How Does Three Phase Power
Works?
There is nothing magical about
how three phase power works, it is simply three single phases
synchronized and offset by 120 degrees. There are four wires coming
out of the power plant, the three phases plus a ground or neutral
common to all three. The diagram above shows you what three phase
would look like like relative to ground.
Why Three Phase Power Works
Why do we use three
phase instead of single, two or four phase? The main reason is
the even power output. In single phase and two phase power, there
are 120 moments per second when a sine waive is crossing zero volts
. In three phase power, at any given moment one of the three phases
is nearing a peak. With four phases it would not significantly
improve things but would add a fourth wire. High-power three phase
motors that are used in industrial application require that even
power output. We all know what electrical surges and lighting can do
to motors and equipment.
How Three Phase Power Works-
Transmission Substation
The three phase power leaves
the
generators and enter a substation.
These voltages range from 154,000 to 765,000, the high voltage is
for long distance transmission because as it travels it losses some
of it voltages. High voltage transmission lines are quite
obvious, their are normally made of huge steel towers and the
typical distance they travel are around 300 miles.
All power towers have three wires
for the three phase, but some may have extra wires, these are used
as ground wires and are used primarily to attract lightning. For
this power to be used in our homes and businesses it is stepped-down
by using transformers to the distribution grid. The place where the
conversion occurs is in a power substation. The job of the power
substation is to have
transformers that step down
voltages from the thousands of voltages down to typically less than
10,000. It then splits the distribution power off in multiple
directions. These substations usually have breakers and switches so
the substation can be disconnected from the transmission grid or
separate distribution lines can be disconnected from the substation
when necessary. How
Three Phase Power Works - Distribution Bus
The power goes from the
transformers to the distribution bus. The bus distributes power to
two separate sets of distribution lines at two different voltages.
The smaller transformers attached to the bus are stepping the power
down to standard line voltage usually around 7,200 volts. The other
line leaves in the other direction at the higher voltage of the main
transformer. The power leaves this substation in two sets of three
wires, each headed down the road in a different direction.
As mention above, one of the
lines carries higher voltage and will need to be stepped down again,
which will often happen at another substation or in small
transformers somewhere down the line. Some time you will often see a
large green box near the entrance to a subdivision, it is performing
the step-down function so the subdivision can use the power. They
also have regulator banks located along the line, this
regulate the voltage on the line to prevent under voltage and over
voltage conditions. There are usually switches that allow these
regulator bank to be disconnected for maintenance when necessary.
How Three Phase Power Works -
At the House
 Finally
we are down to the wire that brings power to your home or business.
There is a transformer drum attached to a pole or if it is
underground there are green transformer boxes at every house or two.
The transformer job is to reduce the 7,200 down to the normal
household electrical service.
If you are looking for
transformers, phase converters, generators or any other electrical
products contract ACE
Phase Converters. They offer
high quality produces with a highly trained staff to help you in all
your electrical power needs.
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