Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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Which of the following is a category of three-phase AC motors?
a. | Induction motor | d. | Both A and B | b. | Synchronous motor | e. | None of these | c. | Compound
motor |
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2.
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About ______ of the AC motors used in industry are induction motors.
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3.
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The squirrel-cage motor gets its name from the design of its __________.
a. | rotor | c. | stator | b. | frame | d. | shaft |
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4.
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The three phases that are fed to the stator windings of a three-phase motor are
____ degrees apart.
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5.
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The average range of slip for a squirrel-cage induction motor is _____.
a. | 5 - 10 % | c. | 2 - 6% | b. | 8 - 12 % | d. | 15 - 18 % |
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6.
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Which of the following is an advantage of a three-phase induction motor?
a. | High efficiency | d. | All of these | b. | High power factor | e. | None of these | c. | Excellent speed
regulation |
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7.
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Which of the following is an application of a three-phase motor?
a. | Large conveyor systems | d. | All of these | b. | Machine tools | e. | None of these | c. | Conveyors |
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8.
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Which of the following is a three-phase electrical distribution
configuration?
a. | Wye | d. | All of these | b. | Compound | e. | None of these | c. | Beta |
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9.
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The most common configuration used at a substation is _____________.
a. | the delta configuration | c. | both wye and
delta | b. | the wye configuration | d. | neither wye or delta |
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10.
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Which of the following is not a voltage available from a wye system?
a. | 208 VAC | c. | 240 VAC | b. | 480 VAC | d. | 600 VAC |
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11.
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The _________ configuration is most often used in applications where most of the
loads require three-phase power and single-phase power is only needed for lighting and office
equipment.
a. | wye | c. | beta | b. | delta | d. | reverse |
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12.
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Which of the following is not a voltage available from a delta system?
a. | 208 VAC | c. | 240 VAC | b. | 480 VAC | d. | 600 VAC |
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13.
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On a 4-wire wye system, the __________ conductor provides a common return path
to the source for each phase.
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14.
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Which of the following is a wiring configuration for a three-phase induction
motor?
a. | Wye | d. | Both A and C | b. | Split-phase | e. | None of these | c. | Delta |
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15.
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If the winding halves on a wye dual-voltage three-phase motor are connected in
series, the motor is connected for ____________ operation.
a. | low voltage | c. | reduced voltage start | b. | reverse | d. | high voltage |
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16.
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Connecting the winding halves of a delta motor in parallel connects the motor
for __________ operation.
a. | low voltage | c. | reduced voltage starting | b. | reverse | d. | high voltage |
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17.
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The accepted industry standard for reversing a three-phase motor is to switch
lines _____________.
a. | L2 and L3 | d. | All of these | b. | L1 and L3 | e. | None of these | c. | L1 and
L2 |
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Matching
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SEGMENT 1
a. | squirrel-cage | f. | induction | b. | 10 | g. | are | c. | high | h. | are
not | d. | identical | i. | low | e. | 6 |
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18.
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The two most common categories of three-phase motors are synchoronous and
___________.
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19.
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About 95% of the motors used in industry are _________ motors.
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20.
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Two common types of induction motors are __________ and wound rotor.
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21.
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The windings on a three-phase motor are __________ (identical/different).
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22.
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The average range of slip for squirrel-cage induction motors is 2% to ____%.
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23.
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Three-phase induction motors ________ (are/are not) the most efficient type of
electric motors available next to synchronous motors.
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24.
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A three-phase motor usually has a service life of ______ years or better.
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25.
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A three-phase induction motor has a _________ (high/low) power factor.
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SEGMENT 2
a. | the same | e. | 120 | b. | the square-root of three | f. | speed regulation | c. | 1.73 | g. | machine tools | d. | different |
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26.
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Large conveyor systems rely on the good ___________ of the three-phase
induction motor to provide constant speed even if the load changes.
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27.
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Most ______________ use three-phase induction motors because of their
efficiency and easy speed control through gear of belt drive systems.
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28.
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The input current on each line to a three-phase motor should be ________ (the
same/different).
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29.
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Each phase in a 3-phase circuit is _______ electrical degrees apart.
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30.
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The square root of 3 is ____________.
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31.
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For a 3-phase circuit, the product of the line voltage and current must be
multiplied by ___________.
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SEGMENT 3
a. | low voltage | d. | delta | b. | current | e. | high | c. | wye | f. | dual
voltage |
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32.
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The ________ three-phase distribution system is the safest of the two systems.
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33.
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Two wiring configurations for a three-phase motor are the ___________ and delta
configurations.
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34.
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Some times, the three phases in a three-phase motor are divided in half to
allow ___________ operations.
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35.
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If the phase halves are connected in series on a three-phase motor, the motor
is configured for ___________ (high/low) voltage operation.
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36.
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Anytime a motor can be operated on different voltages, it is better to select
the high voltage configuration because the motor will draw less _________.
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37.
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In a ____________ configured three-phase motor, the phase windings are
connected end-to-end to form a closed loop.
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38.
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If the winding halves of a dual-voltage delta motor are connected in parallel,
the motor is wired for _________ operations.
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SEGMENT 4
a. | pushbuttons | d. | safety measures | b. | two | e. | magnetic contact | c. | L3 |
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39.
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By switching ____________ of the supply line to a three-phase motor you can
reverse the direction of rotation.
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40.
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The industry standard method for reversing a three-phase motor is to switch
lines L1 and ______.
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41.
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In many cases, the switching of lines to reverse a three-phase motor is
accomplished through two sets of _________.
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42.
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The two sets of contacts used to reverse a three-phase motor are often
controlled using __________, one for forward and one for reverse.
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43.
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Devices used to switch the lines to a three-phase motor often include built-in
safety _________ to prevent phase-to-phase shorts.
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