HW6 Nuclear Engineering

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Time taken

Monday, 30 March 2015, 01:11 PM Monday, 30 March 2015, 02:05 PM 53 mins 40 secs

Marks 136.00/140.00 Grad Gr ade e

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Question 1

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Correct

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Mark 10.00 out of 10.00 Flag que question stion

97.14 97.1 4 out of a maximum of 100.00

Match the circuit to its f unction. 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 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 milliam p input to an amp output – Amplification

Question 2 Correct Mark 4.00 out of 4.00 Flag que question stion

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 alternating current, 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.

Question 3 Correct

The phase windings of a 3 phase AC motor are spaced ________ ________ degrees apart aro und the stator frame to produce a rotating magnetic field:

Mark 4.00 out of 4.00

Select one:

Flag que question stion

a. 120 b. 60 c. 90 d. 180

The correct answer is: 120

Question 4

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

Correct Mark 4.00 out of 4.00 Flag question

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

Question 5

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 the rotating magnetic field of the stator.

Question 6

A voltage regulator:


Select one: a. Maintains the output voltage of a generator at a desired value. b. Decreases the voltage f or 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.

Question 7 Incorrect Mark 0.00 out of 4.00 Flag question

In an AC induction motor , as __________ increases from zero to appro ximately 25%, the __________ will increase to a maximum value, beyond which any increase in load will cause the motor to __________ ; Select one: a. slip, torque, stall b. speed, tor que, slip c. slip, speed, stall d. torque, speed, sleep e. orque, slip, stall The correct answer is: slip, torque, stall

Question 8

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

Question 9

What type of circuit protection is provided by a f use?


Select one: a. Overfrequency b. Undercurrent c. Underfrequency d. Undervoltage e. Overcurrent

The correct answer is: Overcurrent

Question 10 Correct Mark 4.00 out of 4.00 Flag question

Calculate the percent slip in an AC motor to the nearest whole percentage 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%

Question 11

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.

Question 12

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

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

Question 13 Correct

Large AC induction motors typically have limitations on the number of starts in an hour to prevent


Select one:

Flag question

a. overheating the rotor b. excessive torque def ection of the r otor bars c. damage to the motor bearings d. overheating the stator windings

The correct answer is: over heating the stator windings

Question 14

What is the purpose o f circuit breakers?


Select one: a. Connects and disconnects relatively high capacity circuits b. Prot ects 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

Question 15

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?

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 to the normal power source. b. When a low voltage condition occurs, the moto r continues to run until voltage is 0 volts. Upon regaining power, the motor automatically restarts. c. When a low voltage condition occurs, the motor continues to run until voltage is 0 volts. Upon regaining power, the motor r emains 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 deenergizing the motor. Upon regaining power, the motor r emains de-energized.

Question 17

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

Correct Mark 8.00 out of 8.00

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 point

Ground voltage

Flag question

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 connection between a circuit and the earth – Ground

Question 18

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


three-phase power source? Select one: a. The load is connected between two phases and the remaining phase is grounded 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 f uses, 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

Question 20

What are protective f eatures 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 overlo ads, and magnetic overloads

Question 21

What type of circuit protection is provided by a f use?


Select one: a. Undervoltage b. Underfreq uency c. Overfrequency d. Overcurrent e. Undercurrent The correct answer is: Overcurrent

Question 22 Correct

Define the following terms by matching the definitions.

Mark 12.00 out of 12.00

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

Flag question

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 – Eff iciency

Question 23

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

Correct Mark 15.00 out of 15.00

Steps down and voltage for operation of devices such as ammeters, voltmeters, and protective relays

Instrument potential

Flag question

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

Low power, variable voltage

Auto

Instrument current

Steps down current for measurement purposes

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 fo 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

Question 24 Correct

Chose statement that best describes the difference between delta and wye connections in a transformer


Select one:

Flag question

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

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 proper term. 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 voltage

Mutual 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 flux from one coil cutting the windings of another coil creating a voltage – Mutual induction Definite tur ns 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 will be u sed Steps down voltage for operation of devices such as ammeters, voltmeters, and protective relays

Instrument 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

Used in power distribution and transmission systems

Isolation

Distribution

The correct answer is: Steps down voltage for operation of devices such as ammeters, voltmeters, and protective re lays – Instrument potential, Steps do wn 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

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HW6 Nuclear Engineering

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