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Nuclear Power Plant Fundamentals You are logged in as Lord Mvoula (Logout)

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Started on Monday, 30 March 2015, 01:11 PM

Completed on Monday, 30 March 2015, 02:05 PM

Time taken 53 mins 40 secs

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Grade 97.14 out of a maximum of 100.00

Match the circuit to its function. Not all circuits will be used.

Maintains constant output for reference Reference

Slows down circuit response Feedback

Monitors output voltage of the AC generator. Sensing

Controls field excitation of the AC generator Signal output

Changes the milliamp input to an amp output Amplification

The correct answer is: Maintains constant output for reference – Reference, Slows

down circuit response – Feedback, Monitors output voltage of the AC generator. –

Sensing, Controls field excitation of the AC generator – Signal output, Changes the

milliamp input to an amp output – Amplification

The voltage applied to a three-phase AC motor produces a magnetic field whose

position shifts through a certain angle, so that at the end of one cycle of alternatingcurrent, the magnetic field will have shifted through one revolution describes:

Select one:

a. the relationship of speed and torque in an induction motor.

b. how speed is regulated in an AC motor.

c. how the rotor produces torque in an AC motor.

d. an example of slip in an AC motor.

e. how a rotating field is produced in an AC motor.

The correct answer is: how a rotating field is produced in an AC motor.

The phase windings of a 3 phase AC motor are spaced ________ degrees apart aro u

the stator frame to produce a rotating magnetic field:

Select one:

a. 120

b. 60

c. 90

d. 180

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The correct answer is: 120

What does a synchronous AC motor have in common with an AC induction motor?

Select one:

a. Stator windings that produce a rotating magnetic field

b. Insulated windings on the rotor

c. Brushes

d. Slip rings

The correct answer is: Stator windings that produce a rotating magnetic field

Torque in an induction AC motor is produced by:

Select one:

a. the prime mover overcoming the induced magnetic force of the stator.

b. the stator moving faster than the roto r.

c. the CEMF created between the magnetic fields of the rotor and the stator.

d. the induced magnetic field of the rotor trying to line up with the rotating

magnetic field of the stator.

e. the rotor twisting against the load it is trying to drive.

The correct answer is: the induced magnetic field of the rotor trying to line up with th

rotating magnetic field of the stator.

A voltage regulator:

Select one:

a. Maintains the output voltage of a generator at a desired value.

b. Decreases the voltage for public consumption.

c. Regulates phase output on main feed lines at power facilities.

d. Decreases the friction and wear on the brushes in a motor.

e. Regulates the RPM's of the stator in a generator.

The correct answer is: Maintains the output voltage of a generator at a desired value.

In an AC induction motor, as __________ increases from zero to approximately 25

the __________ will increase to a maximum value, beyond which any increase in lo

will cause the motor to __________ ;

Select one:

a. slip, torque, stall

b. speed, torque, slip

c. slip, speed, stall

d. torque, speed, sleep

e. orque, slip, stall

The correct answer is: slip, torque, stall


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Multiple starts of a large AC induction motor in a single hour could cause:

Select one:

a. overheating of the stator windings

b. increased starting current

c. overload protection actuation

d. rotor insulation damage

The correct answer is: overheating of the stator windings

What type of circuit protection is provided by a fuse?

Select one:

a. Overfrequency

b. Undercurrent

c. Underfrequency

d. Undervoltage

e. Overcurrent

The correct answer is: Overcurrent

Calculate the percent slip in an AC motor to the nearest whole percenta

when the speed of the rotating f ield = 1200 RPM and t he rotor speed =

1025 RPM.

Select one:

a. 14.6%

b. 16.5%

c. 20.5%

d. 19.5%

The correct answer is: 14.6%

Multiple starts of a large AC induction motor in a single hour could cause:

Select one:

a. rotor insulation damage.

b. overheating of the stator windings.

c. overload protection actuation.

d. increased starting current.

The correct answer is: overheating of the stator windings.

Starting an AC induction motor under load will

Select one:

a. Increase the starting torque

b. Reduce the length of t ime for the motor to reach running speed


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c. Lengthen the time before starting current decays to normal

operating current

d. Overheat the rotor

e. Increase the counter EMF in the stator

The correct answer is: Lengthen the time before starting current decays to

normal operating current

Large AC induction motors typically have limitations on the number of

starts in an hour to prevent

Select one:

a. overheating the rotor

b. excessive torque defection of the rotor bars

c. damage to the motor bearings

d. overheating the stator windings

The correct answer is: overheating the stator windings

What is the purpose of circuit breakers?

Select one:

a. Connects and disconnects relatively high capacity circuits

b. Protects loads from dangerously high impedances

c. Allows only one power source to supply loads

d. Interlocks commercial and diesel power systems

e. Provides reverse power protection for motors

The corre ct answer is: Connects and disconnects relatively high capacity circuits

Circuit breakers

Select one:

a. Allow only one power source to supply loads

b. Interlock commercial and diesel power systems.

c. Protect loads from dangerously high impedances.

d. Connect and disconnect relatively high capacity circuits.

e. Provide reverse power protection for motors

The corre ct answer is: Connect and disconnect relatively high capacity circuits.

What happens when power is lost and subsequently regained to the controller circuit

shown in the above diagram?


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Question 18

Select one:

a. When a low voltage condition occurs, the M coil supplies the power required to

keep the motor running. Upon regaining power, the motor automatically switches t

the normal power source.

b. When a low voltage condition occurs, the motor continues to run until voltage

0 volts. Upon regaining power, the motor automatically restarts.

c. When a low voltage condition occurs, the motor continues to run until voltage i

0 volts. Upon regaining power, the motor remains de-energized.

d. When a low voltage condition occurs, the M coil drops out de-energizing the

motor. Upon regaining power, the motor remains de-energized.

e. When a low voltage condition occurs, the M coil drops out de-energizing the

motor. Upon regaining power, the motor automatically restarts.

The correct answer is: When a low voltage condition occurs, the M coil drops out de-

energizing the motor. Upon regaining power, the motor remains de-energized.

Match the power distribution system term to its definition. Not all terms will be used

The greatest effective difference of potential between any two

legs of the circuitPhase voltage

The amount of current a conductor can carry continuously

without exceeding its temperature ratingCapacity

Potential between any given conductor and any ground point Ground voltage

A conducting connection between a circuit and the earth Ground

The correct answer is: The greatest effective difference of potential between any two

legs of the circuit – Phase voltage, The amount of current a conductor can carry

continuously without exceeding its temperature rating – Capacity, Potential between

any given conductor and any ground po int – Ground voltage, A conducting connectio

between a circuit and the earth – Ground

Which best describes the phase-to-ground scheme of connecting a single-phase load


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three-phase power source?

Select one:

a. The load is connected between two phases and the remaining phase is grounde

b. The load is connected to o ne phase and the two remaining phases are grounded

c. The load is connected in a wye configuration with the neutral to ground

d. The load is connected between one of the three phases and ground

e. The load is connected in a delta configuration with one phase to ground

The correct answer is: The load is connected between one of the three phases and

ground

In addition to fuses, motor controllers commonly use ______________and

________ overloads

Select one:

a. grounding, thermal

b. frequency, magnetic

c. thermal, magnetic

d. grounding, frequency

e. frequency, thermal

The correct answer is: thermal, magnetic

What are protective features incorporated into a motor controller?

Select one:

a. Breakers, switches, and magnetic overloads

b. Fuses, thermal overloads, and magnetic overloads

c. Failure-free grounding, thermal overloads, and magnetic overloads

d. Breakers, fuses, and switches

e. Breakers, switches, and thermal overloads

The correct answer is: Fuses, thermal overloads, and magnetic overloads

What type of circuit protection is provided by a fuse?

Select one:

a. Undervoltage

b. Underfrequency

c. Overfrequency

d. Overcurrent

e. Undercurrent

The correct answer is: Overcurrent

Define the following terms by matching the definitions.


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Ratio of turns of wire in the primary to turns of wire in the

secondary

Turns ratio

Definite turns ratio matching impedance of primary &

secondary Impedance ratio

Lines of flux from one coil cutting the windings of another coil

creating a voltageMutual induction

Ratio of power output to power input Efficiency

The correct answer is: Ratio of turns of wire in the primary to turns of wire in the

secondary – Turns ratio, Definite turns ratio matching impedance of primary &

secondary – Impedance ratio, Lines of flux from one coil cutting the windings of

another coil creating a voltage – Mutual induction, Ratio of power output to power

input – Efficiency

Match the application to the proper type transformer. Not all types will be used.

Steps down and voltage for operation of devices such as

ammeters, voltmeters, and protective relaysInstrument potential

Used in circuits for constant voltage or current; low power Control

Low power, variable voltage Auto

Steps down current for measurement purposes Instrument current

Used to block noise from power or ground circuits Isolation

The correct answer is: Steps down and voltage for operation of devices such as

ammeters, voltmeters, and protective relays – Instrument potential, Used in circuits

constant voltage or current; low power – Control, Low power, variable voltage – Aut

Steps down current for measurement purposes – Instrument current, Used to block

noise from power or ground circuits – Isolation

Chose statement that best describes the difference between delta and w

connections in a transformer

Select one:

a. In a delta connection, the three phases are connected in series forming a loop; while in a wye connection, each of the three phases has one leg of the phase connecte

to a common point.

b. In a wye connection, the three phases are connected in series from a common

point; while in a delta connection, each of the three phases are connected in parallel

forming a ladder arrangement

c. In a wye connection, the three phases are connected in series forming a loop;

while in a delta connection, each of the three phases has one leg of the phase connect

to a common point.

d. In a delta connection, the three phases are connected in parallel forming a loop

while in a wye connection, each of the three phases are connected in series also

forming a loop.


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e. In a delta connection, the three phases are connected in series from a common

point; while in a wye connection, each of the three phases are connected in parallel

forming a ladder arrangement.

The correct answer is: In a delta connection, the three phases are connected in series

forming a loop; while in a wye connection, each of the three phases has one leg of the

phase connected to a common point.

Define the following terms by matching the definitions with the properterm. Not all terms will be used.

Ratio of power output to power input Efficiency

Lines of flux from one coil cutting the windings of another coil

creating a voltageMutual induction

Definite turns ratio matching impedance of primary &

secondary Impedance ratio

Ratio of turns of wire in the primary to turns of wire in the

secondary Turns ratio

The correct answer is: Ratio of power output to power input – Efficiency, Lines of flu

from one coil cutting the windings of another coil creating a voltage – Mutual inducti

Definite turns ratio matching impedance of primary & secondary – Impedance ratio,

Ratio of turns of wire in the primary to turns of wire in the secondary – Turns ratio

Match the application to t he proper type transformer. Not all types wil

be u sed

Steps down voltage for operation of devices such as

ammeters, voltmeters, and protective relaysInstrument potential

Steps down current for measurement purposes Instrument current

Used in circuits for constant voltage or current; low power Control

Used to block noise from power or ground circuits Isolation

Used in power distribution and transmission systems Distribution

The correct answer is: Steps down voltage for operation of devices such as ammeters

voltmeters, and protective re lays – Instrument potential, Steps down current for

measurement purposes – Instrument current, Used in circuits for constant voltage o

current; low power – Control, Used to block noise from power or ground circuits –

Isolation, Used in power distribution and transmission systems – Distribution

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