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Transformer. Agus Purwadi, Qamaruzzaman & Nana Heryana. Laboratorium Penelitian Konversi Energi Elektrik Institut Teknologi Bandung. Transformer. A transformer is a device that convert ac electric energy at one voltage level at another voltage level. Definition.

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## Transformer

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**Transformer**Agus Purwadi, Qamaruzzaman & Nana Heryana Laboratorium Penelitian Konversi Energi Elektrik Institut Teknologi Bandung**Transformer**A transformer is a device that convert ac electric energy at one voltage level at another voltage level. Definition**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**High Voltage**Efficient**Transformer are important to modern power system**LV HV High Voltage Low voltage Inefficient Efficient**Real Application on Power System**20 kV/380 V 380 V/20 kV**Frequency**• Power Frequency , 50/60 Hz • Radio frequency, > 30 kHz Teknik Tenaga Elektrik • Power Transformer • Instrument Transformer Transformer**3. The Ideal Transformer**Turn ratio a**The Ideal Transformer**Turn ratio a**The Ideal Transformer**In term of phasor quantities**Power in ideal Transformer**Power input Power input ideal Turn ratio equation**Power in ideal Transformer**Active power reactive power Apparent power**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.**Impedance Transformer**Impedance = ratio of the phasor voltage across it ti the phasor current**Theory of operation of real single-phase transformers**The basis transformer operation can be derived from Faraday’s law Flux linkage**EMF equation of a transformer**Faraday law of electromagnetic induction RMS Value**Transformer Losses**• Copper (I2R) losses • Eddy current losses • Hysteresis losses • Leakage flux**The equivalent circuit of a transformer**the model of a real transformer**Test on transformers**• Open-Circuit Test • Result : VOC IOC POC**Open-Circuit Test Result**Conductance of the core-loss resistor Susceptance of the magnetizing inductor Admittance Magnitude admittance**Open-Circuit Test Result**Power Factor Power Factor angle Admittance**Test on transformers**Short-Circuit Test Result : VSC ,ISC ,POC**Short-Circuit Test Result**Series impedance Power Factor of the current Lagging - Current angle (-),Impedance angle (+) Therefore,**Short-Circuit Test Result**Series impedance Admittance**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**The per-unit system of measurement**In single-phase system :**Voltage Regulation & Efficiency**Voltage Regulation Efficiency**Autotransformer**Step-down autotransformer**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 :**Three-phase transformer**A three-phase transformer bank composed of independent transformer A three-phase transformer wound on a single three-legged core**Three-phase transformer connections**• Wye-wye (Yy) • Wye-delta (Yd) • Delta-wye (Dy) • Delta-delta (Dd)**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.**Instrument transformers**• Potential transformer (PT) • Current transformers (CT)

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