Building System Voltages Flashcards
expressed as a nominal voltage
because it varies slightly. __________ can vary from about ______% of the nominal voltage under
normal conditions. Variations from
nominal voltages are caused by a
number of reasons, including
variations in load and changes in
conditions in the power supply system.
Supply voltage, nominal voltage, Supply voltage, 90 to
105%
The principle voltages available in
a building.
SYSTEM VOLTAGE
Carry voltages above 600 V may be used in special cases such as fo large signage
Medium and high voltage systems
carry voltages less than 600 V are
typically used in buildings.
Low voltage systems
is expressed as a nominal voltage because it
varies slightly for the reasons mentioned earlier.
System voltage
is the initial current-carrying
conductor in an AC system.
Is
frequently known as the hot
or live conductor because it
feeds current to the circuit.
UNGROUNDED (HOT)
CONDUCTOR
is required to complete a
single-phase circuit by
connecting the ungrounded
(hot) conductor to ground.
GROUNDED (NEUTRAL)
CONDUCTOR
grounded conductor that
serves more than one circuit.
The neutral conductor
A third conductor that provides
supplementary but important
grounding protection. Not normally
a current-carrying conductor, but is
energized only on a temporary,
emergency basis when there is a
fault between an ungrounded (hot)
conductor and any metal
associated to the electrical
equipment.
GROUNDING (GROUND) CONDUCTOR
The most basic system voltage used. It was
used in the first electrical services to
buildings; however, nearly all have since
been upgraded.
120 Volt, Alternating Current,
Single-Phase, Two-Wire System
(120 V AC, 1-2W)
The ___________
provided to the switch-board or panelboard is
by two conductors: one ungrounded (hot)
conductor carrying 120 V and one neutral
conductor. Volt-age measured between the
ungrounded (hot) and neutral conductors is
______.
service entrance, 120V
The most common residential
electrical service in use today. It is also used
on a limited basis in light commercial
buildings such as small office buildings,
churches, and retail shops and stores
120/240 Volt, Alternating Current,
Single-Phase, Three-Wire System
(120/240 V AC, 1-3W)
a 120 V branch circuit
provides electrical energy to convenience
outlets, small appliances, and light fixtures.
120/240 V system
A _______ branch circuit serves large
appliances and equipment such as electric-
resistance baseboard heaters, water heaters,
and air conditioning equipment.
240 V
___________
branch circuit provides both 120 V and 240 V to
an appliance such as a range and clothes dryer;
controls, and lightfixtures.
120/240 V
_______ run on 120 V and ________
operate on 240 V.
small
motors, heating elements
A ___________ runs
continuously through all branch circuits and
serves as a Safety circuit incase of a shot
circuit.
grounding conductor
An older electrical service found in small
commercial buildings and high-rise buildings
where three-phase motors, above about _________, and equipment such as large air
conditioners are used. It is not used very
often in industry because a ________ is
more economical for largeCmotor loads.
208 Y/120 Volt, Alternating Current,
Three-Phase, Four-Wire System
(208Y/120 V AC, 3-4W), 1/2
horsepower, 480 V system
Is a common electrical service in most modern
medium to large commercial buildings.
480 Y/277 Volt, Alternating
Current, Three-Phase, Four-Wire
System(480Y/277 V AC, 3-4W)
used to power specially
designed heavy machinery.
480 V three-phase power
fluorescent lighting and other single-phase devices have also been developed specifically for use with this system.
high-voltage, 277 V
has economic advantages from the standpoint of equipment and conductor
480 Y/277 Volt, Alternating
Current, Three-Phase, Four-Wire
System(480Y/277 V AC, 3-4W)
ls a less common electrical service in large
commercial and industrial buildings that is
used to power specially designed heavy
machinery.
600Y/346 Volt, Alternating
Current, Three-Phase, Four-Wire
System(600Y/346 V AC, 3-4W)
has additional
economic advantages from the standpoint of
equipment and conductor sizing in
comparison to the 208Y/120 V and 480Y/277
V systems.
600Y/346 Volt, Alternating
Current, Three-Phase, Four-Wire
System(600Y/346 V AC, 3-4W)
ls another fairly common electrical service
found in commercial and industrial buildings where three-phase motors, above about 1/2 horsepower, and equipment such as large air conditioners are used.
240/120 Volt, Alternating Current, Three-Phase, Four-Wire System(240/120 V AC, 3-4W)
Between _________ there is 208 V
available.
Phase Y and ground
is known as the high leg
or wild leg because it has a higher voltage to
ground than the other legs.
Phase Y
The relationship between the building system voltage, current ( Amperage),
and required conductor size for a 20 KVA load and a power factor of 1.0
higher voltage means _________ (and smaller conductor size) for a
__________.
lower amperage, specific load
is the target voltage entering the service
panel.will vary slightly
for different buildings because of
variations of voltage available at the
transformer and voltage drop in the
service conductors.
System Voltage
The standard for the
system voltage is actually _______
120/240 V.
A voltage drop occurs as current flows
from the service equipment through the
branch circuit conductors to the outlet.
Utilization Voltage
On a _________, approximately
115/230 V is available at the outlet of the
Branch Circuit.
120/240 V system
Measured voltage at an
outlet or connection is called the ________
line
voltage
The
highest voltage to which a wiring device can be exposed is known as the _______
Maximum Voltage
