Sarvottam Deshpande presented a seminar on power transformers. Power transformers are used to transfer power between different voltage levels by electromagnetic induction without changing frequency. They are generally rated at 500kVA or greater. Power transformers can be classified as small (500-7500kVA), medium (7500-100MVA), or large (over 100MVA) and have an average lifespan of 30 years. The core is made of silicon steel to reduce losses and hysteresis losses use cold rolled grain oriented silicon steel. Various winding types like spiral, helical, and sandwich are used depending on current rating. Insulation uses oil-impregnated paper and cooling is provided by the insulating oil or separate radiators.

1. SEMINAR
ON
POWER TRANSFORMER
PRESENTED BY:
Sarvottam Deshpande
Class TE(EEP)
Roll no .14

2. POWER TRANSFORMER

3. INTRODUCTION:
A TRANSFORMER CAN BE DEFINED AS A STATIC ELECTRICAL DEVICE WHICH
TRANSFERS POWER FROM ONE CIRCUIT TO ANOTHER BY MEANS OF
ELECTROMAGNETIC INDUCTION. THE TRANSFER IS ACCOMPANIED WITHOUT
ANY CHANGE IN THE FREQUENCY.
THE TERM POWER TRANSFORMER IS GENERALLY USED TO REFER TO
TRANSFORMERS WITH A RATING OF 500KVA OR GREATER.
POWER TRANSFORMERS ARE USED IN DISTRIBUTION SYSTEMS WHEREVER THERE
IS A NEED TO INTERFACE BETWEEN DIFFERENT VOLTAGE LEVELS I.E. TO STEP UP
AND STEP DOWN VOLTAGES.

4. Power transformers are generally of the liquid-immersed type. However,
Power transformers used for indoor applications may be air-cooled.
Based on the size ranges, transformers can be classified into three types.
Small Power Transformers : 500 to 7500kVA
Medium power transformers : 7500 to 100MVA
Large power transformers : 100MVA and beyond
The average life of a transformer is around 30 years.
.

5. CORE MATERIAL
Basic material are Alloy Steel having main content Silicon & carbon
Which increases permeability & reduces losses
CRGO
(cold rolled grain
oriented silicon steel)
CRGOS shows excellent Magnetic properties.
The purpose of using CRGO is to reduce the hysteresis losses.
So CRGOS is more used

6. Power transformer core

7. CORE AND ACTIVE PART
ACTIVE PART
C.R.G.O. STRIPS
1-STRIP HAS WIDTH OF 0.27 mm
COIL OR WINDING ASSEMBLY
PROCEDURE
Manufacturing of LIMB
Core Insulation

8. CORE AND ACTIVE PART
 Removal of TOP FRAM for Coil assembly
 Winding insulation detail
 TOP YOKE FILLING
 VAPOUR PHASE OVEN
 HV & LV leads from top & bottom to the bushings
 REGULATING COILS to the tap changer

9. TYPE OF WINDING

11. SPIRAL
• It is used 100 A& for low Voltage Winding
 Mechanically very strong
Helical
 Intermediate range of current
 Suitable for LV winding of large transformer

12. Cross over
• Cross-over suitable of current not exceeding 20 A.
• Use for HV winding of small transformer
 Continuous disc:
• No of turns wound radially over one another
• separated by spacers
• HV winding
• Mechanically strong

13. Sandwich
 mostly used for shell type transformer
 Control leakage reactance
 HV & LV are near so leakage flux is reduced
 mmf of each section is same.

14. INSULATION
kinds of Insulations:
Major Insulation:
Insulating between LV & core
Also between HV & LV
Insulating barriers between limbs, coils & core yoke
Oil impregnated paper used as it has high dielectric
strength

15. MINOR INSULATION
• Insulation between individual turns &
between layers
Conductor Insulation
• paper & cotton
• Air insulated Transformer insulation
used is glass tap

16. TRANSFORMER TANK
 Plain sheet steel Tank
 Tube Tank
 Radiator Tank
 Tank with separate coolers

18. TRANSFORMER OIL
 Double purpose , cooling & Insulating
 Permittivity is 2.5
 Breakdown strength of oil used must be 50kv RMS
 Major disadvantage is sluging
 To overcome this, synthetic oil is prefered

19. FINAL ASSEMBLY
 Installation of active part and assembly of accessories
 TRANSFORMER TANK

20. WORK SHOP

21. QUALITY TEST
 Design
 Process Time
 M/C size specification
 Process of manufacturing
 Dimension specification
 Testing specification

22. THANK YOU