working

1. Transformer
• Electrical device that transfers AC power from
one circuit to another at same frequency.

2. Definition
• A transformer is a static device that transfers
electrical energy between two or more circuits
through electromagnetic induction.

3. Purpose
• • Step-up or step-down voltage
• • Electrical isolation
• • Efficient power transmission

4. Working Principle
• Based on mutual induction. AC in primary
creates magnetic flux, inducing emf in
secondary winding.

5. Construction
• • Core (laminated silicon steel)
• • Primary winding
• • Secondary winding
• • Insulation

6. Types of Transformers
• • Step-up
• • Step-down
• • Power transformer
• • Distribution transformer
• • Auto transformer

7. Losses in Transformer
• • Copper losses
• • Core losses (hysteresis & eddy current)
• • Stray losses

8. Testing of Transformer
• • Open Circuit Test
• • Short Circuit Test
• • Determines losses and efficiency

9. Applications
• • Power transmission
• • Distribution systems
• • Industrial equipment
• • Electronic devices

10. Components
• • Core
• • Windings
• • Tap changer
• • Conservator
• • Breather

11. Protection of Transformer
• • Buchholz relay
• • Overcurrent protection
• • Differential protection
• • Surge arresters

12. Factors Affecting Selection
• • Voltage rating
• • Power rating
• • Efficiency
• • Cooling method
• • Application

13. Example Calculation
• Given:
• 220 kV / 22 kV, 100 MVA, 50 Hz
• Step-down transformer

14. Turns Ratio
• K = V2 / V1 = 22 / 220 = 0.1
• Since K < 1 → Step-down transformer

15. Primary Current Calculation
• S = √3 V I
• I1 = 100×10^6 / (√3 × 220×10^3)
• I1 ≈ 262.37 A

16. Secondary Current Calculation
• I2 = 100×10^6 / (√3 × 22×10^3)
• I2 ≈ 2627.43 A