WHAT IS A TRASFORMER?

Transformer is a device used in the power transmission of electric energy. The

transmission current is AC. It is commonly used to increase or decrease the supply

voltage without a change in the frequency of AC between circuits. The transformers

works on basic principles of electromagnetic induction and mutual induction.

TRANSFORMER TYPES

Transformers are used in various fields like power generation grid, distribution sector,
transmission and electrical energy consumption.

There are various types of transformers which are classified based on the following
factors;

 Working voltage range.

 The medium used in the core.

 Winding arrangement

 Installation location.
 BASED ON VOLTAGE LEVEL

Commonly used transformer type, depending upon voltage they are classified as:

 STEP UP TRANSFORMER:
They are used between the power generator and the power grid. The
secondary output voltage is higher than the input voltage.

 STEP DOWN TRANSFORMER:

These transformers are used to convert high voltage primary supply to
low voltage secondary output.

BASED ON THE MEDIUM OF CORE USED

In a transformer, we will find different types of cores that are used.

 AIR CORE TRANSFORMER

The flux linkage between primary and secondary winding is
through the air . The coil or windings wound on the non-magnetic strip.

 IRON CORE TRANSFORMER

Windings are wound on multiple iron plates stacked together,
which provides a perfect linkage path to generate flux.

BASED ON THE WINDING TRANSFORMER

 AUTO TRANSFORMER:
It will have only one winding wound over a laminated core. The
primary and secondary share the same coil. Auto means “self” in language greek.

BASED ON INSTALL LOCATION

POWER TRANSFORMER:
It is used at power generation stations as they are suitable for high
voltage application.

DISTRIBUTION TRANSFORMER:
 Mostly used at distribution lanes for domestic purposes. They are
designed for carrying low voltages. It is very easy to install and characterized by low
magnetic losses.

MEASUREMENT TRANSFORMERS:
These are further classified. They are mainly used for measuring
voltage, current, power.

PROTECTION TRANSFORMERS:
They are used for component protection purposes. In circuits, some
components must be protected from voltage fluctuation etc. Protection transformers
ensure component protection.
 WORKING PRINCIPLE OF A TRANSFORMER

The transformer works on the principle of Faraday’s law of electromagnetic induction

and mutual induction.

There are usually two coils primary coil and secondary coil on the transformer core. The
core laminations are joined in the form of strips. The two coils have high mutual
inductance. When an alternating current pass through the primary coil it creates a
varying magnetic flux. As per faraday’s law of electromagnetic induction, this change in
magnetic flux induces an emf (electromotive force) in the secondary coil which is linked
to the core having a primary coil. This is mutual induction.

Overall, a transformer carries the below operations:

 Transfer of electrical energy from circuit to another

 Transfer of electrical power through electromagnetic induction

 Electric power transfer without any change in frequency

 Two circuits are linked with mutual induction

The figure shows the formation of magnetic flux lines around a current-carrying wire.
The normal of the plane containing the flux lines are parallel to normal of a cross-
section of a wire.

The figure shows the formation of varying magnetic flux lines around a wire-wound.
The interesting part is that reverse is also true, when a magnetic flux line fluctuates
around a piece of wire, a current will be induced in it. This was what Michael faraday
found in 1831 which is the fundamental working principle of electric generators as well
as transformers.
 PARTS OF A SINGLE-PHASE GROUP

The major parts of a single-phase transformer consist of;

 Core:
The core acts as a support to the winding in the transformer. It also provides a low
reluctance path to the flow of magnetic flux. The winding is wound on the core as
shown in the picture. It is made up of a laminated soft iron core in order to reduce the
losses in a transformer. The factors such as operating voltage, current, power etc
decide core composition. The core diameter is directly proportional to copper losses
and inversely proportional to iron losses.

 Windings:
Windings are the set of copper wires wound over the transformer core.
Copper wires are used to:

 The high conductivity of copper minimizes the loss in a transformer because when
the conductivity increases, resistance to current flow decreases.
 The high ductility of copper is the property of metals that allows it to be made into
very thin wires.

There are two types of windings. Primary windings and secondary windings

 Primary winding: The set of turns of windings to which supply current is fed.
 Secondary winding: The set of turns of winding from which output is taken.

The primary and secondary windings are insulated from each other using insulation
coating agents.
 Insulation Agents
Insulation is necessary for transformers to separate windings from each
other and to avoid short circuit. This facilitates mutual induction. Insulation agents
have an influence on the durability and the stability of a transformer.

Following are used as an insulation medium in a transformer:

 Insulating oil
 Insulating tape
 Insulating paper
 Wood-based lamination
 EMF EQUATION OF TRANSFORMER

N1 – number of turns in primary.

N2 – number of turns in secondary.
Φm – maximum flux in weber (Wb).
T – time period. Time is taken for 1 cycle.
The flux formed is a sinusoidal wave. It rises to a maximum value Φm and decreases to
negative maximum Φm. So, flux reaches a maximum in one-quarter of a cycle. The time
taken is equal to T/4.
Average rate of change of flux = Φm/(T/4) = 4fΦm
Where f = frequency
T = 1/f
Induced emf per turn = rate of change of flux per turn
Form factor = rms value / average value
Rms value = 1.11 (4fΦm) = 4.44 fΦm [form factor of sine wave is 1.11]
RMS value of emf induced in winding = RMS value of emf per turn x no of turns
Primary Winding
Rms value of induced emf = E1 = 4.44 fΦm * N1
Secondary winding:
Rms value of induced emf = E2 = 4.44 fΦm * N2
Explain why power plants transmit electricity at high voltages and low currents and how
they do this?

Develop relationships among current, voltage, and the number of windings in step-up and
step-down transformers.

Although ac electric power is produced at relatively low voltages, it is sent

through transmission lines at very high voltages (as high as 500 kV). The same power
can be transmitted at different voltages because power is the product IrmsVrms.(For
simplicity, we ignore the phase factor cosφcosφ.) A particular power requirement can
therefore be met with a low voltage and a high current or with a high voltage and a
low current. The advantage of the high-voltage/low-current choice is that it results in
lower I2rmsR ohmic losses in the transmission lines, which can be significant in lines that
are many kilometers long.

Typically, the alternating emfs produced at power plants are “stepped up” to very high
voltages before being transmitted through power lines; then, they must be “stepped
down” to relatively safe values (110 or 220 V rms) before they are introduced into
homes. The device that transforms voltages from one value to another using induction
is the transformer.
As the below figure illustrates, a transformer basically consists of two separated coils,
or windings, wrapped around a soft iron core. The primary winding has NP loops, or
turns, and is connected to an alternating voltage vP(t). The secondary winding
has NS turns and is connected to a load resistor RS. We assume the ideal case for which
all magnetic field lines are confined to the core so that the same magnetic flux
permeates each turn of both the primary and the secondary windings. We also neglect
energy losses to magnetic hysteresis, to ohmic heating in the windings, and to ohmic
heating of the induced eddy currents in the core. A good transformer can have losses
as low as 1% of the transmitted power, so this is not a bad assumption.
 CONTENTS

01
Acknowledgement
02
Certificate

03
What is a transformer
04
Based on voltage level,
and its types? medium of
core and winding transformer

05 06
Working principle Parts of a single phase
Of a transformer transformer

07 08
EMF equation of transformer Why power plants
transmit
electricity?

TRANSFORMER
 NAME: V.P.SAMIKSHA

CLASS: XII B

SUBJECT: PHYSICAL

TOPIC: 400 METER TRACK

TEACHER : MR.MOHAN
INCHARGE

ACADEMIC YEAR: 2022 - 23

This is to certify that the project titled “400 METER TRACK ,
Physical education core is a bonafide work carried out by
V.P.SAMIKSHA of class XII B Of VELAMMAL VIDYALAYA
MANGADU. I also certify that the work was carried out with atmost sincerity
and skill.

As per Cbse guidelines for the fulfillment of the requirement leading to the
successful completion of the project.

TEACHER IN-CHARGE PRINCIPAL

EXTERNAL EXAMINER SCHOOL STAMP

On the very outset of this report, I would like to extend my sincere
and heartfelt obligations towards all the personages who has helped
me in this endeavor. Without their active guidance, cooperation and
encouragement, I would not have made headway in this project.

I am extremely thankful and pay my gratitude to my faculty guide

Mr.Mohan for his valuable guidance and support in completion of
this project .

I also acknowledge with a deep sense of reverense, my gratitude

towards my members of my family, who has supported me always
both morally and economically.

At last but not the least gratitude goes to all my friends, who directly
or indirectly helped me to complete this project.