Harmonic cancellation is performed with harmonic canceling
transformers also known as phase-shifting transformers. A harmonic
canceling transformer is a relatively new power quality product for
mitigating harmonic problems in electrical distribution systems. This
type of transformer has patented built-in electromagnetic technology
designed to remove high neutral current and the most harmful harmonics
from the 3rd through 21st.
Electronic nonlinear loads as the reason for the generation of
harmonics. Nonlinear loads range from the little plug-in power sources
to the massive automation equipment in factories. Harmonics slowly erode
the electrical environment causing high maintenance, premature failures
and fires. It is important that they are addressed.
What problems do harmonics create in a electrical
1. Large load currents in the neutral wires of a 3 phase system.
Theoretically the neutral current can be up to the sum of all 3
phases therefore causing overheating of the neutral wires. Since
only the phase wires are protected by circuit breakers of fuses,
this can result in a potential fire hazard.
2. Overheating of standard electrical supply transformers which
shortens the life of a transformer and will eventually destroy it.
When a transformer fails, the cost of lost productivity during the
emergency repair far exceeds the replacement cost of the transformer
3. High voltage distortion exceeding IEEE Standard 1100-1992
"Recommended Practice for Powering and Grounding Sensitive
Electronic Equipment" and manufacturer’s equipment specifications.
4. High current distortion and excessive current draw on branch
circuits exceeding IEEE Standard 1100-1992 "Recommended Practice for
Powering and Grounding Sensitive Electronic Equipment" and
manufacturer’s equipment specifications.
5. High neutral-to-ground voltage often greater than 2 volts
exceeding IEEE Standard 1100-1992 "Recommended Practice for Powering
and Grounding Sensitive Electronic Equipment."
6. High voltage and current distortions exceeding IEEE Std. 519-1992
"Recommended Practices and Requirements for Harmonic Control in
Electrical Power Systems."
7. Poor power factor conditions that result in monthly utility
penalty fees for major users (factories, manufacturing, and
industrial) with a power factor less than 0.9.
8. Resonance that produces over-current surges. In comparison, this
is equivalent to continuous audio feedback through a PA system. This
results in destroyed capacitors and their fuses and damaged surge
suppressors which will cause an electrical system shutdown.
9. False tripping of branch circuit breakers.
How do harmonics affect a site or facility?
Voltage distortion and voltage drop as mentioned in above items #3 and
#6 cause the equipment connected to the branch circuit to draw more
current to maintain the power rating (watts) of the unit. The bigger the
current draw from the unit, the more it produces excess heat within the
unit that was not factored for by its original design. In turn, the
excessive heat causes premature component level failures within the
unit. Additionally, you will experience computers locking up and other
operational malfunctions that are unexplainable. Think about how many
times we have experienced the "no problem found" syndrome with our
computers! The excessive heat produced can directly contribute to
downtime. Therefore, downtime is identified as any event that incurs or
contributes to lost productivity, lost revenues, lost savings, and more
importantly lost time. As we all have heard in the business world, "Time
In special facilities such as call centers or data centers, the
excessive heat produced due to the large concentration of monitors and
PCs will also cost money in energy dollars. The air computer room
(CRAC) or building air conditioning system will run longer or harder,
therefore requiring more energy to maintain the desired temperature.
Telecommunications cabling is commonly run right next to power cables.
If harmonics are above normal tolerances (more than 5% THD) as outlined
in IEEE Standard 519-1992, then high frequency harmonics can be induced
into phone lines and data cabling. The end result is noisy phone lines
and unexplained data lose or data corruption in your LAN or WAN.
Why are harmonics unknown or untreated in electrical
First, one must understand that the electrical distribution system of
most sites or facilities was never designed to deal with an abundance of
non-linear loads. It’s a problem that has only recently begun to be
recognized in the building industry. Within the last decade, the
widespread use of computers and SMPS equipment is turning modern office
buildings, factories, and industrial plants into high-tech computer
environments. Even older buildings that are renovated are not
retrofitted with modern harmonic treatment or cancellation. The end
result is a building or facility unable to fully support today’s
technology and the high-tech problems that it brings along with it.
Obviously, given the problems harmonics can cause, it is imperative that
today’s electrical distribution systems be designed for non-linear
electronic loads, not just linear electrical loads. Unfortunately
standard building codes and engineering designs do not meet the
requirements of today’s technology. With the advent of newer SMPS
equipment the harmonic problem will continue to get worse along with
inadequate facility grounding.
How can we wire electrical distribution systems
These are recommended ways to wire for the harmful effects that
harmonics cause. However, these recommendations only keep the electrical
distribution systems safe. These wiring recommendations do not eliminate
or cancel high levels of harmonics.
1. Use double-size neutral wires or separate neutrals for each phase.
2. Specify a separate full-size insulated ground wire rather than
relying on the conduit alone as a return ground path.
3. On a branch circuit use an isolated ground wire for sensitive
electronic and computer equipment.
4. Segregate sensitive electronic and computer loads on separate branch
circuits all the way back to the electrical panel.
5. Run a separate branch circuit for every 10 Amps of load.
6. Install a comprehensive exterior copper ground ring and multiple deep
driven ground rods as part of the grounding system to achieve 5 ohms or
less resistance to earth ground.
7. Oversize phase wires to minimize voltage drop on branch circuits.
8. Shorten the distance on branch circuits from the power panel to
minimize voltage drop.
The elimination of harmonics can be accomplished through a variety of
techniques and applications. First, know that power factor correction
capacitors do not remove harmonics. The inclusion of power factor
capacitors can make the matter worse. Active filters are good, but are
the most expensive and complex. Active filters digitally create and
control reactive power to cancel the harmonics.
The most effective, basic method to take care of harmonics is through
transformers. The principal is to take harmonics generated from separate
sources, shift one source of harmonics 180 degrees with respect to the
other and then combine them together; this will result in cancellation.
In a three-phase power distribution system, the 5th and 7th harmonics
are the most predominant causes of distortion and heating problems.
These harmonics will easily cause standard distribution
transformers to overheat, burn neutral conductors and naturally fail at
the worst possible time.
Picture a sinewave, which contains the 5th and 7th order harmonics with
the waveform. The K-Factor transformer shifts the 5th harmonic 150
degrees and the shifts the 7th harmonic 210 degrees. When the shifted
harmonics return back onto the line, the shifted 5th will be
approximately 30 degrees away from a perfect 180 degrees with respect to
the non-shifted 5th. Likewise the 7th will be 30 degrees from 180 with
respect to the non-shifted 7th. This is an excellent blend for these two
most corruptive harmonics. Now, within the electrical distribution
system, the shifted 5th harmonics are opposite in phase and cancel with
each other, as do the shifted 7th harmonics.
In closing, it is important to consult with
a power quality manufacturer before applying any of the recommendations
or methods as discussed throughout this paper. A manufacturer consultant
will be able to analyze the severity of the harmonics problem and design
a plan tailored to your specific harmonics situation.
allows signal or power to be taken from one device and fed into
another without electrically connecting the two.
are devices that transfer electrical energy from one electric
circuit to another, without changing the frequency, by
are designed to meet certain performance specifications and size
requirement that you require. There is a wide range of custom
Buck Boost Transformers
is a ideal solution for changing line voltage by small amounts.
Often used to buck (lower), or boost (raise) the voltage from 208v
to 240v for lighting applications.
Pole Mounted Transformers
are mounted to poles for overhead electrical lines. Used in various applications.
Are available in single phase or three phase transformers.
Medium Voltage Transformers
are used with a medium range of voltages. They come in a full
range from liquid-filled, convention dry type as well as cast coil.
Pad Mounted Transformers
are a excellent choice for commercial and industrial such as
manufacturing facilities, refineries, office buildings, schools,
hospitals, restaurants, and retail stores. They come in various
sizes and can be used underground as well.
typically these voltage transformers are used in power transmission
applications. High voltage transformers are also used in microwave.
- With Acme Electric being in business over 80 years, they
have always believed in offering there customers superior service,
quality and technical expertise in the transformer market.
AMVECO Transformers -
AMVECO designs and manufactures toroids transformers, current
transformers, and auto transformers. Most AMVECO products are custom
designed utilizing their state-of-art proprietary CAD programs.
The AMVECO engineers can quickly generate designs in a matter of
hours, if needed.
Federal Pacific Transformers -
Federal Pacific is a division of Electro- Mechanical
Corporation, a privately held, American owned company founded in
1958. Federal pacific offers dry-type transformers from .050 KVA
through 10,000 KVA single and three phase, up to 34.5 KV, 150 KV BIL
with UL approval through 15 KV.
Marcus Transformer - Ever since they opened their doors for
business a half a century ago, they have been a leader in innovative
transformer design. As a family-owned company they are proud of the
reputation they have earned for making quality-built transformers
that deliver exceptional performance and savings.
Hammond Transformers - Hammond Manufacturing was
founded in 1917 in Guelph, Ontario, Canada. In the last 3 decades it
has expanded to the US and the international markets offering many
types of power transformers.
- TEMCo Transformer, a family-owned business which has been
manufacturing and distributing electrical products since 1968.
They focus on transformers that significantly reduce power
consumption over 30 percent compared to competitive makes.
Transformers - GE has been a key player in the energy
industry for more than a century. Since the installation of
their first steam turbine in 1901. They have become number one
provider of high-technology power generation and distribution
Jefferson Electric Transformers - Jefferson Electric has
been a pioneer and innovator of magnetic products since 1915.
Jefferson broad line of dry-type transformers are backed by quality
assurance systems so stringent that each and every unit gets
thoroughly tested before it goes out there door.
Distribution Transformers - Distribution transformers are
generally used in electrical power distribution and transmission
power. This class of transformer has the highest power, or
volt-ampere ratings. and the highest continuous voltage
Substation Transformers - Substation Transformers are large
devices which usually weigh tens of thousands of pounds.
They are filled with tens of thousands of gallons of heat transfer
fluid. Although they are typically 99.8% efficient in the
transforming of electricity from one voltage to another, processing
hundreds of Mega Volts-Amps of electricity force the liberation of
hundreds of BTUs per second.
Medical Grade Isolation
Medical Grade Transformers generally refer to the transformers
used in medical devices as well as hospital, biomedical and patient
care equipment. There are a number of strict safety rules,
guidelines and laws governing the design, construction and the test
of these transformers.
Drive Isolation Transformer -
They are used to isolate a drive from a main power line to
prevent the transmission of harmonics that the drives produce back
into the power line. They stop drive harmonics from disrupting
computers and other sensitive equipment.
Toroidal Transformers -
Toroidal Transformers are more efficient than the cheaper laminated
EI types of similar power level. Some of the advantages are smaller
size, lower weight, less mechanical hum, (making them superior in
audio amplifier), low-off-load loss.
Step-Up Transformers - A Step-Up Transformer is one whose
secondary voltage is greater than its primary voltage. This
kind of transformer "steps up" the voltage applied to it. -
- A Step-Down Transformer is designed to reduce
voltage from primary to secondary. They can range from sizes
from .05 KVA to 500 KVA
Isolation Transformers -
An Isolation Transformer is a device that transfers energy from
the alternating current (AC) supply to an electrical or electronic
load. It isolates the windings to prevent transmitting certain
types of harmonics.
Buck Boost Transformers - Buck Boost Transformers make small
adjustments to the incoming voltage. They are often used to change
voltage from 208v to 240v for lighting applications. Major
advantages of Buck boost transformers include; low cost, compact
size and light weight.
High Voltage Transformer - There are many different types of
voltage transformers. A High Voltage Transformer operates with high
voltages. Typically, these voltage transformers are used in power
transmission applications, where voltages are high enough to present
a safety hazard.
Medium Voltage Transformers -
A Medium Voltage Transformer can be connected directly to a primary
distribution circuit and generally has the most load diversity.
These voltage transformers have installation practices that are
generally in accordance with application recommendations from the
Institute of Electrical and Electronic Engineers (IEEE).
Low Voltage Transformers
- A Low Voltage Transformer is an electrical device that
transforms 120 volts (line voltage) into 12 volts or 24 volts (low
voltage). Some uses for low voltage transformer are in landscaping
Single Phase Transformers - In electrical engineering,
single-phase electric power refers to the distribution of electric
power using a system in which all the voltages of the supply vary in
unison. Single-phase distribution is used when loads are mostly
lighting and heating, with few large electric motors.
Three Phase Transformers - Three Phase Transformers must
have 3 coils or windings connected in the proper sequence in order
to match the incoming power and therefore transform the power
company voltage to the level of voltage needed while maintaining the
proper phasing or polarity.
Custom Transformers -
Custom Transformers are designed for a certain performance
specifications and size requirements. The company works with
your engineering specification.
Industrial Control Transformers -
Industrial Control Transformers are used to convert the
available supply voltage to the required voltage to supply
industrial control circuits and motor control loads.
Pad Mounted Transformers - Pad Mounted Transformers are
usually single phase, or three phase, and used where safety is a
main concern. Typical applications; restaurant, commercial building,
shopping mall, institutional.
Pole Mounted Transformers -
Pole Mounted Transformers are used for distribution in areas
with overhead primary lines. Outside a typical house one can see one
of these devices mounted on the top of an electrical pole.
Oil Filled Transformers -
Oil Filled Transformers are transformers that use insulating oil as
insulating materials. The oil helps cool the transformer.
Because it also provides part of the electrical insulation between
internal live parts, transformer oil must remain stable at high
temperatures over an extended period.
Type Transformers - Dry-Type Transformers are available for
voltages up through 34.5 kV (although the most common upper limit is
15) and KVA ratings up through 10,000 (with 5000 as the usual
limit). Dry-type use air as a coolant, lowering health and
Auto Transformers -
An Autotransformer is an electrical transformer with only one
winding. The winding has at least three electrical connection points
called taps. Autotransformers are frequently used in power
applications to interconnect systems operating at different voltage
classes, for example 138 kV to 66 kV for transmission. Another
application is in industry to adapt machinery built for 480 V
supplies to operate on the local 600 V supply.
Electrical Transformers are devices used to raise or lower the
voltage of alternating current. For instance, power is transported
over long distance in high voltage power lines and then transformers
lower the voltage so that the power can be used by a business or household.
An Isolating Transformer is a transformer, often with
symmetrical windings, which is used to decouple two circuits.
An Isolation transformer allows an AC signal or power to be taken
from one device and fed into another without electrically connecting
the two circuits. Isolation transformers block transmission of DC
signals from one circuit to the other, but allow AC signals to pass.
Power Lines - A Transmission Line is the material medium or structure that forms
all or part of a path from one place to another for directing the
transmission of energy, such as electromagneticor acoustic waves as well as electric power
transmission. Components of transmission lines include wires, coaxialcables, dielectric slabs, option fibers,electric power lines, and waveguides.
Transformer Voltage - The measure of the amount of force on a
unit charge because of the surrounding charge.
Transformer Frequency -
The transformer cannot change the frequency of the supply. If the
supply is 60 hertz, the output will also be 60 hertz.
Transformer K Factor - Some transformers are now being offered
with a k-factor rating. This measure the transformer's ability to
withstand the heating effects of non-sinusoidal harmonic currents
produced by much of today's electronic equipment and certain
Primary Voltage - The coil winding that is directly connected
to the input power.
Harmonic Cancellation -
Harmonic cancellation is performed with harmonic canceling
transformers also known as phase-shifting transformers. A harmonic
canceling transformer is a relatively new power quality product for
mitigating harmonic problems in electrical distribution systems.
This type of transformer has patented built-in electromagnetic
technology designed to remove high neutral current and the most
harmful harmonics from the 3rd through 21st.
Enclosed transformers come with a weatherproof standard set by
Epoxy Encapsulated -
A process in which a transformer or one of its components is
completely sealed with epoxy or a similar material. This process is
normally preferred when a unit might encounter harsh environmental
Voltage Regulators - A
Voltage Regulator is an electrical regulator designed to
automatically maintain a constant voltage level.
It may use an electromechanical mechanism, or passive or active
electronic components. Depending on the design, it may be used to
regulate one or more AC or DC voltages.
AC Line Reactor -
AC Line Reactors is a three phase transformer used in
conjunction with AC variable frequency and DC motor drive.
They are a bi-directional protective filtering device.
Line Power Conditioners -
Power or Line Conditioners regulate, filter, and suppress noise in
AC power for sensitive computer and other solid state equipment.
DC Power Supplies -
Conversion of one form of electrical power to another desired
form and voltage. This typically involves converting 120 or 240 volt
AC supplied by a utility company to a well-regulated
lower voltage DC for electronic devices.
Rotary Phase Converters -
Rotary Phase Converters are commonly used in home or small
commercial or industrial settings. Rotary phase converters convert
single-phase power into three-phase power. This is a very
cost-effective way to power three-phase electric motors and other
three phase equipment.
Frequency Converters -
A Frequency Changer or Frequency Converter is an
electronic device that converts alternating current (AC) of one
frequency to alternating current of another frequency.
Voltage Converters -
A Voltage Converter changes the voltage of an electrical power
source and is usually combined with other components to create a
Magnetic Motor Starters - Magnetic Motor Starters are
essentially heavy duty relays mounted in boxes, often equipped with
heater/thermal overloads matched to the motor they start.
Motor Starting Auto Transformers - An Auto
Transformer starter uses an auto transformer to reduce
the voltage applied to a motor during start. The auto transformer
may have a number of output taps and be set-up to provide a single
stage starter, or a multistage starter.