3 Phase Contents |
|
 |
|
 |
|
| |
Welcome To The 3 Phase Power Resource Site
|
|
| |
3
Phase Electrical Power
The 3 Phase Power Resource Site is a
not-for-profit organization which helps individuals
and businesses answer
questions and give resources about where, how and why "3
phase" power is used. For information on 3
phase wiring, mathematics
and power calculation, principles of three phase
power solutions see the links to the left and 3 phase
power notes and articles below.
3
phase power
is a common form of electrical power and a popular method of
electric power
transmission. This is due to its inherent
benefits for high power transmission and its smooth
wave form quality which allow 3
phase electrical equipment to run smoothly and
last longer. There are many other benefits to 3
phase power. Three
phase has properties that make it very desirable in power
distribution. First, all three wires can carry the same
current. Secondly, power transfer is constant into a linear
and balanced load. Most
domestic utility supplied power is single phase only.
In most cases three phase
power either is not available from a utility company
to domestic houses, rural business and farms, at all, or
in rare cases where it is, it is split out at the main
distribution board. See 3
phase power generating phase converters for
solutions to getting 3 phase power where utility
companies do not offer it or where it is cost
prohibitive. In these situations 1 phase
power can be converted to 3 phase power with a phase
converter from a company such as
ACE Phase
Converter or TEMCo
Phase
Converter. The 3 phase power generated
from some of today's high quality Rotary
Phase Converters is better balanced with closer
voltage tolerances and a smoother wave form than
utility supplied power. For this reason the 3
phase power output from these 3 phase generating
converters is preferred for sensitive equipment than
what is available from utility supplied 3 phase power.
|
3 Phase
Power Wave Form
Pictured
to the left is one
voltage cycle of a 3 phase system. It is labeled 0 to
360° ( 2 π radians) along the time axis. The
plotted lines show the variation of instantaneous
voltage (or current) over time. This power wave cycle
will repeat usually 50
(50Hz), 60 (60Hz), or 400 (400Hz) times per second, depending on
the power system frequency
(Hz). The colors of the lines are in the American
Color Code for 3-phase wiring. It is black=VL1 red=VL2 blue=VL3 |
 |
Three
phase systems may or may not have a neutral wire. The neutral wire allows
3 phase systems to use a
higher voltage while still supporting lower voltage 1 phase appliances. In
high voltage
3 phase distribution
situations it is common not to have a neutral wire as
the loads can simply be connected between phases
(phase-phase connection).
3 Phase
Power Wiring Color Coding
The
3 phases are typically indicated visually in
electrical diagrams by colors. The standards for
these colors vary by country. See the 3
phase wiring color code table for details.
Conductors
of a 3 phase system are usually marked by color code, to allow for balanced loading and to
assure the correct phase rotation for 3
phase induction motors. Colors used vary widely
and may adhere to old standards or to
no standard at all, and sometimes vary even within an
installation. However, the current National Electrical
Code (2005) does not require color identification
of conductors other than that of the neutral (white or
white with a color stripe), the ground (green or green
with a yellow stripe), or in the case of a High Leg
Delta system, the High Leg must be identified with orange.
Click here to read more on 3 Phase Wiring and Color
Coding.
3 Phase
Power Generation
There
are several types
of 3 phase power generators. These can vary
from a utility power station, to a prime source power
generator to portable
diesel (and other fuels) generators, to 3
phase generators which run on 1 phase power (some
models of phase converters). The most common
fuel type
are generally
diesel
generators. At
a utility
power station, an electrical generator converts
mechanical power into a set of alternating electric
currents (AC), one from each electromagnetic coil or
winding of the
power generator. The currents are sinusoidal
functions of time, all at the same frequency but with
different phases. In a three phase power system the phases
are spaced equally, giving a phase separation of
120°. The frequency is typically 50 Hz in Europe and
60 Hz in the US (see List of countries with mains
power plugs, voltages and frequencies). See Frequency
Converters for changing 50 Hz to 60 Hz or the reverse
of 60 Hz to 50 Hz frequency. (See also
Motor-Generator
Frequency Converters) Read more about
3
phase power generators and power generation here.
3 Phase
Power Distribution and Transmission
After
numerous further conversions in the transmission and
distribution network the 3 phase power is finally transformed
with a
power transformer to the standard mains voltage (the voltage of
"house" or "household" current in
American English). This is done with step down
3 phase transformers. The power may already have been
split into single phase at this point or it may still
be three phase power. Where the step-down is 3
phase, the
output of this transformer is usually star connected
with the standard mains voltage (120V
in North America and 230V in Europe) being the
phase-neutral voltage. Another system commonly seen in
the USA is to have a delta connected secondary on the step
down transformer with a center tap on one of the windings supplying the ground
and neutral. This allows for 240V 3 phase as well
as three different single phase voltages (120V
between two of the phases and the neutral, 208V
between the third phase (sometimes known as a wild leg) and
neutral and 240V between any two phases) to be made
available from the same supply.
Click here to read more about 3
phase distribution.
3 Phase
Power Calculation
There
are several mathematical
3 phase power calculations that you can use to
calculate your 3
phase power distribution to make sure that your
wiring distributes your load evenly maintaining a
balanced system. These calculations are useful
for many purposes including when you have single phase
equipment and 3 phase equipment running on the same
power lines.
Read more about 3
phase power calculation here.
3 Phase
Loads
The
most common class of 3 phase
load is the 3
phase electric motor. A 3 phase induction motor has a
simple design, inherently high starting torque, and
high efficiency. Such motors are applied in industry
for 3
phase pumps, fans, blowers, compressors, conveyor
drives, and many other types of motor-driven
equipment. A 3 phase motor is more compact
and less costly than a 1-phase motor of the same
voltage class and rating; also 1-phase AC motors
above 10 HP (7.5 kW) are not as efficient and thus not
usually manufactured. Many times a 3 phase
motor may be started with a
soft start drive can be used to start a motor and
without as much of an inrush current, or a
variable frequency drive which can vary the speed
of the motor. Large
air conditioning equipment (for example, most York
air conditioning units above 2.5 tons (8.8 kW) cooling capacity) use
3 phase motors for reasons of economy and efficiency.
There are many other common 3 phase loads such as
3 phase welders, 3 phase battery chargers, 3 phase
lasers, and 3 phase computer controlled equipment,
etc. When the load includes sensitive
electronics such as 3 phase computer equipment often
it is isolated from the power source to protect it
with
isolation transformers. Read more about 3
phase power loads here.
3 Phase
Loads from 3 Phase Power Generated on 1 Phase
Power
There
are many places and instances where 1 phase power is
all that is available, or where the power company
wants to charge tens, or even hundreds of thousands of
dollars to install and supply 3 phase power.
When this is the case a quality 3
phase generating phase converter can be run on 1
phase to power 3 phase equipment of any type.
Click here to read more about powering
3 phase loads with 3 phase power generated from 1
phase power.
3 Phase
Converters
Often
the advantages of 3 phase
motors, and other 3 phase
equipment, make it
worthwhile to convert single-phase power to 3 phase. Small
and large customers, such as residential, rural
businesses, or farm
properties may not have access to a 3 phase supply, or may not want to pay for the extra cost of a
3 phase service, but may still wish to use 3 phase equipment.
A 3 phase generating Rotary Phase Converter can
benefit these situations or where high quality 3 phase
power is required. Some of the Rotary Phase
Converters manufactured today produce 3 phase power
output that is better quality and will allow 3 phase
equipment to run better and last longer than the 3
phase power from provided by a utility
company. Such
3
phase converters may also allow
the frequency (see also frequency
converters) to be varied allowing for different
equipment frequency requirements (50Hz, 60Hz, 400Hz,
etc.) and also for motor speed control (VFDs).
Some locomotives are driven by 3-phase motors with 3
phase converters converted from the incoming supply of
either DC or 1 phase AC.
The
two main types of 1 phase to 3 phase converters are
Rotary Phase Converters and Static Phase
Converters.
One very important resource is
the rating system that the U.S.
Phase Converter Standards Organization offers of
various phase
converter types and technologies. Click here to read more about 3
phase converters. Read what this very important
industry organization has to say about the different
technologies. As a non-profit organization run
by 3 phase converter specialized electricians the have
excellent insight into this technology. Their wisdom
gives a great run down on how Rotary
Phase Converters produce some of the most balanced
3 phase power output of all the solutions
available. On their site you can read about why Static
Phase Converters can be harmful to the equipment
it is intended to run due to the fact that they don't
actually put out a 3rd phase. Today many people
and individuals sell " Build
Your Own Phase Converter Plans ", but these
tend to be just a potentially damaging static phase
converter and an electric motor giving a time
consuming inferior solution. Other companies use
circuit board controlled 3 phase systems that they
call Digital
Phase Converters. For milling machines and
other 3 phase computer controlled machinery there are CNC
Phase Converters. With all these choices it
is valuable to be able to use this organizations
comparisons with their rating system to carefully consider
your options. They even have a useful phase
converter purchasing checklist page. Some
engineers also appreciate recommended sources for
finding highly rated phase converters that their phase
converter resource page provides.
Phase
and Frequency Converters
There
are several instances where the equipment may need not
only the phase changed from 1-phase, or the rare
2-phase (in the US this is mostly used in Chicago) to
3 phase power, but also the frequency
converted from 50Hz to 60Hz or 400Hz (400Hz is
mostly used in ships and aircraft). Click here
to read more about 3
phase frequency converters.
1 Phase
Loads on 3 Phase
Power
Single-phase
loads may be connected to a 3 phase system in two
ways. This can be done either
by connecting across two live conductors (a
phase-to-phase connection), or by connecting between a
phase conductor and the system neutral, which is
either connected to the center of the Y (star)
secondary winding of the supply transformer, or is
connected to the center one winding of a delta
transformer (High leg Delta system). Single-phase
loads should be distributed evenly between the phases
of the 3 phase system for efficient use of the supply
conductors and
supply transformer.
Click here to read more about connecting a 1
phase load to a 3 phase power supply line.
Continue
And Read About Additional 3 Phase Power Details:
Contribute
3 Phase Power Articles to The 3 Phase Power Resource
Site:
If you would like to contribute additional 3 phase
info to our 3 phase power resource site please feel
free to email your 3 phase power article to us at
info@3phasepower.org. By doing so you are giving
us full rights to edit and distribute the info freely
worldwide in perpetuity in any way we see fit.
Note that The 3 Phase Power Resource Site is run by
all volunteers and thus we do not have the ability to
respond to all emails. Also not all info
submitted will be added to the site. It is at
the sole discretion of our electrical editors.
Thank you for contributing!
|
|
|
|
