Chapter 17 quiz 181

Solid neutral

A ___ is made of copper bar or brass tubing that has exactly the same physical dimensions as a fuse for a given ampere rating and voltage rating.

copper, aluminum

Fused switches are for use with ___ conductors unless marked to indicate that the terminals are suitable for use with ____ conductors.

14-1AWG, 1/0 AWG +

Fused switches are rated based on 60 degrees C ____, and 75 degrees C ____ unless marked otherwise.

Line-to-load

Reading from the ___ side of a good fuse should show zero voltage or else an extremely small voltage across the fuse.

Resistance

Remove the fuse from the switch and then take a ___ reading across the fuse using an ohmmeter.

RMS

Root mean square

Fuses and circuit breakers

The two most commonly used overcurrent protection devices are ___`

Voltmeter

Using a ___, the first step is to be sure to set the scale to the correct voltage setting.

Voltage rating

____ is the voltage that a circuit can be operated without any damage. It shall be greater than the voltage of the circuit in which the fuse or CB is to be used.

Current limitation

___ is the process of imposing the maximum current limit to the electrical equipment for the purpose of protecting the circuit.

Speed of response

___ is the time required by the fusible element of a fuse to open which varies inversely with a magnitude of the current that flows through the fuse.

240.24(A)

article ____ covers switches containing fuses and circuit breakers be readily accessible and installed so that the center of the grip of the operating handle of the switch or circuit breaker; when in its highest position, is not more than 6'7" above the floor.

I(2)t

Total clearing energy (ampere-square seconds)

open (blown)

An ____ fuse will generally show a high resistance reading or an open circuit indication.

Class J

Are considered to be dual-element time delay fuses, and are physically smaller than Class H fuses., Has a minimum interrupting rating of 200,000 rms symmetrical amperes.

240.24(B)

Article ___ covers accessibility for every occupant to the overcurrent devices protecting the conductors supplying the occupancy.

properly

If one is to ____ match the short-circuit current rating of electrical equipment with the let-through current values of the overcurrent protective devices (fuses, or circuit breakers)

Ip

Peak let-through current

Corner ground

The connection of one phase conductor to ground in a delta-connection, 3-phase system is sometimes called a ____.

Time current characteristic curves, peak let-through charts

The electrician must be able to use the following types of fuse data:

Molded case, Power, Insulated-case

There are three types of Circuit breakers:

OSHA

___ act clearly states that electrical equipment must not be worked on when its energized.

UL, NEMA

___ and ____ establish standards for rating, types, classes, and testing procedures for fuses and circuit breakers.

Class CC

___ are primarily used for control-circuit protection, for the protection of motor control circuits, ballasts, small transformers, and so on.

Cable limiters

___ are short circuit devices that can isolate a faulted cable rather than having the fault open the entire phase. They are available for cable-to-cable or cable-to-bus installation for either aluminum or copper conductors.

Fast-acting current limiting fuses (non time delay)

___ have extremely fast response in low overload and short circuit ranges, have the lowest energy let-through values, and provides better protection to mains, feeders, CB's, bus duct, switchboards, etc.

Cube fuse

___ is physically smaller than ordinary fuses and is available in both fast-acting and dual-element time delay types. It has a 10 second opening time at 500% of its ampere rating.

Short circuit current-rating

___ is the ability to withstand fault current to or less than the short circuit rating for the length of time it takes the specified overcurrent device to open the circuit to the equipment.

Interrupting rating

___ is the highest current at rated voltage that a device is intended to interrupt under standard test conditions.

Peak let-through

___ is the maximum current that flows in protective devices during an overcurrent condition.

ampere rating, voltage rating, interrupting rating when greater than 10,000 amperes, current-limiting type, and trade name or name of manufacturer.

Article 240, part VI states that all fuses must be marked to show:

430.52

Article ___ covers maximum size permitted for duel element fuses is based on a maximum of 175% of FLC of the motor.

240 part V

Article ____ spells out the requirements for plug fuses.

J, L, T, G

Class __ are current limiting fuses with a minimum interrupting rating of 200,000 rms symmetrical amperes.

5, 10

Dual-element time delay fuses, current limiting fuses can handle current ___ times their ampere rating for at least ___ seconds.

250v and 600v

Fused switches are available in ____ and ___.

time-current

Make sure to check ___ curves of fuses and circuit breakers to make sure that they will handle the momentary motor starting inrush currents without nuisance opening or tripping.

Class H

Most low-cost, common, standard, nonrenewable, one-time fuses are ___ fuses.

Live circuits

On ___ extreme caution must be exercised when checking fuses.

Dual-element time delay fuse

___ provides a time delay in low-overload range to eliminate unnecessary opening of the circuit because of harmless overloads. This fuse is extremely responsive in opening on short circuits.

Class K

____ are grouped into three categories, _1, _5, _9, and have varying degrees of current-limiting ability, depending on the _ rating.

Plug fuses

____ have three types: 1. Standard fuse link type 2. loaded link type 3. dual-element time-delay type

Class R

____ is a nonrenewable cartridge type and has a minimum interrupting rating of 200,000 rms symmetrical amperes.

Over current device

____ is required to be installed in series with ungrounded conductors for overcurrent protection.

Continuous current rating

____ is the amount of current that the device can carry continuously without interrupting the circuit.

Energy-efficient, high starting currents

____ motors have higher starting current characteristics than older style motors. (Design B motors). Their ____ can cause nuisance opening of fuses and nuisance tripping of circuit breakers.