VOCATIONAL TRAINING REPORT FOR COLLEGE

1
Submitted By: Ram Krishna Pandey
Junior Undergraduate in Department of Electrical & Electronics Engineering,
At NIET Greater Noida
INDUSTRIAL TRAINING REPORT
On
“THE MANUFACTURING OF 500/600MW STATOR WINDING BAR”
(JUNE-JULY 2015)
B.H.E.L. Haridwar
Submitted in partial fulfilment of the requirements
Of the Degree of
Bachelor of Technology
In
Electrical & Electronics Engineering
Submitted By
(RAM KRISHNA PANDEY)
(1213321153)
Submitted To
Mr. A K DHIMAN Mr. KAILASH
(MGR-CIM Department) (Project Mentor)
(Department of Electrical and Electronics Engineering)
NIET
GREATER NOIDA
2012-2016

2
Certificate
This is to certify that the Project report on “THE MANUFACTURING OF
500/600MW STATORWINDING BAR” is a record of the bonafide work
done by Ram Krishna Pandey Roll no.-1213321153
under our supervision and guidance.
This report is submitted to the B.H.E.L. Haridwar as a part of syllabus
prescribed by B.H.E.L. Haridwar for the Degree of BachelorofTechnologyin
Electrical& Electronics Engineering During the academic year of 2015-16.
We wish bestfor his endeavor.
Mr. A K DHIMAN Mr. KAILASH
(MGR-CIM Department) (PROJECT MENTOR)

3
Acknowledgement
“There are times when silence speaks so much more loudly than words of praise
to only as good as belittle a person, whose words do not express, but only put a
veneer over true feelings, which are gratitude at this point of time.”
Our report will remain incomplete if we do not mention the efforts of those
people who helped us in completing this project I take this opportunity to thanks
Mr. A K DHIMAN for guiding me throughout the competition of this project
as well as boosting my moral when in crisis. I express my humble gratitude to
the entire faculty members of Electrical and Electronics Engineering
Department for showing their interest in my project belief in our capabilities for
their support.
I would also like to express our sincerely regards to Mr. KAILASH to getting
us throughout the minor details of this project. I also want to thank the
remaining staff of the BHEL HARIDWAR which helps me throughout the
training. I thank “My Parents” for keeping me strong with high spirit till the end
of this project. We also want to thank my co-trainees from various colleges who
supported us in work. Their presence made our stay at BHEL HARIDWAR a
pleasant and learning experience in all aspects of life.
RAM KRISHNA PANDEY

4
TABLE OF CONTENT
1. CERTIFICATE
2. ACKNOWLEDGEMENT
3. INTRODUCTION ABOUT BHEL.
4. INTRODUCTION TO BHEL HARIDWAR.
5. COIL & INSULATIOON MANUFACTURING SHOP (BLOCK-4)
6. MANUFACTURING PROCESS OF BARS
 BAY-1
 BAY-2
 BAY-3
7. ELECTRICAL MACHINES BLOCK (BLOCK — I)
8. CONSTRUCTIONALFEATURES OF STATOR WINDING
9. CONSTRUCTIONALFEATURES OF ROTOR
10.CONCLUSION
11.BIBLIOGRAPHY

5
INTRODUCTION ABOUT BHEL
Bharat Heavy Electricals Limited (BHEL), owned by Government of India,
is a power plant equipment manufacturer and operates as engineering and
manufacturing company based in New Delhi. Established in 1964, BHEL is
India’s largest engineering and manufacturing company of its kind. The
company has been earning profits continuously since 1971-72 and paying
dividends uninterruptedly since 1976-77.
BHEL was established in 1964. Heavy Electricals (India) Limited was merged
with BHEL in 1974. In 1982, it entered into power equipment, to reduce its
dependence on the power sector. It developed the capability to produce a variety
of electrical, electronic and mechanical equipment’s for all sectors, including
transmission, transportation, oil and gas and other industries. In 1991, it was
converted into a public limited company.
The wide network of BHEL’s 17 manufacturing divisions, 2 repair units, 4
regional offices, 8 service centers, 8 overseas offices, 15 regional centers, 7
joint ventures, and infrastructure allowing it to execute more than 150 projects
at sites across India and abroad. The company has established the capability to
deliver 20,000 MW p.a. of power equipment to address the growing demand for
power generation equipment.
BHEL has attained ISO 9001:2000 certifications for quality management and
all the manufacturing units divisions of BHEL have been upgraded to the latest
ISO 9001:2000 version. All the major divisions of BHEL have been awarded
ISO 14001 certification for Environmental Management System and OHSAS-
18001 certification for Occupational Health and Safety management system.
BHEL become the first public sector company in the country to win the coveted
prize for in Haridwar unit under the CII Exim Award for the management.

6
BHEL is the only PSU among the 12 Indian companies to figure in “Forbes
Asia Fabulous 50” list. The company received MoU excellence award for 2004-
05 and Merit Certificate for MoU excellence for 2005-06.
BHEL's equity shares are listed on Exchange and National Stock Exchange of
India. Central Government of India and State governments in India hold
majority of the shares of BHEL.
Shareholders (as on 31-December-2014) Shareholding
Central Government of India and State governments 63.06%
Foreign Institutional Investors (FII) 15.95%
Insurance companies 10.52%
Banks, Financial Institutions and Mutual Funds 06.80%
Individual shareholders 02.33%
Others 1.34%
Total 100%
AWARDS AND RECOGNITION
 It is the 7th largest power equipment manufacturer in the world.
 BHEL was adjudged the Best Power Equipment Manufacturing
Organization by CBIP.
 The company bagged PSE Excellence Award 2014 for R&D &
Technology Development.
 BHEL received the National Intellectual Property Award 2014 and WIPO
Award for Innovative Enterprises.

7
 In 2014, BHEL won ICAI National Award for Excellence in Cost
Management for the ninth consecutive year.
 BHEL received two awards in CII-ITC Sustainability Awards 2012 from
the President of India.
 In the year 2011, it was ranked ninth most innovative company in the
world by US business magazine Forbes.
 The company won the prestigious ‘Golden Peacock Award for
Occupational Health & Safety 2011’ for significant achievements in the
field of Occupational Health & Safety.
 It is also placed at 4th place in Forbes Asia's Fabulous 50 List of 2010.

8
INTRODUCTION OF BHEL HARIDWAR
At the foothills of the majestic Himalayas, on the bank of the Holy Ganges in Ranipur,
Uttrakhand is located Heavy electrical equipment plant (HEEP) of B.H.E.L.
BHEL, completely owned by the Government of India is an integrated engineering
complex consisting of several plants of India, where about 70,000 workers are
employed in the design and manufacturing of heavy electrical equipment. At present,
70 % of country’s electrical equipment is generated at BHEL Haridwar.
Embarking upon the 50th Golden Year of its journey of engineering excellence, BHEL
is an integrated power plant equipment manufacturer and one of the largest engineering
and manufacturing company of its kind in India engaged in the design, engineering,
manufacture, construction, testing, commissioning and servicing of a wide range of
products and services for the core sectors of the economy, viz. Power, Transmission,
Industry, Transportation (Railway), Renewable Energy, Oil & Gas and Defence with
over 180 products offerings to meet the needs of these sectors. Establishment of BHEL
in 1964 was a breakthrough for upsurge in India's Heavy Electrical Equipment industry.
Consistent performance in a highly competitive environment enabled BHEL attain the
coveted 'Maharatna' status in 2013.
BHEL as a part of Pt. Jawaharlal Nehru's vision was bestowed with the onus to make
the country self-reliant in manufacturing of heavy electrical equipment. This dream has
been more than realised and the contribution in nation building endeavour is going to
continue likewise. Today, with 20,000 MW per annum capacity for power plant
equipment manufacturing, BHEL's mammoth size of operations is evident from its
widespread network of 17 Manufacturing Units, two Repair Units, four Regional
Offices, eight Service Centres, eight Overseas Offices, six Joint Ventures, fifteen
Regional Marketing Centres and current project execution at more than 150 project
sites across India and abroad. The total installed capacity base of BHEL supplied
equipment -138 GW in India speaks volumes about the contribution made by BHEL to
Indian power sector.
BHEL's 57% share in India's total installed capacity and 65% share in the country's
total generation from thermal utility sets (coal based)as of March 31, 2014 stand
testimony to this. The company has been earning profits continuously since 1971-72
and paying dividends since 1976-77 which is a reflection of company's commendable
performance throughout.

9
BHEL also has a widespread overseas footprint in 76 countries with cumulative
overseas installed capacity of BHEL manufactured power plants nearing 10,000 MW
including Malaysia, Oman, Libya, Iraq, the UAE, Bhutan, Egypt and New Zealand.
The high level of quality & reliability of BHEL products and systems is an outcome of
strict adherence to international standards through acquiring and adapting some of the
best technologies from leading OEM companies in the world together with technologies
developed in our own R&D centres. Most of our manufacturing units and other entities
have been accredited to Quality Management Systems (ISO9001:2008), Environmental
Management Systems (ISO14001:2004) and Occupational Health & Safety
Management Systems (OHSAS18001:2007).
Our greatest strength is our highly skilled and committed workforce of 47,525
employees. Every employee is given an equal opportunity to develop himself/herself
and grow in his/her career. Continuous training and retraining, career planning, a
positive work culture and participative style of management -all these have engendered
development of a committed and motivated workforce setting new benchmarks in terms
of productivity, quality and responsiveness.

10
COIL & INSULATION MANUFACTURING SHOP
(BLOCK-IV)
INTRODUCTION
As the complete one peace coil is not practicable so the coils are manufactured in two
parts, upper and lower bars. Out of the various blocks as mentioned before the coil and
insulation manufacturing block is BLOCK-4. This block is known as the COIL AND
INSULATION MANUFACTURING block. Block-4 is a feeder blocks for insulating
items, winding with class B Bituminous insulation and sheet metal components for all
the products of Block-1 i.e., Turbo Generator, Hydro Generator, A.C. and D.C.
machines. There are three BAYS in this block each bay manufactures stator bars and
coils for different machines as mentioned below:
BAY-1 Bar winding shop: Manufacturing of stator winding bars of generator.
BAY-2 Manufacturing of heavy duty generator stator bars with New CNC
machine i.e., Robelbar centre.
BAY-3 Insulation detail shop: Manufacturing of hard insulation & machining of
hares insulation part (Glass Textolite) such as packing, washer, insulation box,
wedges etc. & CNC taping machine.
Bar Shop: This shop is for manufacturing of stator winding coils TG and HG.
Why do we call it bar?
It is quite difficult to manufacture, handle and wind in the stator slot of generators of
higher generation capacity because of its bigger size and heavy weight. That is why we
make coil in two parts. One part is bottom part of a coil called Lower Bar and other
part of coil is called Upper Bar.
Turbo-Generator: The manufacturing of bars of standard capacity such as 100MW,
130MW, 150MW, 210/235MW, 500MW, 600MW. The plant has a capacity and
technology to manufacture 800MW and 1000MW generators.
Types of Generators:The generator may be classified based upon the cooling system
used in the generators such as-THRI, TARI, THDI, THDD, THDF, THFF, and
THW.
T-> First alphabet signifies the type of generator i.e. turbo-generator or Hydro-

11
generator.
H/A-> Second alphabet stands for the coding media used for the cooling of rotor i.e.
hydrogen gas or air.
R/D/F/I-> Third alphabet signifies the type of cooling or rotor e.g. radial, indirect,
forced, direct etc.
I/D/F-> Last alphabet stands for the type of cooling of stator e.g. indirect cooling,
direct cooling, and forced cooling.
W-> Cooling media used for cooling of stator coil e.g. water.
Sections in Block-IV
(a)Assembly Section
 Mechanical Assembly Section: It is equipped with small size drilling machines,
welding sets and hydraulic testing equipment for turbo generator mechanical
assemblies.
 Close Cubical Assembly Section.
(b)StatorBar Winding Section
 Conductorcutting, insulation and transposition section having facilities to
transporting the bars.
 Stack consolidation section, forming and lug brazing section have block type
hydraulic press, steel former and induction brazing installations respectively.
 Insulation taping section with automatic taping facilities in air conditioned
temperature covering maximum slot portion each overhung by both ends.
 Baking and pressing section having baking molds for simultaneous curving of
straight and overhead portion with electrical heating.
(c)Armature winding, Rotor coiland Statorbar Section:-
Coils are diamond pulled type with Class-B and Class-F and Class-H Silicon
insulation for machine ranging from 5 to 460 KW capacities.
This sections has the following work centers:-

12
 Conductors cutting, U bending and terminal conductorcutting machine, U bending
machines and terminal baths.
 Forming and Insulation of DC coils.
 Main and Interpole winding:- It is having semiautomatic winding machine.
 Planking, boat pulling and diamond pulling machine.
(d)Impregnation Section:-
It is equipped with impregnation tank, ovens for impregnation of DC pole coils.
(e)Insulation Section:-
 Insulating details, machining is equipped with small size lathes, milling and radial
drilling machines and jet cutting saw.
 Press Molding Section: - It has electrical ovens, hydraulic presses, shearing and
circular saw cutting machines for manufacturing molded components of all the
electrical machines.
 Plastic Molding Section: - Is equipped with various presses for plastic molded parts.
 Bitumen Mica Tape Manufacture: - Is equipped with mica tape manufacturing
machine and lathe for slitting mica tape to the required size.

13
MFG. Process flow chart of 500MW TG stator bar
1. Conductordraws from store.
2. Conductorcutting and end cleaning.
3. Transposition of conductor.
4. Assembly of all conductors to be used in stator bars.
5. Cross over insulation.
6. Consolidation if slot portion of bar.
7. I.S Test (i.e. inter strand test).
8. Forming of bar (to shape overhang portion).
9. Pickling of bar ends (1).
10.Mounting of contactsleeve & bottompart of water box.
11.Brazing of contact sleeve & bottom part of water box.
12.Pickling of bar ends (2).
13.Mounting of water boxleak test.
14.Re-Pickling.
15.Water flow and Nitrogen test.
16.Thermal ShockApplication.
17.Helium leak test.
18.Reforming of bar (i.e. overhang portion).
19.Insulation of bar on CNC machine.
20.Impregnation & curing of bar insulation.
21.Surface finishing of stator bar.
22.OCP on stator bar.
23.Preparation of bar for HV and Tan δ test.
24.If O.K. Dispatch to Block-1 for lying in the generator.

14
Block Diagramof CIM, Block-4
Main Product of CIM, Block-4

15
MANUFACTURING PROCESS OF BARS
BAY-1
Some points of manufacturing process is in brief as below –
1. Insulation Check
For the manufacturing of stator bars insulated copperconductorsare brought
from Bangalore, it’s of two type’s i.e. solid copperconductor& hollow copper
conductors which are used in water cooled stator layer glass insulation.
 Insulating materials and the conductors are ensured to be certified.
 If required the insulation is checked by the respective agencies.
2. ConductorCutting
This process is done by automatic CNC machine. In this process the pre-
insulated copperconductoris cut into number of pieces of required length
(length given in drawing as per design) insulation is removed from bothends of
the copperconductorout.
LOWER BAR:
Conductor Size Length Number of Conductors
8*4.6*1.5mm(hollow) 10200mm Hollow – 20
8*2.8mm(solid) 10200mm Solid - 20
UPPER BAR:
Conductor Size Length Number of Conductors
8*4.6*1.5mm(hollow) 10500mm Hollow – 20
8*1.3mm(solid) 10500mm Solid – 40

16
3. Transposition:
Transposition means changing/shifting of position of each conductor in active
core (slot) part. After cutting the required number of conductors, the conductors
are arranged on the comb in staggered manner and then bends are given to the
conductors with the help of bending die at required distance. Then the
conductors are taken out from the comb and die and placed with their ends in a
line and transposition is carried out. This process is repeated for making another
half of the bar which would be mirror image of the first half. The two halves of
the bar are overlapped over each other and a spacer is placed between the two
halves. Transposition is done in two ways:
 Half Pitch Transposition: - In this transposition, the first conductor at one
end of the bar becomes the last conductor at the other end of the bar.
 Full Pitch Transposition: - In this method of transposition, the first
conductor at one end of the bar becomes the last conductor in the mid of
the bar and then again becomes the first conductor at the other end of the
bar.
1. To reduce eddy current losses.
2. Equalize the voltage generator.
3. To minimize skin effect of ac current, small cross section of conductor is
used and also hollow conductors are used to effect cooling by D.M water.
4. Crossover Insulation:
The pre insulation of the copper conductor may get damaged due to mechanical
bending in die during transposition, hence the insulating spacers are provided at
the crossover portion of the conductors. A filler material (insulating putty of
moulding micanite) is provided along the height of the bar to maintain the
rectangular shape and to cover the difference of level of conductors. To
eliminate inter turn short at bends during edge wise bending and levelling of
bars in slots portion for proper stacking.

17
5. Stack Pressing:
This process is basically done to consolidate the solid as well as the hollow
conductors into a single bar, the insulating material provide at crossover
positions which has gluing properties melts and helps in the proper
consolidation of the bar. In this process the bar is pressed both vertically and
horizontally in the Pressing Machine. The pressing machines are also provided
with the heaters.
Each bar is loaded on each tier of heating plate and it is then provided with
an initial pressure of 35±5 kg per cm2 and an initial temperature of 100-110° C.
then the temperature is allowed to raise to the maximum of 160°C, this
temperature is kept for at least one hour with a final pressure of 80±10 kg per
cm2 vertically and 70±10 kg per cm2 horizontally.
After pressing the bar at specified pressure and maximum temperature for
one hour, the bars are then cooled placing them on cooling plates through which
water is allowed to follow below 50°C. The cooled bars are checked for their
heights and widths at pressed portion of the bar.
This complete process performed above is for one half of the bar. The same
process is then repeated for the other half of the bar similarly and then checked
for bar’s height and width at pressed portions as done before. Then the ends of
both the bars are cleaned with rectified spirit and sand paper for the inter strand
test.
6. Inter Strand Short Test:
The consolidation bar stack is tested for the short between any two conductors
in the bar, if found then it has to be rectified. This is done to ensure that no local
current is flowing due to short circuit between conductors. (300V A/C supply).
For this test all the bare conductors at both the ends are separated from each
other so that they do not short circuit. Then a live wire is connected to a
conductor and received from it consecutive conductor to light a lamp. Hence if
the lamp lights up it shows short circuit between the two conductors due to
improper insulation between them. It shows insulation failure between the
conductors, these conductors are then replaced and bar is followed through all
the previous processes. Similarly all the conductors are checked for any short
circuit.
After passing both the half bars from I.S.T. the bars are combined together
and pressed into a single bar. A sheet of mica glass insulation is provided
between the two halves as the insulation also has some gluing property to
consolidate the two halves into a single bar. All the steps of pressing are again
followed for the complete bar and then it is allowed to cool.

18
7. Forming:
In heavy generators each stator coil is very large in size and hence its
manufacturing is difficult as it will be very difficult to handle and process the
complete coil. So each coil is manufactured in two halves i.e. Upper half and
Lower half. The bars which are processed till this process are straight and hence
they are required to be formed into the upper half or the lower half. Hence this
process of forming is very important as in this process the bars are bending from
both the ends of the bar i.e. at exciter side and turbine side at specific angles and
shape as per design. This process is done manually. First the former is set
according to the design making different angles at different positions. Each bar
of a variant is bent or formed at same angle. Once the former is set, the bar is
mounted on it and formed manually by melting it from both the ends. After
forming the formed portion of the bars are assumed to get loose creating air
gaps between the conductors due to such a heavy melting. Thus the formed
portion of the bar are clamped at different places and provided with heaters to
reconsolidate the formed portion. After few hours the bar is then allowed to cool
at room temperature.
8. End Conductor Cutting:
Due to heavy malting of the bar for forming it from both the side i.e. exciter
side and turbine side, the conductors of the bar are produced at the ends of the
bar. Therefore to bring all the conductors of the bar in a plane End Conductor
Cutting is required to be done. Both the solid and hollow conductors are cut and
from both the sides of the bar. Also this process of cutting of the hollow
conductors helps in opening of vents of hollow conductors from both the ends
of the bar.
9. Pickling Process:
After the forming and cutting process of the bar and due to the transportation of
the bar, there accumulate very minute particles of dust on the ends of the bar.
These particles may cause hindrances at the time of brazing and may create
some air gaps. So, in order to remove these unwanted particles, basically the oil
particles pickling process is performed. The basic solution used for this process
is called pickling solution. The constituents of the pickling solution are:
 Sulphuric acid (H2SO4)-10%

19
 Phosphoric acid (H3PO4)-5%
 Hydrogen peroxide (H2O2)-5%
 Water (H2O)
There are many other solutions used in this process, these are:
 Ammonia
 Thinner
 Water
 Rectified spirit
 Nitrogen
In this process the following steps are involved:
 The end of the bar is dipped in thinner to remove the dust or oil particles.
 The end is then dried with the help of N2 gas.
 Then the bar end is dipped in pickling solution for 5 to 10 minutes.
 This is then followed with dipping in water.
 As there is acid in the pickling solution, so accordingly to neutralize the
acidic effect of the acid it has to be treated with some base, so the bar is
then dipped in Ammonia (10%).
 It is then followed with dipping in water.
 As water takes a lot of time to evaporate, it may let the tiny chemical
particles on the bar to react with it and leave spots on the bar, this may
weaken the insulation at those particular points and thus damage it,
further it may lead to poor brazing. So in order to avoid such a damage
the bar is dipped in rectified spirit to make the water contents evaporate
as soon as possible.
 The bar is then dried with N2 gas.
 Finally it is wrapped with cotton cloth to avoid any manual touch which
may deposit any dust particle on it until it is ready for brazing. The same
process of pickling is then preformed on the other end of the bar.

20
10. Contact Sleeve Mounting:
After the pickling process is complete, contact sleeve and water box bottom
parts are mounted on both the ends of the bar. Contact sleeve, as clear from the
name itself, it is a rectangular sleeve which is used to make contact between
upper and lower bars when laid out in the generator to form a complete coil. All
the solid conductors are cut from the ends of the bar after the contact sleeve
except the outer solid conductors. None of the conductor is cut before the
contact sleeve so that to make proper contact between the upper and the lower
bars. The water box is mounted in two halves; first the water box bottom part is
mounted after the contact sleeve keeping some distance between them. Both the
ends of the bar are then again pickled along with contact sleeve and water box
bottom part following the same procedure of pickling.
11.Brazing of coil lugs:-
For water cooled generator bars, the electrical connection contact and water box
for inlet and outlet of water are brazed. The contact sleeves, which are used to
make contact between the upper bar and the lower bar to form a complete coil
and the water box bottom part, both together are called Coil Lug, so the brazing
of these two parts at the end of a bar is called Coil Lug Brazing. Brazing is
basically the process offixation of both the contactsleeve and water box bottom
part or we can say both are properly consolidated using brazing material at high
temperatures. Consolidation is properly done so that no air gap is left which
would adversely affect the conducting properties of the contact sleeve and the
bar. The two types of brazing processes are:
 Thermal brazing (using LPG).
 Induction brazing
As induction brazing is more beneficial than thermal brazing as it does not
requires any inflammable gas for heating. So now a day’s Induction brazing
process is used. For brazing as we use very high temperature so that is possible
due to carbon strips fixed on the braze. Carbon has very high resistance and
when the current is allowed to pass through it due to induction the material to be
brazed i.e. Contact Sleeve gets super-heated. Induction heating is hence faster
and even more efficient than thermal heating.
When the contact sleeve becomes red hot at 750ºC, the brazing material is
then pushed to fill the air gaps and to consolidate the contact sleeve on the bar.
It is then allowed to cool. The types of brazing materials used are:
 LAG 15P (Alloy Silver 15 Phosphorous)

21
 LAG 40Cd (Alloy Silver 40 Cadmium)
Same process of brazing is then repeated for the water box bottom part. After
the brazing of water box bottom part the bar is then allowed to cool at room
temperature.
12. End Conductor Cutting:
As is clear from the name itself this is the process of cutting of extra conductors
i.e. the hollow conductors left after the water box bottom part are cut from both
the ends of the bar. These conductors are required to be cut so that water box
top part with a nozzle is to be mounted on the water box bottom part. The vents
of the hollow conductors are visible from the ends of the water box bottom part.
The openings of the vents of the hollow conductors are then checked to be
uniform. After cutting of extra conductors from both the ends of the bar,
pickling process is done. Same pickling process as mentioned before is then
done at both the ends of the bar for removing the dust particles, oil particles and
other unwanted impurities which we assume to be there after the brazing
process of the contact sleeve and water box bottom part. After pickling the bar
ends are then wrapped in cotton cloth until the water test is performed.
13. WaterTest:
Water test is performed so that there not any blockage in the vents and also to
check the flow of water. Flow should be uniform i.e. all the vents should have
same water flow. In this test water is supplied from one side of the bar and is
collected from the other side of the bar in a tank and is supplied back to the first
end. Flow of the water is checked by measuring the distance of the flow of
water. If there is any kind of blockage inside the hollow conductors of the bar
then it is indicated by flow of water i.e. flow of water will be not uniform and
the bar is assumed to be chocked. Then cocked conductors are changed or
repaired and the bar is reformed and water test is again performed to check the
flow of water.
14. Brazing Of Water BoxTop Part:
Brazing of water box top part is done with water box bottom part in brazing
section of Block-4.For this it should be kept in mind that water box bottom part
should have same material as that of water box top part. The difference in

22
previous brazing and this brazing is that, now flux is also introduced with
brazing material and also flux is mixed with copper chips. Copper chips are
added to make the electrical contact between the top and bottom part without
the copper chips this will be not possible. In this brazing material is formed in
the shape as that of water box side where it has to be brazed. Brazing material is
formed in square shape for top and bottom part and in ring shape for the brazing
of nozzle for water flow. Then both the parts are heated with induction brazer as
done earlier. It is heated until they become red hot then the brazing material
melts due to its low melting temperature then the melting temperature of the
water box top and bottom part. Brazing material is also introduced at the
boundaries until it is completely consolidated that is the entire air gap is
completely filled. After the brazing of water box top part the bar is then allowed
to cool at room temperature.
15.Checking Of Threads and Pickling Process:
As mentioned earlier that water box top part has got nozzle for flow of water, it
also has got threads which is provided for the proper fixation of water supply
through water pipe to the bar. These threads are checked for its uniformity by
fixing water pipe to the nozzle. If threads are not found satisfactory than the
nozzle is replaced with new one and again its threads are checked. Also the
pickling process is again done for the removal of any dust particles and
lubricants etc. the detail of this process is same as mentioned earlier in pickling
process.
16. Nitrogenleak test:
As the name suggests Nitrogen gas is the main constituent of the test. This test
is similar to puncture test that is inflated tube is dipped in water for any leakage,
the air bubbles gives us the exact position of the puncture. Similarly on the
same steps this test is performed. Basically this test is performed to check any
leakage in bar i.e. to check the brazing. In this test nitrogen at a pressure of
10Kg/Cm2 is forced from one end of the bar and other end of the bar is blocked
then the pressure of 10Kg/Cm2 is maintained and both the ends of the bar are
dipped in water. The bubbles if there any tells us that brazing is weak or not

23
done properly. So if bubbles appear then brazing is done again and same test is
performed for the proper brazing of water box top and bottom part.
Then both the ends of the bar wrapped in cotton cloth so that it is not
disturbed i.e. to avoid any manual touch which may deposit any dust particle on
it until it is ready for brazing.
17.Internal Pickling:
After various test performed on the bar the pickling process i.e. removal of any
dust particles lubricants etc is done only on outer surface of the bar (ends). But
from inside it is assumed that there must be some impurities, foreign material
must be present. For this purpose inside pickling is done.
As mentioned earlier same process is repeated but from inside of the hollow
conductors this time. In this process the following steps are involved:
 The thinner is passed through the bar to remove the dust or oil particles.
 The dried with the help of N2 gas.
 Then the pickling solution is passed for 5 to 10 minutes.
 Then water is flowed in the bar.
 As there is acid in the pickling solution, so accordingly to neutralize the
acidic effect of the acid it has to be treated with some base, so the bar is
filled with Ammonia (10%).
 It is then followed flowing of water again.
 As water takes a lot of time to evaporate, it may let the tiny chemical
particles in the bar to react with it and leave spots in the bar, this may
weaken the insulation at those particular points and thus damage it,
further it may lead to poor brazing. So in order to avoid such a damage
the rectified spirit is flowed in the bar to make the water contents
evaporate as soon as possible.
 The bar is then dried with N2 gas.
 Finally it is wrapped with cotton cloth to avoid any manual touch which
may deposit any dust particle on it until it is ready for brazing.
18. Baroscopic Testing
This test is performed to check the impurities or foreign material inside the bar.
To look inside with naked eye is not possible so we use baroscopic for this
purpose. So after internal pickling we use a baroscopic to look inside the bar.
Baroscopic is having a probe having a LED (light emitting diode). LED is used
to provide light inside the bar. The probe of the baroscopic is inserted from one

24
end of the bar and seen from a magnifying lens. The probe gives a light which is
reflected by the sides of the bar (inside) and with the help of magnifying lens
we get a clear image that what is there in the bar. If impurities are present then
these are removed then only after the bar is send to next operation.
19.WaterTest:
Here again water test is performed. In earlier water test water flow was checked
without the water box top part. But now the top part is brazed to the bottom part
and to check its flow this test is performed. Also to check the proper flow from
the nozzle this test is performed. In this test water is forced or pushed from one
end of the bar and flow of water is checked from other end of the bar. This test
tells us the presence of any choke vents of water box top part. If any choke vent
is present then it is repaired or whole of the water box top part is changed with
new one.
20. Thermal Shock Test:
Thermal shock test is performed to check whether the bar can withstand
extreme conditions i.e. when the generator is working or running at about 3000
Rpm. This is achieved by thermal shock test.
Thermal shock test consist of series of hot water & cold water cycles
alternatively. So firstly hot water at temperature of about 90ºC is passed through
the bar and then cold water at about room temperature 27ºC approx. is flowed
inside the bar alternatively. This process is repeated again and again.
This process is repeated for about 26 times i.e. it has 26 cycles of hot and
cold water. So this test tells us the strength of the bar so that it can withstand the
working conditions of the generator. Temperature of the bar is taken in account
according to the working temperature of the generator. The cycles of hot (800C)
and cold (300C) water are flown through the bar to ensure the thermal
expansion and contraction of the joints.
21. Helium LeakageTest:
Helium test is the most important test of all, because helium test is performed to
check any minute leakage within the bar and at the brazed portion. Any minute

25
leakage which couldn’t be checked by water test can easily be observed by
helium test because helium is one of the lightest gases.
So this is also the customers check point, before performing this test customer is
by called and they see themselves the test being performed and if They find the
test all right then only the bar is send to next process. In helium test, whole of
the bar is wrapped in the polythene excluding the end points. The helium gas at
pressure of 11Kg/Cm2 is passed through the bar and a probe connected to the
gauge is inserted inside the polythene at different places. The gauge will show
deflection if there is any helium atom present. Gauge will show reading even if
1 helium atom in 100000 atoms is present. This test checks the strength of
brazing and insulation.
22. Reforming:
After all the previous processes which had undergone on the bar it is assumed
that the shape of the bar is deformed from its original shape due to handling of
the bar from one place to another for different processes. So to keep the shape
of the bar as per design, the bar is checked if it is found distorted then it is
reformed in the previous former machine by placing the bar on the former and
malting.
23. Insulation:
The bar is insulated with the given number of layers to build the wall thickness
of insulation subjected to the generating voltage of the machine. Insulation is
basically done to prevent any kind of short circuit between the bar and the stator
core when the bar is assembled in the stator of the machine. The stator bars are
insulated with Micalastic (trade name) insulation. High quality mica, selected
epoxy resins and a matching vacuum impregnation process are the characteristic
features of the micalastic insulation for large turbo generators.
The bar is provided with 14 layers of insulation. Out of these fourteen layers, 12
layers are provided by using a machine called CNC TAPPING MACHINE
manufactured by a company named MICAMATION. The rest of the two layers
are provided manually.

26
The insulating material varies as according to the rating of the machines as
follows:
 For 500 MW : Mica Splitting Tape
 For THRI : Mica Glass
During machine taping in the slot portion the transition from machine to hand
taping is adjusted at the start of the bend for a tape width for every layer from
bar centre. After about half the number of layers, the taping is to be started
further at the bend. The mica tape consists of a thin high strength baking
material to which the mica is bounded by synthetic resin. The number of layers
i.e. the thickness of insulation is determined by the voltage of the machine.
24. Impregnation and baking:
a) Thermo reactive System: In case of rich resin insulation the bar is pressed
in closed box in heated condition and baked under pressure and temperature
as per requirement for a given period.
b) Micalastic System: In case of poor resin system the insulated bars are
heated under vacuum and the impregnated (dipped) in heated resin so that all
the air gaps are filled, layer by layer, with resin. Then extra resin is drained
out and bars are heated and baked under pressed condition in closed box
fixture.
c) VPI Micalastic System: The bars already lay in closed fixture and full
fixture is impregnated (dipped) in resin and then fixture with box is baked
under given temperature for given duration.
d) VIP Micalastic System: The individual (Separate) bar is heated in vacuum
and impregnated in resin. Then bar is taken out and pressed in closed box
fixture and then baked at given temperature for given duration.
25. Micalastic Insulationand Impregnation:
For insulation with micalastic, the conductor strands are arranged together to
form a compact assembly and set to the required shape. This assembly is then
baked with epoxy resin to give it mechanical strength required for further
processing.
The bars are then dried under vacuum and impregnated with synthetic resin,
which by reason of its low viscosity penetrates the insulation thoroughly and

27
eliminates all voids. After impregnation under vacuum, the bars are subjected to
pressure, with nitrogen being used as pressurizing medium. The impregnated
bars with direct conductor cooling are then brought to the required dimensions
in moulds and cured in an oven at a high temperature. This complete process
involves pressing of the bars, drying by heating, impregnation in resin and
finally curing. These processes are discussed briefly below:
 Pressing: The bars are pressed to bring them back to the original
dimensions.
 Drying: The stator windings are to be dried under vacuum 0.1 m bar at
(60±5) °C for 15 hours, minimum. The drying temperature is to be increased
to (65±2) °C if the initial viscosity of the impregnating resin mixture is high.
The temperature distribution should be as uniform as possible. The
drying under vacuum can be stopped if the pressure rises, 10 minutes after
closing of vacuum valve is less than 0.06 m bar.
 Impregnation: The impregnation resin mixture is to be heated in the
working tank, to (60±3) °C or in case of higher initial viscosity. At a
temperature of 50ºC, the impregnating resin mixture is to be degassed with
1-5 m bar vacuum. Subsequently the stator windings are to be dipped
continuously in resin hardener mix such that the highest locations of the
windings are at least 100 mm below the resin level. After 10 minutes of resin
stabilization, pressure is increased by application of nitrogen. Pressure is to
be gradually increased in uniform stages within 80 minutes to 4 bars and to
be maintained for 120 minutes in the impregnation tank.
The impregnation of the stator winding is to be monitored
continuously. Further it is to be decided whether to increase the pressure
or to stop the impregnation process, however the total period of nitrogen
pressure cycle shall in any case not exceed 4 hours. The impregnation
tank during shut down is to be closed and kept either filled with nitrogen
(1.1bar) or low vacuum.
 Curing: To prevent heating in the overhang portion, the curing of the
impregnated stator winding is to be done with a maximum 160°C hot air.
The curing period is extended for such a long time till the measurement
positions in the core indicate (140±5) ºC for minimum 8 hours.
26. Finishing: The baked and dimensionally correct bars are sanded - off to
smoothen the edges and the surface is calibrated, if required, for the dimension.
27. Conducting varnish coating:

28
a) OCP (Outer Corona Protection) Coating: - The black semi-conducting
varnish coating is applied on the bar surface on the core length.
b) ECP (End Corona Protection) Coating: The grey semi-conducting
varnish is applied at the bend outside core end of bars in gradient to
prevent from discharge and minimize the end corona.
ResinSystem:
a) Rich resin or Thermo reactive insulation system: In this type of insulation
system the bond content in resin is 35-37%. The raw materials are ready to
use and require preservation and working on temperature 20-250C. Its shelf
life is one year when kept at temperature 200C which could be increased
when kept at temperature of 50C.
b) Poor resin or Micalastic insulation system: In this type of insulation the
bond content in the resin is 5-7% and insulating material is prepared with
accelerator treatment. The temperature control need not required. The
insulating material is applied on job and then the same is impregnated (fully
dipped) in the resin.
Testing:
When the bar is dried it is wrapped with aluminum sheet to make outer surface
of the bar conducting so that tan δ and H.V. (High voltage test) can be
performed. After these tests the coating of red gel is applied at both the ends of
the bar.
TanΔ Test:
Test is performed to find the capacitance of the bar because bar will act as
capacitor when it is laid in the stator of the generator. In this test Schearing
Bridge which works on the principle of wheat-stone bridge is used to find the
unknown capacitance of the bar.
For good efficiency, capacitance of the bar should be high but we never
approach pure capacitance. In this test also same bar which is wrapped with
aluminium is used to make the bar conductive throughout the outer surface of
the bar. The two conducting material i.e. the aluminium sheet and the
conductors of the bar act as two plates of the capacitor and the insulation on the
bar act as dielectric medium for the capacitor. The capacitance of the bar is
found and of angle of deviation due to impurity in the insulation is obtained
from the formula: C4 * R4 * 10-4 = tan δ For different ratings of the bar the
acceptable value of tan δ is fixed according to their insulation requirement as
per design considerations.

29
H.V. (High Voltage)Testing:
This test is also known as insulation test because this test is performed to check
the insulation of the bar. In this test the bar which is already wrapped with
aluminium is used. High voltage is applied to the bar using auto-transformer
and it is increased in steps according to the working voltage of the generator. If
the insulation is weak the bar will puncture at the place of weaker insulation.
For 500 MW the working voltage of the bar is 64.5 KV & for 210 MW the
working voltage of the bar is 63 KV. If any of the bar fails this test i.e. bar is
punctured at any point then the bar is sent back for re-insulation and all the
processes are repeated again.

30

31
BAY-2
Introduction:
Bay 2 is the manufacturer of stator bars of hydro generators, stator coils of
Motors and stator coils of DC Exciter. The stator coils of AC motors of up to 11
KV, stator bars of Hydro generators of 200 MW and DC Exciters of all the 500
MW THRI generators are manufactured in this bay.
The processes involved in the manufacturing of AC motors are as follows:
Insulation Check
For the manufacturing of stator coils of AC motors, insulated copperconductors
of specific dimensions rolled on the drums are brought from Bangalore. Before
performing any process on that conductor, the insulation of the conductor is
checked.
 Insulating materials and the conductors are ensured to be certified.
 If required the insulation is checked by the respective agencies.
Conductor Tapping
The copper conductor is first provided with two layers of insulation, this is also
known as double layer tapping. The insulation tape used in this is
Micafabriglass Tape. In this process the copper drums are loaded on the stand
and tapping rolls on taping heads of the Tapping machine. The copper
conductor is insulated with two layer of tape in butt as per design and hence the
insulated copper conductor is again rolled on the drum from other side of the
machine. The insulation on the copper is checked, which is provided by the
automatically moving tapping rolls with some tension.

32
Winding Boat Coil
The next process is forming a boat shape coil with the insulated copper
conductor. In this process the former of the boat shape coil, which is adjustable
in length, is first set as per length of the coil required according to the design.
The number of conductors per turn and the total number of turns in a coil are all
set according to the design. The insulated copperconductordrums are loaded on
stand on one side of the former, the former is then rotated and hence a boat
shaped coil of specified length and specific number of turns is formed. The boat
coil is then checked for its length and number of turns.
Boat Insulation
The boat coil is then sending to the insulation block for its insulation. Here the
complete boat coil is insulated with single layer of polythene and then the stack
consolidation length of the coil is marked and the coil is send for the next
process.
Stack Pressing
In this process the press plank is first cleaned then the boat coil is loaded in the
press. The boat coil is cured for 35 minutes at 155 ± 5 °C under high pressure
(to ensure closing of box) after attaining the temperature. 0.1 mm filler gauge
should not go inside the box. The stack length and width of the boat coil is
checked at slot portions. The pressing of the boat coil is done for the
consolidation of the coil. The length of heating plates should be approximately
equal to the stack consolidation length of coil.
Forming
The forming of the boat coil is done in an automatic machine i.e. Schumann
Pulling Machine. The machine is first set, and then the forming plates are
mounted for overhang on the machine. The forming plates mounted are
according to the overhang design of the coil. The required variant of boat coil is
pulled into the diamond shape. The loading of boat coil should be as per the
variant of boat coil given in the design. The coil dimensions and geometry of
the coil is then checked on the Universal Model. The terminals of the coil are
set according to the design and also the first bends and the overhang portions
are marked.
Insulation
In this process the slot portion and the first bends of the coil are insulated with
accelerator treated Mica Tape as per design. For the stator coil of 11 KV AC

33
motor, total 8 layers of insulation tapping are provided i.e. three layers at the
slot portion and the rest five layers all over the coil. Generally for the stator
coils of low rating motors total five layers of insulation tapping is provided. The
insulation tape used is Epoxy Mica Paper tape. Red tape is the finishing tape
provided at the overhang portions of the coil. The black coloured insulation tape
in conducting in nature and it is provided at the slot portion of the coil. The
insulation tape at the bend portions of the coil is grey in colour and is semi
conducting in nature. Then the perimeters and width of the insulated coil is
checked at the slot portion of the coil. A release film is to be provided on the
entire coil including coil terminals. On slot portion two layers of release film is
provided. The coil is now sending for the next process.
Impregnation
For impregnation pressing strips are mounted on the coil. The pressing strips are
checked to be closed properly. The coils are then impregnated in micalastic
resin as per design.
The impregnation resin mixture is to be heated in the working tank, to
(60±3) °C or in case of higher initial viscosity. At a temperature of 50ºC, the
impregnating resin mixture is to be degassed with 1-5 m bar vacuum.
Subsequently the stator windings are to be dipped continuously in resin
hardener mix such that the highest locations of the windings are at least 100 mm
below the resin level. After 10 minutes of resin stabilization, pressure is
increased by application of nitrogen. Pressure is to be gradually increased in
uniform stages within 80 minutes to 4 bars and to be maintained for 120
minutes in the impregnation tank. The impregnation of the stator winding is to
be monitored continuously. Further it is to be decided whether to increase the
pressure or to stop the impregnation process, however the total period of
nitrogen pressure cycle shall in any case not exceed 4 hours. The impregnation
tank during shut down is to be closed and kept either filled with nitrogen
(1.1bar) or low vacuum.
Curing
After the impregnation of the coil, it is then cured at 140 ± 10 ºC for 18 hours
after attaining the required temperature. Curing of the coil is done for the proper
consolidation of the coil. The regime is then required to be checked. The

34
pressing strips are disassembled after the curing of the coil. The dimensions of
the coil are then checked.
Finishing
In this process the release film is removed and the coil is finished with sand
paper. The straight length of the coil is marked. The coil is then coated with
corona protection varnish as per design and then the coil is allowed to dry
properly for 6 hours. The slot portion dimensions and the quality coating
varnish are then checked. The coil is checked for its insulation using tan δ and
H.V. (High Voltage) Test.

35
BAY -3
Introduction:
Bay 3 is the manufacturer of insulating material of different shapes and sizes as
required according to the design. This bay is also called as I.D. Section
(Insulation Design Section). For the manufacturing of insulations, different raw
materials having insulating properties are brought by this section. The raw
materials having different insulating properties are then processed in this section
and moulded to different shapes as per design.
The raw materials used in this bay are:
 Glass based Textolite Sheet
 Cotton based Textolite Sheet
 Paper based Textolite Sheet
 Mica Glass sheet
 Teflon Sheet
 Mica Sheet
 Nylon Sheet
 Ebonite
 Perpex Glass Sheet
 Nomex Paper
 Asbestos Sheet
 Asbestos Paper
All the insulating raw materials mentioned above are in the decreasing order of
their insulating property. The insulating materials used in the manufacturing of
insulation moulds are categorized according to their laying requirement in the
machine i.e. if an insulation mould is to be fixed in the place where the risk of
fire is more than at those places moulds of Glass based Textolite sheet are
preferred because cotton based or paper based textolite sheet could catch fire at
those places.

36
Teflon Sheet has an important property and i.e. Teflon is non-heat
transferring material. So an insulating mould of Teflon is placed above the
bearings of the rotor so that is any fault in the bearings of the rotor produces any
heat then it is prevented by this material to get transferred to the rotor, and
hence prevents the rotor of the machine.
For the manufacturing of insulation moulds, the glass insulation raw material
in fibres is first pressed into blocks in a pressing machine with the help of
heaters and hydraulic pressure. Fibres are made into blocks because if fibre is
used as it is then volume of the material will be very large. So blocks are placed
on weighing machine and then weighed equal to the product required according
to design. So then these blocks are placed in the mould and heated and moulded
in the shape as that of the mould by applying sufficient pressure and
temperature.

37
ELECTRICAL MACHINES BLOCK (BLOCK -I)
Introduction:
1. Block-I is designed to manufacture Turbo Generators.
2. The block consists of 4 bays- Bay-I (36*482 meters), Bay-II (36*360
meters) and Bay-III and Bay-IV (Of size 24*360 meters each).
3. For handling and transporting the various components over-head crane
facilities are available, depending upon the products manufactured in
each Bay. There are also a number of self-propelled electrically driven
transfer trolleys for the inter-bay movement of components / assemblies.
4. Testing facilities for Turbo generator are available in Bay-II.
5. There is a special test bed area for testing of T.G. of capacity of 500 MW
Unit sizes.
Manufacturing Process:
Fabricated components are received in respective machine sections from
Fabrication blocks (Block — II, V, VI, VIII), while castings and forgings are
received from sister unit CFFP and other indigenous and foreign sources for
Turbo Generators. Stampings are received from stampings manufacture block,
block—VI and coils, bars, insulating details and sheet metal components are
received from coils and insulation manufacture and apparatus and control gear
box (block — IV).
1. Turbo Generators:
a) Making of blanks is done for checking the availability of machining
allowances.
b) Machining of the major components is carried out in Bay - I & Bay - II
and other small components in Bay - III and Bay - IV. The boring and
facing of stators are done on CNC horizontal boring machine using a
rotary table. The shaft is turned on lathe having swift 2500 mm and the
rotor slots are milled on a special rotor slot milling machines.
c) In case of large size Turbo Generators core bars are welded to stator
frame with the help of telescopic centring device. The centering of core
bar is done very precisely. Punching is assembled manually and cores are
heated and pressed in number of stages depending on the core length.
d) Stator winding is done by placing stator on rotating installation. After
lying of lower and upper bars, these are connected at the ends, with the
help of ferrule and then soldered by resistance soldering.
e) Rotor winding assembly is carried out on special installation where coils
are assembled in rotor slots. The pressing of overhang portion is carried
out on special ring type hydraulic press, whereas slot portion is pressed

38
manually with the help of rotor wedges. Coils are wedged with special
press after laying and curing. The dynamic balancing of rotors is carried
out on the over speed balancing installation. 500 MW Turbo Generators
are balanced in vacuum balancing tunnel.
f) General assembly of Turbo Generators is done in the test bed. Rotor is
inserted in the stator and assembly of end shields; bearings etc. are
carried out to make generators ready for testing. Prior to test run the
complete generator is hydraulically tested for leakages.
g) Turbo Generators are tested as per standard practices and customer
requirements.
Turbo Generator
500 MW Turbo generators at a glance –
2-Pole machine with the following features:-
 Direct cooling of stator winding with water.
 Direct hydrogen cooling for rotor.
 Micalastic insulation system
 Spring mounted core housing for effective transmission of vibrations.
 Brushless Excitation system.
 Vertical hydrogen coolers.
Salient technical data:
 Rated output : 588 MVA , 500 MW
 Terminal voltage : 21 KV
 Rated stator current : 16 KA
 Rated frequency : 50 Hz
 Rated power factor : 0.85 Lag
 Efficiency : 98.55%
Important dimensions & weights:
 Heaviest lift of generator stator : 255 Tons
 Rotor weight : 68 Tons
 Overall stator dimensions [L*B*H] : 8.83m*4.lm*4.02m
 Rotor dimensions(Dia. and length) : 1.15m and 12.11m

39
 Total weight of turbo generator: 428 Tons.
Unique installations:
Heavy Electrical Equipment Plant, Haridwar is one of the best equipped and
most modern plants of its kind in the world today.
Some of the unique manufacturing and testing facilities in the plant are:
TG Test Bed:
New LSTG [Large Scale Turbo Generator] Test Bed has been put up with
indigenous know- how in record time for testing Turbo generators of ratings
500 MW and above up to 1000 MW. It caters to the most advanced requirement
of testing by employing on-line computer for data-analysis.
Other major facilities are as follows:
 Major facilities like stator core pit equipped with telescopic hydraulic lift,
micalastic plant for the manufacture of stator bars, thermal shocks test
equipment, rotor slot milling machine etc. have been specially developed
by BHEL.
 12 MW/10.8 MW, 6.6 KV, 3000 RPM AC non salient pole, synchronous
motor have been used for driving the 500 MW Turbo-generator at the
TEST Bed. The motor has special features to suit the requirement of TG
testing (500 MW and above). This is the largest 2-pole (3000 rpm).
Over speed balancing vacuum tunnel –
For balancing and over speeding large flexible Turbo generators rotors in
vacuum for ratings up to 1,000 MW, an over speed and balancing tunnel has
been constructed indigenously. This facility is suitable for all types of rigid
and flexible rotors and also high speed rotors for low and high speed
balancing, testing at operational speed and for over speeding.
Generator transportation –
 Transport through300 Tons 24-Axle carrier beam railway wagon
specially designed indigenously and manufactured at Haridwar.
 The wagon has been used successfully for transporting one
generator -from Calcutta Port to Singrauli STPP.

40
CONSTRUCTIONAL FEATURES OF STATOR
WINDING
1. General:
The stator has a three phase, double layer, short pitched and bar type of
windings having two parallel paths. Each slots accommodated two bars. The
slot lower bars and slot upper are displaced from each other by one winding
pitch and connected together by bus bars inside the stator frame in conformity
with the connection diagram.
2. Conductor Construction:
Each bar consists of solid as well as hollow conductor with cooling water
passing through the latter. Alternate arrangement hollow and solid conductors
ensure an optimum solution for increasing current and to reduce losses. The
conductors of small rectangular cross section are provided with glass lapped
strand insulation.
A separator insulates the individual layers from each other. The transposition
provides for mutual neutralization of voltage induced in the individual strands
due to the slots cross field and end winding field. The current flowing through
the conductor is uniformly distributed over the entire bar cross section reduced.
To ensure that strands are firmly bonded together and give dimensionally
stability in slot portion, a layer of glass tape is wrapped over the complete stack.
Bar insulation is done with epoxy mica thermosetting insulation. This insulation
is void free and posses better mechanical properties. This type of insulation is
more reliable for high voltage. This insulation shows only small increases in
dielectric dissipation factor with increasing test voltage. The bar insulation is
cured in an electrically heated process and thus epoxy resin fill all voids and
eliminate air inclusions.
3. Method Of Insulation:
Bar is tapped with several layers of thermosetting epoxy tape. This is
applied continuously and half overlapped to the slot portion. The voltage of
machine determines the thickness of insulation. The tapped bar is then pressed
and cured in electrical heated press mould for certain fixed temperature and
time.

41
4. Corona Prevention:
To prevent corona discharges between insulation and wall of slots, the
insulation in slot portion is coated with semiconductor varnish.
The various tests for manufacturing the bar are performed which are as
follows:
a) Inter turn insulation test on stuck after consolidation to ensure absence of
inter short.
b) Each bar is subjected to hydraulic test to ensure the strength of all joints.
c) Flow test is performed on each bar to ensure that there is no reduction in
cross section area of the ducts of the hollow conductor.
d) Leakage test by means of air pressure is performed to ensure gas tightness
of all joints.
e) High voltage to prove soundness of insulation.
f) Dielectric loss factor measurement to establish void free insulation.
5. Laying Of Stator Winding:
The stator winding is placed in open rectangular slots of the stator core,
which are uniformly distributed on the circumference. A semi conducting
spacer is placed in bottom of slots to avoid any damage to bar due to any
projection. Driving in semi conducting filler strips compensates any
manufacturing tolerances.
After laying top bar, slot wedges are inserted. Below slots wedges, high
strength glass texolite spacers are put to have proper tightness. In between top
and bottom bars, spacers are also put.
6. Ending Winding –
In the end winding, the bars are arranged close to each other. Any gaps
due to design or manufacturing considerations are fitted with curable prepag
with spacer in between. The prepag material is also placed between the brackets
and binding rings. Lower and upper layers are fixed with epoxy glass ring made
in segment and flexible spacer put in between two layers.
Bus bars are connected to bring out the three phases and six neutrals. Bus
bars are also hollow from inside. These bus bars are connected with terminal
bushing. Both are water-cooled. Brazing the two lugs properly makes
connection.

42
CONSTRUCTIONAL FEATURES OF ROTOR
The rotor comprises of following component:
1. Rotor shaft
2. Rotor winding
3. Rotor wedges and other locating parts for winding
4. Retaining ring
5. Fans
6. Field lead connections
RotorShaft –
The rotor shaft is a single piece solid forging manufactured from a
vacuum casting. Approximately 60 % of the rotor body circumference is with
longitudinal slots, which hold the field winding. The rotor shaft is a long
forging measuring more than 9m in length and slightly more than one meter in
diameter. The main constituents of the steel are chromium, molybdenum, nickel
and vanadium. The shaft and body are forged integral to each other by drop
forging process.
Following tests are done:
a) Mechanical test
b) Chemical analysis
c) Magnetic permeability test
d) Micro structure analysis
e) Ultrasonic examination
f) Baroscopic examination
On 2/3 of its circumference approximately the rotor body is provided with
longitudinal slot to accommodate field winding. The slot pitch is selected in
such a way that two solid poles displaced by 180o C are obtained. For high
accuracy the rotor is subjected to 20% over speeding for two minutes. The solid
poles are provided with additional slots in short lengths of two different
configurations. One type of slots served as an outlet for hydrogen which has
cooled the overhang winding and other type used to accommodate finger of
damper segments acting as damper winding.

43
RotorWinding:
After preliminary turning, longitudinal slots are milled on sophisticated
horizontal slot milling machine. The slot house the field winding consists of
several coils inserted into the longitudinal slots of rotor body–
1. Copper Conductor –
The conductors are made of hard drawn silver bearing copper. The
rectangular cross section copper conductors have ventilating ducts on the two
sides thus providing a channel for hydrogen flow. Two individual conductors
placed-one over the other is bent to obtain half turns. Further these half turns are
brazed in series to form coil on the rotor model.
2. Insulation:
The individual turns are insulated from each other by layer of glass
prepag strips on turn of copper and baked under pressure and temperature to
give a monolithic inter turn insulation. The coils are insulated from rotor body
by U-shaped glass laminate module slot through made from glass cloth
impregnated with epoxy varnish.
At the bottom of slot D-shaped liners are put to provide a plane seating
surfaces for conductors and to facilitate easy flow of gas from one side to
another. These liners are made from moulding material. The overhang winding
is separated by glass laminated blocks called liners. The overhang winding are
insulated from retaining rings segments having L-shape and made of glass cloth
impregnated by epoxy resin.
3. Cooling Of Winding:
The rotor winding are cooled by means of direct cooling method of gap
pick-up method. In this type of cooling the hydrogen in the gap is sucked
through the elliptical holes serving as scoop on the rotor wedges and is directed
to flow along lateral vent ducts on rotor cooper coils to bottom of the coils. The
gas then passes into the corresponding ducts on the other side and flows
outwards and thrown into the gap in outlet zones.
In this cooling method the temperature rise becomes independent of length
of rotor. The overhang portion of the winding is cooled by axial two systems
and sectionalized into small parallel paths to minimize temperature rise. Cold
gas enters the overhang from under the retaining rings through special chamber
in the end shields and ducts under the fan hub and gets released into the air gap
at rotor barrel ends.

44
Rotor Wedges:
For protection against the effect of centrifugal force the winding is
secured in the slots by slot wedge. The wedges are made from duralumin, an
alloy of copper, magnesium and aluminium having high good electrical
conductivity and high mechanical strength.
The wedges at the ends of slot are made from an alloy of chromium and
copper. These are connected with damper segments under the retaining ring for
short circuit induced shaft current. Ventilation slot wedges are used to cover the
ventilation canals in the rotor so that hydrogen for overhang portion flows in a
closed channel.
Retaining Ring:
The overhang portion of field winding is held by non-magnetic steel
forging of retaining ring against centrifugal forces. They are shrink fitted to end
of the rotor body barrel at one end; while at the other side of the retaining ring
does not make contact with the shaft.
The centring rings are shrinking fitted at the free end of retaining ring that
serves to reinforce the retaining ring, securing, end winding in axial direction at
the same time. To reduce stray losses, the retaining rings are made of non-
magnetic, austenitic steel and cold worked, resulting in high mechanical
strength.
Fans:
Two single stage axial flow propeller type fans circulate the generator
cooling gas. The fans are shrinking fitted on either sides of rotor body. Fans
hubs are made of alloy steel forging with three peripheral grooves milled on it.
Fan blades, which are precision casting with special alloy, are machined in the
tail portion so that they fit into the groove of the fan hub.
Field Lead Connections –
1. Slip Rings:The slip ring consists of helical grooved alloy steel rings shrunk
on the bodyshaft and insulated from it. The slip rings are provided with

45
inclined holes for self-ventilation. The helical grooves cut on the outer
surfaces of the slip rings improve brush performance by breaking the
pressurized air pockets that would otherwise get formed between the brush
and slip rings.
2. Field Lead: The slip rings are connected to the field winding through semi
flexible copperleads and current-carrying bolts placed in the shaft. The
radial holes with current carrying bolts in the rotor shafts are effectively
sealed to prevent the escapeof hydrogen.
A field lead bar, which has similar construction as, does the resin
for low resistance connection between current carrying bolt and field
winding that of semi flexible copperleads (they are insulated by glass
cloth impregnated with epoxy and ease of assembly).

46
CONCLUSION
The second phase of training has proved to be quite faithful. It proved an
opportunity for encounter with such huge machines like turbo-generator hydro
generator etc. The architecture of B.H.E.L., the way various units are linked and
the way working of whole plant is controlled make the students realize that
Engineering is not just structural description but greater part is planning and
management. It provides an opportunity to learn tech. Used at proper place and
time can save a lot of labour. However, training has proved to be satisfactory. It
has allowed us an opportunity to get an exposure of the practical
implementation of theoretical fundamentals.

47
BIBLIOGRAPHY
 Bharat Heavy Electrical Ltd. BHEL Turbo Generators Manual. In BHEL,
BHEL product technical Manual.
 Bharat Heavy Electricals Limited. (2005). Bharat Heavy Electricals Ltd.
Product Information. Retrieved May 2010, from http://www.bhel.com
 Bharat Heavy Electricals Ltd. (1993). BHEL Pro/E Manuals. Haridwar:
BHEL.
 www.wikipedia.org
 www.slideshare.com
 www.scribd.com

VOCATIONAL TRAINING REPORT FOR COLLEGE

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (6)

Similar to VOCATIONAL TRAINING REPORT FOR COLLEGE

Similar to VOCATIONAL TRAINING REPORT FOR COLLEGE (20)

VOCATIONAL TRAINING REPORT FOR COLLEGE