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Transformer Basics and Principles

This document provides an introduction to transformers, including their basic components and principles of operation. It describes how a transformer uses two coils - a primary and secondary winding - wrapped around a common core to increase or decrease voltage levels while maintaining power. Key points covered include: - Transformers consist of primary and secondary coils wound around a laminated iron core, and work by inducing an alternating voltage in the secondary from the primary. - Transformers can be used to step up or step down voltages depending on the winding ratios, and maintain the same power between primary and secondary circuits. - An ideal transformer is lossless, but practical transformers come close, with properties like winding resistance and leakage flux causing some losses.

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Apna Veer
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92 views3 pages

Transformer Basics and Principles

This document provides an introduction to transformers, including their basic components and principles of operation. It describes how a transformer uses two coils - a primary and secondary winding - wrapped around a common core to increase or decrease voltage levels while maintaining power. Key points covered include: - Transformers consist of primary and secondary coils wound around a laminated iron core, and work by inducing an alternating voltage in the secondary from the primary. - Transformers can be used to step up or step down voltages depending on the winding ratios, and maintain the same power between primary and secondary circuits. - An ideal transformer is lossless, but practical transformers come close, with properties like winding resistance and leakage flux causing some losses.

Uploaded by

Apna Veer
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Experiment 8

Introduction to Transformer

Name:________________________ Date:_________________________

OBJECTIVE
To get familiar with working, principle and construction of transformer

EQUIPMENT USED
Item Serial Number
Digital Multimeter
1-phase transformer
Set of experiment cables
Power Supply

THEORY
A transformer is a static piece of equipment used either for raising or lowering the voltage of an
a.c. supply with a corresponding decrease or increase in current. It essentially consists of two
windings, the primary and secondary, wound on a common laminated magnetic core as shown in
Fig. (2.1). The winding connected to the a.c. source is called primary winding (or primary) and
the one connected to load is called secondary winding (or secondary). The alternating voltage V1
whose magnitude is to be changed is applied to the primary. Depending upon the number of
turns of the primary (N1) and secondary (N2), an alternating e.m.f. E2 is induced in the
secondary. This induced e.m.f. E2 in the secondary causes a secondary current I2. Consequently,
terminal voltage V2 will appear across the load. If V2 > V1, it is called a step up-transformer. On
the other hand, if V2 < V1, it is called a step-down transformer.

Fig:- 2.1
An ideal transformer is one that has
a) no winding resistance
b) no leakage flux i.e., the same flux links both the windings
c) no iron losses (i.e., eddy current and hysteresis losses) in the core
Although ideal transformer cannot be physically realized, yet its study provides a very powerful
tool in the analysis of a practical transformer. In fact, practical transformers have properties that
approach very close to an ideal transformer.

E.M.F. Equation of a Transformer:


Consider that an alternating voltage V1 of frequency f is applied to the primary

Above equations are calculated from the e.m.f. E1 induced in primary and rms values of E

In an ideal transformer, E1 = V1 and E2 =V2.

Voltage Transformation Ratio (K):

For an ideal transformer:


(i) E1 = V1 and E2 = V2 as there is no voltage drop in the windings.

(ii) there are no losses. Therefore, volt-amperes input to the primary are equal to the output volt-
amperes i.e.
V1 I1 = V2 I2

Hence, currents are in the inverse ratio of voltage transformation ratio. This simply means that if
we raise the voltage, there is a corresponding decrease of current.

Step-Down Transformer:
If the number of turns on the secondary winding is less than the number of turns on the primary
winding, then the secondary output voltage will be less than the primary input voltage. This type
of transformer is called a step-down transformer and is illustrated in Figure 02.

Step-Up Transformer:
If the number of turns on the secondary winding of a transformer is greater than the number of
turns on the primary winding, then the secondary output voltage will be greater than the primary
input voltage. This type of transformer is called a step-up transformer
Losses in Transformer

Copper Loss in Transformer


Copper loss is I2R loss, in primary side it is I12R1 and in secondary side it is I22R2 loss,
where I1 & I2 are primary & secondary current of transformer and R1 & R2 are
resistances of primary & secondary winding. As the both primary & secondary
currents depend upon load of transformer, copper loss in transformer vary with load.

Core Losses in Transformer


Hysteresis loss and eddy current loss, both depend upon magnetic properties of the
materials used to construct the core of transformer and its design. So these losses in
transformer are fixed and do not depend upon the load current. So core losses in
transformer which is alternatively known as iron loss in transformer can be
considered as constant for all range of load.

Voltage Regulation of Transformer


The voltage regulation is the percentage of voltage difference between no load and
full load voltages of a transformer with respect to its full load voltage.
VR = (VNL – VFL) / VFL * 100

Efficiency of Transformer
Efficiency of a transformer can be defined as the output power divided by the input
power. That is   Efficiency = output / input .
Or Efficiency = (input - losses) / input
For maximum Efficiency
Copper losses = Iron Losses

REMARKS
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