Electrical Distribution Systems

TN

• 3-Phase, 4-Wire 400Y/230 V
• used in Europe and others

IT

• 3-Phase, 3-Wire 230 V Wye (No neutral)
• used in Norway

Three Phase Three Wire Delta

• used to provide power for three-phase motor loads in industry, and utility power distribution systems
• voltage typical 240, 400, 480, 600 and higher

277/480V Three Phase Four Wire Wye

• used in larger US facilities with voltage 277/480. 277 volt is used as single phase for lighting and 480 volt is used for larger loads like HVAC systems
• in western Canada 347/600V is commonly used

120/240V Three Phase Four Wire Delta

• used in older manufacturing facilities with mostly three-phase motor loads and some 120 volt single-phase lighting and plug loads

120/240V Single Phase Three Wire

• grounded neutral system
• known as the Edison system, split-phase or center-tapped neutral
• common as residential service in North America

120/208V Three Phase Four Wire Wye

• grounded neutral system
• the most common commercial building electric service in North America

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm