INFORMATIONAL TECHNOLOGY IN EDUCATION

Name: Farah Eliza Binti MansorMatrix: db130320

Name: Faridah Zahirah Binti IsmailMatrix: Db130321

Name: Fatinnazihah Binti Abdul RahmanMatrix: DB130322

Name:Nurul Qurraisyia Binti ZulkafliMatrix: DB130085

CONTENTS

No Title

1 1.0 Introduction

2 2.0 Basic Construction Of A Transformer 2.1 Core 2.2 Windings

3 3.0 Operation Of Transformers 3.1 Winding Ratio 3.2 Voltage Ratio 3.3 Current Ratio

4 4.0 Loss And Efficiency Of Transformers 4.1 Ideal Transformers 4.2 Non-ideal Transformers 4.3 Transformers Efficiency

5 5.0 Application Of A Power Transformer

6 Quiz

INTRODUCTION OF

TRANSFORMER

Electrical device that transfers electrical energy from one

circuit to another

Made up of two electromagnetic coils

Self inductance

Mutual inductance

Only operate with AC or DC that is constantly changing

2.0 BASIC CONSTRUCTION OF A TRANSFORMER

Consist of 2 conductor wound around a core as shown in Figure 1.2.1

Figure 1.2.1

Core is wounded with insulated copper conductor with specific number of turns

2.1 CORE

Constructed by : laminated sheets of silicon steel insulated from each other

:soft iron , powdered iron and ferrite

Thickness of the laminated sheets : between 1mm – 5 mm

Charecteristics : robust , low hysteresis

Made up of thin layers (Avoid power loss by the build-up of eddy currents )

Two major construction of the core of transformer

Shell-type form ( E-I)

Core-type form (U-I)

2.2 WINDINGS

Transformer consist of 2 kind of windings around the core

Winding that is connected to the voltage source ( primary winding )

Winding that is connected to load circuit and is the output path for the transformer ( secondary winding )

In an auto transformer , one winding serves as both the primary and secondary winding . The secondary winding is tapped from the primary winding

Types of winding methods :

Common winding

Coupling winding

TYPES AND SYMBOLS OF TRANSFORMERS

Transformer Name

Air-core Transformer

Iron-core Transformer

IronPowder-core Transformer

Auto Transformer

Centre-tapped Transformer

Multiple Winding

Transformers

Types Of Core

Air-core Iron-core Powdered Iron-core

Iron-core Iron-core Iron-core

Symbol

BASIC OPERATION OF TRANSFORMERS

3.1 WINDING RATIO Ratio of number of turn in the primary winding to the number of turn in the secondary winding

winding ratio , n = =

Step up transformer : number of turns in secondary winding exceed the number of turns in the primary winding

Step down transformer : number of turns in primary winding exceed the number of turns in the secondary winding

Isolation transformer : same number of turns in primary and secondary winding

3.2 VOLTAGE RATIO Ratio between the primary voltage , V1 and the secondary voltage V2 is called the

voltage ratio of a transformer

Formula of voltage ratio : =

Voltage ratio is related to the winding ratio.

Formula of voltage ratio : = = n

3.3 CURRENT RATIO When AC supply is connected to transformer’s primary winding , the existing flux around the winding

produces self – induction

Flux shifts to secondary winding through the transformer core to produce inductance at the secondary winding

This indicates the emf at the secondary winding is equivalent to the emf of the primary winding

LOSS AND EFFICIENCY OF TRANSFORMERS

4.1 IDEAL TRANSFORMERS An Ideal Transformer is an imaginary transformer which does not have any loss in it, means no core

losses, copper losses and any other losses in transformer. Efficiency of this transformer is considered as 100%.

4.2 NON-IDEAL TRANSFORMERWe can replace a nonideal transformer with an idealized transformer by including a lumped resistance equal to the winding resistance of series with each winding

The efficiency is less than 100% because power losses in corand its primary windings.

Power loss : iron & copper

4.3 TRANSFORMER EFFICIENCY

For an ideal transformer, the power received by the load is equivalent to the power transferred by the primary winding

Non-ideal transformer does not reach 100% efficiency because there is power loss that is unavoidable in the core and winding

By choosing an optimum size for your winding wire and designing a suitable core that reduces iron loss to minimum, up to 99.5% efficiency can be achieved

Transformer efficiency,

Non-ideal transformer OR

V2 = Output voltage or secondary voltage I2 = Secondary current

Cos = power factor at the load = copper loss

= iron loss

5.0 APPLICATION OF POWER TRANSFORMER The most important uses and applications of a transformer are:

1) It can rise or lower the level of level of Voltage or Current

2) It can increase or decrease the value of capacitor, an inductor or resistance in an AC circuit.

3) It can act as an impedance transferring device.

4) It can be used to prevent DC from passing from one circuit to the other.

5) It can isolate two circuits electrically

QUIZ1.By referring to the figure , calculate the winding ratio of the transformer .

Answer : 4:3

2. A step up transformer as shown in figure below has a turns ratio of 1:4 and is connected to a voltage source of 240 V , 50 Hz . Calculate :

a) The secondary voltage

b) The numbers of turn in the secondary winding if the number of turns in the primary winding is 480

Answer : a) 960V b) 1920

CHECK ANSWER SCHEMES

3. Figure shows a transformer with a turn ratio of 3:2 is connected to a 240V voltage source . If a resistive load of 1Ω is connected to the terminal of the secondary winding , calculate the quantities below :

a)Secondary voltage

b)Secondary current

c)Primary current

Answer : V2 = 160V , I2 = 0.16A , I1 = 0.11A

4. A 20kVA transformer with 0.8 power factor has a power loss comprising of 400W iron loss and 600W copper loss . Calculate the efficiency of the transformer operating at

(a) full load (b) half load

Answer : a) 94.1% b) 91.95%

CHECK ANSWER SCHEMES

THE ENDHAPPY LEARNING !