500 MW synchronous generator rotor construction report

1. INDUSTRIAL TRAINING REPORT
on
MANUFACTURING PROCESS
OF
500MW TURBO ROTOR
IN
BHEL HARIDWAR
Submitted for partial fulfillment of award of
B.Tech. Degree
in
Electrical and Electronics Engineering
SUBMITTED BY
Name: Sumit Kumar Singh Roll.No:1013321102
SUBMITTED TO
Ankit Kumar Srivastava
Training and placement co-ordinator
Deptt. Of Electrical and Electronics
NOIDA INSTITUTE OF ENGINEERING & TECHNOLOGY, GREATER
NOIDA 2013-2014
i

2. ACKNOWLEDGEMENT
I take this opportunity to express my ineffable sense of profound gratitude to Mr. Rajendra
kumar, for his expert guidance and encouragement during the execution of the project.
I extend my sincere thanks to Shri Mayank Singh, Engineer, Planning, ACM-Block,
BHEL, Haridwar, for his help in extending all possible facilities during course of
ii
my project work.
I owe my deep sense of indebtedness to Shri Raj Kumar, Engineer Production,
BHEL, Haridwar for his guidance and suggestions for completion of my project report.
I would also like to thank to the following persons, who helped me directly or indirectly
in completing this project work.
 Shri Shailendra Kumar Mishra, Dy. Manager, EME, BHEL, Haridwar.
 Shri K. N. Arora, Manager, EMT, BHEL, Haridwar.
 Shri R. K. Khanna, Senior Engineer, MRL, BHEL, Haridwar.
 Shri Veekesh Kumar, Astt. Engineer, Rotor Assembly Section, BHEL, Haridwar.
 Shri Pankaj Kumar Gupta, Astt. Engineer, Planning (ACM), BHEL, Haridwar.

3. CERTIFICATE
This is to certify that I (Sumit Kumar Singh) student of Electrical Engineering have
completed the project work titled “Manufacturing process of Rotor for a 500 MW
Turbo generator”.
This report is a record of the work carried out independently and systematically, by me
under the guidance of Mr. Rajendra Kumar.
This project work has been carried out in partial fulfillment of the requirement for
passing Section–B of the Institution of Engineers (India). It is further certified that,
this is an original work and no part of its contents have been submitted to any other
Institution for the award of any Certificate, Diploma or Degree.
iii
Sumit Kumar Singh
(1013321102)

4. TABLE OF CONTENS
CONTENTS Page No.
Introduction 1
Synopsis 2-3
CHAPTER 1 Technical Detail 5-14
1.1 Technical Requirement of Rotor Bar Material:- 6-7
1.2 Copper Material for Rotor Bars:- 8-13
1.3 Material Testing Result:- 14
CHAPTER 2 Cooling System of Rotor 15-17
CHAPTER 3 Manufacturing Process of Rotor Bar 18-27
3.1 Marking of coils 18
3.2 Drilling of Rotor Bars 18
3.3 Counter Sinking of radial cooling holes 21
3.4 Cleaning of Canal 21
3.5 Caulking of holes 21
CHAPTER 4 Rotor Assembly & Dynamic Balancing 28-31
4.1 Rotor Assembly 28-31
4.2 Dynamic Balancing of Rotor 31
CHAPTER 5 Testing of Rotor 32
5.1 High Voltage (HV) Test 32
5.2 Impedance Test 32
CHAPTER 6 Conclusion 33
iv

5. LIST OF FIGURS
Figure No. Figure Name. Page No.
Figure - 1 Positions of slots in Rotor 7
Figure - 2 Cross-section of Flat Copper Conductor 8
Figure - 3 Filler 8
Figure - 4 Cross-section of Flat Copper Conductor 11
Figure - 5 Slot Cross Section 12
Figure - 6 Filler 13
Figure - 7 Small & Big Support with Conductor 14
Figure - 8 Rotor Cross-section with H2 flow path 16
Figure - 9 Cooling Path for Hydrogen in Turbo Generator 17
Figure - 10 Schematic Diagram of Drilling for cooling duct
for coil A of 4 layers 19
Figure - 11 Schematic Daigram of Drilling for cooling duct
for coil B,C,D,E,F and G of 9 layers 20
Figure - 12 Caulking Chiesel 21
Figure - 13 Conductor Shape after edge bending 22
Figure - 14 Radius Bending Tool 25
Figure - 15 Assembly of coil in a rotor slot 28
Figure - 16 Electrical Connection at Exciter End 30
Figure - 17 Graph 32
v

6. INTRODUCTION
BHARAT HEAVY ELECTRICAL LIMITED (BHEL)
BHEL is the largest engineering and manufacturing enterprise in India in the
energy-related equipment sector. BHEL was established more than 50 years ago, ushering
in the indigenous Heavy Electrical Equipment industry in India - a dream that has been
more than realized with a well-recognized track record of performance
BHEL manufactures over 180 products under 30 major product groups and caters
to core sectors of the Indian Economy viz., Power Generation & Transmission, Industry,
Transportation, Renewable Energy, etc. etc. The wide network of BHEL consist of 14
manufacturing divisions, four Power Sector regional centers, over 100 project sites, eight
service centers, 18 regional offices.
The company has been accorded NAVARATNA status by Government of
India.
HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP) BHEL
HARIDWAR
At Hardwar, there are 2 important manufacturing units of BHEL viz. Heavy
Electrical Equipment Plant (HEEP) & Central Foundry Forge Plant (CFFP). HEEP started
manufacturing in 1967 and CFFP in 1976.
Product Profile of HEEP:
Thermal and Nuclear sets:-
Turbines, Condensers and Auxiliaries of unit capacity up to 800 MW
Electrical Machines:-
Electrical Machines group manufactures the turbo generator and its auxiliaries up to
capacity of 800 MW.
1

7. SYNOPSIS
1. Title of the project:-
“Manufacturing process of Rotor for a 500 MW Turbo generator.”
2. Objective of the study:-
i. Detail knowledge of materials used in manufacturing of
rotor bars for TG.
ii. To study about technical requirement of raw materials. iii.
To learn about manufacturing process for TG rotor bars.
iv. To learn about final assembly of the rotor.
3. Rationale for the study:-
To study about the cooling system of rotor, manufacturing process of rotor bars, their
laying in machined rotor forging and final assembly of rotor.
4. Detailed Methodology used for carrying out the study:-
I. Study of configuration of TG rotor bar and cooling system at Electrical Machine
Engineering Department (EME).
II. Study of manufacturing process of TG rotor bars at Electrical Machine Technology
Department (EMT).
III. Study of standards and specifications for material used for rotor bars, fillers and
support.
IV. Supply of rotor bar material from foreign manufacturer, its testing at Material
Research Laboratory (MRL), BHEL HEEP Haridwar and material receipt in
Apparatus Control Gear & Coil Manufacturing Shop (ACM).
V. In depth study of rotor bar manufacturing in ACM, its assembly, testing and dynamic
balancing in Electrical Machine Block (Block-1).
2

8. 5. The expected contribution from the study:-
The study of this project is expected to ensure consistent, reliable product at low
manufacturing cost and high productivity.
6. Milestone Bar Chart of Activities:-
Milestone bar chart of activities is given on page – 4.
7. Places visited during the project:-
Electrical Machine Engineering Department (EME). ii. Electrical Machine Technology
Department (EMT). iii. Rotor bar manufacturing area (ACM). iv. Rotor bar laying in
rotor assembly section, testing and dynamic balancing in Electrical Machine Block.
8. Test places visited during the project:-
I. Material Research Laboratory (MRL)
II. Overspeed Balancing Tunnel (OSBT)
Countersigned by : Signed by:
Mr. Rajendra Kumar Sumit Kumar Singh
3

9. Milestone Chart for Completion of TG Rotor Manufacturing
4
Duration
12 14 16 18 20 22 24 26 28 30 02 04 06 08 10 12 14 16 18 20 22 24
Study about Turbo generator major component.
1 9
Discussion in Electrical Machine Engineering
department about Rotor.
2 26
Discussion in Electrical Machine Technology
department.
3 18
Study of plant standards and material
specifications.
4 15
Study of docket for TG Rotor manufacturing.
5 15
Study of manufacturing process of rotor bar in
ACM shop.
6 15
Study of rotor bar laying & complete assembly.
7 20
Preparation of final report.
8 18
Planned Date
Activities
Days
June-13 July-13

10. Chapter-1
Technical Detail
5
Turbo-Generator: -
Technical details of 500 MW Turbo generator:-
1. Stator
It is the stationary part of the machine and is built up of electro technical sheet-steel
laminations having slots on its inner circle which are fixed in a robust steel body called
STATOR FRAME. A 3-phase winding is laid in these slots which form stator winding of
the alternator.
Capacity:-588 MVA, PF:-0.85 lag, Stator Voltage:-21KV ±5%
Stator Current:-16,200 amps, Phase:-3 phase,
Frequency: - 50Hz, Connection: - Y, Insulation class: - F
2. Rotor
The rotor of a turbo-generator is the rotating component of the generator. The rotor
is driven by the generator’s prime mover which is a steam turbine coupled with rotor shaft.
Rotor acts as moving field having 340 volt DC supply with 2 poles:-
Rotor Volts: - 340 volt, Rotor Current: - 4040 amps, Speed: - 3000 rpm
Rotor Dia: - 1150 mm, Core Length: -6040 mm Pressure: - 3.5 Bar
Cooling Medium: - Hydrogen
A. Rotor Forging:-
The rotor forging is received in rough machined condition from supplier; it is finish
machined in electrical machine manufacturing block. There are 14 slots on either side of
the center line, which are cut on slot milling machine along the length of rotor. The slot
length is 6040 mm. The shaft is hollow in the center.
The cross-section of rotor, indicating slot positions are given in figure 1.
B. Machined Rotor:-
The rotor has 2 poles (Pole-I and Pole-II) with 28 slots. Four nos. of slots viz.

11. AL1, AL2, AR1 and AR2 (see figure 1) are of smaller depth (142.0 mm) and the remaining 24
slots are deeper viz.-196.5 mm table 3 gives the slot dimension.
Seven types of coils are laid in these slots, which are titled A, B, C, D, E, F and G.
The configuration details of slots are shown in figure 1.
Since there are two poles (Pole-I and Pole-II), 14 slots for coils A to G are made
in left half portion of rotor and another14 slots are made in its right half portion.
Refer figure 1.
1.1 Technical Requirement of Rotor Bar Material:-
1.1.1 Chemical Composition of Copper-
The required chemical composition of copper for rotor bar is:- Silver-
0.09 to 0.12 %; Phosphorus- 0.001 to 0.007 %; Copper- remaining %
6
1.1.2 Mechanical Properties:-
Tensile Strength- 245 to 300 N/mm2
Brinell hardness- 70 to 79 HB
Modulus of Elasticity- 108 x103 N/mm2
Elongation on length- min 14%.
1.1.3 Electrical Property:-
Resistivity- Max 0.01786 ohm-mm2/meter at 20 0C.
Conductivity- Min 56 mho-meter/mm2

12. 7

13. 1.2 Copper Material for Rotor Bars:-
A. This is a formed copper section having double ‘D’ canals on both sides along the length
of the flat. See cross-section at figure 2. This is the main rotor bar material, weighing
2109 kg. There are 9 sizes of rotor copper.
Cross-section of Flat Copper Conductor
Figure-2
B. ‘D’ shaped Copper rod called ‘filler’ Cross-section at figure 3. There are 9 sizes of filler.
Filler
Figure-3
C. Flat copper strip pieces of sizes 40X50X5 mm thick and 10X15X8 mm thick. These are
8
called ‘Support’.

14. 1.2.1 Double Canalled Flat Copper Conductor supplied by
Manufacturer:-
Rotor bar copper is supplied by M/S Swissmetal Industries Ltd. Weidenstrasse,
Doranach, Switzerland in 9 nos. of wooden boxes of size 9000x300x200 mm per rotor
as given in table 1.1. Total numbers of bars for a rotor are 240 numbers.
One box contains copper for one layer of all the coils for slot viz. for A, B, C, D, E,
F and G. Since coils in slot A have only six layers, so the boxes from 1 to 6 have a total
of 28 bars in each. While boxes 7 to 9 have 24 bars in each for coils in slot B to G (see
table 1.1).
The lengths of bars vary from one coil to other coil as well as from one layer to
other layer. These bars are supplied in cut lengths as detailed in table 1.2 & 1.3.
Details of box numbers containing the bar material
9
Coil
Layer
Number of coil for Slot Box Number
A B C D E F G Total
I 4 4 4 4 4 4 4 28 1
II 4 4 4 4 4 4 4 28 2
III 4 4 4 4 4 4 4 28 3
IV 4 4 4 4 4 4 4 28 4
V 4 4 4 4 4 4 4 28 5
VI 4 4 4 4 4 4 4 28 6
VII - 4 4 4 4 4 4 24 7
VIII - 4 4 4 4 4 4 24 8
IX - 4 4 4 4 4 4 24 9
Table-1.1

15. Table for Length of Bars
10
In mm
Coil
in
Slot
Layer Length Coil
in
Slot
Layer Length Coil
in
Slot
Layer Length Coil
in
Slot
Layer Length
A I 6750 B I 7200 C I 7300 D I 7750
II 6750 II 7200 II 7300 II 7750
III 6750 III 7200 III 7300 III 7750
IV 6700 IV 7000 IV 7250 IV 7550
V 6700 V 7000 V 7250 V 7550
VI 6700 VI 7000 VI 7250 VI 7550
- - VII 6950 VII 7200 VII 7450
- - VIII 6950 VIII 7200 VIII 7450
- - IX 6950 IX 7200 IX 7450
Table-1.2
Table for Length of Bars
In mm
Coil
in
Slot
Layer Length Coil
in
Slot
Layer Length Coil
in
Slot
Layer Length
E I 7900 F I 8300 G I 8450
II 7900 II 8300 II 8450
III 7900 III 8300 III 8450
IV 7800 IV 8100 IV 8350
V 7800 V 8100 V 8350
VI 7800 VI 8100 VI 8350
VII 7800 VII 8000 VII 8300
VIII 7800 VIII 8000 VIII 8300
IX 7800 IX 8000 IX 8300
Table-1.3

16. Cross sections of rotor bar vary from one to another layer depending upon
width of the slot. There are 9 sizes of rotor bar copper. However the total cross-sectional
area remains the same. Please refer figure 4 & 5 and table 2.
Cross-section of Flat Copper Conductor
Figure-4
Table for Layer wise cross section of Bars
11
In mm
Layer A B1 B2 C1 C2 D E1
I 14.30 44.60 43.60 7.80 7.45 24.80 10.30
II 14.70 43.60 42.50 7.60 7.20 24.20 10.70
III 15.10 42.50 41.30 8.65 8.20 21.00 11.10
IV 15.60 41.30 40.10 8.35 7.90 20.40 11.60
V 16.10 40.10 38.90 8.20 7.75 19.50 12.10
VI 16.60 38.90 37.60 8.50 8.00 17.70 12.60
VII 17.10 37.60 36.30 8.30 7.80 16.80 13.10
VIII 17.70 36.30 35.00 8.05 7.55 16.00 13.70
IX 18.30 35.00 33.70 7.90 7.40 15.00 14.30
Table-2

17. Slot Cross Section
12
Figure-5
Slot Dimension
In mm
Slot for coils W1 W2 H
A ( 6 layer) 50.9 40.3 142.0
B to G (9 layer) 50.9 36.3 196.5
Table-3

18. 1.2.2 Details of ‘D’ shaped copper rod called ‘filler’:-
Filler is used to fill the hollow area of conductor where cooling hydrogen flow path
is not required i.e. the path for hydrogen flow in rotor bars is terminated. In other words it
blocks the ‘D’ canal at required places so as to guide the path of cooling Hydrogen flow.
There are 9 sizes of filler.
The dimension and shape of filler differs with each layer of rotor bar.
Figure 6 & Table 4 gives the dimensions for different layers from layer I to IX.
Filler
Figure-6
Layer wise Table for filler dimensions
In mm
Layer C3 C4 E2
I 7.40 7.05 9.90
II 7.20 6.80 10.30
III 8.25 7.80 10.70
IV 7.95 7.50 11.20
V 7.80 7.35 11.70
VI 8.10 7.60 12.20
VII 7.90 7.40 12.70
VIII 7.65 7.15 13.30
IX 7.50 7.00 13.90
Table-4
13

19. 14
1.2.3 Details of support:-
At the exit point of the rotor slot the bottom most layers (viz. layer VI and IX) are
securely supported by flat copper strip. These supports are joined with bar by brazing them
with ‘D’ canalled copper conductor. There are two types of supports small and big. Small
support has the dimension 10x15x8 mm and big support has 40x50x5 mm. Small support
is used in the bottom most layer, viz. VIth layer for Coil in slot A and IXth layer for other
slot coils. Big support is used with bottom most conductor of Coil in slots E and G. Please
see figure 7.
Small & Big Support with conductor
Figure-7
1.3 Material Testing Result:-
Copper material is tested in Material Research Laboratory (MRL) before starting
the manufacturing. Result:-
Silver- 0.15%; Phosphorus- 0.005%; Copper- 99.8 %
Technical requirement:-
Silver- 0.09 to 0.12 %; Phosphorus- 0.001 to 0.007 %; Copper- remaining %

20. Chapter-2
Cooling System of Rotor
The cooling medium for Turbo generator used is Hydrogen. Hydrogen is supplied to
Turbo generator at 3.5 bar. The scheme of cooling in the 500 MW Turbo generator is axial
cooling. Hydrogen travels throughout the length of bars and cools it. It enters in bars from both
ends of the rotor at 44 0C temp. and exits radially through different ventilating ducts on the
rotor surface at 70 0C. In the bottom most layer no. IX / VI hydrogen travels longest and exits
from the radial surface of the rotor in the middle. In subsequent upper layers hydrogen travel
distance reduces. In this way efficient cooling of all the coil layers IX / VI to layer-I is achieved.
Schematic diagram for hydrogen flow path for rotor cooling is shown in Figure 8. Figure 9
gives a three dimensional view of rotor cross-section.
The hydrogen is circulated in the generator interior in a closed circuit by one multi-stage
compressor hub shrunk fit on the rotor at the turbine end. Hot gas is drawn by the fan
from the air gap and delivered to the coolers, where it is re-cooled and then divided into three
flow paths after each cooler.
Flow path I is directed into the rotor at the turbine end below the compressor hub for cooling
of the turbine end half of the rotor.
Flow path II is directed from the coolers to the individual frame compartments for cooling of
the stator core.
Flow path III is directed to the stator end winding space at the exciter end through guide ducts
in the frame for cooling of the exciter end half of the rotor and of the core end portions.
The three flows mix in the air gap. The gas is then returned to the coolers via the axial-flow.
For direct cooling of the rotor winding, cold gas is directed to the rotor end windings at
the turbine and exciter ends. The rotor winding is symmetrical relative to the generator center
line and pole axis. Each coil quarter is divided into two cooling zones. The first cooling zone
consists of the rotor end winding and the second one of the winding portion between the rotor
body end and the mid-point of the rotor. Cold gas is directed to each cooling zone through
separate openings directly before the rotor body end. The hydrogen flows through each
individual conductor in closed cooling ducts. The gas of the first cooling zone is discharged
from the coils at the pole center into a collecting compartment within the pole area below the
end winding.
15

21. From there the hot gas passes into the air gap through pole face slots at the end of the
rotor body. The hot gas of the second cooling zone is discharged into the air gap at mid-length
of the rotor body through radial openings in the hollow conductors and slot wedges refer figure
9 on page 17.
Rotor Cross - section with H 2 flow Path
16
Figure - 8

22. 17

23. Chapter-3
Manufacturing Process of Rotor Bar
18
3.1 Marking of Coils:-
Marking at center line on both sides of width of double canalled flat conductor of first layer of
coil is done for each slot.
Quality Checkpoint: - Marking is inspected as per drawing with the help of measuring tape (10 meter).
3.2 Drilling of Rotor Bars for Making Cooling Ducts:-
Since laying of bars are done in layers, coil in slot A has six layers and coil in slots
B, C, D, E, F and G have nine layers. The drilling of holes along the coil depth of the packet
(of 6 / 9 layers) is done. In coil A, layer number VI has four holes, layer-V has six holes,
layer-IV has eight holes, layer-III has ten holes, layer-II has twelve holes and layer-I has
fourteen holes.
While in case of coil B, C, D, E, F and G layer number IX has four holes, layer-VIII
has six holes, layer-VII has eight holes, layer-VI has ten holes, layer-V has twelve holes,
layer-IV has fourteen holes, layer-III has sixteen holes, layer-II has eighteen holes and
layer-I has twenty holes.
After keeping all the 6 / 9 rotor bars in the clamping jig, which firmly holds all the
6 / 9 coils, technological packing of 2 mm thickness is inserted in between each layer. Both
mechanical & hydraulic clamping is applied from both the sides of the jig. Drilling is done
with drill bit Ø 21 mm at both ends as per figure 10 and 11. In the overhang portion coils
3 nos. of holes are also drilled.

24. 19

25. 20

26. 3.3 Counter Sinking of radial cooling holes:-
After drilling the packet of 6 / 9 layers, coil layers are separated and counter sinking
of each hole is done with the help of counter sinking tool. The conductors are laid straight
on the table for this purpose. Quality Checkpoint: -Countersinking is inspected visually.
21
3.4 Cleaning of Canal:-
After counter sinking, cleaning of canal is done with the help of perlon brush twice.
Care is taken so that no dust and chip remains inside the canal, which can later choke the
flow path of Hydrogen later on.
Quality Checkpoint: - Quality is to be checked visually.
3.5 Caulking of holes:-
Caulking operation is carried out to make path for flow of cooling hydrogen in the
rotar bars as per figure 10 and 11. Fillers are inserted in hollow portion of the conductor
as per scheme, with the help of Caulking Chiesel. Figure 12 shows the drawing of caulking
chiesel and scheme of caulking is shown as per figure 10 and 11.
Caulking Chiesel
Figure-12

27. 3.6 Annealing of Overhang Portion of Rotor Coil for Edge Bending:-
Ends of the bar have to be annealed to make them soft to enable horizontal edge bending
without cracks. The regime for annealing is- heating at 520±20 0C for 15 minutes. After
about 8-10 minutes of taking out the bar from the oven, water is sprayed by a hose pipe.
The annealed length varies for slot coils A to G ranging from 410 mm to 1285 mm from
both ends. 24 numbers of bars are kept in one go for Coil A and 36 numbers for other coil
B, C, D, E, F and G inside the oven for annealing.
3.7 Edge bending of Rotor coil conductor:-
After annealing, the packet of 6 / 9 bars is clamped in the die fixed on the edge
bending machine. The desired shape at the overhang portion of rotor bar is achieved in one
go. This action is done on all the 28 packets of coils.
The straight length left at the end of each layer of a packet varies as detailed in table 5.1 &
22
5.2.
Conductor Shape after Edge Bending
Figure-13

28. Table for Overhang Length of Bars
23
In mm
Coil
in
Slot
Layer
Length
(L)
Coil
in
Slot
Layer
Length
(L)
Coil
in
Slot
Layer
Length
(L)
Coil
in
Slot
Layer
Length
(L)
A
I 355
B
I 580
C
I 630
D
I 855
II 355 II 580 II 630 II 855
III 355 III 580 III 630 III 855
IV 355 IV 480 IV 605 IV 755
V 330 V 480 V 605 V 755
VI 330 VI 480 VI 605 VI 755
- - VII 455 VII 580 VII 705
- - VIII 455 VIII 580 VIII 705
- - IX 455 IX 580 IX 705
Table-5.1
Table for Overhang Length of Bars
In mm
Coil
in
Slot
Layer
Length
(L)
Coil
in
Slot
Layer
Length
(L)
Coil
in
Slot
Layer
Length
(L)
E
I 930
F
I 1130
G
I 1205
II 930 II 1130 II 1205
III 930 III 1130 III 1205
IV 880 IV 1030 IV 1155
V 880 V 1030 V 1155
VI 880 VI 1030 VI 1155
VII 880 VII 980 VII 1130
VIII 880 VIII 980 VIII 1130
IX 880 IX 980 IX 1130
Table-5.2

29. After edge bending the thickness of the conductor at radius of bent portion increases
beyond the permitted thickness. To make the thickness of conductor as per allowable limits
(see table 6) pressing of bent portion is done by a hydraulic press machine. The pressure
of hydraulic press is adjusted to remove unevenness of the conductor thickness at bent
portion.
Table for Thickness of Conductors
Conductor Layer Number Thickness (mm)
I 14.37
II 14.77
III 15.17
IV 15.67
V 16.17
VI 16.67
VII 17.17
VIII 17.77
IX 18.37
Table-6
Quality Checkpoint: - Check the thickness of conductors with the help of thickness gauge and the
thickness of conductors as per table 6.
3.8 Annealing for Radius Bending:-
Second annealing of bars is done in the same way as carried out for first annealing for radius
24
bending.

30. 3.9 Radius bending of overhang portion of coils:-
The conductor packet is set on the manual bending fixture. A packet is kept on the
table and aligned with respect to bending fixtures. Right angle is checked and unevenness
of layers is removed. End conductors at both ends are bent at overhang portion by hand one
by one.
Radius Bending Tool
Figure-14
Table for Radius Layer wise
25
Conductor Layer Number
Radius of Bending Tool (mm)
I 115.4
II 116.4
III 117.5
IV 118.7
V 119.9
VI 121.1
VII 122.4
VIII 123.7
IX 125.0
Table-7

31. 26
3.10 Brazing of Supports:-
Big and small supports are brazed with bottom most conductors of a coil. Brazing is done
with the help of filler metal and brazing flux.
• Two forms of filler metals Shim (0.2x50 mm) and Wire (Ø 3mm) are used for brazing
composition of metal is
Silver-39 to 41%; Cadmium- 18 to 22%
Copper- 18 to 20%; Zinc-remaining %
• Working temp. range- 550 to 800 0C
• Compositions of Brazing Flux- Potassium Hydroxo Fluor Borate
• Viscosity- 150-250 Newton-sec/meter2, Density- 1.6 g/cm2 at 20 0C
3.11 Filing of Bend Portion of Conductors:-
After clamping each conductor in two bench vices at two ends of straight portions, filling
along the width of conductor is done, to bring it back to its original thickness.
Quality Checkpoint: - Thickness of each conductor is checked with the help of thickness gauge as
per table 6 on page no-26.
3.12 Finishing:-
Before sending the rotor coils for winding, annealed surface is finished. Since all
the conductors get oxidized during annealing process fine wire grinding disc is used to
remove the oxide layer of copper.
3.13 Cleaning:-
To make conductors absolutely free from burs and dust, cleaning with emery cloth
is done then compressed air is passed through cooling canal. In the end cotton tape wrapped
on a wire & soaked in trichloroethylene is pulled through every vent passage to ensure dust
free vent passages.

32. 3.14 Inspection by QC:-
Before sending the rotor bars to rotor assembly section in Electrical Machine Block, bars are
inspected by QC department.
Ready bars are dispatched in a fixture prepared specially for bar transportation, to
Electrical Machine Block for laying in machined rotor.
27

33. Chapter-4
Rotor Assembly & Dynamic Balancing
4.1 Rotor Assembly:-
4.1.1 Assembly of Slot Angle before laying the rotor coil in slots:-
Before starting the laying, rotor slot is cleaned and two nos. of epoxy laminated fabric
sheet of ‘L’ shape named ‘Slot Angle’ are inserted in it. These slot angles are used to
electrically insulate copper conductor from rotor forging. In this way every slot has two
slot angles see figure 15.
28
4.1.2 Coil Laying:-
Rotor forging is placed on roller supports during laying of coils. Coils are laid layer
wise viz. in slot A six nos. and in slots B to G nine nos. in each. After every coil epoxy
laminated fabric sheet of 2 mm thick is placed before laying the next layer of coil and so
on. On the top of the last coil lamination of epoxy laminated fabric sheet of 11 mm thick is
placed. See figure 15.
The entire epoxy laminated fabric sheets have Ø 21 mm holes done with the same
drilling jig which is used for rotor bar drilling, before placing them between the layers &
on the top layer.
Assembly of coil in a Rotor Slot
Figure-15

34. 29
4.1.3 Assembly of Slot Wedges:-
Slot wedges are inserted in the slot groove of rotor. The wedges are slided by textolite
mallet so that it presses the coils in the slot without damaging the epoxy layer. The purpose
is to firmly hold & press the coils in the slots, so that they are not loose. The holes of the
slot wedges as well as the epoxy laminate must match the cooling ducts of coils. Assembly
of slot wedges is done as per figure 15.
4.1.4 Connection of Coils:-
Electrical connections are done at both ends of rotor i.e. Turbine End (TE) and Exciter
End (EE) of rotor.
4.1.4.1 Connection at Turbine End: - At Turbine End, every layer of a coil laid in
a slot on left side is connected with same layer of coil placed on the right side slot of Pole-
I. In other words layer-I of coil in slot AL1 is connected with layer-I of coil in slot AR1,
layer-II of coil in slot AL1 is joined with layer-II of coil in slot AR1 and so on for all the 6 /
9 layers of coils, of a slot. Similar joining is done for coils of pole-II. Thus all the 14 slots
on left side are joined with 14 slots on right side.
4.1.4.2 Connection at Exciter End: -At exciter end of rotor connections are made
in the following way:-
A. Inter connection of coils: - Layer-I of coil laid in slot AR1 is connected with
layer-II of coil laid in slot AL1, layer-II of coil laid in slot AR1 is joined with layer-III of
coil laid in slot AL1 and so on up to layer-V of AR1. Now layer-VI of coil laid in slot AR1
is connected with layer-IX of coil laid in slot BL1 with the help of ‘Z’ shape connecting
piece. Connections in this fashion are made for all the coils of Pole-I and Pole-II up to slot
F. Layer I of AL1 and AL2 are left unconnected.
Layer-IX of coils of slot GR1 and GR2 are connected as detailed in B below.

35. B. Inter connection of poles: -Layer- IX of GR1 and GR2 are joined to make
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coils of Pole-I in series with those of Pole-II.
C. Connection to field lead bar: -Layer-I of AL1 and AL2 are connected with
two terminals of field lead bars. These are further connected to core bar. The schematic
diagram below (figure 16) shows the electrical connections made.
Electrical Connection at Exciter End
Figure-16
4.1.5 Connection of field lead bars with core bars:-
Core bar is the half round copper bar to carry the current from exciter to field lead bar of
the rotor. Two nos. of core bar are used in a rotor for this purpose.
These are firmly secured inside the rotor shaft bore from the exciter end up to the
overhang portion of coils.
The core bars are connected with field lead bar with the help of silver coated current carrying
bolt.
4.1.6 Assembly of Packers between overhang conductor portion:-
Packers are the insulating material used in overhang portion of conductor to check the
vibration of overhang coils. These are assembled in rotor after assembly of slot wedges.

36. 31
4.1.7 Mounting of Retaining Ring:-
Retaining ring is used to firmly hold the overhang portion of rotor coils. The ring
is heated by induction heating to a temp. of 360 0C and then mounted with the help of EOT
crane on the overhang coils on both the ends of the rotor.
After this Multi stage Compressor hub is shrunk fitted on the TE end of
shaft.
4.2 Dynamic Balancing of Rotor :-
Rotor balancing is done in Over Speed Balancing Tunnel (OSBT) at Turbine
Manufacturing Block. The speed at which dynamic balancing is done is 3600 rpm i.e. 20%
more than the rated speed of rotor. Correction weights are mounted to dynamically balance
the rotor.

37. Chapter-5
Testing of Rotor
After balancing of rotor following tests are performed on rotor:-
5.1 High Voltage (HV) Test
It is done to check the insulation resistance between conductor and rotor body. High
Voltage Test is performed at 5 KV and the minimum value of insulation resistance should
be 100 MΩ at 20 0C. The variation of insulation resistance with respect to temperature
should be according to the graph given below in Figure 17.
Figure-17
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5.2 Impedance Test
Impedance test is carried out to ensure the equal voltage drop at both poles. The
measurement is taken at 10 amp max & frequency 50 Hz. In this test voltage drop across
both poles should be equal or within 2% of the total applied voltage.
Normally 308 volts AC is applied.

38. Conclusion
The project deals with the study of manufacturing process of 500 MW Turbo generator rotor
bars, assembly of rotor, dynamic balancing and its testing.
Use of proper quality of copper & insulating material, adopting rigid regimes and
taking up precautions during various manufacturing stages it is ensured that assured quality
of product is manufactured and delivered to the customer. It will strengthen the reliability
of power system of our country which will ultimately reflect on the progress of our country
and the people.
By adopting various quality check points and adherence to manufacturing practices
the outages due to Earth fault, Inter Turn fault at overhang, Insulation Damage due to
excessive heating etc. will be checked.
Utility of the Case study
The rotor bar manufacturing process in its entirety is a very sophisticated learning which is
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necessary for anybody engaged in its process.