types of starters in ERoom
a. DOL (Direct On-Line)
b. Star-delta
c. Auto-transformer.
d. Face plate starter

30. Types of Motors in Eroom
a. Induction Motor.
b. Synchronous Speed Motor.
c. DC Motor.
d. Shunt motor
e. Series Motor

31. How do you check continuity.
By using the multimeter, continuity is checked. Continuity is checked between the earth & the motor connection.

32. Meaning of open and short circuit. How checked.

33. Voltage generated in megger.
500 V.

34. What is explosion proof equipment?
It is an equipment:
(a) Having an enclosure capable of withstanding an explosion within it of a specified flammable gas or vapor & preventing the ignition of the specified flammable gas or vapor in the atmosphere surrounding the enclosures by the sparks, flashes or explosion of the gas or vapor within.
(b) That operates at such an external temperature that a surrounding flammable atmosphere will not be ignited.

35. What precautions to take while using megger ion circuits containing Electronic components.

36. What precautions to take before starting a work on electric equipment?
a. Do get to know the electrical circuit or system.
b. Rubber gloves, insulated tools to be used.
c. Portable lamp, if used should be fully insulated without metal guards.
d. Precautions must be observed to isolate and lock off the apparatus. Where, fuses are there, these should also be removed.
e. Before commencing work, it should be confirmed that the system is dead using live line tester.
f. Men at Work signboard to be put.


37. how does tube light work.

38,. Trips on Electric Motor.
Short Circuit trip.
Overload trip.
Reverse power trip.
Reverse current trip
Fuse

39. Overhaul of an Electric Motor.
a. Disconnect the electric circuit.
b. Isolate the system.
c. Remove the fuse & check the electric supply is not coming.
d. Put MEN at Work tag.
e. Remove the coupling bolts.
f. Lift the motor with the help of lifting gear.
g. Open the end cover & remove the fan and clean the fan.
h. Remove the bearing and renew it.
i. Check the condition of winding visually & check the insulation resistance by using megger.
h. If low, then apply varnish on it & dry it with gentle heat.
i. Check the continuity.
j. Assemble the motor.
k. Before putting it into operation, check the load being taken & any noise coming from it.


40. Purpose of AVR
AVR :- Automatic Voltage Regulator
The AVR is used as an exciter. The purpose of AVR is to maintain terminal voltage of an alternator constant on load.

41. What is shaft generator

42 how does air compressor start stop automatically
There is a pressure switch provided which is having a bellow inside which increases & decreases in its size if the pressure rises to reqd. to start the compressor .

43 Main switchboard safeties.
a. Ebonite Rod.
b. Rubber pad infront of switchboard.
c. Dead-front type switchboard.
d. 0.6 meter gap behind the switchboard.
e. Fuse
f. Circuit Breakers.
g. Earth Fault indicators.
h. Panel doors are earthed.
i. No water, steam or oil pipelines to pass in its vicinity.
j. Undervoltage Relay
k. Reverse Power trip.
l. Preferential trip.
m. Overcurrent trip
n. Arc Chute
o. Short-circuit trip.

44. Precautions while connecting shore power?
a. Check terminal box cover screws/nuts to remove(Find out location), lightly greased & ease up.


45 Why load picked by crane does not fall if power goes off
Because Electro-magnetic brakes get operated.

46. How electricity is generated.

47.Maintenance on Alternator?
a. Ventilation passages & air filters to clean.
b. Insulation resistance to check for Stator, rotor winding. If low, then varnish to be done
c. Air gap to check using plastic feeler gauge.
d. Bearing oil to be renewed.
e. Use vaccum cleaner to remove dirt/ dust.
f. Terminal box cover gasket integrity to check.
g. Terminal connections to check for tightness.
h. AVR components, diodes to keep free from oil, moisture or any dirt.
i. Heaters to be checked.

48. What is the function of Diode?
The function of a diode is to allow current in one direction and to block current in the opposite direction.

48. How to carry out Open Circuit & Short circuit test?
Open Circuit Test: The purpose of this test is to determine no load loss or core loss.
One winding of the transformer, usually high voltage side if left open and the other is connected to its supply of normal voltage and frequency. A wattmeter, voltmeter and the ammeter are connected in the low voltage winding.
With the normal voltage applied to the low voltage side, normal flux will be set up in the core, hence normal iron losses will occur which are recorded by the Wattmeter.
The load current on the low voltage winding will be small(2 to 5 % of rated full load current ), the copper loss in the winding will be negligible and will be nil in the high voltage side winding..
So, the wattmeter reading will represent practically the core loss under no load condition.

Short-Circuit Test: This is also known as Impedance test.
In this test, the low voltage winding is short circuited by using a thick conductor (or Ammeter, which serves additional purpose of Indicating Rated load current).
A low voltage at correct frequency is applied to the primary and is cautiously increased till full load current is flowing the high voltage side.
In this test, the applied voltage is small percentage of its rated value, hence flux produced is small with the result that iron losses will be negligible and the Wattmeter reading will represent the full load Cu-loss.

49. Suppose your motor has short-circuited, then how much value will you get on Megger.

51. An example of each.
- Where does magnetic field cuts the conductor?
-where does conductor cuts the magnetic field?

52. How is signal transmitted from Navigational bridge to steering gear?

53. How is the load decided on AC Compressor & how does it works?

54. What is Open-circuit & short-circuit in a control unit ?

55. Safeties in motor?
a. Fuse
b. Overload trip
c. Short-circuit trip
d. Reverse power relay


56. Working principle of Explosimeter?


An explosimeter is a device which is used to measure the amount of combustible gases present in a sample. When a percentage of the lower explosive limit (LEL) of an atmosphere is exceeded, an alarm signal on the instrument is activated. "Explosimeter"
The device, also called a combustible gas detector, operates on the principle of resistance proportional to heat—a wire is heated, and a sample of the gas is introduced to the hot wire. Combustible gases burn in the presence of the hot wire, thus increasing the resistance and disturbing a Wheatstone bridge, which gives the reading.
A flashback arrestor is installed in the device to avoid the explosimeter igniting the sample external to the device.
The combustible gas indicator shown diagrammatically above consists of a Wheatstone bridge with current supplied from a battery. When the bridge resistances are balanced, no current flows through the galvanometer. One resistance is a hot filament in a combustion chamber. An aspirator bulb and flexible tube are used to draw a gas sample into the chamber. The gas will burn in the presence of the red hot filament causing the temperature of the filament to rise. Rise of temperature increases the resistance of the filament and this change of filament unbalances the bridge. The current flow registers on the meter which is scaled in percentage of LFL or ppm.


57. Safeties and precautions on portable electrical equipments?
58. what is the routine maintenance on the starter of main air compressor which is of automatic start stop type?

59. How to test a fuse? -apart from multimeter.




60. Types of Fuses & diagram?

a. Catridge Type.
b. HRC(High Rupturing Capacity)

61. Which is the largest induction motor used onboard?
Alternator
62. Which current is coming out from Alternator?

63. How will know proper working of Megger?

64. Types of Switchboard?
a. Open Type
b. Dead front type.

65. Whats the use of apparent power(kva) & reactive power(kvar)??????
Apparent power consists of active and reactive power. Active power is the share of the apparent power which transmits energy from the source (generator) to the user. Reactive power is the share of the apparent power which represents a useless oscillation of energy from the source to the user and back again
66. What is a Thyristor?

67. Maintenance carried out in Stator.

68. Why Star-Delta starters are used?

69. What all testing equipment is used for testing an electric motor?

70. Basic meaning of Intrinsically safe motor?
An intrinsically safe circuit is one that is designed for a power so low that any spark or thermal effect produced by it whether there is fault or not, is incapable of igniting the surrounding gas or vapor.



71. Difference between Intrisically safe & Explosion proof?
An intrinsically safe circuit is one that is designed for a power so low that any spark or thermal effect produced by it whether there is fault or not, is incapable of igniting the surrounding gas or vapor.

Explosion proof :-

72.Circuit diagram of Megger?
73.What is the function of Commutator?

74.What is the supply given to shipboard general alarm.
24 Volt DC.
75. Maintenance on switchboard?
a. Check contacts of Circuit breaker for damage & dirt.
b. Cleaning of contact using electro-cleaner.
c. Interlocks fitted to check for proper functioning.

  1. How to make sure motor is in good condition?
While Running
  1.  
  2. No noise
  3. No vibrations
  4. Motor frame temperature normal.
  5. Current drawn by the motor is normal.
  6. No dirt or dust or no corrosion on fins.
  7. Drawing rated current.
During Stop condition.
  1. Isloate the system
  2. Dismantle the parts
  3. Check condition of internal parts, like bearing, fan.
  4. No damage to rotor, stator.
  5. Insulation resistance to check.
  6. No signs of overheating should be there.
While starting
  1. Developing correct torque & high starting current.
  2. Coming back to its normal rated current in designated time.

76. Draw star, delta 3 phase connections?

77. What are various portable electrical equipment used?
a. Megger
b. Multimeter
c. Clampmeter
d. Live line tester.

78. what is the difference between KW and KVA?
KW means that it is the power deliverd to the load. where as the kva is the power can be meet the load demand. so that kva is not with respect to load.


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