The document summarizes an industrial training seminar on transformer construction held at BHEL Bhopal from May 29th to June 25th, 2014. It was presented by Mandeep Singh, an electrical engineering final year student from B.I.E.T Jhansi, under the guidance of Shri Shailendra Kumar Somi from BHEL Bhopal. The seminar covered topics such as transformer core building, winding, coil assembly, power assembly, case fitting, insulation, testing, and dispatch. It provided details on the manufacturing process and testing standards for power transformers.

1. INDUSTRIAL TRAINING SEMINAR
ON
“TRANSFORMER CONSTRUCTION”
AT
BHEL BHOPAL
DURATION: 29TH MAY – 25TH JUNE,
2014
HEAD OF DEPARTMENT
Dr. Deepak Nagaria
PRESENTED BY
Mandeep Singh
EE Final Yr
B.I.E.T Jhansi
Roll No: 1104320020
UNDER GUIDENCE OF
Shri Shailendra Kumar Somi
Sr. Er. TRM Div BHEL Bhopal

2. 1. INTRODUCTION
2. TRANSFORMER CORE BUILDING
3. WINDING
4. COILASSEMBLY
5. POWER ASSEMBLY
6. CASE FITTING
7. INSULATION SHOP
8. TESTING
9. DISPATCH
10. REFERENCES
CONTENTS

3. BHEL, Bhopal established in 1964, is an integrated power plant
equipment manufacturer and one of the largest engineering and
manufacturing companies in India in terms of turnover.
It has 15 manufacturing divisions, two repair units, four regional
offices, eight service centers and 15 regional centers.
It has been acquiring and adapting some of the best technologies
from leading companies in the world including General Electric
Company, Alstom SA, Siemens AG and Mitsubishi Heavy
Industries Ltd.
INTRODUCTION TO BHEL BHOPAL

4. a) Block 1A :- Fabrication
b) Block 1B :- Hydro Turbine, Tanks
c) Block 2 :- Electrical Machine
d) Block 3 :- Transformer Manufacturing, Capacitor & Bushing
e) Block 4 :- Switchgear, Control gear
f) Block 5 :- Foundry Division
g) Block 6 :- Steam Turbine
h) Block 7 :- Factory Store
i) Block 8 :- Coils & Insulation
j) Block 9 :- Traction motor block
k) Block 10 :- Lamination Cutting
BLOCK DISCRIPTION

5. POWER TRANSFORMER CONSTRUCTION
Fig: Block Diagram representation of Transformer Construction

6. TRANSFORMER CORE BUILDING
Following steps are involved in power transformer core
construction:
1) Cutting & punching of CRGO
2) Stacking of CRGO
3) Fiber Glass End Frame insulation
4) Insulated Bolting of End Frame.

7. Fig: Cutting & punching of CRGO Fig: Stacking of CRGO
Fig: End Frame insulation & End Frame bolted Fig: Erecting of Core

8. WINDING
TYPES OF WINDING MACHINES
Winding Machines are of two types:
1) Horizontal Winding machines
2) Vertical Winding machines
Fig: Horizontal Winding machines Fig: Vertical Winding machines

9. TYPES OF WINDINGS:
1) Spiral Winding (L.V.L.C.)
2) Helical Winding (L.V.H.C.)
3) Disc Winding
4) Interleaved Disc Winding
Fig: Helical Winding
Fig: Interleaved Disc Winding
Fig: Disc Winding

10. The various types of conductors used in coil winding are
1) CTC (Continuously Transposed Conductor)
2) PICC (Paper Insulated Copper Conductor)
3) BPICC (Bunch Paper Insulated Copper Conductor)
TYPES OF WINDING CONDUCTORS
Fig: CTCFig: PICC Fig: BPICC

11. COILASSEMBLEY
Coil Sequence
L.V. Coil is placed adjacent to the CRGO steel core and
H.V coil outside, in order to minimize the amount of
insulation required.
While assembling the different coils (i.e. Tap coil, L.V. Coil
& H.V. Coil) tap coil can be placed in either of three positions
depending upon the length of tap coil i.e. if tap coil is small it
is placed inside of LV coil, if it is medium then between LV &
HV coil, and if large then outside of HV coil.
The coils are specified in the design may be of following types
on the basis of operating voltage:
1) L.V. Coil Winding
2) H.V. Coil Winding
3) Tap Coil Winding

12. Fig: Vertical Winding (HV)Fig: Horizontal Winding (LV & Tap)
Fig: Coil Assembly
Fig: Oven Baking
Fig: Hydraulic Press

13. POWER ASSEMBLEY
 Core - Coil Assembly 1
a) Unlatching of core
b) Fitting of bottom insulation
c) Core coil assembly as per drawing/electrical specification
 Core - Coil Assembly 2
a) Fitting of top insulation
b) Relacing of core
 Terminal Gear Mounting 1
a) Crimping & Brazzing
b) Insulation Wrapping
c) OLTC Connection
d) Electrical Circuit manufacturing
 Terminal Gear Mounting 2
a) Vapour Phase Drying
b) Servicing.
Steps involved in Power Assembly are :

14. Fig: Unlatching of core
Fig: Core coil assembly as per drawing
Fig: Relacing of core
CORE COILASSEMBLY 1 & 2

15. Fig: Electrical Circuit manufacturing

16. Fig:Vapour Phase Drying of core & winding alone
Fig: Vapour Phase Drying of Transformer

17. CASE FITTING
1) CT connections & Feed positions
2) Conservator
3) Bushing Connections
4) Magnetic Oil Gauge
5) Oil Temperature Indicator
6) Buchholz Relay
7) Radiator
8) Breather
9) Control panel
Case Fitting involves connecting accessories of transformer, these
accessories include following :

18. 1. Transformer tank
2. High voltage bushing
3. Low voltage bushing
4. Cooling fins radiator
5. Cooling fans
6. Conservator tank
7. System ground terminal
8. Drain valve
9. Breather
10. Oil temperature gauge
11. Current xmer terminals
12. Control panel
Fig: Parts of Transformer

19. INSULATION MATERIALS
Fig: Press Board Material
Fig: Udel Wood
Fig: Bushing Insulation
Fig: Fiber Glass Material Fig: Oil Insulation
Fig: Bakellite

20. Items made up of PBM:-
1) Former Base Cylinder
2) DOF Separator
3) T-Block
4) Static Ring
Items made up of Udel Wood:-
1) T-Spacers
2) Full ring segment
3) Half ring segment
4) Shunts
Fig: Items made up of Udel Wood
Fig: Items made up of PBM

21. 1) TESTING TO THE BRITISH STANDARDS
2) ROUTINE TEST FOR TRANSFORMER AS
PER IS 2026
TYPES OF TESTS

22.  Routine tests:
1) Voltage ratio and polarity.
2) Winding resistance.
3) Short-circuit impedance and load loss.
4) Dielectric test.
5) No-load losses and current.
6) On-load tap-changer.
 Type tests:
1) Temperature rise test.
2) Lightning impulse test.
TESTING TO THE BRITISH STANDARDS

23. 1) Dimensional Check
2) Winding Resistance Test
3) Short Circuit Test
4) Open Circuit Test
5) Induced Over Voltage Test
6) Separate Source Voltage
7) Insulation Resistance Test
8) B.D.V of Oil
9) Turns Ratio Test
ROUTINE TEST FOR TRANSFORMER AS PER
IS 2026

24. DISPATCH
After successful completion of testing, transformer is handed over
to dispatch sections. At this stage after checking oil leakage,
dismantling of all bushings, turrets etc. and covered with the
blanking plates and the tank is fitted with nitrogen gas and then
the transformer is dispatched to the concerned site.
There are generally three separate shipments made:
1) The main tank c/w core and coils,
2) The accessories that have been removed and packaged, and
3) The insulating oil.

25. Fig: Dispatch of power transformer

26. [1] Dr. P. S. Bhimbra, “Electrical Machines”, Khanna
Publications, New Delhi.
[2] D. P. Kothari and I. J. Nagrath, “Electrical Machines” , 3rd
Edition, TMH, New Delhi.
[3] BHEL , “Transformers” 2nd Edition ,Tata Mcgraw Hill
Education Private Limited.
REFERENCES

27. THANK YOU