Supply Voltage Study Guide
L2 of a 230 Volt/ 30 voltage source is referred to as the
"wild leg" or the "stinger".
10 Supply Voltages
110 V or 11SV or 120 V 208V 220V or 230V or 240V 277V 440V or 460V or 480V
Devices that use a single phase supply voltage will use one of the hot lines and neutral for
120 V equipment
With a 230 V / 30 supply voltage the voltage measured from L1 to ground or L3 to ground is
120 Volts
Voltage measured between either hot line and ground (Ll to Ground or L2 to Ground) is
120 Volts.
Voltage measured between either hot line and neutral (Ll to Neutral or L2 to Neutral) is
120 Volts.
With a 208 V / 30 supply voltage the voltage measured between any two of the three hot lines is 208 Volts. The voltage measured from any of the three hot lines to ground is
120 Volts.
The most common three phase voltage supplies are
208 Volt/ 30, 230 Volt/ 30, and 480 Volt/ 30.
With a 230 V / 30 supply voltage the voltage measured from L2 to ground is
208 Volts.
30 (three phase) Supply Voltages
208V 230V 440V or 460V or 480V
Devices that use a single phase supply voltage will use the two hot lines for
230 V equipment.
With a 230 V / 30 supply voltage the voltage measured between any two of the three hot lines is
230 Volts.
Voltage measured between the two hot lines (Ll and L2) in a three phase
230/30 Volts
The voltage measured from any one of the three hot lines (three phase) to ground is
277 Volts.
The symbols 0 or <I> may be used in place of the word
3 PHASE
Three Phase Example 230/3<1>
3<1>
With a 480 Volt/ 30 supply voltage the voltage measured between any two of the three hot lines is
480 Volts.
Three phase (30) voltage supplies are found in
Commercial and Industrial applications.
The ground line is designated as
G (the ground symbol). The ground line is for safety.
The three hot lines in a three phase are designated as
L1, L2 and L3.
The two hot lines are designated as
Ll (Line l) and L2 (Line 2).
The neutral line is designated as
N.
30 =
Three phase Example 230/30 the /30
The ground line provides
an alternative, low resistance path to ground in case of a short to ground.
Neutral and ground are
at the same potential.
A short to ground is called a
ground fault
The most common Supply Voltage for Residential areas
is 230 Volt single phase.
The 0 symbol
is more commonly used to inidicate 3 phase
Single phase equipment will use one or two hot lines depending on which voltage (120V or 230 V)
the equipment uses.
If voltage of more than zero is measured between neutral and ground
there is a problem in the voltage supply.
The 230 Volt single phase supply voltage has
two hot lines and one neutral line and usually includes a ground wire to provide electrical safety.
Voltage measured between neutral and ground should be
zero volts.
