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
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
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
17.
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