Transformer Professor Mohamed A. El-Sharkawi

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TransformerProfessor Mohamed A. El-Sharkawi
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Why do we need transformers?

• Increase voltage of generator output
• Transmit power and low current
• Reduce cost of transmission system
• Adjust voltage to a usable level
• Create electrical isolation
• Match load impedance
• Filters

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Basic Components
Iron Core
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Basic AnalysisVoltage

• Volts/turn is constant
• Voltages are in phase (no phase shift)
• Magnitudes vary with turns ratio.

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Basic Analysis Power and current

• Currents are in phase.
• Current ratio is opposite to the voltage ratio

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Basic Analysis Reflected impedance
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Ideal Transformer Ratings

• 100 MVA, 13.8/138 KV

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Ideal Transformer Ratings
100 MVA, 138/13.8 KV
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Actual Transformer

• Windings
• Resistance
• Inductance
• Core
• Eddy Current
• Hysteresis

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Windings Impedance
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Core Hysteresis
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i
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Core Model
Let
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Core Model
Let
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Equivalent Circuit
X1
R1
R2
X2
N1
N2
Io
I1
I2
V1
E1
V2
E2
Ro
Xo