Electrical Machines LSEGG216A 9080V. Transformer Operation Week 4.

Electrical Machines

LSEGG216A9080V

Transformer Transformer OperationOperation

Week 4 Week 4


V+ CIVILCIVIL

Voltage Current

Magnetic Flux


Applied Voltage

Induced Voltage

Induced Voltage in Secondary

Resultant Current

V1

V’1V’2

IM

Induced VoltageInduced Voltage

• Φmax =Maximum instantaneous flux• F = Frequency• N = Number of turns• Bmax = Maximum permissible flux density in Wb• A = CSA of core in m2

fN44.4V max AfNB44.4V max


V1

IM

Ie

Io

Ie= Iron loss currentIo = No load current


V1

V’1V’2

Io

I’2

I’1

I1


V1

V’1V’2

Io

I’2 I’1

I1

Transformation Transformation RatioRatio

Magnetic flux is common coils

fN44.4V max

Therefore the voltage can be varied by changing the number of turns


V1= N1

N2V2== k = Transformation Ratio


V1x I1

N1

N2

= V2 x I2

=I1

I2


V1x I1

VA

V2 x I2

kVAPower In Power Out


V1x I1V2 x I2

200

200V 100V

400

K = 2

Voltage Voltage RegulationRegulation

EI

Voltage Drop Due to R

Voltage Drop Due to XL

V

• Resistance• Inductance

Coils have both


EI V

Lagging PF of 45

V less than E


EI

V

Leading PF of 45

V More than than E


100 x VNo Load – V Full Load

VFull Load

R% =

If PF = Unity

100 x I x (R x cos + XL x sin)

VFull Load

R% =

Transformer Basic Transformer Basic TestsTests• Open Circuit Test• Short Circuit Test• Oil Tests• Electrical Insulation• Polarity• Continuity

Open Circuit TestOpen Circuit TestUsed to determine Iron Losses

Supply = Rated Voltage

Open Circuit TestOpen Circuit Test

Wattmeter reading

V1

IMIo

Ie

Supply Voltage

Ammeter reading

Short Circuit TestShort Circuit TestUsed to determine Copper Losses

Supply Adjusted = Rated Secondary Current

Electrical Machines LSEGG216A 9080V. Transformer Operation Week 4.

Documents

Transcript of Electrical Machines LSEGG216A 9080V. Transformer Operation Week 4.