Deck 17: Overcurrent Protection: Fuses and Circuit Breakers

Question 1

____ and the National Electrical Manufacturers Association establish standards for the ratings, types, classifications, and testing procedures for fuses and circuit breakers.

A)Applied Research Laboratories, Inc.
B)Entela, Inc.
C)The Underwriters Laboratories, Inc.
D)TUV Rheinland of North America, Inc.

Answer 1

C

Question 2

What are some prohibitions on the location of overcurrent devices?

Answer 2

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Overcurrent devices are not permitted to:
.be exposed to physical damage
.be installed in the vicinity of easily ignitable material
.be installed in clothes closets
.be installed in bathrooms. This requirement is for dwelling units and guest rooms of hotels and motels, not for commercial and industrial buildings.
.be installed over the steps of a stairway

Question 3

For motor branch circuits, the maximum setting of a conventional inverse-time circuit breaker must not exceed ____ percent of the full-load current of the motor.

A)100
B)125
C)200
D)250

Answer 3

D

Question 4

____ circuit breakers are the most common type in use today.

A)Power
B)Molded-case
C)Air-frame
D)Insulated-case

Question 5

When compared to other types of fuses, the ____ fuse has the lowest energy let-through values.

A)dual-element, time-delay
B)straight current-limiting
C)dual-element, nontime-delay
D)low-overload

Question 6

​What are some factors that influence speed of response of an overcurrent device?

Question 7

An interrupting rating is a(n)____ rating, and measures the fuse's or circuit breaker's ability to safely open an electrical circuit under fault conditions, such as an overload, short circuit, or ground fault.

A)recommended
B)maximum
C)minimum
D)average

Question 8

____ is the ability of the equipment (the entire assembly)to withstand a fault current equal to or less than the rating for the length of time it takes the specified overcurrent device to open the circuit to the equipment.

A)Short-circuit rating
B)Interrupting minimum
C)Interrupting capacity
D)Open-circuit rating

Question 9

How do thermal-magnetic circuit breakers work?

Question 10

What is the purpose of peak let-through charts?

Question 11

When you remove a fuse from a switch, and then take a resistance reading across the fuse using a(n)____, a good fuse will show zero or a very minimal resistance.

A)ohmmeter
B)wattmeter
C)voltmeter
D)delimiter

Question 12

Low-voltage power circuit breakers are listed under UL Standard ____.

A)844
B)1066
C)1215
D)1362

Question 13

In the case of a delta, 3-phase, corner-grounded "B" phase system, a device called a ____ can be installed in the "B" phase.

A)service entrance
B)switchboard
C)cube fuse
D)solid neutral

Question 14

Class ____ fuses formerly were called NEC or Code fuses.

A)H
B)J
C)K
D)R

Question 15

Name and describe the class of fuses used for control circuit protection.

Question 16

The Class ____ fuse is a nonrenewable cartridge type and has a minimum interrupting rating of 200,000 RMS symmetrical amperes.

A)H
B)K
C)R
D)T

Question 17

A dual-element, time-delay fuse has one or more fusible elements (links)connected ____.

A)in parallel
B)in series
C)during overload conditions
D)every 10 seconds

Question 18

Series-rated equipment is also referred to as ____.

A)series-connected
B)parallel-rated
C)inverse-parallel
D)series-broken

Question 19

Fused switches are available in ratings of up to ____ amperes in both 250 and 600 volts.

A)400
B)600
C)4000
D)6000

Question 20

Conventional plug fuses have a base referred to as a(n)____ base. This base is of the same shape as the base on a light bulb.

A)Edison
B)Tesla
C)filamentous
D)Shrader