Transformer

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Transformer
Agus Purwadi, Qamaruzzaman Nana Heryana
Laboratorium Penelitian Konversi Energi
Elektrik Institut Teknologi Bandung
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Transformer
Definition

• A transformer is a device that convert ac
  electric energy at one voltage level at another
  voltage level.

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Transformer are important to modern life
Why
1.

• Thomas A. Edison (1882)
• Power Distribution System New York-USA 120
  Vdc
• Problems Losses Voltage Drop inefficient

Example
Inefficient
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High Voltage
Efficient
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Transformer are important to modern power system
LV
HV
High Voltage
Low voltage
Efficient
Inefficient
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Real Application on Power System
20 kV/380 V
380 V/20 kV
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Transformer
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2. Type and Construction Of Transformer
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3. The Ideal Transformer
Turn ratio a
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The Ideal Transformer
Turn ratio a
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The Ideal Transformer
In term of phasor quantities
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Power in ideal Transformer
Power input
Power input
ideal
Turn ratio equation
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Power in ideal Transformer
Active power
reactive power
Apparent power
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Evaluasi

• Untuk memahami konsep trafo ideal berikan ke
  mahasiswa, contoh sederhana misalnya
• Cara mendapatkan tegangan sekunder y volt jika
  tegangan primernya x volt.
• Arus sekunder b ampere pada tegangan y volt,
  cari arus primer a ampere pada tegangan X volt.
• Ambil nilai x dan y yang bedanya sangat besar
• Soal pada sistem 1 fasa dulu saja.

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Impedance Transformer
Impedance ratio of the phasor
voltage across it ti the phasor current
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Impedance Transformer
if
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Theory of operation of real single-phase
transformers
The basis transformer operation can be derived
from Faradays law
Flux linkage
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EMF equation of a transformer
Faraday law of electromagnetic induction
RMS Value
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Transformer Losses

• Copper (I2R) losses
• Eddy current losses
• Hysteresis losses
• Leakage flux

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The equivalent circuit of a transformer
the model of a real transformer
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The equivalent circuit of a transformer
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Phasor diagram corresponding referred to primary
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The equivalent circuit of a transformer
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Test on transformers

• Open-Circuit Test

• Result VOC IOC POC

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Open-Circuit Test Result
Conductance of the core-loss resistor
Susceptance of the magnetizing inductor
Admittance
Magnitude admittance
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Open-Circuit Test Result
Power Factor
Power Factor angle
Admittance
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Test on transformers

• Short-Circuit Test

Result VSC ,ISC ,POC
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Short-Circuit Test Result
Series impedance
Power Factor of the current
Lagging - Current angle (-),Impedance angle ()
Therefore,
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Short-Circuit Test Result
Series impedance
Admittance
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Test
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Solution
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The per-unit system of measurement
In single-phase system
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Voltage Regulation Efficiency
Voltage Regulation
Efficiency
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Autotransformer
Step-down autotransformer
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Power rating -autotransformer
SIO Input and Output apparent powers SW
apparent power in the transformer windings
For example, a 5000 kVA autotransformer
connecting a 110 kV system to a 138 kV system
would have an NC/NSE turn of ratio of 110 28.
Such an autotransformer would actually have
windings rated at
Example
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Three-phase transformer
A three-phase transformer bank composed of
independent transformer
A three-phase transformer wound on a single
three-legged core
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Three-phase transformer connections

• Wye-wye (Yy)
• Wye-delta (Yd)
• Delta-wye (Dy)
• Delta-delta (Dd)

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Wye-wye (Yy) Connection
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Wye-delta (Yd) Connection
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Delta-wye (Dy) Connection
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Delta-delta (Dd) Connection
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Test

• A 50 kVA 13.800 / 208 V, Dy distribution
  transformer has a resistance of 1 percent and
  reactance of 7 percent per unit.
• What is the transformers phase impedance
  referred to the high-voltage side?
• Calculate this transformers voltage regulation
  at full load and 0,8 PF lagging, using the
  calculated high-side impedance.
• Calculate this transformers voltage regulation
  under the same conditions, using the per-unit
  system.

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Instrument transformers

• Potential transformer (PT)
• Current transformers (CT)