Question 1

Most motor circuits are protected by dual-element time-delay fuses or _________.

Accepted Answer

A)   dual-time circuit breakers
B)   instantaneous trip circuit breakers
C)   nontime delay fuses
D)   inverse-time circuit breakersE) A) and D)
F) All of the above

Question 2

Which NEC table lists the running currents for single-phase ac motors?

Accepted Answer

A)   430.247
B)   430.248
C)   430.249
D)   430.250E) C) and D)
F) B) and D)

Question 3

The starting current of a squirrel-cage motor can be determined by multiplying the kVA rating by the_________ rating and then dividing by the applied voltage.

Accepted Answer

A)   nameplate
B)   horsepower
C)   locked-rotor
D)   resistanceE) B) and C)
F) A) and B) B

Question 4

A 25-horsepower, three-phase induction motor has a nameplate rating of 32 amperes. The nameplate also shows a temperature rise of 30 degrees C. What is the overload size for this motor in amperes?

Accepted Answer

A)   20
B)   30
C)   40
D)   50E) B) and C)
F) A) and C)

Question 5

Most common squirrel-cage motors used in industry fall into the design _________classification.

Accepted Answer

A)   A
B)   B
C)   C
D)   DE) A) and B)
F) B) and D)

Question 6

How does temperature rating impact conductor size selection?

Accepted Answer

Another factor that must be taken into consideration when determining the conductor size is the temperature rating of the devices and terminals. The conductor will be selected and coordinated so as to not exceed the lowest temperature rating of any connected termination, any connected conductor, or any connected device. This means that regardless of the temperature rating of the conductor, the allowable ampacity must be selected from a column that does not exceed the temperature rating of the terminations. The conductors listed in the first column of NEC Table
310.16 have a temperature rating of 60 degrees C (140 degrees F), the conductors in the second column have a rating of 75 degrees C (167 degrees F), and the conductors in the third column have a rating of 90 degrees C (194 degrees F). The temperature ratings of devices such as circuit breakers, fuses, and terminals are found in UL product directories. The temperature rating may be found on the piece of equipment. As a general rule, the temperature rating of devices will not exceed 75 degrees C (167 degrees F).

Question 7

What is the relationship between the rotor bars of a squirrel-cage motor and the starting current?

Accepted Answer

If the nameplate lists code letters that...

Question 8

A 100-horsepower, three-phase squirrel-cage induction motor is connected to a 240-volt line. A dual-element time- delay fuse is to be used as the short-circuit protective device. What is the correct fuse rating?

Accepted Answer

A)   300
B)   350
C)   400
D)   450E) B) and C)
F) B) and D)

Question 9

If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.

Accepted Answer

A)   decreased by 90%
B)   decreased by 10%
C)   increased by 10%
D)   increased by 90%E) C) and D)
F) A) and D)

Question 10

A 150-horsepower, three-phase squirrel-cage induction motor is connected to 440 volts. The motor nameplate lists the following information:
Amps 175
SF 1.25
NEMA code B
The conductors are to be copper with type THHN insulation. The short-circuit protective device is to be an inverse- time circuit breaker. The termination temperature rating is not known.
Determine the conductor size and overload size.

Accepted Answer

The conductor size is determined from th...

Question 11

What should be done if a dual-element time-delay fuse will not let the motor start?

Accepted Answer

If for some reason this fuse will not pe...

Question 12

The temperature ratings of devices such as circuit breakers, fuses, and terminals are found _________.

Accepted Answer

A)   on the nameplate
B)   in the NEC tables
C)   in UL product directories
D)   through individual testingE) A) and D)
F) All of the above

Question 13

Two-phase motors that are especially designed for_________ applications use the same rules for determining full-load currents as single-phase motors.

Accepted Answer

A)   high speed-high torque
B)   low speed-high torque
C)   high speed-low torque
D)   low speed-low torqueE) C) and D)
F) B) and D) B

Question 14

What is included in the NEC motor tables, and how is this information used?

Accepted Answer

The tables list the amount of current th...

Question 15

What percentage of the full-load current of a thermally protected continuous-duty motor of more than one hp can the trip current be, if the full-load current is 15 amperes?

Accepted Answer

A)   122
B)   140
C)   156
D)   170E) A) and B)
F) A) and C)

Question 16

A one-horsepower motor will have a full-load current of_________ amperes when connected to 90 volts dc.

Accepted Answer

A)   6.8
B)   9.5
C)   9.6
D)   12.2E) B) and C)
F) C) and D)

Question 17

The motor overload size is to be determined by using the current listed _________.

Accepted Answer

A)   on the nameplate
B)   in the NEC tables
C)   in the UL tables
D)   on the statorE) C) and D)
F) B) and D)

Question 18

The voltages of a two-phase system are_________ degrees out of phase with each other.

Accepted Answer

A)   90
B)   120
C)   150
D)   180E) A) and D)
F) None of the above

Question 19

When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by_________ .

Accepted Answer

A)   the square root of two
B)   two
C)   the square root of three
D)   threeE) None of the above
F) A) and B)

Question 20

_________motors are often made to have a leading power factor by overexcitation of the rotor current.

Accepted Answer

A)   Unity
B)   Squirrel-cage
C)   Wound-rotor
D)   SynchronousE) All of the above
F) A) and C)

Exam 10: Motor Installation

Most motor circuits are protected by dual-element time-delay fuses or _________.

Correct Answer
verified

Which NEC table lists the running currents for single-phase ac motors?

Correct Answer
verified

The starting current of a squirrel-cage motor can be determined by multiplying the kVA rating by the_________ rating and then dividing by the applied voltage.

Correct Answer
verified
B

A 25-horsepower, three-phase induction motor has a nameplate rating of 32 amperes. The nameplate also shows a temperature rise of 30 degrees C. What is the overload size for this motor in amperes?

Correct Answer
verified

Most common squirrel-cage motors used in industry fall into the design _________classification.

Correct Answer
verified

How does temperature rating impact conductor size selection?

What is the relationship between the rotor bars of a squirrel-cage motor and the starting current?

Correct Answer
verified
If the nameplate lists code letters that...
View Answer

A 100-horsepower, three-phase squirrel-cage induction motor is connected to a 240-volt line. A dual-element time- delay fuse is to be used as the short-circuit protective device. What is the correct fuse rating?

Correct Answer
verified

If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.

Correct Answer
verified

Correct Answer
verified
The conductor size is determined from th...
View Answer

What should be done if a dual-element time-delay fuse will not let the motor start?

Correct Answer
verified
If for some reason this fuse will not pe...
View Answer

The temperature ratings of devices such as circuit breakers, fuses, and terminals are found _________.

Correct Answer
verified

Two-phase motors that are especially designed for_________ applications use the same rules for determining full-load currents as single-phase motors.

Correct Answer
verified
B

What is included in the NEC motor tables, and how is this information used?

Correct Answer
verified
The tables list the amount of current th...
View Answer

What percentage of the full-load current of a thermally protected continuous-duty motor of more than one hp can the trip current be, if the full-load current is 15 amperes?

Correct Answer
verified

A one-horsepower motor will have a full-load current of_________ amperes when connected to 90 volts dc.

Correct Answer
verified

The motor overload size is to be determined by using the current listed _________.

Correct Answer
verified

The voltages of a two-phase system are_________ degrees out of phase with each other.

Correct Answer
verified

When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by_________ .

Correct Answer
verified

_________motors are often made to have a leading power factor by overexcitation of the rotor current.

Correct Answer
verified

Exam 10: Motor Installation

Most motor circuits are protected by dual-element time-delay fuses or _________.

Correct AnswerverifiedShow Answer

Which NEC table lists the running currents for single-phase ac motors?

Correct AnswerverifiedShow Answer

The starting current of a squirrel-cage motor can be determined by multiplying the kVA rating by the_________ rating and then dividing by the applied voltage.

Correct AnswerverifiedB

A 25-horsepower, three-phase induction motor has a nameplate rating of 32 amperes. The nameplate also shows a temperature rise of 30 degrees C. What is the overload size for this motor in amperes?

Correct AnswerverifiedShow Answer

Most common squirrel-cage motors used in industry fall into the design _________classification.

Correct AnswerverifiedShow Answer

How does temperature rating impact conductor size selection?

What is the relationship between the rotor bars of a squirrel-cage motor and the starting current?

Correct AnswerverifiedIf the nameplate lists code letters that...View AnswerShow Answer

A 100-horsepower, three-phase squirrel-cage induction motor is connected to a 240-volt line. A dual-element time- delay fuse is to be used as the short-circuit protective device. What is the correct fuse rating?

Correct AnswerverifiedShow Answer

If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedThe conductor size is determined from th...View AnswerShow Answer

What should be done if a dual-element time-delay fuse will not let the motor start?

Correct AnswerverifiedIf for some reason this fuse will not pe...View AnswerShow Answer

The temperature ratings of devices such as circuit breakers, fuses, and terminals are found _________.

Correct AnswerverifiedShow Answer

Two-phase motors that are especially designed for_________ applications use the same rules for determining full-load currents as single-phase motors.

Correct AnswerverifiedB

What is included in the NEC motor tables, and how is this information used?

Correct AnswerverifiedThe tables list the amount of current th...View AnswerShow Answer

What percentage of the full-load current of a thermally protected continuous-duty motor of more than one hp can the trip current be, if the full-load current is 15 amperes?

Correct AnswerverifiedShow Answer

A one-horsepower motor will have a full-load current of_________ amperes when connected to 90 volts dc.

Correct AnswerverifiedShow Answer

The motor overload size is to be determined by using the current listed _________.

Correct AnswerverifiedShow Answer

The voltages of a two-phase system are_________ degrees out of phase with each other.

Correct AnswerverifiedShow Answer

When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by_________ .

Correct AnswerverifiedShow Answer

_________motors are often made to have a leading power factor by overexcitation of the rotor current.

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
B

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
If the nameplate lists code letters that...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
The conductor size is determined from th...
View Answer

Correct Answer
verified
If for some reason this fuse will not pe...
View Answer

Correct Answer
verified

Correct Answer
verified
B

Correct Answer
verified
The tables list the amount of current th...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified