Mustafa Gökhan Günay-150609027

8/4/2019 Mustafa Gkhan Gnay-150609027

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TRANSFORMERS

Mustafa Gkhan Gnay

150609027


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DEFINITION

Device used to transfer energy from primarywinding to secondary winding by

electromagnetic induction.

Based on Faradays Law of induction

Where:-

EMF (V)

B Magnetic flux (Wb)


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TRANSFORMER USES

Impedance matching

Electrical Isolation

AC power transmission

STEP-UP Transformer

STEP-DOWN Transformer


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HISTORY

1831Michael Faraday invented the

Induction Ring.

1881Lucien Gaulard and John Gibbs

exhibited a device called secondary generator.

1885William Stanley developed the fist

commercially used practical device while

working for Westinghouse Electric Companyin US.


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INDUCTION THEORY

Transformers behaviour is based on

Faradays Law of Induction

Where:-

EMF (V)N No of turns of wire

B Magnetic flux (Wb)


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INDUCTION THEORY


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POWER GENERATION AND

TRANSMISSION


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TRANSFORMER MODELS

Ideal Transformer

-

Vs(t)

Np Ns

+

Vp(t)

ip(t)

-

+

is(t)

Np = No of windings on the primary Ns = No of windings on the secondaryip = Current into the primary is = Current out from the secondaryVp = Voltage across the primary Vs = Voltage across the secondary


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VP = NP = a = iS

VS NS iP

Note; a < 1 = Step up transformer

a > 1 = Step down transformer

Voltage and current angles are NOT affected hence, P

= S=

Primary and Secondary Relationship


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Transformers have losses and these losses

must come into consideration.

Copper losses (I^2 R)

Leakage Flux losses

Core losses

Eddy currents

Hysteresis losses

LOSSES


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REAL TRANSFORMER LOSSES

Vp(t) jXm

Rp

Vs(t)Rc

is(t)Lp Ls

Np

Rsip(t)

Ns

Copper losses (I^2 R)

Leakage Flux losses Core losses

Eddy currents

Hysteresis losses


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EQUIVALENT CIRCUIT

jXm aVsRc

Is/aLeqpReqp

Vp

Approximate Transformer Model referredto the primary side


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TYPES

Auto-TransformerUsed to change a desirable voltage by only a small

amount. For example: 120/132 V

IH +

-

+

-

VL

VSE

NC

NSE

VH

ISE

IL


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TYPES

Three Phase TransformersThree phase transformers

can be constructed in two

different ways i.e. :-

1. A three phase bank consists

of three single phase

transformers.

2. Three windings wrapped

around a common core.


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THREE PHASE TRANSFORMER

CONNECTIONS

Deltawye ( Y)

Wye delta (Y- )

Deltadelta ( )

Wye wye (Y Y)


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TYPES

Two types of special purpose transformers usedin power systems for taking measurements.

Potential Transformer

Current Transformer


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EFFICIENCY

Efficiency () is the ratio of the power out to the

power in of a transformer.

in anIdeal transformer, no power losses

PIN = VPIP cos P

POUT = VSIS cos S

PIN = POUT = VPIP cos P = VSIS cos S

SOUT = SIN = VPIP = VSIS Ideal = 100%


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Efficiency for a single phase

real transformer As mentioned previously, losses occur in a real

transformer and these losses must be taken into count.

Hence, Real = POUT x 100%

PIN

= POUT x 100%

POUT + PLOSS

= VSIScosS_________

VSIS cos S + i2R + (VP/a)2 RC


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Voltage regulation (VR) is the ability of a system to

provide near constant voltage over a wide range of load

conditions. Also it compares the VO at no load to VO at

full load.

VOLTAGE REGULATION

An Ideal transformer has a voltage regulation,

VR = 0%

Mustafa Gökhan Günay-150609027

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