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Transformer

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  1. Transformer Agus Purwadi, Qamaruzzaman & Nana Heryana Laboratorium Penelitian Konversi Energi Elektrik Institut Teknologi Bandung

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

  3. Transformer are important to modern life 1. Why • Thomas A. Edison (1882) Power Distribution System : New York-USA ; 120 Vdc Problems : Losses & Voltage Drop = inefficient Example : Inefficient

  4. High Voltage Efficient

  5. Transformer are important to modern power system LV HV High Voltage Low voltage Inefficient Efficient

  6. Real Application on Power System 20 kV/380 V 380 V/20 kV

  7. Frequency • Power Frequency , 50/60 Hz • Radio frequency, > 30 kHz Teknik Tenaga Elektrik • Power Transformer • Instrument Transformer Transformer

  8. 2. Type and Construction Of Transformer

  9. 3. The Ideal Transformer Turn ratio a

  10. The Ideal Transformer Turn ratio a

  11. The Ideal Transformer In term of phasor quantities

  12. Power in ideal Transformer Power input Power input ideal Turn ratio equation

  13. Power in ideal Transformer Active power reactive power Apparent power

  14. 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.

  15. Impedance Transformer Impedance = ratio of the phasor voltage across it ti the phasor current

  16. Impedance Transformer if

  17. Theory of operation of real single-phase transformers The basis transformer operation can be derived from Faraday’s law Flux linkage

  18. EMF equation of a transformer Faraday law of electromagnetic induction RMS Value

  19. Transformer Losses • Copper (I2R) losses • Eddy current losses • Hysteresis losses • Leakage flux

  20. The equivalent circuit of a transformer the model of a real transformer

  21. The equivalent circuit of a transformer

  22. Phasor diagram corresponding – referred to primary

  23. The equivalent circuit of a transformer

  24. Test on transformers • Open-Circuit Test • Result : VOC IOC POC

  25. Open-Circuit Test Result Conductance of the core-loss resistor Susceptance of the magnetizing inductor Admittance Magnitude admittance

  26. Open-Circuit Test Result Power Factor Power Factor angle Admittance

  27. Test on transformers Short-Circuit Test Result : VSC ,ISC ,POC

  28. Short-Circuit Test Result Series impedance Power Factor of the current Lagging - Current angle (-),Impedance angle (+) Therefore,

  29. Short-Circuit Test Result Series impedance Admittance

  30. 2.2 The equivalent circuit impedances of a 20 kVA, 8000 / 240 V, 60 Hz transformer are to be determined. The open circuit test were performed on the primary side of the transformer, and the following data were taken : Open-circuit test (on primary) Shots-circuit test (on primary) VOC = 489 V IOC = 2,5 A POC = 240 W VOC= 8000 V IOC = 0,214 A POC = 400 W Test

  31. Solution

  32. The per-unit system of measurement In single-phase system :

  33. Voltage Regulation & Efficiency Voltage Regulation Efficiency

  34. Autotransformer Step-down autotransformer

  35. Power rating -autotransformer SIO =Input and Output apparent powers SW = apparent power in the transformer windings Example 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 :

  36. Three-phase transformer A three-phase transformer bank composed of independent transformer A three-phase transformer wound on a single three-legged core

  37. Three-phase transformer connections • Wye-wye (Yy) • Wye-delta (Yd) • Delta-wye (Dy) • Delta-delta (Dd)

  38. Wye-wye (Yy) Connection

  39. Wye-delta (Yd) Connection

  40. Delta-wye (Dy) Connection

  41. Delta-delta (Dd) Connection

  42. 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 transformer’s phase impedance referred to the high-voltage side? • Calculate this transformer’s voltage regulation at full load and 0,8 PF lagging, using the calculated high-side impedance. • Calculate this transformer’s voltage regulation under the same conditions, using the per-unit system.

  43. Instrument transformers • Potential transformer (PT) • Current transformers (CT)