Transformer basic

• 1. Transformer Basic-B. PrasadCharteredEngineeramieclub@gmail.com

2. working principleA transformerworks on theFaraday,slawofelectromagnetic induction.A transformerconsists of alaminatedmagnetic 3. Transformerparts 4. Winding 5. Type of transformer Distribution Power. Control. Auto. Isolation. Instrument potential. Instrument current Indoor Outdoor Oil type Dry type Core type Shell type Natural cool Forced air/watercool 6. Distribution transformerPrimaryvoltageSecondaryvoltageCapacity(KVA)Construction Impedancerange3-11 380-440 25,40,63 Dry type 3-7%100,150,250 Dry type300,400,500 Oil/dry type630,750,1000 Oil type1250,1600 Oil type2000,2500 Oil type 7. Star delta connection 8. Star delta diagram 9. Star delta voltage current Line voltage on Primary side = 3 X Phase voltage onPrimary side. So Phase voltage on Primary side = Line voltage on Primaryside / 3 Transformation Ration (K) = Secondary Phase Voltage /Primary Phase Voltage Secondary Phase Voltage = K X Primary Phase Voltage. As Secondary in delta connected: Line voltage on Secondary side = Phase voltage onSecondary side. Secondary Phase Voltage = K X Primary Phase Voltage.=K X (Line voltage on Primary side / 3) 10. Advantages of StarDelta Connection The Y-D connection has no problem with thirdharmonic components fewer numbers of turns are required The neutral available on the primary can beearthed to avoid distortion. Neutral point allows both types of loads(single phase or three phases) to be met Large unbalanced loads can be handledsatisfactory 11. Disadvantages of star delta The secondary voltage is not in phase with theprimary If secondary of this transformer should beparalleled with secondary of another transformerwithout phase shift, there would be a problemApplication: commonly employed for power supplytransformers. Y connection on the HV side reduces insulationcosts the neutral point on the HV side can begrounded. 12. Tap changerIt is a device fitted inthe transformer,which is used tovary the voltagetransformationratio. Off load tapchanger Onloadtapchanger(OLTC) 13. BUSHINGTransformer Bushingsare specially designedelectrical terminals fortaking out windingends (leads) throughthe openings providedon the top cover orwall of the oftransformer tank andconnecting to theincoming andoutgoing lines. 14. CT =CURRENTTRANSFORMERTypical specification fora 11kV CT System voltage:11 KV Insulation level voltage (ILV) :12/28/75 kV Ratio: 200/1 - 1 - 0.577 A Core 1: 1A, metering, 15VA/class 1, ISF