KOTSONS PVT. LTD.

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A

SEMINAR REPORT

ON

KOTSONS PVT. LTD.

K.P.L.

ALWAR, RAJASTHAN

THE UNIVERSITY OF RAJASTHAN IN PARTIAL FULFILLMENT FOR
THE AWARD OF DEGREE OF BACHELOR IN ENGG. IN
ELECTRICAL BRANCH OF THE UNIVERSITY OF RAJASTHAN,
JAIPUR

SESSION 2008-09

Submitted To: - Submitted By:-
Mr.Maal Singh Shekhawat Ghanshyam Meena
Seminar Incharge VIIth Sem (Electrical Engg)
Lect. Of Electrical Deptt. KITE-SOM, Jaipur
KITE-SOM, Jaipur

DEPARTMENT OF ELECTRICAL ENGINEERING
KUTILYA INSTITUTE OF TECHIOLOGY &
ENGINEERING

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DEPARTMENT OF ELECTRICAL ENGINEERING
KUTILYA INST. OF TECH. & ENGG.
SITAPURA, JAIPUR (RAJ.) 302022

SESSION 2008-2009

CIRTIFICATE
This is to certify that the seminar entitled “Kotsons Pvt. Ltd.” was
successfully presented by Mr. Ghanshyam Singh Meena of the B.E. Final
Year (VII semester) under my supervision for the partial fulfillment of B.E.

Date:

Mr. M. Sashilal Mr. Maal Singh Shekhawat
HOD, Electrical Engg. Seminer Incharge
KITE, Jaipur Lect. Of Electrical Deptt.
KITE, Jaipur

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AKNOWLEGMENT

First and the foremost, I would like to thank my respected parents,
who always encouraged me and tough me to think and work out innovatively
whatever be the field of life.
I wish to express my sincere thanks to the UNIVERSITY OF
RAJASTHAN which has taken an initiative in providing of practical
training to the B.E. student.
I feel a deep sense of gratitude to Mr. M. SASHILAL, Head of
Department of Electrical engineering of “KAUTILYA INSTITUTE OF
TECHNOLOGY & ENGINEERING”, Jaipur for all kind of help has been
granted. My heartily thanks to our training incharge Er. SANDEEP JAIN
for all kind of help.
I greatly thankful to Hr. Mr. Devendra Jain at K.P.L, Alwar for
granting me the permission for training and for describe the manufacture of
x-mer as possible as.
Last but not least, I am also thankful to all the staff member of KITE
and my friends.

GHANSHYAM MEENA
IV B.E (ELECTRICAL)

PREFACE

A rapid rise in the use of electricity is placing a very heavy
responsibility on electrical undertakings to maintain their electrical network

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in perfect condition, so young engineers is called upon to do design system
planning and construction and maintenance of electric system before he had
much experience and practice soon he may be responsible for specialize
operation in an ever expanding industry. Theoretical knowledge gained in
their college courses need to be supplemented with practical know-how to
face this professional challenge, so…....
As a part of our practical training we have to attempt the rule of
university of Rajasthan, Jaipur. I took my practical training at K.P.L. Alwar,
Rajasthan.
Since my training centre was of Manufacture of transformer hence I
have included all updated information, to the extent possible, including
general introduction and brief description of starting K.P.L. in this study
report.
During my 45 working days practical training, I had undertaken my
training at K.P.L. Alwar, Rajasthan.
The period of training was from 28/07/08 to 10/09/08.
This report dealt with the practical knowledge of general theory and
technical data/details of equipments, which I have gained during the training
period at K.P.L. Alwar, Rajasthan.

GHANSHYAM MEENA
IV B.E (ELECTRICAL)

ABOUT KOTSON:-
KPL (Kotsons Pvt. Ltd.) established its transformer manufacturing unit back in
1979 at Alwar, India to produce distribution & power transformers of 33 KV class voltage, to
meet the needs of public utilities organizations and of private industrial sector in India. It was
KPL vision of becoming integrated global transformer manufacturing company that the
company's manufacturing facilities were later expanded and second & third plant was setup at

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Agra (U.P) and Bazpur (Uttranchal), India and product range was expanded up to 25 MVA with
33 KV class, to cater the needs of international demands.
Today, with over more than two & half decades of experience in the manufacturing, KPL
has grown in geographical reach, market size and product range to become one of the leading
transformer manufacturing company Our product comprehensively fulfilled the requirements of
local and international standard specifications and their stringent requirement.

KPL is ISO 9001:2000 & ISO 14001:2004 certification from Det Norske Veritas, The
Netherlands and commits itself to introduce and maintain a quality system that ensures quality
products and services to total satisfaction of the customer. The quality control department
controls and monitor all quality control documents and carries out its inspection at all strategic
points in the production process. TQM (Total Quality Management) programme is in place,
which is backed by strong in house R & D and a crew of service engineers for providing after
sales services.
At transformer's quality & soundness point, KPL's transformer range from 100 KVA to
1000 KVA are being type tested for temperature rise test and impluse test at world's renowned
testing laboratory , The Netherlands.

At KPL, R & D is a continuous process and department has consistently produced innovative
concepts that have now become industry standards. A highly qualified and experienced technical
personnel keeps an eye upon the latest development in technology and the product to supply a
prime quality product at competitive price.

KPL has in house facilities for conducting all routine test as per IEC, DIN, BS, ANSI, NEMA &
IS and temperature rise type test.

KPL Infrastructure:

Plant Year Total Land Area(Sq.Mtrs.); Covered Land Area (Sq.Ft.)
AGRA 1991 8500 40,000
ALWAR 1979 I – 6000 & 50,000
II – 54000
Bazpur 2007 26000 1,50,000

Valuable Customers:
Overseas Customers Indian Customers

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• Central Electricity • Torrent Power
Board, Mauritius Limited.
• General • Schneider Electric
Establishment for Limited.
Electricity • ABB Limited.
Distribution in the • Reliance Energy
middle, Baghdad, Limited.
Iraq. • BSES.
• Rural • JVVNL.
Electrification • JdVVNL.
Board, Dhaka, • AVVNL.
Bangaladesh. • DVVNL.
• General Company • Areva T & D
for Baghdad Limited.
Electricity • L & T Ltd.
Distribution, Iraq • Siemens Ltd.
• NDTV Ltd.
• Schneider Electric
Limited. • CPRI.

Awards :
• Winner of highest prestigious export awards "Niryat Shree" for year 2000-01 from
Vice President of India.
• Received certificate in the Category of Export House-SSI for Excellent Export
Performance for the year 2001-02 from Vice President of India.
• Winner of Trophy for Highest Export in the Category of Capital Goods for the
year 2000-2001 from EEPC.
• Winner of UP State Export Award for the year 2001-02 from Chief Minister of
U.P.

In 2005, Win excellent award for Export.

KOTSON PVT. LTD., ALWAR

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Installation of kotson pvt. Ltd. , Alwar is situated in Matsya Industrial area (M.IA). MIA is
about 10km from alwar city. This is usual factory area under consideration of RIICO. Here
mainly distribution transformers are made.Transformers are made just of kva ratings.

Kotson private limited ,alwar is covered in 50,000 square feet area(including I & II). Here
transformers with following ratings are made:-
Transformers rating(kva) Connections(primary-secondary)
5 Delta-Star
10 Delta-Star
16 Delta-Star
25 Delta-Star
50 Delta-Star
100 Delta-Star
200 Delta-Star

300 Delta-Star
500 Delta-Star

Basic Principle of Transformer:-
The transformer is based on two principles: firstly, that an electric current can produce a
magnetic field (electromagnetism) and secondly that a changing magnetic field within a
coil of wire induces a voltage across the ends of the coil (electromagnetic induction). By

Page no.8
changing the current in the primary coil, it changes the strength of its magnetic field;
since the changing magnetic field extends into the secondary coil, a voltage is induced
across the secondary.

An ideal step-down transformer showing magnetic flux in the core

A simplified transformer design is shown to the left. A current passing through the
primary coil creates a magnetic field. The primary and secondary coils are wrapped
around a core of very high magnetic permeability, such as iron; this ensures that most of
the magnetic field lines produced by the primary current are within the iron and pass
through the secondary coil as well as the primary coil.

Induction law

The voltage induced across the secondary coil may be calculated from Faraday's law of
induction, which states that:

where VS is the instantaneous voltage, NS is the number of turns in the secondary coil and
Φ equals the magnetic flux through one turn of the coil. If the turns of the coil are
oriented perpendicular to the magnetic field lines, the flux is the product of the magnetic
field strength B and the area A through which it cuts. The area is constant, being equal to
the cross-sectional area of the transformer core, whereas the magnetic field varies with
time according to the excitation of the primary. Since the same magnetic flux passes
through both the primary and secondary coils in an ideal transformer,[1] the instantaneous
voltage across the primary winding equals

Taking the ratio of the two equations for VS and VP gives the basic equation[5] for stepping
up or stepping down the voltage

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Ideal power equation

The ideal transformer as a circuit element

If the secondary coil is attached to a load that allows current to flow, electrical power is
transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is
perfectly efficient; all the incoming energy is transformed from the primary circuit to the
magnetic field and into the secondary circuit. If this condition is met, the incoming
electric power must equal the outgoing power.

Pincoming = IPVP = Poutgoing = ISVS

giving the ideal transformer equation

If the voltage is increased (stepped up) (VS > VP), then the current is decreased (stepped
down) (IS < IP) by the same factor. Transformers are efficient so this formula is a
reasonable approximation.

The impedance in one circuit is transformed by the square of the turns ratio.[1] For
example, if an impedance ZS is attached across the terminals of the secondary coil, it

appears to the primary circuit to have an impedance of . This relationship is
reciprocal, so that the impedance ZP of the primary circuit appears to the secondary to be

.

Detailed operation

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The simplified description above neglects several practical factors, in particular the
primary current required to establish a magnetic field in the core, and the contribution to
the field due to current in the secondary circuit.

Models of an ideal transformer typically assume a core of negligible reluctance with two
windings of zero resistance.[6] When a voltage is applied to the primary winding, a small
current flows, driving flux around the magnetic circuit of the core.[6]. The current required
to create the flux is termed the magnetising current; since the ideal core has been assumed
to have near-zero reluctance, the magnetising current is negligible, although still required
to create the magnetic field.

The changing magnetic field induces an electromotive force (EMF) across each winding.
[7]
Since the ideal windings have no impedance, they have no associated voltage drop, and
so the voltages VP and VS measured at the terminals of the transformer, are equal to the
corresponding EMFs. The primary EMF, acting as it does in opposition to the primary
voltage, is sometimes termed the "back EMF".[8] This is due to Lenz's law which states
that the induction of EMF would always be such that it will oppose development of any
such change in magnetic field.

Transformer types:- Autotransformer
Main article: Autotransformer

An autotransformer with a sliding brush contact

An autotransformer has only a single winding with two end terminals, plus a third at an
intermediate tap point. The primary voltage is applied across two of the terminals, and the
secondary voltage taken from one of these and the third terminal. The primary and
secondary circuits therefore have a number of windings turns in common.[21] Since the
volts-per-turn is the same in both windings, each develops a voltage in proportion to its
number of turns. An adjustable autotransformer is made by exposing part of the winding
coils and making the secondary connection through a sliding brush, giving a variable
turns ratio. [22]

Polyphase transformers

For three-phase supplies, a bank of three individual single-phase transformers can be
used, or all three phases can be incorporated as a single three-phase transformer. In this
case, the magnetic circuits are connected together, the core thus containing a three-phase
flow of flux.[23] A number of winding configurations are possible, giving rise to different

Page no.11
attributes and phase shifts.[24] One particular polyphase configuration is the zigzag
transformer, used for grounding and in the suppression of harmonic currents.[25]

Leakage transformers

Leakage transformer

A leakage transformer, also called a stray-field transformer, has a significantly higher
leakage inductance than other transformers, sometimes increased by a magnetic bypass or
shunt in its core between primary and secondary, which is sometimes adjustable with a set
screw. This provides a transformer with an inherent current limitation due to the loose
coupling between its primary and the secondary windings. The output and input currents
are low enough to prevent thermal overload under all load conditions – even if the
secondary is shorted.

Leakage transformers are used for arc welding and high voltage discharge lamps (neon
lamps and cold cathode fluorescent lamps, which are series-connected up to 7.5 kV AC).
It acts then both as a voltage transformer and as a magnetic ballast.

Other applications are short-circuit-proof extra-low voltage transformers for toys or
doorbell installations.

Resonant transformers

A resonant transformer is a kind of the leakage transformer. It uses the leakage inductance
of its secondary windings in combination with external capacitors, to create one or more
resonant circuits. Resonant transformers such as the Tesla coil can generate very high
voltages, and are able to provide much higher current than electrostatic high-voltage
generation machines such as the Van de Graaff generator.[26] One of the application of the
resonant transformer is for the CCFL inverter. Another application of the resonant
transformer is to couple between stages of a superheterodyne receiver, where the
selectivity of the receiver is provided by tuned transformers in the intermediate-frequency
amplifiers.[27]

Instrument transformers

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Current transformers, designed to be looped around conductors

A current transformer is a measurement device designed to provide a current in its
secondary coil proportional to the current flowing in its primary. Current transformers are
commonly used in metering and protective relaying, where they facilitate the safe
measurement of large currents. The current transformer isolates measurement and control
circuitry from the high voltages typically present on the circuit being measured.[28]

Voltage transformers (VTs)--also referred to as potential transformers (PTs)--are used for
metering and protection in high-voltage circuits. They are designed to present negligible
load to the supply being measured and to have a precise voltage ratio to accurately step
down high voltages so that metering and protective relay equipment can be operated at a
lower potential.[29]

Classification

Transformers can be classified in different ways:

• By power level: from a fraction of a volt-ampere (VA) to over a thousand MVA;
• By frequency range: power-, audio-, or radio frequency;
• By voltage class: from a few volts to hundreds of kilovolts;
• By cooling type: air cooled, oil filled, fan cooled, or water cooled;
• By application function: such as power supply, impedance matching, output
voltage and current stabilizer, or circuit isolation;
• By end purpose: distribution, rectifier, arc furnace, amplifier output;
• By winding turns ratio: step-up, step-down, isolating (near equal ratio), variable.

Construction:-

Cores

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Laminated core transformer showing edge of laminations at top of unit.

Laminated steel cores

Transformers for use at power or audio frequencies typically have cores made of high
permeability silicon steel.[30] The steel has a permeability many times that of free space,
and the core thus serves to greatly reduce the magnetising current, and confine the flux to
a path which closely couples the windings.[31] Early transformer developers soon realised
that cores constructed from solid iron resulted in prohibitive eddy-current losses, and their
designs mitigated this effect with cores consisting of bundles of insulated iron wires.[32]
Later designs constructed the core by stacking layers of thin steel laminations, a principle
that has remained in use. Each lamination is insulated from its neighbors by a thin non-
conducting layer of insulation.[23] The universal transformer equation indicates a minimum
cross-sectional area for the core to avoid saturation.

The effect of laminations is to confine eddy currents to highly elliptical paths that enclose
little flux, and so reduce their magnitude. Thinner laminations reduce losses,[30] but are
more laborious and expensive to construct.[33] Thin laminations are generally used on high
frequency transformers, with some types of very thin steel laminations able to operate up
to 10 kHz.

Laminating the core greatly reduces eddy-current losses

One common design of laminated core is made from interleaved stacks of E-shaped steel
sheets capped with I-shaped pieces, leading to its name of "E-I transformer".[33] Such a
design tends to exhibit more losses, but is very economical to manufacture. The cut-core
or C-core type is made by winding a steel strip around a rectangular form and then
bonding the layers together. It is then cut in two, forming two C shapes, and the core

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assembled by binding the two C halves together with a steel strap.[33] They have the
advantage that the flux is always oriented parallel to the metal grains, reducing reluctance.

A steel core's remanence means that it retains a static magnetic field when power is
removed. When power is then reapplied, the residual field will cause a high inrush current
until the effect of the remanent magnetism is reduced, usually after a few cycles of the
applied alternating current.[34] Overcurrent protection devices such as fuses must be
selected to allow this harmless inrush to pass. On transformers connected to long,
overhead power transmission lines, induced currents due to geomagnetic disturbances
during solar storms can cause saturation of the core and operation of transformer
protection devices.[35]

Distribution transformers can achieve low no-load losses by using cores made with low-
loss high-permeability silicon steel or amorphous (non-crystalline) metal alloy. The
higher initial cost of the core material is offset over the life of the transformer by its lower
losses at light load.[36]

Solid cores

Powdered iron cores are used in circuits (such as switch-mode power supplies) that
operate above main frequencies and up to a few tens of kilohertz. These materials
combine high magnetic permeability with high bulk electrical resistivity. For frequencies
extending beyond the VHF band, cores made from non-conductive magnetic ceramic
materials called ferrites are common.[33] Some radio-frequency transformers also have
moveable cores (sometimes called 'slugs') which allow adjustment of the coupling
coefficient (and bandwidth) of tuned radio-frequency circuits.

Toroidal cores

Small transformer with toroidal core

Toroidal transformers are built around a ring-shaped core, which, depending on operating
frequency, is made from a long strip of silicon steel or permalloy wound into a coil,
powdered iron, or ferrite.[37] A strip construction ensures that the grain boundaries are
optimally aligned, improving the transformer's efficiency by reducing the core's
reluctance. The closed ring shape eliminates air gaps inherent in the construction of an E-I
core.[38] The cross-section of the ring is usually square or rectangular, but more expensive
cores with circular cross-sections are also available. The primary and secondary coils are
often wound concentrically to cover the entire surface of the core. This minimises the
length of wire needed, and also provides screening to minimize the core's magnetic field
from generating electromagnetic interference.

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Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar
power level. Other advantages compared to E-I types, include smaller size (about half),
lower weight (about half), less mechanical hum (making them superior in audio
amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making
them more efficient in standby circuits), single-bolt mounting, and greater choice of
shapes. The main disadvantages are higher cost and limited rating.

Ferrite toroidal cores are used at higher frequencies, typically between a few tens of
kilohertz to a megahertz, to reduce losses, physical size, and weight of switch-mode
power supplies. A drawback of toroidal transformer construction is the higher cost of
windings. As a consequence, toroidal transformers are uncommon above ratings of a few
kVA. Small distribution transformers may achieve some of the benefits of a toroidal core
by splitting it and forcing it open, then inserting a bobbin containing primary and
secondary windings.

Air cores

A physical core is not an absolute requisite and a functioning transformer can be produced
simply by placing the windings in close proximity to each other, an arrangement termed
an "air-core" transformer. The air which comprises the magnetic circuit is essentially
lossless, and so an air-core transformer eliminates loss due to hysteresis in the core
material.[8] The leakage inductance is inevitably high, resulting in very poor regulation,
and so such designs are unsuitable for use in power distribution.[8] They have however
very high bandwidth, and are frequently employed in radio-frequency applications,[39] for
which a satisfactory coupling coefficient is maintained by carefully overlapping the
primary and secondary windings.

Windings:-

Windings are usually arranged concentrically to minimise flux leakage

Page no.16

Cut view through transformer windings. White: insulator. Green spiral: Grain oriented
silicon steel. Black: Primary winding made of oxygen-free copper. Red: Secondary
winding. Top left: Toroidal transformer. Right: C-core, but E-core would be similar. The
black windings are made of film. Top: Equally low capacitance between all ends of both
windings. Since most cores are at least moderately conductive they also need insulation.
Bottom: Lowest capacitance for one end of the secondary winding needed for low-power
high-voltage transformers. Bottom left: Reduction of leakage inductance would lead to
increase of capacitance.

The conducting material used for the windings depends upon the application, but in all
cases the individual turns must be electrically insulated from each other to ensure that the
current travels throughout every turn.[11] For small power and signal transformers, in
which currents are low and the potential difference between adjacent turns is small, the
coils are often wound from enamelled magnet wire, such as Formvar wire. Larger power
transformers operating at high voltages may be wound with copper rectangular strip
conductors insulated by oil-impregnated paper and blocks of pressboard.[40]

High-frequency transformers operating in the tens to hundreds of kilohertz often have
windings made of braided litz wire to minimize the skin-effect and proximity effect
losses.[11] Large power transformers use multiple-stranded conductors as well, since even
at low power frequencies non-uniform distribution of current would otherwise exist in
high-current windings.[40] Each strand is individually insulated, and the strands are
arranged so that at certain points in the winding, or throughout the whole winding, each
portion occupies different relative positions in the complete conductor. The transposition
equalizes the current flowing in each strand of the conductor, and reduces eddy current
losses in the winding itself. The stranded conductor is also more flexible than a solid
conductor of similar size, aiding manufacture.[40]

For signal transformers, the windings may be arranged in a way to minimise leakage
inductance and stray capacitance to improve high-frequency response. This can be done
by splitting up each coil into sections, and those sections placed in layers between the
sections of the other winding. This is known as a stacked type or interleaved winding.

Both the primary and secondary windings on power transformers may have external
connections, called taps, to intermediate points on the winding to allow selection of the
voltage ratio. The taps may be connected to an automatic on-load tap changer for voltage
regulation of distribution circuits. Audio-frequency transformers, used for the distribution

Page no.17
of audio to public address loudspeakers, have taps to allow adjustment of impedance to
each speaker. A center-tapped transformer is often used in the output stage of an audio
power amplifier in a push-pull circuit. Modulation transformers in AM transmitters are
very similar.

Certain transformers have the windings protected by epoxy resin. By impregnating the
transformer with epoxy under a vacuum, one can replace air spaces within the windings
with epoxy, thus sealing the windings and helping to prevent the possible formation of
corona and absorption of dirt or water. This produces transformers more suited to damp or
dirty environments, but at increased manufacturing cost.[41]

Three-phase oil-cooled transformer with cover cut away. The oil reservoir is visible at the
top. Radiative fins aid the dissipation of heat.

Coolant:-

High temperatures will damage the winding insulation. [42] Small transformers do not
generate significant heat and are self-cooled by air circulation and radiation of heat.
Power transformers rated up to several hundred kVA can be adequately cooled by natural
convective air-cooling, sometimes assisted by fans.[43] In larger transformers, part of the
design problem is removal of heat. Some power transformers are immersed in transformer
oil that both cools and insulates the windings.[44] The oil is a highly refined mineral oil
that remains stable at high temperatures. Liquid-filled transformers to be used indoors
must use a non-flammable liquid, or must be located in fire-resistant rooms.[2]

The oil-filled tank often has radiators through which the oil circulates by natural
convection; some large transformers employ forced circulation of the oil by electric
pumps, aided by external fans or water-cooled heat exchangers.[44] Oil-filled transformers
undergo prolonged drying processes to ensure that the transformer is completely free of
water vapor before the cooling oil is introduced. This helps prevent electrical breakdown

Page no.18
under load. Oil-filled transformers may be equipped with Buchholz relays, which detect
gas evolved during internal arcing and rapidly de-energize the transformer to avert
catastrophic failure.[34]

Polychlorinated biphenyls have properties that once favored their use as a coolant, though
concerns over their toxicity and environmental persistence led to a widespread ban on
their use.[45] Today, non-toxic, 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.[42][2] Before 1977, even transformers that were nominally filled only
with mineral oils commonly also contained polychlorinated biphenyls as contaminants at
10-20 ppm. Since mineral oil and PCB fluid mix, maintenance equipment used for both
PCB and oil-filled transformers could carry over small amounts of PCB, contaminating
oil-filled transformers. [46]

Some "dry" transformers (containing no liquid) are enclosed in sealed, pressurized tanks
and cooled by nitrogen or sulfur hexafluoride gas.[42].

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.[47]

Terminals:-

Very small transformers will have wire leads connected directly to the ends of the coils,
and brought out to the base of the unit for circuit connections. Larger transformers may
have heavy bolted terminals, bus bars or high-voltage insulated bushings made of
polymers or porcelain. A large bushing can be a complex structure since it must provide
careful control of the electric field gradient without letting the transformer leak oil.[48]

History:-
The transformer principle was demonstrated in 1831 by Michael Faraday, although he
used it only to demonstrate the principle of electromagnetic induction and did not foresee
its practical uses. The first widely used transformer was the induction coil, invented by
Irish clergyman Nicholas Callan in 1836.[49] He was one of the first to understand the
principle that the more turns a transformer winding has, the larger EMF it produces.
Induction coils evolved from scientists efforts to get higher voltages from batteries. They
were powered not by AC, but DC from batteries which was interrupted by a vibrating
'breaker' mechanism. Between the 1830s and the 1870s efforts to build better induction
coils, mostly by trial and error, slowly revealed the basic principles of transformer
operation. Efficient designs would not appear until the 1880s,[50] but within less than a
decade, the transformer was instrumental during the "War of Currents" in seeing
alternating current systems triumph over their direct current counterparts, a position in
which they have remained dominant.[50]

Russian engineer Pavel Yablochkov in 1876 invented a lighting system based on a set of
induction coils, where primary windings were connected to a source of alternating current

Page no.19
and secondary windings could be connected to several "electric candles". The patent
claimed the system could "provide separate supply to several lighting fixtures with
different luminous intensities from a single source of electric power". Evidently, the
induction coil in this system operated as a transformer.

A historical Stanley transformer.

Lucien Gaulard and John Dixon Gibbs, who first exhibited a device with an open iron
core called a 'secondary generator' in London in 1882 and then sold the idea to American
company Westinghouse.[32] They also exhibited the invention in Turin in 1884, where it
was adopted for an electric lighting system.

Hungarian engineers Zipernowsky, Bláthy and Déri from the Ganz company in Budapest
created the efficient "ZBD" closed-core model in 1885 based on the design by Gaulard
and Gibbs.[51] Their patent application made the first use of the word "transformer".[32]
Russian engineer Mikhail Dolivo-Dobrovolsky developed the first three-phase
transformer in 1889. In 1891 Nikola Tesla invented the Tesla coil, an air-cored, dual-
tuned resonant transformer for generating very high voltages at high frequency. Audio
frequency transformers (at the time called repeating coils) were used by the earliest
experimenters in the development of the telephone.

While new technologies have made transformers in some electronics applications
obsolete, transformers are still found in many electronic devices. Transformers are
essential for high voltage power transmission, which makes long distance transmission
economically practical.

Single phase transformers:-
single phase transformers are mainly used where load is very small , generally in rural
areas.Company makes two types of single hase transformers:-

1.CRGO CORE TRANSFORMERS

2.AMORPHOUS METALL TRANSFORMERS

Page no.20

SINGLE PHASE TRANSFORMER

CRGO Core Transformers

Applicable standards

IEC (International Electro technical Commission)
ANSI (American National Standard Institution)
BS (British Standards) .
IS (Indian Standard)

Specification :

Kotsons make conventional type, 1 Phase, 50 Hz, Oil immersed,
naturally cooled, Pole mounted / Platform mounted, double wound
with Aluminium / Copper, Step up/Step down core type
continuous duty transformers having no load voltage ratio from 5
KVA to 167 KVA upto 33 KV Class with ‘A’ Class Insulation and
designed to withstand Short Circuit, & Impulse Test in accordance
to ANSI / IEC / BS / IS.

Completely self Protected type Transformers are also available for
protection on both HV & LV Side.

Details of Characteristics & dimensions of Kotsons standard
transformers with standard fittings manufactured in accordance
with ANSI C 57 latest., readily available in stock and can be delivered within 1 weeks
from the date of order confirmation.

The temperature rise will be 60/65° C in Oil/Winding respectively over a maximum
ambienttemperature as per ANSI. The transformers will be manufactured as per ANSI C
57 latest, complete with fittings/accessories as stated below.

KVA Efficiency Voltage W D H Oil Weight
(%) Regulation (mm) (mm) (mm) (l) (kg)
(%)
5 97.60 2.05 400 520 770 12 69
10 98.00 1.79 450 570 800 17 97
15 98.23 1.56 480 600 850 23 120
25 98.25 1.58 530 620 1030 65 205
37.5 98.58 1.26 650 650 900 38 244
50 98.29 1.60 670 650 950 45 253

Page no.21

75 98.53 1.30 740 720 950 62 340
100 98.72 1.18 795 750 1000 78 440
167 98.92 1.15 850 825 1065 116 675

Note :

Due to improvements continuously taking place in design, the details given may vary
marginally in respect of No Load Losses, Load Losses and overall dimensions. However
the variations will be within permissible limits as per Applicable Standards.

The details given here are for kotsons standard transformer with standard fittings. The
details may depend upon the optional fittings/specific requirement of customer. For
details, Please contact our Marketing Office or fill our enquiry/feedback form.

Fitting & accessories provided with standard Transformer are as under.
S.No Accessories 5 to 25 KVA 26 to 167 KVA
1 Support Lug
2 Name Plate
3 Grounding Terminal
4 Hand Hole
5 Bird Guard
6 H.V Bushing with fittings
7 Pressure Release Valve
8 Lifting Lug
9 L.V Bushings with fittings
10 Grounding Pad
11 Radiator X X
12 Capacity Mark

Optional fittings can be provided on extra cost as per customer requirements.

Optional Fittings
1 Arrestor O O
2 Protective Fuse O O

Page no.22

3 Breaker O O
4 Extra Bushing O O
5 External Tap changer O O

SINGLE PHASE TRANSFORMER
Amorphous metal Transformers

“Kotsons” Amorphous metal transformers are manufactured in
technical collaboration with Hitachi Met glass Inc., the only
Producer of Amorphous Metal in the World. Kotsons has set up
state of the art amorphous metal transformer manufacturing
facility by importing the latest amorphous metal cores
manufacturing equipment from M/S Bergers Machinenbau
GMBH, Germany.

This plant has the latest equipment in India to produce energy
efficient amorphous metal transformers. Quality of process is
given overriding importance to the quantity. Cores are annealed
under absolute inert atmosphere to get at most lower losses
thereby enhancing the energy savings in comparison with the
similar manufacturing facilities in this line in the world.

Advantages :

• Energy Efficient
• AMDT can reduce No Load losses by 80 % Since No load losses represent a
major portion of the energy lost during Power distribution Hence reduce cost
investment for power generation & translate into reduction in carbon di-oxide
emissions created during power generation.
• Lower Temperature
• Slower ageing of insulation
• Higher overloading capability
• Longer Life
• Superior electrical performance under harmonics conditions

Description : In order to achieve significant improvement in efficiency, amorphous metal
is used to make transformer core. Amorphous metal exhibits a unique random molecular
structure unlike rigid grain structure of silicon steel, which enables easy magnetization &
demagnetization, thereby reducing hysteresis loss. Further processing of amorphous metal
in very thin lamination (appropriate 1/10th of silicon steel lamination thickness) enable
significant reduction in eddy current losses.

The Advantages of AMDT is not limited to reduction in losses alone. Since these losses

Page no.23
are converted in to heat energy , cooling oil inside the transformer tank will be heated up
and it will lead to emissions and significant fuel savings. AMDTs helps utilities reduce
harmful emissions such as sulphur dioxide, Nitrogen Oxides and Carbon dioxide, the
pollutants that cause acid rain & global warming.

Comparisons among typical silicon steel distribution transformer, high efficiency silicon
steel distribution transformer & amorphous metal distribution transformer (AMDT) is
given under:

Hi-efficiency
Typical Silicon
Rating (KVA) Silicon Amorphous Metal
Steel
Steel
Single Phase
10 40 30 10
15 60 45 15
Three Phase
25 100 80 25
63 180 150 45
100 260 195 60

Specification :

Kotsons make Amorphous Metal Single Phase transformers 50 Hz or 60 Hz with primary
Voltage up to 33 KV class & Secondary voltage up to 250 Volts, 120/240 Volts or as
required, Oil immersed, naturally cooled, Pole mounted , double wound with Aluminium /
Copper, Step up/Step down core type continuous duty transformers having no load
voltage ratio from 5 KVA to 167 KVA up to 33 KV Class with ‘A’ Class Insulation and
designed to withstand Short Circuit, & Impulse Test in accordance to ANSI / IEC / AS /
IS.

Details of Characteristics & dimensions of Kotsons standard transformers with standard
fittings manufactured in accordance with ANSI C 57 latest readily available in stock and
can be delivered within 1 weeks from the date of order confirmation.

Note :


The details given here are for Kotsons standard transformer with standard fittings. The


Page no.24

Sl.No Accessories 5 to 167 KVA
1 Terminal Connector
2 Primary bushings
3 Secondary bushings
4 Pressure relief device
5 Mounting lugs/brackets
6 Lifting lugs
7 Rating & Diagram plate
8 Grounding/earthing terminal

Optional fittings can be provided on extra cost as per customer requirements.

THREE PHASE TRANSFORMER(3 PHASE ISOLATION
TRANSFORMER)
Page no.25
A 3 phase transformer, there is a three-legged iron core as shown below. Each leg
has a respective primary and secondary winding. Thus a 3 phase isolation
transformers is a 3 phase transformer which has isolated primary and secondary
windings to allow the power input to be isolated from the power output.

There a number of power transformer manufacturers of quality 3 phase isolation transformers
today. The primary 3 phase isolation transformers manufacturers are: GE Industrial,
TEMCo Isolation Transformer, Marcus Transformer, Hammond Transformers, and Acme Transformers
with capacity ranges 0.05 KVA through 5000 KVA. The isolation transformer
manufacturer TEMCo also acts as a one stop wholesale outlet for the other
transformer brands.

Standard 3 Phase Isolation Transformers

3 phase isolation transformers have 3 primary and 3 secondary windings that are
physically separated from each other. Sometimes these isolation transformers are
referred to as "insulated". This is because the windings are insulated from each
other.

In a 3 phase isolation transformer the output windings will be isolated, or floating
from earth ground unless bonded at the time of installation.

3 Phase Shielded Isolation Transformers

Shielded 3 phase isolation transformers have all the feature of the standard 3
phase isolation transformers plus they also incorporate a full metallic shield (usually
copper or aluminum) between the 3 phase primary and 3 phase secondary windings.
This electrostatic shield ("Faraday Shield") is connected to earth ground and
performs two functions:

One, it attenuates (filters) voltage transients (voltage spikes). These shielded 3
phase isolation transformers have an attenuation ratio of 100 to 1.

Two, It also filters common mode noise. Attenuation of approximately 30 decibels.

3 Phase Power Is More Efficient Than Single Phase

Three phase electricity powers large industrial loads more efficiently than single-
phase electricity. When single-phase electricity is needed, It is available between any
two phases of a three-phase system, or in some systems , between one of the
phases and ground. By the use of three conductors a 3 phase system can provide
173% more power than the two conductors of a single-phase system. Three-phase
power allows heavy duty industrial equipment to operate more smoothly and
efficiently. 3 phase power can be transmitted over long distances with smaller
conductor size.

(Also read about 3 phase isolation transformers here.)

In a three-phase transformer, there is a three-legged iron core as shown below.
Each leg has a respective primary and secondary winding.

The three primary windings (P1, P2, P3) will be connected at the factory to provide

Page no.26
Description

Kotsons manufactures a wide range of distribution and power transformers ranging from
25 KVA to 20 MVA with voltage class of 33 KV. These transformers can be free
breathing or hermetically sealed. Conventional
transformers are fitted with a conservator with breather for
free breathing while hermetically sealed are without
breathing with bolted cover. Hermetically sealed
transformers are totally maintenance free and are
particularly suited for use in exposed outdoor environments
such as moisture, salt or dust laden atmospheres. They are
used extensively in chemical plants, oil and gas terminals
where poor accessibility makes regular maintenance
undesirable. Transformers immersed in synthetic coolants
are suitable for use indoors, with adequate ventilation, or
near to the load centre where oil would not be considered
environmentally acceptable.

The liquid filled transformers can be supplied with cooling
either by corrugations on the side of the tank or Pressed steel
radiators mounted on tank body. Transformers can be filled with
either oil or one of several low flammability synthetic fluids
such as midel. Both types can be supplied with HV and LV
Switchgear incorporated into substations.

Kotsons can supply conventional/hermetically sealed/bolted
type, indoor/outdoor type, pole/platform mounted 3 phase,
50/60 Hz, oil immersed, ONAN/ONAF/ OFWF cooled, step up/
step down, double wound with Al/Cu conductor, Continuous
duty transformers from 5 KVA to 20 MVA upto 33 KV Class
with ‘A’ Class Insulation and designed to withstand Short
Circuit, & Impulse Test in accordance to IEC / BS / ANSI / IS / NEEMA.

KOTSONS STANDARD TRANSFORMERS

In order to meet the growing demand of transformers with short
deliveries, Kotsons have developed a separate production
system called KST (Kotsons Standard Transformers). This
range of KST are manufactured with standard losses and in
accordance to IS : 2026 latest. Kotsons can supply a
comprehensive range as depicted below in short delivery
periods.

The second of our production system known as Kotsons Repeat
transformer enables us to reproduce any of our previous transformer designs again in the
shortest time with the object of keeping delivery time to a minimum.

fittings manufactured in accordance with IS : 2026 latest., and can be delivered in short

Page no.27
delivery period upon order confirmation.

Specification for KST (Kotsons Standard Transformer)

Kotsons make outdoor type, 3 phase, 50 Hz, oil immersed,
conventional bolted cover, ONAN cooled, Pole / Platform
mounted, double wound with Cu conductor, step up, core type
continuous duty transformers with + 2.5% to - 7.5% taps on HT
side for HT variation and leads to be brought out on off circuit
tap changing switch with locking device and outside indicator
arrangement and connected in delta/star as per Vector group ref.
Dyn11.

The temperature rise will be 50/55° C in Oil/Winding
respectively over a maximum ambient temperature as per IS.
The transformers will be manufactured as per IS: 2026 latest,
complete with fittings/accessories as stated below.

ONAN Cooled, Outdoor type, Oil immersed
Rated Primary Voltage : 11KV
Copper Wound, Open Type with
Secondary Voltage : 416/240V
Conservator
Efficiency at Noise Outline
100% load (%) Voltage Level Dimension Total
Capacity Oil qty
Regulation db Approx. (mm) weight
kVA (Litres)
P.F.=1 P.F.=0.8 P.F.=1 (%) (A) : (Kgs.)
1m H L W

50 97.48 96.85 2.26 45 1300 1080 520 115 420
100 97.71 97.14 2.06 46 1400 1230 550 150 600
160 98.19 97.73 1.63 47 1480 1290 630 210 825
200 98.30 97.88 1.52 47 1580 1340 675 260 990
250 98.32 97.90 1.51 48 1655 1385 750 320 1200
315 98.33 97.92 1.50 50 1735 1385 830 360 1400
400 98.44 98.05 1.42 50 1800 1410 950 370 1600
500 98.50 98.13 1.37 52 1850 1520 1000 450 1920
630 98.62 98.27 1.31 52 1920 1620 1030 530 2230
800 98.56 98.20 1.37 54 2000 1830 1030 675 2700
1000 98.63 98.29 1.32 54 2100 2040 1040 780 3160
1250 98.72 98.40 1.29 56 2140 2070 1210 840 3400
1500 98.78 98.48 1.24 56 2240 2150 1240 970 3900
2000 98.81 98.51 1.22 52/3cm 2350 2230 1390 1080 4625

Page no.28

2500 98.88 98.60 1.18 52/3cm 2480 2300 1420 1375 5700
3000 98.92 98.65 1.14 52/3cm 2570 2380 1450 1530 6330

Conservator
Capacity Oil qty
kVA (Litres)
P.F.=1 P.F.=0.8 P.F.=1 (%) (A) : (Kgs.)
1m H L W

50 97.48 96.85 2.26 45 1300 1100 520 120 420
100 97.71 97.14 2.06 46 1410 1230 565 170 640
160 98.19 97.73 1.63 47 1500 1290 640 215 820
200 98.30 97.88 1.52 47 1620 1345 680 280 1025
250 98.32 97.90 1.51 48 1670 1390 760 335 1240
315 98.33 97.92 1.50 50 1735 1390 840 375 1475
400 98.44 98.05 1.42 50 1800 1420 960 415 1630
500 98.50 98.13 1.37 52 1850 1535 1015 495 2050
630 98.62 98.27 1.31 52 1920 1655 1045 580 2410
800 98.56 98.20 1.37 54 2000 1845 1050 715 2925
1000 98.63 98.29 1.32 54 2100 2050 1060 825 3460
1250 98.72 98.40 1.29 56 2140 2090 1230 930 3710
1500 98.78 98.48 1.24 56 2240 2165 1255 1050 4300
2000 98.81 98.51 1.22 52/3cm 2350 2245 1410 1215 5000
2500 98.88 98.60 1.18 52/3cm 2480 2340 1435 1460 6020
3000 98.92 98.65 1.14 52/3cm 2570 2400 1465 1620 6650

Conservator
Capacity Oil qty
kVA (Litres)
P.F.=1 P.F.=0.8 P.F.=1 (%) (A) : (Kgs.)
1m H L W

Page no.29

100 97.70 97.13 2.06 46 1420 1230 575 185 655
160 98.16 97.70 1.63 47 1520 1290 650 235 835
200 98.29 97.86 1.52 47 1580 1350 690 305 1070
250 98.30 97.88 1.51 48 1655 1390 770 360 1310
315 98.35 97.94 1.50 50 1735 1400 850 390 1535
400 98.50 98.13 1.42 50 1800 1430 980 435 1735
500 98.49 98.11 1.37 52 1850 1550 1030 520 2135
630 98.67 98.33 1.31 52 1920 1670 1060 610 2470
800 98.56 98.20 1.37 54 2000 1860 1070 740 2980
1000 98.63 98.29 1.32 54 2100 2060 1080 850 3580
1250 98.68 98.35 1.29 56 2140 2100 1250 985 3830
1500 98.78 98.48 1.24 56 2240 2180 1270 1080 4525
2000 98.79 98.48 1.22 52/3cm 2350 2260 1420 1235 5200
2500 98.84 98.55 1.18 52/3cm 2480 2380 1450 1565 6300
3000 98.92 98.65 1.14 52/3cm 2570 2420 1480 1690 6860

ONAN Cooled, Outdoor type, Oil
immersed Copper Wound, Open Type with
Secondary Voltage : 11KV
Conservator
100% load (%)Voltage Level Dimension Total
Capacity Oil qty
kVA (Litres)
P.F.=1 P.F.=0.8 P.F.=1 (%) (A) : (Kgs.)
1m H L W

3150 99.02 98.75 1.04 54/3m 3000 2800 2900 2000 8450
5000 99.39 99.02 0.79 56/3m 3200 2500 3150 2400 11300
6300 99.51 99.14 0.68 56/3m 3300 3000 3250 3200 15000
8000 99.62 99.21 0.67 58/3m 3430 3300 3350 4100 18000
10,000 99.68 99.32 0.59 58/3m 3600 3400 3800 5800 21000

Note :

• The dimensions and weights shown above apply to a typical range of KST
(Kotsons standard transformers) design to the specification IS : 2026. As all
transformers are usually design and built to customers specification their exact
dimensions and weights can vary.

Page no.30
• Due to improvements continuously taking place in design, the details given here
may vary marginally irrespective of Length, Width, Height, Oil and Total Weight .
However the variations will be within permissible tolerance limits as per IS 2026
latest .

Standard Accessories

Oil Level Gauge, Pressure Release Device, Shut off valve, Off Load Tap Changer
Handle, Breather, Name Plate, Sampling Valve, Drain Valve, Roller, Lifting Eye Oil
Filling hole with Cap, H.V. Porceline Bushing, L.V. Porceline Bushing, Hand Hole,
Lifting Lug, Filter Valve, Radiator/Corrugations, Conservator Drain Valve, Earthing
Terminal, Pulling Eye, Jacking Pad.

Optional Accessories

Buchholz Relay, On load Tap Changer, RTCC, AVR, Marshalling Box, Oil Temperature
Indicator, Winding Temperature Indicator, Skid base.

THREE PHASE TRANSFORMER

Amorphous steel transformer

Introduction

“Kotsons” Amorphous metal transformers are manufactured in technical collaboration
with Hitachi Met glass Inc., the only Producer of Amorphous Metal in the World.
Kotsons has set up state of the art amorphous metal transformer manufacturing facility by
importing the latest amorphous metal cores manufacturing equipment from M/S Bergers
Machinenbau GMBH, Germany.

This plant has the latest equipment in India to produce energy efficient amorphous metal
transformers. Quality of process is given overriding importance to the quantity. Cores are
annealed under absolute inert atmosphere to get at most lower losses thereby enhancing
the energy savings in comparison with the similar manufacturing facilities in this line in
the world.

Advantages:

• Energy Efficient
• AMDT can reduce No Load losses by 80 % Since No load losses represent a
major portion of the energy lost during Power distribution Hence reduce cost
investment for power generation & translate into reduction in carbon di-oxide
emissions created during power generation.
• Lower Temperature
• Slower ageing of insulation
• Higher overloading capability
• Longer Life
• Superior electrical performance under harmonics conditions

Page no.31
Description

In order to achieve significant improvement in efficiency, amorphous metal is used to
make transformer core. Amorphous metal exhibits a unique random molecular structure
unlike rigid grain structure of silicon steel, which enables easy magnetization &
demagnetization, thereby reducing hysteresis loss. Further processing of amorphous metal
in very thin lamination (appropriate 1/10th of silicon steel lamination thickness) enable
significant reduction in eddy current losses.

The Advantages of AMDT is not limited to reduction in losses alone. Since these losses
are converted in to heat energy , cooling oil inside the transformer tank will be heated up
and it will lead to emissions and significant fuel savings. AMDTs helps utilities reduce
harmful emissions such as sulphur dioxide, Nitrogen Oxides and Carbon dioxide, the
pollutants that cause acid rain & global warming.

Comparisons among typical silicon steel distribution transformer, high efficiency silicon
steel distribution transformer & amorphous metal distribution transformer (AMDT) is
given under:

Typical Silicon
Rating (KVA) Hi-efficiency Silicon Steel Amorphous Metal
Steel
Single Phase
10 40 30 10
15 60 45 15
Three Phase
25 100 80 25
63 180 150 45
100 260 195 60

Specification :

Kotsons make Amorphous Metal Three Phase transformers 50 Hz or 60 Hz with primary
Voltage up to 33 KV class & Secondary voltage up to 480 Volts or 480 Volts or as
required, Oil immersed, naturally cooled, Pole or platform mounted , double wound with
Aluminium / Copper, Step up/Step down core type continuous duty transformers having
no load voltage ratio from 15 KVA to 1000 KVA up to 33 KV Class with ‘A’ Class
Insulation and designed to withstand Short Circuit, & Impulse Test in accordance to
ANSI / IEC / AS / IS.

fittings manufactured in accordance with ANSI C 57 latest readily available in stock and
can be delivered within 1 weeks from the date of order confirmation.

Note:

Page no.32

The details given here are for Kotsons standard transformer with standard fittings. The


Sl.No Accessories 5 to 167 KVA
1 Terminal Connector
2 Primary bushings
3 Secondary bushings
4 Oil Level Indicator/gauge
5 Pressure relief device/vent
6 Lifting lugs
7 Rating & Diagram plate
8 Dehydrating Silica gel breather
9 Drain Valve/Drain pipe
10 Filling plug

Optional fittings can be provided on extra cost as per customer requirements. :

Optional Fittings
1 Thermometer O
2 HT Fuse O
3 LT Circuit Breaker O
4 Lightning Arresters O
5 Filter Valve O
6 Conservator O

VENTILATED DRY TYPE THREE PHASE TRANSFORMER:-

Applicable Standards

Page no.33
• IEC (International Electro technical Commission)
• IS (Indian Standard)

Introduction

Kotsons Pvt. Ltd. in collaboration with E. I. DuPont, U.S.A. has developed Ventilated
Dry Type transformers in India with a DuPont ReliatraN® branded solution.

ReliatraN® Brand Transformers are manufactured with UL® Certified Insulation
Materials and Systems, by a network of ISO 9000 Certified Manufacturers worldwide,
meeting the highest of International Standards for Quality, Design, Construction and
Performance.

Kotsons Pvt. Ltd. is the first and only Operating Licensed Manufacturer of DuPont's
ReliatraN® Brand Transformers in India.

Description

Kotsons manufactures Ventilated Dry Type transformer ranging
from 40 KVA to 5000 KVA with voltage class of 33 KV. These
transformers are fitted in Enclosure confirming to IP 21 to IP 33
for Indoor location and IP 45 for out door location. Kotsons
Ventilated Dry Type Transformer are totally maintenance free
and safe from fire as material used are metals, ceramics, fiberglass and resin. It is
environment friendly as there is no oil, hence handling becomes easier and there are no
chances of spillages and leakages and there is minimal non toxic
smoke in case of fire.

Kotsons offers Ventilated Dry Type Transformers with Class H / C
insulation which can bear heat upto 180 / 220 Deg C and can be
used in humid and chemically polluted atmosphere.

Kotsons can supply Indoor/Outdoor, 3 phase, 50/60 Hz, Resin
Impregnated, AN/FA cooled, step up/step down, double wound with
Cu conductor transformer from 40 KVA to 5000 KVA upto 33 KV
Class with H / C Class Insulation and designed to withstand Short Circuit, & Impulse Test
in accordance to IEC / IS.

Process & Core :

Core structure is of nonaging, Cold Rolled Grain
Oriented, high permeability silicon steel. All core
laminations are free of burr and staked without
gaps The core assembly is painted with a
protective paint to protect against corrosion.

Winding :

Page no.34
LV & HV Windings are done in dust free air conditioned winding shops. Rectangular
copper strips are used for LV winding insulated with Nomex® while HV winding are of
copper wire insulated with Nomex® or suitable material for temperature rise if wrapping
is not possible due to small diameter.

VPI:

The Transformer coils are thoroughly dried in an PLC controlled oven and the coils are
then completely sealed with an insulating Varnish / Resin (Class H/C) through an vacuum
pressure impregnation process. Kotsons is having a state of art PLC controlled VPI
(Vacuum Pressure Impregnation) Plant. The VPI process fully penetrates and seals the
coils into a high strength composite unit for complete environment protection, hence can
be used in humid and chemically polluted atmosphere. Coils are then cured to develop
bonding.

Testing :

After the Core- Coil assembly. All transformers are tested for routine test. Kotsons has in
house facilities for conducting all routine tests as per IEC & IS. Kotsons is equipped with
adequate digital readout measuring devices wherever required and the digital sampling
techniques with computer calculations. Precision digital meters such as digital power
analyser, WT -130 of Yokogawa make are used for measuring of load losses, Impedance
Voltage, No load losses, and no load currents. KPL is having in house Partial Discharge
(PD) testing facility.

Warranty :

KPL VDT Transformer are guaranteed for satisfactorily
performance for a period of 5 years* from the date of
dispatch. Any part found defective during this period, as a
consequence of bad design, manufacturing or
workmanship should be repaired, free of cost, by us
within mutually agreed schedule.

* Warrantee for 5 Years on active part only.

Environmental Impact Operational Aspects

• Transformers insulated with NOMEX® brand
materials are extremely safe, even when exposed to fire.

• High flame resistance, and low smoke and no toxic off-gasses.

• Class H & C ventilated dry type transformers can be built smaller, reducing the
footprint to the environment, conserving space.

• Insulation is friendly to use during manufacturing - no skin irritants or surface
chemicals.

End-of-Life Aspects

Page no.35
• NOMEX® insulation can be easily disposed of by incineration or burial, since it is
inert to the environment.

• NOMEX® insulated VDT transformers have low volumes of insulation,
eliminating the burden of disposal of large amounts of resin.

Quality :

KOTSONS PVT. LTD., is certified for ISO 9001:2000 by DET NORSKE VERITAS,
B.V., NETHERLANDS. Kotsons has set up a complete quality management system to
offer the best customer satisfaction. Each and every Ventilated Dry Type Transformer is
identified with ReliatraN ® identification labels.

Specification for KST (Kotsons Standard Transformer)

Kotsons makes Indoor/Outdoor, 3 phase, 50/60 Hz, Resin Impregnated, AN/FA cooled,
step up/step down, double wound with Cu conductor transformer from 40 KVA to 5000
KVA upto 33 KV Class with H / C Class Insulation and designed to withstand Short
Circuit, & Impulse Test in accordance to IEC / IS.

Rating No Outline
Load Total
Load Total Impedance Dimension (mm)
Sl.No. Loss Weight
KVA KV Loss Loss(Watts) (%)
(Watts) L W H (Kg)
(Watts)
1 630 11/0.433 1725 6920 8645 5 1850 1200 1750 2520
2 800 11/0.433 1920 7880 9800 5 1900 1200 1850 2855
3 1000 11/0.433 2235 10145 12380 5 1950 1250 1950 3125
4 1250 11/0.433 2630 12600 15230 5 1950 1250 2100 3520
5 1600 11/0.433 3010 14765 17775 6.25 2050 1350 2250 4230
6 2000 11/0.433 3540 18375 21915 6.25 2150 1450 2450 4940
7 2500 11/0.433 4305 21260 25565 6.25 2250 1550 2550 5855
Note :

• The dimensions and weights shown above apply to a typical range of KST
(Kotsons standard transformers) design to the specification IS : 2026. As all
transformers are usually design and built to customers specification their exact
dimensions and weights can vary.

• Due to improvements continuously taking place in design, the details given here
may vary marginally irrespective of Length, Width, Height and Total Weight .
However the variations will be within permissible tolerance limits as per IS 2026
latest.

ITEM DESCRIPTION STANDARD OPTIONAL

Page no.36

No.
1. H.V. TERMINAL BUSBAR Yes No
2. L.V. TERMINAL BUSBAR Yes No
L.V. SEPERATE NEUTRAL EARTHING
3. No Yes
BUSHING
4. SEPERATOR NEUTRAL EARTH BUSBAR No Yes
5. OFF CIRCUIT TAPPING LINK BOARD Yes No
6. TAP LINK POSITION PLATE Yes No
ACCESS DOORS/WINDOWS FOR TAP
7. Yes No
CHANGING LINKS
8. VENTILATION LOUVERS Yes No
9. RAIN WATER GUARD Yes No
10. RATING AND DIAGRAM PLATE Yes No
LIFTING LUGS FOR TOP COVER &
11. Yes No
COMPLETE TRANSFORMER LIFTING
LIFTING HOLES FOR CORE-COIL ASSY.
12. Yes No
LIFTING
ENCLOSURE (DEGREE OF PROTACTION
13. Yes No
IP-21/23)
14. MARSHLING BO-- Yes No
15. PHASE C.T. Yes No
16. WINDING TEMPERATURE INDICATOR Yes No
17. SPACE HEATER No Yes
DETACHABLE H.V. CABLE GLAND PLATE
18. Yes No
WITH 1 KNOCKOUT
19. H.V. CABLE GLAND No Yes
20. H.V. CABLE LUG WITH INSIDE KNURLING No Yes
21. H.T. CABLE CLAMP Yes No
22. SURGE ARRESTER No Yes
23. SURGE ARRESTER GROUNDING BUSHING No Yes
24. SURGE ARRESTER GROUNDING BUSBAR No Yes
DETACHABLE L.V. CABLE GLAND PLATE
25. Yes No
WITH REQD. KNOCKOUTS
26. L.V. CABLE GLAND No Yes
27. L.V. CABLE LUG WITH INSIDE KNURLING No Yes

Page no.37

28. L.T. CABLE CLAMP Yes No
29. SKID UNDER BASE WITH HAULAGE HOLES Yes No
30. BI – DIRECTIONAL FLAT ROLLERS Yes No
31. BODY EARTHING TERMINALS Yes No
32. PHASE IDENTIFICATION PLATES Yes No
33. DANGER PLATES Yes No
34. H.V. CABLE BO-- No Yes
35. L.V. CABLE BO-- No Yes
36. L.V. BUSDUCT BO-- No Yes
37. Fans No Yes
38. OLTC, AVR, RTCC No Yes

NOTE:- OPTIONAL FEATURES ARE AVAILABLE ON BUYER'S REQUEST & AT
EXTRA COST.

Oil Filled & Dry Transformer Design

HT Distribution and Power Transformer Design Software
This transformer design software can get you the design parameters along with CAD
developed images of different transformer & core assembly parts dynamically. This CAD
feature helps you to confirm and check the authenticity of computer generated design
parameters. Design oil filled & dry type transformers with one software. More over this
software can also be customized as per your requirements.

How does transformer design software work?
1 - Just enter the KVA rating, Impedance, NLL (No Load Losses), LS (Load Losses),
select the flux density and press the "Auto mode". Within seconds you get various design
outputs just showing you the core and copper weights depending upon the entered
impedance value. Select any set of values as per your preferred tolerance and you get the
complete design data of the distribution or power transformer (clearances and certain
other values are added as default values but you can change as per your requirements), 2
- Still you have the "Manual" mode to change and fine tune your design as per your
requirement (if desired),
3 - Change no. of HV coils/discs per limb, size of HV/LV conductor(s) - both round
conductor and strip size, no. of parallel LV conductors,
4 - You can reset various clearances, change current density, conductor insulation as per
your requirement and client specifications,
5 - Select HV winding type - Cross Over to Disc winding and vice -a - versa,
6 - Tapping details for OLTC and Off Load Tap Changer upto 25 steps. Enter any + step
value through - step @ any % step value,
7 - You get values of Axial and radial forces developed in the windings during short

Page no.38
circuits, temp gradients for HV and LV, Thermal Time Constant and ability to withstand
shortcircuits with winding temperature rise,
8 - Pressed Steel Radiator (PSR) data calculation added you get automatic fixing
dimensions of radiators - section width, CD and no. of fins. Options to select 226, 300 and
560 width sections. Tank drawing details are generated automatically. 9-
Feature added to get winding data for an old transformer 10 -
GTP (Guaranteed Technical Particulars), Core details, core & winding assembly details,
estimation and costing sheets are generated in the 'Word Format' for easy access, printing
and sending the same via email to clients for approval, in house departments like design,
QC, purchase, estimation, production, despatch. So this distribution and power
transformer design software saves time, energy and revenue. A must key tool for
transformer design and training professionals and engineering students.

Factors controlling and affecting the design of a transformer
Principle of operation of a transformer

Theory of Transformer losses:-
Core losses are caused by two factors: hysteresis and eddy current losses. Hysteresis loss
is that energy lost by reversing the magnetic field in the core as the magnetizing AC rises
and falls and reverses direction. Eddy current loss is a result of induced currents
circulating in the core.

Efficiency of a transformer can be calculated as per equation (a),(b),(c)

Efficiency = power outut / power input

Efficiency = power outut / ( power output + core oss + copper loss)

Efficienct = VI*PF/(VI*PF + core loss + copper loss)

Where PF= power factor

Applications:
A key application of transformers is to increase voltage before transmitting electrical
energy over long distances through wires. Wires have resistance and so dissipate
electrical energy at a rate proportional to the square of the current through the wire. By
transforming electrical power to a high-voltage (and therefore low-current) form for
transmission and back again afterwards, transformers enable economic transmission of
power over long distances. Consequently, transformers have shaped the electricity supply
industry, permitting generation to be located remotely from points of demand.[3] All but a
tiny fraction of the world's electrical power has passed through a series of transformers by
the time it reaches the consumer.[4] Transformers are used extensively in electronic
products to step down the supply voltage to a level suitable for the low voltage circuits
they contain. The transformer also electrically isolates the end user from contact with the
supply voltage.

Page no.39

Transformers:
In a previous section (Switching Power Supplies), I touched on transformers. You should
remember that a transformer has a primary winding and a secondary winding wrapped
around a core. In car audio, the core is usually a donut shaped toroid. A transformer can
be designed to step voltage up or down, and/or isolate. We discussed isolation in a
previous section. This section will deal with stepping the voltage up or down.

Winding Ratio:
Remember that the transformer windings are enamel coated magnet wire which is
wrapped around the core (as seen below). The number of windings is determined by the
number of times that a piece of wire makes a complete turn around the core. The primary
winding is the winding which is driven (in car audio amplifiers, it's usually driven by
transistors). The secondary winding is the output winding. The secondary is driven by the
magnetic field that the primary induces in the core. A transformer with a ratio of 1:1 will
not cause a voltage increase or decrease (disregarding small losses) from the primary to
the secondary (as measured across each of the individual windings). If the ratio is 1:2
(primary:secondary), the voltage across the secondary will be twice the voltage across the
primary. A ratio of 1:3 will result in a secondary voltage 3 times as high as the voltage on
the primary. Of course all of this applies to a transformer which is very lightly or not
loaded (minimal current flow). When current is drawn from the secondary winding, there
may (will) be a voltage drop and therefore a primary to secondary voltage ratio which
may not match the winding ratio exactly. This loss of voltage is primarily due to the less
than 100% efficiency of the magnetic coupling of the primary and the secondary windings
through the core and also some copper (resistance) losses. Remember that the primary and
the secondary windings are not generally electrically connected together. This means that
all of the power transfer between the primary and secondary is transferred (magnetically)
through the core. The transformer below is similar to one that you would find in a small
car audio amplifier. The winding ratio is 1:2. The different colors are each half of the
center tapped primary and secondary. Notice that there are twice as many secondary
windings as there are primary windings. The schematic symbol shows how the windings
relate to each other. The center tap of the primary (red) is connected to the battery. The
center tap of the secondary (black) is connected to ground.

Page no.40

As a side note:
The power driven into the primary will equal the power produced at the output of
the secondary (if we ignore wire and core loss). If we have a 'step-up' transformer
with a 1:2 ratio being driven with 24 volts A.C., the secondary output voltage
(disregarding losses) will be 48 volts. If we load the secondary so that 5 amps of
current is flowing through the secondary windings, the power output is P=I*E;
P=5*48; P=240 watts. Since the power driven into the primary equals the power
out of the secondary, we know that the power being driven into the primary is 240
watts. If we use the formula I=P/E, we see that the I=240/24; I=10 amps. If we
were stepping the voltage down, the current flowing through the primary would be
less than the current being drawn through the secondary windings

Advanced Info:
When designing a transformer you have to calculate the number of primary
windings so that the transformer will operate properly/efficiently. There are a few
different variables that have to be taken into account.
Ac: Ac is the effective cross sectional core area. This number is supplied by the core
manufacturer.

Primary Voltage:
The primary voltage for a push-pull system is double the primary input voltage.
For car amplifier switching power supplies, the input voltage is 12VDC. This
means that the total primary voltage is 24 volts. If we use 13.5 volts as the input
voltage, the primary voltage would be 27 volts.
Operating Frequency:
The operating (oscillation) frequency is simply the frequency at which the primary
is driven. Generally between 25,000hz and 100,000hz in car audio amplifiers.
Primary Turns:
The number of primary turns returned by the calculator is the total number of turns
on the primary side of the transformer. Of course, with a push pull system, the
number of turns on each half of the primary must be equal. If the output says that
you need 13 turns, you'd round up to 14 turns and each half of the primary would
have 7 turns. From the previous diagram, you'd have 7 orange turns and 7 green
turns on the core

Page no.41

Shell-Core Transformers

The most popular and efficient transformer core is the SHELL CORE, as illustrated in
figure 5-4. As shown, each layer of the core consists of E- and I-shaped sections of metal.
These sections are butted together to form the laminations. The laminations are insulated
from each other and then pressed together to form the core.

TRANSFORMER WINDINGS

As stated above, the transformer consists of two coils called WINDINGS which are
wrapped around a core. The transformer operates when a source of ac voltage is
connected to one of the windings and a load device is connected to the other. The winding
that is connected to the source is called the PRIMARY WINDING. The winding that is
connected to the load is called the SECONDARY WINDING. (Note: In this chapter the
terms "primary winding" and "primary" are used interchangeably; the term: "secondary
winding" and "secondary" are also used interchangeably.)

Figure 5-5 shows an exploded view of a shell-type transformer. The primary is wound in
layers directly on a rectangular cardboard form.

Figure 5-5. - Exploded view of shell-type transformer construction.

Page no.42

In the transformer shown in the cutaway view in figure 5-6, the primary consists of many
turns of relatively small wire. The wire is coated with varnish so that each turn of the
winding is insulated from every other turn. In a transformer designed for high-voltage
applications, sheets of insulating material, such as paper, are placed between the layers of
windings to provide additional insulation.

Figure 5-6. - Cutaway view of shell-type core with windings.

Page no.43

When the primary winding is completely wound, it is wrapped in insulating paper
or cloth. The secondary winding is then wound on top of the primary winding. After the
secondary winding is complete, it too is covered with insulating paper. Next, the E and I
sections of the iron core are inserted into and around the windings as shown.

The leads from the windings are normally brought out through a hole in the enclosure of
the transformer. Sometimes, terminals may be provided on the enclosure for connections
to the windings. The figure shows four leads, two from the primary and two from the
secondary. These leads are to be connected to the source and load, respectively.

SCHEMATIC SYMBOLS FOR TRANSFORMERS

Figure 5-7 shows typical schematic symbols for transformers. The symbol for an air-core
transformer is shown in figure 5-7(A). Parts (B) and (C) show iron-core transformers. The
bars between the coils are used to indicate an iron core. Frequently, additional
connections are made to the transformer windings at points other than the ends of the
windings. These additional connections are called TAPS. When a tap is connected to the
center of the winding, it is called a CENTER TAP. Figure 5-7(C) shows the schematic
representation of a center-tapped iron-core transformer.

HOW A TRANSFORMER WORKS

Up to this point the chapter has presented the basics of the transformer including
transformer action, the transformer's physical characteristics, and how the transformer is

Page no.44
constructed. Now you have the necessary knowledge to proceed into the theory of
operation of a transformer.

NO-LOAD CONDITION

You have learned that a transformer is capable of supplying voltages which are usually
higher or lower than the source voltage. This is accomplished through mutual induction,
which takes place when the changing magnetic field produced by the primary voltage cuts
the secondary winding. A no-load condition is said to exist when a voltage is applied to
the primary, but no load is connected to the secondary, as illustrated by figure 5-8.
Because of the open switch, there is no current flowing in the secondary winding. With
the switch open and an ac voltage applied to the primary, there is, however, a very small
amount of current called EXCITING CURRENT flowing in the primary. Essentially,
what the exciting current does is "excite" the coil of the primary to create a magnetic
field. The amount of exciting current is determined by three factors: (1) the amount of
voltage applied (Ea), (2) the resistance (R) of the primary coil's wire and core losses, and
(3) the XL which is dependent on the frequency of the exciting current. These last two
factors are controlled by transformer design. Figure 5-8. - Transformer under no-load
conditions.

This very small amount of exciting current serves two functions:

• Most of the exciting energy is used to maintain the magnetic field of the primary.
• A small amount of energy is used to overcome the resistance of the wire and core
losses which are dissipated in the form of heat (power loss).

Exciting current will flow in the primary winding at all times to maintain this magnetic

Field.

MAGNETIC FIELD OF A COIL

Figure 1-3(A) illustrates that the magnetic field around a current-carrying wire exists at
all points along the wire.

Page no.45
Figure 1-5 illustrates that when a straight wire is wound around a core, it forms a coil and
that the magnetic field about the core assumes a different shape. Figure 1-5(A) is actually
a partial cutaway view showing the construction of a simple coil. Figure 1-5(B) shows a
cross-sectional view of the same coil. Notice that the two ends of the coil are identified as
X and Y.

Figure 1-5. - Magnetic field produced by a current-carrying coil.

When current is passed through the coil, the magnetic field about each turn of wire links
with the fields of the adjacent turns. (See figure 1-4(A)). The combined influence of all
the turns produces a two-pole field similar to that of a simple bar magnet. One end of the
coil is a north pole and the other end is a south pole.

Strength of an Electromagnetic Field

The strength or intensity of a coil's magnetic field depends on a number of factors. The
main ones are listed below and will be discussed again later.

• The number of turns of wire in the coil.
• The amount of current flowing in the coil.
• The ratio of the coil length to the coil width.
• The type of material in the core.

Losses in an Electromagnetic Field

When current flows in a conductor, the atoms in the conductor all line up in a definite
direction, producing a magnetic field. When the direction of the current changes, the
direction of the atoms' alignment also changes, causing the magnetic field to change
direction. To reverse all the atoms requires that power be expended, and this power is lost.
This loss of power (in the form of heat) is called HYSTERESIS LOSS. Hysteresis loss is

Page no.46
common to all ac equipment; however, it causes few problems except in motors,
generators, and transformers. When these devices are discussed later in this module,
hysteresis loss will be covered in more detail.

BASIC AC GENERATION

From the previous discussion you learned that a current-carrying conductor produces a
magnetic field around itself. In module 1, under producing a voltage (emf) using
magnetism, you learned how a changing magnetic field produces an emf in a conductor.
That is, if a conductor is placed in a magnetic field, and either the field or the conductor
moves, an emf is induced in the conductor. This effect is called electromagnetic
induction.

Factors Affecting Coil Inductance There are several physical factors which affect the
inductance of a coil. They include the number of turns in the coil, the diameter of the coil,
the coil length, the type of material used in the core, and the number of layers of winding
in the coils.

Inductance depends entirely upon the physical construction of the circuit, and can only be
measured with special laboratory instruments. Of the factors mentioned, consider first
how the number of turns affects the inductance of a coil. Figure 2-5 shows two coils. Coil
(A) has two turns and coil (B) has four turns. In coil (A), the flux field set up by one loop
cuts one other loop. In coil (B), the flux field set up by one loop cuts three other loops.

Page no.47
Doubling the number of turns in the coil will produce a field twice as strong, if the same
current is used. A field twice as strong, cutting twice the number of turns, will induce four
times the voltage. Therefore, it can be said that the inductance varies as the square of the
number of turns.

Figure 2-5. - Inductance factor (turns).

The second factor is the coil diameter. In figure 2-6you can see that the coil in view B has
twice the diameter of coil view A. Physically, it requires more wire to construct a coil of
large diameter than one of small diameter with an equal number of turns. Therefore, more
lines of force exist to induce a counter emf in the coil with the larger diameter. Actually,
the inductance of a coil increases directly as the cross-sectional area of the core increases.
Recall the formula for the area of a circle: A = pr2. Doubling the radius of a coil increases
the inductance by a factor of four.

Figure 2-6. - Inductance factor (diameter).

Page no.48

The third factor that affects the inductance of a coil is the length of the coil. Figure 2-7
shows two examples of coil spacings. Coil (A) has three turns, rather widely spaced,
making a relatively long coil. A coil of this type has few flux linkages, due to the greater
distance between each turn. Therefore, coil (A) has a relatively low inductance. Coil (B)
has closely spaced turns, making a relatively short coil. This close spacing increases the
flux linkage, increasing the inductance of the coil. Doubling the length of a coil while
keeping the same number of turns halves the value of inductance.

Figure 2 - 7. - Inductance factor (coil length). CLOSELY WOUND

The fourth physical factor is the type of core material used with the coil. Figure 2-8 shows
two coils: Coil (A) with an air core, and coil (B) with a soft-iron core. The magnetic core

Page no.49
of coil (B) is a better path for magnetic lines of force than is the nonmagnetic core of coil
(A). The soft-iron magnetic core's high permeability has less reluctance to the magnetic
flux, resulting in more magnetic lines of force. This increase in the magnetic lines of force
increases the number of lines of force cutting each loop of the coil, thus increasing the
inductance of the coil. It should now be apparent that the inductance of a coil increases
directly as the permeability of the core material increases.

Figure 2-8. - Inductance factor (core material). SOFT-IRON CORE

Another way of increasing the inductance is to wind the coil in layers. Figure 2-9 shows
three cores with different amounts of layering. The coil in figure 2-9(A) is a poor inductor
compared to the others in the figure because its turns are widely spaced and there is no
layering. The flux movement, indicated by the dashed arrows, does not link effectively
because there is only one layer of turns. A more inductive coil is shown in figure 2-9(B).
The turns are closely spaced and the wire has been wound in two layers. The two layers
link each other with a greater number of flux loops during all flux movements. Note that
nearly all the turns, such as X, are next to four other turns (shaded). This causes the flux
linkage to be increased.

Figure 2-9. - Coils of various inductances.

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