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Transformer Professor Mohamed A. El-Sharkawi. 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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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
Insulated Copper Wire Basic Components Iron Core
i1 i2 + + e1 e2 N1 N2 _ _ Primary Secondary
i2 i1 + + e2 e1 N1 N2 _ _ Basic Analysis:Voltage • Volts/turn is constant • Voltages are in phase (no phase shift) • Magnitudes vary with turns ratio.
i2 i1 + + e2 e1 N1 N2 _ _ Basic Analysis: Power and current • Currents are in phase. • Current ratio is opposite to the voltage ratio
I I 1 2 Apparent Power + + V N1 V N2 1 2 - - Primary Voltage Secondary Voltage Ideal Transformer: Ratings 100 MVA, 13.8/138 KV
I I 1 2 + + V N1 V N2 1 2 - - Ideal Transformer: Ratings 100 MVA, 138/13.8 KV
i2 i1 + + e2 e1 N1 N2 _ _ Actual Transformer • Windings: • Resistance • Inductance • Core: • Eddy Current • Hysteresis
X1 R1 R2 X2 N1 N2 Ideal Transformer Windings Impedance
i B + e N _ H Core Hysteresis
i e R i Core Model Let
i e Xl i Core Model Let
i e R Xl i i
Equivalent Circuit X1 R1 R2 X2 N1 N2 Io I1 I2 V1 E1 E2 V2 Ro Xo