Deck 7: Motor and Appliance Circuits

Question 1

What is the minimum starting current for a 240-volt, 3-phase, Code letter J, 7-1/2-horsepower motor?

A)114 amperes
B)128 amperes
C)132 amperes
D)144 amperes

Answer 1

B

Question 2

An appliance is rated at 4500 volt-ampere, 240 volts.What is the maximum size fuse permitted?

A)20-ampere
B)30-ampere
C)40-ampere
D)50-ampere

Answer 2

B

Question 3

What are the rules that govern air-conditioning and refrigerating equipment disconnect means?

Answer 3

Be careful about locating the disconnecting means for air-conditioning and refrigeration equipment!
It is required that the disconnecting means be:
∙ located within sight from the air-conditioning or refrigerating equipment.
∙ readily accessible.
∙ permitted to be installed on or within the air-conditioning or refrigerating equipment.
∙ located to allow access to panels that need to be accessed for servicing the equipment.
∙ mounted so as not to obscure the equipment nameplate(s).
∙ provided with a lock-off provision that remains in place with or without the lock installed.
Snap-on covers for circuit breakers do not meet this requirement.

Question 4

When referring to motor controllers in the United States , we prefer to use the term instead of coordination because coordination has a different meaning.

A)protection
B)isolation
C)breaking
D)service

Question 5

For most applications, the motor circuit switch for a motor must be .

A)general-use
B)isolating
C)overcurrent
D)horsepower rated

Question 6

A motor may be loaded continuously up to the horsepower obtained by multiplying the rated horsepower by the ____.

A)switch rating
B)ambient temperature
C)service factor
D)insulation rating

Question 7

The reason the Code uses the term instead of motor is that, in many instances, the motor is inside an enclosure and is out of sight until an access panel is removed.

A)motor location
B)lock-out
C)start-stop
D)motor vicinity

Question 8

What is the relationship between the Code letter and starting current?

Question 9

means the difference between motor winding temperature and the ambient temperature.

A)Operating temperature
B)Service factor
C)Overcurrent
D)Temperature rise

Question 10

Describe Type 2 short-circuit protection.

Question 11

NEMA rated motors are designed to operate at plus/minus percent of their nameplate rated voltage.

A)10
B)20
C)30
D)40

Question 12

fuses are designed to withstand motor-starting inrush currents and will not open needlessly.

A)Ordinary
B)Branch-circuit
C)Dual-element, time-delay
D)Nontime-delay

Question 13

is the most common cause of motor failure.

A)An open contact
B)Unbalanced voltage
C)Single phasing
D)Wrong service factor

Question 14

Color selection for ungrounded "hot" conductors can be just about any solid color except green, white, gray, or any color conductor (except ) that has three continuous white stripes.

A)black
B)blue
C)red
D)green

Question 15

For every degree Celsius rise above the motor's rated temperature, the motor's insulation life is cut in half.

A)5
B)10
C)32
D)50

Question 16

Motors marked with Insulation Class B are suitable for use in ambient temperatures of up to degrees Celsius.

A)105
B)130
C)155
D)180

Question 17

What are some reasons behind the failure of motors?

Question 18

NEC 430.24 requires that the conductors supplying several motors, or a motor(s) and other load(s), shall have an ampacity not less than percent of the full-load current rating of the highest rated motor.

A)75
B)100
C)125
D)150

Question 19

In three-phase motors, each phase is degrees out of phase (symmetrical) with the other phases.

A)60
B)90
C)120
D)360

Question 20

What are some possible causes of unbalanced voltage?