body of assignment 1

8/19/2019 Body of Assignment 1

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INTRODUCTION

A transformer is electrical equipment that transfers energy by inductive coupling beteen its

inding circuits! A varying current in the primary inding creates a varying magnetic flu" in the

transformer#s core and thus a varying magnetic flu" through the secondary inding! This varying

magnetic flu" induces a varying electromotive force $emf% or voltage in the secondary inding!

Transformers can be used to vary the relative voltage of circuits or isolate them& or both! It has ' general

types of transformer hich is step up transformer and step don transformer!

The transformer is based on to principles! (irst& that an electric current can produce a magnetic

field and second that a changing magnetic field ithin a coil of ire induces a voltage across the ends of

the coil $electromagnetic induction%! Changing the current in the primary coil changes the magnetic flu"that is developed! The changing magnetic flu" induces a voltage in the secondary coil!

The current passing through the primary coil creates a magnetic field! The primary and secondary

coils are rapped around a core of very high magnetic permeability& usually iron& so that most of the

magnetic flu" passes through both the primary and secondary coils! Any secondary inding connected

load causes current and voltage induction from primary to secondary circuits in indicated directions!

In this sub)ect e learn an ideal transformer! An ideal transformer means it based on these

assumption hich are the core has infinite permeability& e"ample it has *ero reluctance! +esides that&there is no core loss! As a result an ideal transformer does not dra any magneti*ing current to establish

core flu"! An ideal transformer also no flu" can lea, through such a core& for e"ample all the core lin,

primary and secondary inding! As a consequence primary and secondary lea,age reactances are *ero!

-astly& the primary and secondary inding resistances are *ero! As a consequence there is no copper loss!

Thus& the output poer of an ideal transformer is equal to its input poer!

.hile& in practical transformer the lea,age flu" is occur! +esides that& there is a copper loss and

core has permeability& thus there is releuctance& hich means magneti*ing current cannot be neglible!

There also have a core loss!

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http://en.wikipedia.org/wiki/Inductive_couplinghttp://en.wikipedia.org/wiki/Inductive_couplinghttp://en.wikipedia.org/wiki/Inductive_couplinghttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Magnetic_fluxhttp://en.wikipedia.org/wiki/Magnetic_fluxhttp://en.wikipedia.org/wiki/Magnetic_corehttp://en.wikipedia.org/wiki/Magnetic_corehttp://en.wikipedia.org/wiki/Magnetic_corehttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Electromotive_forcehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Isolation_transformerhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Permeability_(electromagnetism)http://en.wikipedia.org/wiki/Permeability_(electromagnetism)http://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Magnetic_fluxhttp://en.wikipedia.org/wiki/Magnetic_corehttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Electromotive_forcehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Isolation_transformerhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Permeability_(electromagnetism)http://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Inductive_coupling


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The reason analy*e of circuits containing ideal transformers is to easiest ay to analy*e the

circuit for its voltages and currents that contain an ideal transformer is to replace the portion of the circuit

on one side of the transformer by an equivalent circuit ith the same terminal characteristics! +esides

that& the process of replacing one side of a transformer by its equivalent at the other side/s voltage level is

,non as referring the first side of transformer to the second side! There are the ma)or items to be

considered in construction of any model of transformer such as copper losses& 0ddy current losses&

1ysteresis losses& and lea,age flu"!

The open circuit test is used to determine the value of Rc and 2m by opening the output line at

the secondary side of transformer! Then the full line voltage is applied to the primary of the transformer&

and input voltage& input current& and input poer to the transformer are measured! (rom those values& it is

possible to determine the poer factor of the input current and both the magnitude and the angle of the

e"citation impedence! In short circuit test& the secondary terminal of the transformer is short circuited& and

the primary terminals are connected to a fairly lo voltage source! The current floing in e"citation

branch is neglect since the input voltage is lo during the short circuit test! Thus& the entire voltage drop

in the transformer can be attributed to the series element in the circuit! The impendence angle& 3 ill be

positive since current lagging the voltage! In this topic e also analy*e the transformer voltage regulation

and efficiency! The voltage regulation is a quantity that compares the output voltage of the transformer at

no load ith the output voltage at full load! The transformer phasor diagram are used because it is easy to

determine the effect of the impedance and the current pahse angles on the transformer voltage regulation!

There are three condition of poer factor hich are lagging unity and leading! The efficiency of

transformer is calculated because to see the abilty of the transformer! Other than that& it is also to measure

the ma"imum efficiency of the transformer!

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4U05TION

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5O-UTION

a%

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b%

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c% 6 -agging Condition

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7RA81 ANA-95I5

7raph 5econdary Current $Is % versus :oltage Regulation $:R%

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6-eading Condition

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7RA81 ANA-95I5


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6Unity Condition

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7RA81 ANA-95I5


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d%

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Table 1; shon the differences style and symbol used in manual calculation and 5 b=c

a > d

Convert rectangular form

to real form

0"ample;

Req> ?!???@

0"ample;

Absolute

$convert rectangular form

to polar form%

0"ample;

: > $''!B )?!'EF%V

: > ''!? V

0"ample;

Rectangular (orm

0"ample; 0"ample;

Inverse cos 3 =sin 3

0"ample;

cosGH 3

sinGH 3

0"ample;

:alue of teta&3

0"ample;

eq > ?!??? )J!?KE?@

eq > F!BL KK!?M@

0"ample;

-oop (unction

0"ample;

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DI5CU55ION

+ased on the assignment given& e have ansers all the questions by using the 5


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CONC-U5ION

+ased on the graph& e can conclude that the differences value of theta or the differences of the poer

factor ill give the differences shape of graph! (or e"ample the lagging factor give large value of positive

in graph& unity factor give smaller positive in graph and leading factor give negative value in graph! These

graph ill shon the output voltage of the transformer at no load ith the output voltage at full load and

the used of current in three difference factor such as lagging& leading& and unity! +eteen these three

graphs the lagging graph give the higher value compare to the leading and unity!

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R0(0R0NC05

! Transformer $.i,ipedia%& http;==en!i,ipedia!org=i,i=Transformer & accessed on ?=='E!

'! 5

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