Transformer

1. Top 20 things To Know Before Selecting A Power Transformer
1. What is a Transformer and how does it work?
A transformer is an electrical device designed to transfer alternating current or voltage from one electric
circuit to another by means of electromagnetic induction. It can be designed to "step-up" or Step-
down" voltages. Because transformer has no moving parts and is a completely static solid state device,
under normal operating conditions, are usually insure a long and trouble-free life. The simplest type of
transformer consists of two or more coils of insulated wire wound on a laminated steel core. When
voltage is introduced to one coil, called the primary, it magnetizes the iron core. A voltage is then
induced in the other coil, called the secondary or output coil. The change of voltage between the
primary and secondary depends on the turns ratio of the two coils. Transformers are not limited to one
output coil. They can provide a whole range of voltage sources from the one input coil by using
separate windings on the secondary side. This makes transformers very useful for supplying complete
systems with all of their voltage requirements from one source.
The amount of electricity being produced depends on the number of times the coil is wound around the
core. The more times it's wound around, the higher the voltage. So if the input coil has more loops and
the output coil has a couple of loops, the input coil will be a higher voltage than the output coil. If the
coils have an equal number of loops, their input and output will be equal. If the output coil has more
voltage, it's called a "step-up transformer." If the input coil has more voltage, it's called a "step-down
transformer."
Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a
stage microphone to huge gigawatt units used to interconnect large portions of national power grids. All
operate with the same basic principles and with many similarities in their parts.
2. How to selection the right transformer
 Determine primary voltage and frequency.
 Determine secondary voltage required.
 Determine the capacity required in volt-amperes
This is done by multiplying the load current (amperes) by the load voltage for single phase. For
example, if the load is 40 amperes, such as a motor, and the secondary voltage is 240 volts, then 240 x
40 equals 9600 VA.A 10 KVA (10,000 volt-amperes) transformer is required. Always select the
transformer larger than the actual load. This is done for safety purposes an allows for expansion. For 3
phase KVA, multiply rated volts x load amps x 1.73 (square root of 3) then divide by 1000.
Suppose you've got the job of designing the power distribution for an entire building, you'll have to
select the service transformer and the distribution transformers.
First you must determine the largest load you can expect at any given time. Example, you don't
normally run electric heat and air conditioning at the same time. so your calculations would include only
the larger of the two loads. You might not operate all equipment simultaneously either, however you
would run some loads at the same time. Determine what those loads are-based on operational
requirements, then determine the kVA each will draw. Once you done the individual calculations and
added them up to arrive at the maximum load, you should add in factors for reasonable unplanned
load growth (20% is common) and for planned addition load.
But don't stop there. The following includes some additional factors you'll have to consider when
choosing a transformer.
 Pole-mounted, pad-mounted, indoor or outdoor
 primary voltage: delta or wye (usually dictated by the utility)
 Secondary voltage (480V for small facilities) or delta-wye
 3,4,or 5 wire configuration (4 is the most common)

2.  power factor and efficiency
 Impedance
 Temperature rise
 Case style (consider footprint, height, access, cooling)
 Location, space requirement
 Seismic requirement
 Accessories (including taps) and instrumentation
 Dry-type or liquid-filled
 Basic impulse level, which is the withstand rating in kV
Based on these criteria, you can work with a manufacturer to select the correct transformer for your
service entrance.
Once you've selected the service entrance transformer, you can supply the feeder circuits. You want to
distribute at the highest voltage possible to minimize losses and power quality problems. In a large
facility, you probably 14.4kV onsite, through many facilities distribute at 24kV. To select the
transformer for these feeders, follow the same steps.
Distribution Transformers
The next layer of distribution is usually 4160V, then 480V, you normally begin to power equipment at
these levels. Don't assume loads start at 480V. Some large production equipment requires a 4160V
supply. Reactor coolant pumps, chiller pumps, and other high-inertia loads also run on 4160V. A
transformer's function is straightforward: to step down the voltage and provide isolation between
primary and secondary. When supplying a particular piece of equipment or equipment grouping,
however, transformer selection gets more complicated. Motors that run at 4160V, for example, tend to
be large, expensive, and mission-critical. Usually, you'll put such a motor on its own transformer and
panel with few, if any, other loads. Use the earlier load calculations to size these individual load
transformers, and carefully note the load characteristics — this is crucial information to supply to the
manufacturer.
Low-Voltage Distribution
Before you size your low-voltage distribution transformers, decide how you're going to lay out your
branch circuits. For example, you might use one transformer to supply a motor control center (MCC),
another for lighting loads, another for convenience receptacles, and so on. You could also provide an
individual transformer for infrastructure equipment (plant air, elevators, electric doors), or individual
transformers for individual equipment. A good planner will also provide a transformer for emergency
equipment (fire control, security, emergency egress lighting) that resides on a UPS and may even have
an alternate transformer supplying the switchgear or panels through a transfer switch.
In each case, size your distribution transformer based on the maximum load you can expect — just as
you did for the service entrance. Also, a piece of large equipment — such as a robotic machine that
automates sequential stamping, cutting, and welding operations — may require its own 4160V supply
(integral OEM transformers step down to other voltages) while also requiring a 480V supply to corollary
equipment. That corollary equipment should not run off the same 4160V supply as the main machine,
so you may have two 4160V transformers with very different operating requirements.
What about distributed vs. centralized and size vs. quantity? By using several small transformers, you
can reduce loss of function in the event of a transformer failure. Match transformers to load type and
use as few transformers as possible (which means maximizing the load per transformer) to effectively
reduce voltage drop. However, blindly following either of these approaches ignores the real issues: The
small-transformer approach is expensive and inefficient — the money spent on transformers would go
much further for maintenance.
Also look at transformers that can provide some flexibility in specialized way. Using a Autotransformers
where primary and secondary winding are magnetically isolated from each other, but electrically
connected. Advantages are lower cost, smaller size, less weight, high efficiency, and better voltage
regulation. A buck boost transformer allows you to raise or lower voltage to particular equipment. If you
have 230V equipment but 208V/120V distribution, a buck boost transformer can raise the voltage to

3. that equipment from 208V to 228.8V, which is close enough for proper operation.
When choosing a transformer, your job is defining the load size and the nature of the load. Often,
industry experience makes transformer selection easy once you've done this. But sometimes an
application does not lend itself to straightforward decisions. In such cases, you'll need to consult the
appropriate standards and references, and work with your manufacturer. The factors outlined here will
help you make that a successful collaboration.
3. What voltage power output do you need?
Voltage in the world different in the United States and Canada usually run on 110/120 and most of the
rest of the world runs on 220/240 and industrial plant may use 440 to 480. Most utilities will provide a
customer with one service or electrical system. You may wonder why anyone would need a transformer.
Let say a new industrial plant comes in town. They have many motors in use at their company so they
requested a 480Y/277 volts three-phase system. This takes care of their motor load at 480 volts and
their office and plant lighting loads at 277 volts. However to operate their office machinery and
incandescent lighting they require 120 volts. They also have some small horsepower motors they want
to operate at 208 volts. Since the utility will only provide them with 480Y/277 volt three-phase system,
they require a transformer to provide the rest of there needs. A buck boost transformer is the ideal
solution for changing line voltage by small amounts. The major advantages are their low cost, compact
size and light weight. They are also more efficient and cost less than equivalent isolation transformers.
When connected as an autotransformer, they can handle loads up to 20 times the name plate rating.
4.Single Phase or three phase transformer?
Single-phase power distribution is used especially in rural areas, where the cost of a three-phase
distribution network is high and motor loads are small and uncommon.
In North America, individual residences and small commercial buildings with services up to about 100
kV·A (400 amperes at 240 volts) will usually have three-wire single-phase distribution, often with only
one customer per distribution transformer. Larger consumers such as large buildings, shopping centers,
factories, office blocks, and multiple-unit apartment blocks will have three-phase service. In densely-
populated areas of cities, network power distribution is used with many customers and many supply
transformers connected to provide hundreds or thousands of kV·A load concentrated over a few
hundred square meters.
A single-phase supply connected to a pure single-phase induction motor does not produce a revolving
magnetic field, and so practical single-phase motors always have some means of producing a revolving
field to generate starting torque. Aside from certain traction power applications, single-phase induction
motors greater than 10 or 20 kW are very uncommon.
In Some application a phase converter is used. A phase converter is simply a rotating machine that
converts single-phase utility power into 3-phase electricity to operate 3-phase equipment. Phase
converters are typically applied where utility 3-phase is unavailable or too expensive to install. A
properly sized and selected converter will operate any load just as well as utility 3-phase and will
provide years of trouble-free service.
A rotary phase converter is actually a rotating transformer. Through transformer action a phase
converter splits off and phase shifts a portion of the single-phase supply from the utility creating true 3-
phase power. When energized, the rotary phase converter uses the single-phase 2-line supply from the
utility and creates a manufactured third line of power. The 3 lines (or phases) look identical to utility 3-
phase with all three lines shifted 120°. The output of a rotary phase converter is true 3-phase. Each of
the three output voltages will be shifted 120 electrical degrees. If the converter is properly sized, these
voltages will remain in a balanced state over the entire range of connected loads.
5.What are the different frequencies of power and there uses?
The incoming electric transformers voltage is an important factor. The three common frequencies
available are 50 Hz, 60Hz and 400 Hz. European power is typically 50 Hz while North American power is
usually 60hz. The 400 Hz is reserved for high-powered applications such as aerospace technologies. It
is also important to consider the secondary power specifications when evaluating transformers. Other

4. specifications to keep in mind when selecting an electric transformer are: the maximum ratings of the
following: secondary current and voltage rating, power and output rating. Power transformers have
various configurations according to phase and connections. The most common phases are single-phase
and three-phase. Both the size and expense of electric transformers increases in proportion to the
number of primary windings.
A frequency converter is used in some application. A frequency converter is an electronic device that
converts alternating current (AC) of one frequency to alternating current of another frequency. The
device may also change the voltage, but if it does, that is incidental to its principal purpose. Aside from
the obvious application of converting bulk amounts of power from one distribution standard to another,
frequency changers are also used to control the speed and the torque of the AC motors. In this
application, the most typical frequency converter topology is the three-phase two-level voltage source
inverter. The phase voltages are controlled using the power semiconductor switches and pulse width
modulation (PWM). Semiconductor switching devices and anti-parallel connected freewheeling diodes
form a bridge, which can connect each motor phase to the positive or negative dc-link potential. The
PWM changes the connections of the phases between the positive and the negative dc-link potentials so
that the fundamental wave voltage has the desired frequency and amplitude. The motor reacts
primarily to the fundamental voltage and filters out the effects of the harmonic voltages.
Another application is in the aerospace and airline industries. Often airplanes use 400 Hz power so 50
Hz or 60 Hz to 400 Hz frequency converter is needed for use in the ground power unit used to power
the airplane while it is on the ground.
Frequency changers are typically used to control the speed of pumps and fans. In many applications
significant energy savings are achieved. The most demanding application areas are found on the
industrial processing lines, where the control accuracy requirements can be very high.
6.Will Efficiency and Heat be a Consideration?
An ideal transformer would have no losses, and would therefore be 100 efficient. In practice energy is
dissipated due both to the resistance of the windings (known as copper loss), and to magnetic effects
primarily attributable to the core (known as iron loss). Transformers are in general highly efficient, and
large power transformers (around 100 MVA and larger) may attain an efficiency as high as 99.75%.
Small transformers such as a plug- in used to power small consumer electronics may be less than 85%
efficient.
The looses arise from:
 Winding resistance: Current flowing through the windings causes resistive heating of the
conductors.
 Eddy currents: Induced currents circulate in the core and cause it resistive heating.
 Stray losses: Not all the magnetic field produced by the primary is intercepted by the
secondary. A portion of the leakage flux may induce eddy currents within nearby conductive
object such as the transformers support structure, and be converted to heat. The familiar hum
or buzzing noise heard near transformers is a result of stray fields causing components of the
tank to vibrate, and is also from magnetostriction vibration of the core.
 Hysteresis losses: Each time the magnetic field is reversed, a small amount of energy is lost to
hysteresis in the magnetic core. The level of hysteretic is affected by the core material.
 Mechanical losses: The alternating magnetic field causes fluctuating electromagnetic forces
between the coils of wire, the core and any nearby metalwork, causing vibrations and noise
which consume power.
 Magnetostriction: The flux in the core causes it to physically expand and contract slightly with
the alternating magnetic field, an effect known as magnetostriction. This in turn causes losses
due to friction heating in susceptible ferromagnetic cores.
Efficiency gains can be achieved by using materials with lower resistively or greater diameters. For
example, transformer coils made with low resistively conductors, such as copper, can have considerably
lower load losses than those made with other material.

5. Heat
All transformers must have some circulation of coolant to remove the waste heat produced by losses.
Small transformers up to a few kilowatts in size usually are adequately cooled by air circulation. Larger
"dry" type transformers may have cooling fans. Some dry transformers are enclosed in pressurized
tanks and are cooled by nitrogen or sulfur hexafluoride gas.
The windings of high-power or high-voltage transformers are immersed in transformer oil - a highly-
refined mineral oil that is stable at high temperatures. Large transformers to be used indoors must use
a non-flammable liquid. Formerly, polychlorinated biphenyl (PCB) was used as it was not a fire hazard
in indoor power transformers and it is highly stable. Due to the stability of PCB and its environmental
accumulation, it is no longer permitted in new equipment. Today, nontoxic, stable silicone-based oils or
fluorinated hydrocarbons may be used, where the expense of a fire-resistant liquid offsets additional
building cost for a transformer vault. Other less-flammable fluids such as canola oil may be used but all
fire resistant fluids have some drawbacks in performance, cost, or toxicity compared with mineral oil.
The oil cools the transformer, and provides part of the electrical insulation between internal live parts. It
has to be stable at high temperatures so that a small short or arc will not cause a breakdown or fire.
The oil-filled tank may have radiators through which the oil circulates by natural convection. Very large
or high-power transformers (with capacities of millions of watts) may have cooling fans, oil pumps and
even oil to water heat exchangers. Oil-filled transformers undergo prolonged drying processes, using
vapor-phase heat transfer, electrical self-heating, the application of a vacuum, or combinations of
these, to ensure that the transformer is completely free of water vapor before the cooling oil is
introduced. This helps prevent electrical breakdown under load.
Oil-filled power transformers may be equipped with Buchholz relays - safety devices sensing gas buildup
inside the transformer (a side effect of an electric arc inside the windings) and switching off the
transformer.
Experimental power transformers in the 2 MVA range have been built with superconducting windings
which eliminates the copper losses, but not the core steel loss. These are cooled by liquid nitrogen or
helium.
7.Will the transformer be inside or outside?
For harsh environments, whether indoor or outdoor, it's critical that a transformer's core/coil, leads, and
accessories be adequately protected.
In the United States, almost all liquid-filled transformers are of sealed-type construction, automatically
providing protection for the internal components. External connections can be made with "dead front"
connectors that shield the leads. For high corrosive conditions, stainless steel tanks can be employed.
Dry-type transformers are available for either indoor or outdoor installation. Cooling ducts in the
windings allow heat to be dissipated into the air. Dry-types can operate indoors under almost all
ambient conditions found in commercial buildings and light manufacturing facilities.
For outdoor operations, a dry-type transformer's enclosure will usually have louvers for ventilation. But,
these transformers can be affected by hostile environments (dirt, moisture, corrosive fumes, conductive
dust, etc.) because the windings are exposed to the air. However, a dry-type can be built using a sealed
tank to provide protection from harmful environments. These units operate in their own atmosphere of
nonflammable dielectric gas.
Other approaches to building dry-type transformers for harsh environments include cast coil units, cast
resin units, and vacuum pressure encapsulated (VPE) units, sometimes using a silicone varnish. Unless
the dry-type units are completely sealed, the core/coil and lead assemblies should be periodically
cleaned, even in non-harsh environments, to prevent dust and other contaminant buildup over time.
Locating a transformer indoors, on the rooftop, or adjacent to a building in order to minimize the
distance between the unit and the principal load results in reducing energy loss and voltage reduction.
It also reduces the cost of secondary cable.
On the other hand, such placements of high-voltage equipment require closer consideration of electrical
and fire safety issues. These conflicting goals can be satisfied by using transformers permitted by Code

6. and insurance companies.
When liquid-filled transformers are preferred, less-flammable liquids are widely recognized for indoor
and close building proximity installations. Wet-type transformers using less-flammable, or high fire
point liquids, have been recognized by the NEC since 1978 for indoor installation without the need for
vault protection unless the voltage exceeds 35kV. Based on this type of transformer's excellent fire
safety record, Code and insurance restrictions have become minimal. Conventional mineral oil units are
allowed indoors, but only if they are installed in a special 3-hr-rated vault (with a few exceptions) per
the construction requirements of NEC Article 450, Part C. There's a requirement for liquid containment
when wet-type transformers are used, regardless of the type fluid employed.
When dry-type units are preferred, they have fewer code restrictions. Obviously, these types of
transformers do not need liquid containment. Per the requirements listed in NEC Sec. 450-21, there are
minimum clearances that you must observe, and units over 112.5kVA require installation in a
transformer room of fire-resistant construction, unless they are covered by one of two listed exceptions.
As with liquid units, dry transformers exceeding 35kV must also be located in a 3-hr-rated vault.
A liquid-filled transformer may experience leakage around gaskets and fittings; however, if the
installation was carried out correctly, this should not be a problem. Major maintenance procedures may
require inspection of internal components, meaning that the coolant will have to be drained. Coils in
liquid-type units are much easier to repair than coils in dry-type transformers. Cast coils are not
repairable; they must be replaced.
8. Can transformers be operated at voltages other than nameplate
voltages?
Transformers can be operated. in some cases at voltages below the nameplate rated voltage.
Transformer should not be operated in excess of it nameplate rating, unless taps are provided for this
purpose. Taps are provided on some transformers on the high voltage winding to correct for high or low
voltage conditions, and still deliver full rated output voltages at the secondary terminals. Standard tap
arrangements are at two-and-one-half and five percent of the rated primary voltage for both high and
low voltage conditions.
9. What is the difference between Insulating, Isolating, and Shielded
Winding transformers?
Insulating and isolating transformers are the same. they are used to describe the isolation of the
primary and secondary windings, or insulation between the two. A shielded transformer is designed with
a metallic shield between the primary and secondary windings to attenuate transient noise. The
shielded transformer is used in applications such as computers, process controllers and many other
microprocessor controlled devices. All two, three and four winding transformers are of the insulating or
isolating types.
10.Why should Dry-Type Transformers never be over-loaded
When you overloading a transformer excessive temperature can cause overheating which result in
rapid deterioration of the insulation and cause complete failure of the transformer coils.
11. What is meant by impedance in transformers?
Impedance is the current limiting characteristic of a transformer and is expressed in percentage. It is
used for determining the interrupting capacity of a circuit breaker or fuse employed to protect the
primary of a transformer.
The impedance of the load is expressed in ohms, and the relationship between the current and the
voltage in the circuit is controlled by the impedances in the circuit. When a signal source, such as our
composite video output, sees a very low-impedance circuit, it produces a larger than intended current;
when it sees a very high-impedance circuit, it produces a smaller than intended current. These
mismatched impedances redistribute the power in the circuit so that less of it is delivered to the load
than the circuit was designed for--because the nature of the circuit is that it can't simply readjust the

7. voltage to deliver the same power regardless of the rate of current flow. Imagine, riding in your car
down the Interstate in first gear, flooring the gas pedal and going just as fast as you can. It's obvious,
as you watch the cars zip past, that no matter how much horsepower you have under the hood, most of
that horsepower isn't getting delivered to the road; instead, a lot of it is burning up in the engine as
excess heat, and if you keep this driving up for long, you'll damage your engine. The same thing
happens in an impedance mismatch between a source and load; power isn't being transferred properly
because the source circuit wasn't designed to drive the kind of load it's connected to. In some electronic
applications this will burn out equipment.
12. Why are Small Distribution Transformers not used for Industrial Control Application?
Industrial control equipment demands a momentary overload capacity of three to eight times normal
capacity. This is customary in solenoid or magnetic contractor applications where inrush current can be
three to eight times as high as normal sealed or holding currents but still maintain normal voltage at
this momentary overloaded condition. Distribution transformers are designed for good regulation up to
100 percent loading, but their output voltage will drop rapidly on momentary overloads of this type
making them unsuitable for high inrush applications.
Industrial control transformers are designed especially for maintaining a high degree of regulation even
at eight times normal load. This results in a larger and generally more expensive transformer.
13. Can Single Phase Transformers be used for Three Phase Applications?
Yes, but the transformer output will be single-phase. Simply connect any two wires from a 3- or 4-wire
source to the transformer's two primary leads. Three single-phase transformers can be used for three-
phase applications. They can be used in delta-connected primary and wye or delta-connected
secondary. To avoid an unstable secondary voltage, NEVER connect wye primary to delta secondary.
14.How do I know when the temperature rise is too high?
Thermometers are the best way to determine the temperature. Touch is a poor indicator of proper
operating temperature for transformers. Properly designed transformers can reach 50°C (122°F) above
ambient temperature. In an ambient temperature of 20°C (60°F), the total temperature can reach 70°C
(190°F), which is too hot to touch.
15.Can transformers be used in parallel?
Yes, it is very common for transformers to be placed in parallel service. To provide maximum efficiency,
voltage and impedance values must match closely. A failure to match will cause unbalanced loading for
the transformers and may lead to overheating or premature failure.
16.Can I achieve specific sound levels in a transformer?
Before selecting a transformer assure yourself that the sound levels represented have been measured
in accordance with the NEMA standards. If your requirement is lower than that available from the
manufacturer’s standard product, request a specific sound level on your bid.
17. Is one insulation system better than other?
It depends on the application and the cost benefit to be realized. Higher temperature class insulation
systems cost more and larger transformers are more expensive to build. Therefore, expensive insulation
systems are more likely to be found in the larger KVA units.
 Small fractional KVA transformers use insulation class 130 degrees C
 Compound filled transformers use insulation class 180 degrees C

8.  Larger ventilated transformers are designed to use 220 degrees C insulation
18. What is Exciting Current?
Exciting current, is the current or amperes required for excitation. The exciting current on most lighting
and power transformers varies from approximately 10% on small sizes of about 1 KVA. The exciting
current is made up of two components, one of which is a real component and is in the form of losses or
referred to as no load watts; the other is in the form of reactive power and referred to as KVAR.
19. Can Transformers develop Three Phase power from a Single Phase
source?
NO. Phase converters or phase shifting devices such as reactors and capacitors are required to convert
single phase power to three phase.
20. Can air cooled transformers be applied to motor loads?
This is an excellent application for air cooled transformers. Even through the inrush or starting current
is five to seven times normal running current, the resultant lower voltage caused by this momentary
overloading is actually beneficial in that a cushioning effect on motor starting is the result.
Great Power Transformer Articles
1. Top 20 Things to Know before Selecting a Power Transformer - This is a great article to
help educate and inform you on how to select the right transformer before you
buy. It will help you make an informed decision and covers questions including,
what voltage power output do you need?, will it be single phase or three phase?,
etc. We answer the 20 most asked questions so you can be well informed and
choose the right transformer for the job. Choosing the right transformer can be a
daunting task for the inexperienced. This section takes the first step toward
becoming a confident, knowledgeable consumer. This article addresses the process
of choosing these transformers at its most fundamental level.
2. How Does Transformer Manufacturer Company Brand Affect Power Transformer Quality? -
For manufacturers of large power transformers, product design and features seem
fairly standard. But different manufacturers offer unique features. there are several
standards such as ASTM D 3487 and IEEE Standard C57.12.90. Quality
transformers can have a significant impact on cost. Did you know that some
transformers brands improved materials, design and quality can save you 30%, or
more, in energy cost? Understanding the differences can play a key role in making
an informed selection.
3. How Does Winding Metal Type Change a Transformers Properties? - gain knowledge on
how the winding and types of metal used can change transformer properties. The
conducting material used for the winding depends upon the application. Small
power and signal transformers are often wound with solid copper wire. Larger
power transformers may be wound with copper wire, or aluminum and may include
rectangular conducts. When copper wiring is used it will increase the efficiency of
the transformer and will generally generate a lot less heat. Read more to learn
about the many other efficiencies gained by choosing a transformer with a metal
composition that is fit for your needs

9. 4. Understanding Power Transformer "K-Factor Rating" - A great information article on
what "K-Factor Rating" is and the effects they have on transformer choice. The K-
Factor rating assigned to a transformer and marked on the transformer case in
accordance with the listing of Underwriter Laboratories. It is an index of the
transformer's ability to supply harmonic content in its load current while remaining
within its operating temperature limits.
Read Addition Power Transformer Articles - Additional informal helpful articles about
power transformers.
Power Transformer Information:
Power
Transformer
Manufacturer
 ACME
Transformers -
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
Power
Transformer
Types
 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.
-
 Step-Down
Transformers -
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)
Power Transformer Term
Definitions
 Electrical Transformers - 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.
 Isolating Transformers - 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.
 Transmission 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 electromagnetic or acoustic
waves as well as electric power
transmission. Components of transmission
lines include wires, coaxial cables, 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 Phase - Most transformer are
either single phase or three phase.
 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 electrical equipment.

10. 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,
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.
 Primary Voltage - The coil winding that is
directly connected to the input power.
 Secondary Voltage - The coil winding supplying
the output voltage.
 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.
 Weatherproof - Enclosed transformers come
with a weatherproof standard set by NEMA.
 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 conditions.
 More power transformer terms - Such as
inductor, ground fault, core saturation,
current transformer, faraday shield, etc.
Related Transformer Products
 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.

11. Ontario,
Canada. In
the last 3
decades it has
expanded to
the US and
the
international
markets
offering many
types of power
transformers.
 TEMCo
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.
 GE
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
equipment.
 Jefferson
Electric
Transformers -
Jefferson
 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
recommenda
tions 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
lighting.
 Single Phase
Transformers
- In electrical
engineering,
single-phase
electric
power refers
to the
 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 power supply.
 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.
For an additional resource the Best of Industry Web
Directory : Electrical Power Transformer Directory section is
quite useful.

12. 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.
 More power
transformer
brands - Check
out more
companies by
clinking this
link.
Power
Transformer
Types
 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 rating.
 Substation
Transformers -
Substation
Transformers
are large
devices which
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

13. 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
Transformer -
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
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

14. 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.
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
temperature
s over an
extended
period.
 Dry 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
environment
ally
concerns.
 Auto
Transformers
- An
Autotransfor
mer is an
electrical
transformer
with only
one winding.
The winding
has at least
three
electrical
connection
points called

15. taps.
Autotransfor
mers 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.
 More power
transformer
types - Read
further about
additional
transformer
types and
their uses.
Additional Useful Resources:
Transformer Selection Guide • Custom Transformers • Dry-Type Transformers • Auto Transformers • Control
Transformers • Step-Up Transformers • Step-Down Transformers • Harmonic Cancellation • Isolation Transformers • K-
Factor Rated Transformers • 3-Phase Transformers • European Voltage Transformers • Drive Isolation Transformers •
High Voltage Transformers • Epoxy Encapsulated NEMA 4 Transformers • Weatherproof NEMA 3R Transformers •
Transformers • AC Transformer • Voltage Transformer • Buy Transformer • New Transformer • Output Transformer •
Transformer KVA • Converter Transformer • Line Transformer • Toroidal Transformer • Oil Filled Transformers •
Voltage Regulator • Automatic Voltage Regulator • DC Power Supply • PDU • Rack PDU • Power Conditioner • Power
Line Conditioner • Load Center • Switchgear • Voltage Converter • Transformer Wiring • Transformer Circuit • Variable
Transformer • Pole Transformer • Transformer Pad • VA Transformer • WYE Transformer • Potential Transformer •
Transformer Protection • Variac • Transformer Rating • Sunbelt Transformer • Pacific Transformer • Jefferson
Transformer • Electric Transformer • Power Transformer • Transformer Sizing • Transformer Rectifier • Center Tap
Transformer • Power Distribution • Industrial Transformer • Replacement Transformer • Insulation Transformer • Micron
Transformers • Westinghouse Transformer • Power Supply Transformer • Instrument Transformer • Pulse Transformer
• Substation Transformer • Furnace Transformer • Pad Mounted Transformers • Transformer Manufacturer •
Distribution Transformers • GE Transformers • Step Up Transformers • Step Down Transformers • Buck Boost
Transformers • High Voltage Transformers • Isolation Transformer • Single Phase Transformer • Hammond
Transformers • Buck Boost Transformers • Diesel Generators • Diesel Power Generators • Diesel Generator Sets •
Power Generators • Onan Diesel Generators • Kipor Diesel Generator • Kubota Diesel Generator • Cummins Diesel
Generator • Yanmar Diesel Generator • Variable Frequency Drive • Soft Start Drives • Motor Control • Baldor Motors •
Weg Motors • Cold Ironing • Motor Generator