OIC-EW MARINA REVIEWER / QUIZ COMPETENCE 6 - PART 3 - Seaman Kowts

COMPETENCE 6 – Operate Electrical, Electronic and Control Systems

Results

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#1. How are the number of cycles per second developed by the alternator aboard your vessel determined?

the speed of the engine driving the alternator

the resistance applied to the field rheostat

the synchronous speed of induction

the adjustments made to the voltage regulator

Incorrect!

#2. For what purpose are thermal strip heaters provided in DC main propulsion motors?

prevent moisture buildup in windings when motor is idle

maintain a relatively constant temperature in the motor enclosure

prevent the rotor from warping while in operation

provide an additional means of starting resistance

Incorrect!

#3. DC generator circuits are protected against malfunctions due to prime mover power loss by the use of what device (or devices)?

main bus disconnect links

a separate battery backup

reverse current relays

reverse power relays

Incorrect!

#4. Diesel generators #1 and #2 are operating in parallel at near full load capacity. Diesel generator #1 suddenly trips out mechanically due to low lube oil pressure. The reverse power relay functions properly and trips generator #1 electrically off the board. Which of the following actions should you carry out FIRST?

Start the emergency generator

Strip the board of all non vital circuits.

Ascertain cause of the low lube oil pressure.

Secure alarms, reset reverse power relay, and restart #1 engine.

Incorrect!

#5. How is the frequency output of an operating alternator controlled?

number of turns of wire in the armature coil

relative speed of the rotating magnets

strength of the magnets used

output voltage

Incorrect!

#6. How is the rated temperature rise of an electric motor defined?

average temperature at any given latitude

normal temperature rise above the standard ambient temperature at rated load

average temperature rise due to resistance at 10% overload

permissible difference in the ambient temperature of the motor due to existing weather conditions

Incorrect!

#7. D.C. propulsion motor brush pressure depends on the brush grade used. In practice with what device is the proper brush pressure established?

multi meter

manometer

spring scale

compound gauge

Incorrect!

#8. How is the speed of the propeller shaft directly coupled to an AC synchronous drive motor changed when powered by either a dedicated or integrated constant frequency alternator in an AC diesel-electric drive system?

Varying the generator speed

Varying the number of motor poles

Varying the field strength of the generator

Varying the output frequency of the power converter

Incorrect!

#9. How is the output voltage of a 440 volt, 60 hertz, AC generator controlled?

varying the prime mover speed

varying the strength of the excitation field

varying the load on the alternator

varying the number of poles

Incorrect!

#10. Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct?

Each wire must be14 AWG or larger, regardless of locations and use.

Wire must be of the solid copper type.

Wire need not be in an enclosure nor component insulated.

Wire must be of the stranded copper type.

Incorrect!

#11. How are the field windings of a DC shunt generator connected?

in series with the series windings

in parallel with the field rheostat

in series with the armature windings

in parallel with the armature windings

Incorrect!

#12. How are AC and DC generators are similar?

They both rectify the current before delivery.

They both internally generate alternating current voltages.

They are both constructed at the same physical size for the same kilowatt rating.

They both internally produce three-phase power.

Incorrect!

#13. Due to the operating characteristics of the system, time lag fuses (or dual- element fuses) are necessary for use in what types of circuits?

main lighting circuits

motor starting circuit

emergency lighting circuits

general alarm circuits

Incorrect!

#14. How many cells are within a twelve volt lead acid battery?

one cell

three cells

six cells

twelve cells

Incorrect!

#15. During discharge of a lead-acid storage battery, which of the following actions occurs?

The acid becomes weaker

The acid becomes stronger.

Both plates change chemically to ammonium chloride.

Hydrogen gas is liberated.

Incorrect!

#16. How are the line losses in a distribution circuit kept to a minimum?adding rubber insulation conductors to the circuit

adding rubber insulation conductors to the circuit

using higher current and lower voltage

increasing the number of thermal relays in the circuit

using higher voltage and lower current

Incorrect!

#17. How is the power factor of an AC generator operating singularly determined?

the connected load

prime mover speed

the ground current

the generator’s rated voltage

Incorrect!

#18. Consider a three-phase squirrel cage induction motor rated at 450 VAC and60 Hz. What would happen to the motor if the line frequency dropped from the normally supplied 60 Hz to 55 Hz and the voltage remained normal at 450 VAC.

run at a slower speed

operate at a lower current

vibrate excessively

trip off the line

Incorrect!

#19. How are fuses rated?

voltage and amperage only

amperage only

interrupting capacity only

voltage, amperage, and interrupting capacity

Incorrect!

#20. How is the full-load (rated) torque of an induction motor defined?

minimum torque developed by the motor accelerating from rest to the speed at which breakdown torque occurs

torque developed by the motor operating at rated horsepower, speed, and frequency

maximum torque developed by an overloaded motor with rated voltage and frequency with appreciable drop in speed

torque developed by the motor at the instant voltage is applied to the motor at startup

Incorrect!

Finish

There are 20 questions for the actual examination for Competence 6 for OIC-EW with a passing rate of 70%. This means that you are only allowed to make 6 mistakes.

DISCLAIMER

The questionnaires contained in this “reviewer” are extracted from the post released by MARINA on their official website and other review materials. Please note that Seaman Kowts is not affiliated with, endorsed by, or connected to the official website of MARINA. The information provided on this website is for general informational and educational purposes only and should not be relied upon as official or authoritative. If you require official information or services, please visit the official website or any relevant review center. We do not assume any responsibility or liability for any consequences resulting from the use of information or services provided on this website.

Results

#1. How are the number of cycles per second developed by the alternator aboard your vessel determined?

#2. For what purpose are thermal strip heaters provided in DC main propulsion motors?

#3. DC generator circuits are protected against malfunctions due to prime mover power loss by the use of what device (or devices)?

#5. How is the frequency output of an operating alternator controlled?

#6. How is the rated temperature rise of an electric motor defined?

#7. D.C. propulsion motor brush pressure depends on the brush grade used. In practice with what device is the proper brush pressure established?

#8. How is the speed of the propeller shaft directly coupled to an AC synchronous drive motor changed when powered by either a dedicated or integrated constant frequency alternator in an AC diesel-electric drive system?

#9. How is the output voltage of a 440 volt, 60 hertz, AC generator controlled?

#10. Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct?

#11. How are the field windings of a DC shunt generator connected?

#12. How are AC and DC generators are similar?

#13. Due to the operating characteristics of the system, time lag fuses (or dual- element fuses) are necessary for use in what types of circuits?

#14. How many cells are within a twelve volt lead acid battery?

#15. During discharge of a lead-acid storage battery, which of the following actions occurs?

#16. How are the line losses in a distribution circuit kept to a minimum?adding rubber insulation conductors to the circuit

#17. How is the power factor of an AC generator operating singularly determined?

#18. Consider a three-phase squirrel cage induction motor rated at 450 VAC and60 Hz. What would happen to the motor if the line frequency dropped from the normally supplied 60 Hz to 55 Hz and the voltage remained normal at 450 VAC.

#19. How are fuses rated?

#20. How is the full-load (rated) torque of an induction motor defined?

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