This is full summer training report of BHEL,HARIDWAR Block -4 CIM(Coil & Insulation Manufacturing) Heavy Electrical equipments plant

1. 1
TRAINING REPORT
ON
COIL AND INSULATION
MANUFACTURING
(CIM)
800MW STATOR BARS
(TURBO GENERATOR)
Submitted By:-
PRASHANT SRIVASTAV
B.Tech
(Electrical & Electronics Engineering)
Roorkee College of Engineering,Roorkee
Submitted To:-
Mr. BALINDRA SINGH
(Sr. Engineer)
(CIM, Block-4)
BHEL, Haridwar

2. 2
ACKNOWLEDGEMENT
It is always a pleasure to remind the fine people in the engineering
program for their sincere guidance to uphold my practical as well as
theoretical skills in engineering.
Firstly, I would thanks Dr. S.R. PANDEY (Director, Roorkee College
of Engineering) & Mr. VISHAL PRAJAPATI (TPO, Roorkee College
of Engineering) for meticulously planning academic curriculum in such
a way that students are not academically sound but also practically by
including such industrial training patterns.
I express my sincere thanks and gratitude to BHEL authorities for allowing
me to undergo the training in this prestigious organization. Special thanks
Mr. BALINDRA SINGH (Sr. Engineer,Block-4 BHEL, Haridwar)
allowing my training under his able guidance and for his supportive
nature.
I will always remain indebted to them for their constant interest and
excellent guidance in my training work, moreover for providing me with
an opportunity to work and gain experience.
At last but not least I would thank to all the well experienced workers in
the block, who constantly provided me required knowledge at different
stages.
PRASHANT SRIVASTAV
B.Tech
(Electrical & Electronics Engineering)
Roorkee College of Engineering,Roorkee

3. 3
CONTENTS
CHAPTER 1 – BHEL
1.1 Introduction 04
1.2 Heavy Electrical Equipment Plant 05
CHAPTER 2 - Coil & Insulation Manufacturing (CIM) - Block-IV
2.1 Introduction 07
2.2 Flow Chart 08
CHAPTER 3 - Manufacturing Process of 800 MW Bars (Bay I & II)
3.1 Conductor Drawn From Store & Insulation Check 11
3.2 Conductor cutting for Transposition 11
3.3 Crossover insulation 13
3.4 Hydraulic Pressing 13
3.5 Radius Milling 14
3.6 Inter Strand Test (IST) 14
3.7 Water Test 14
3.8 Forming 15
3.9 Pickling & End Cutting of Conductors 15
3.10 Contact Sleeve & Bottom Mounting 16
3.11 Brazing & TIG Welding 16
3.12 Nitrogen Test & Dye Penetration Test 18
3.13 Thermal Shock Test 18
3.14 Helium Leakage Test 19
3.15 Reforming 19
3.16 Main Body Insulation & Impregnation 19
3.17 Pressing Of Bar & Curing 20
3.18 Surface Finishing & OCP 21
3.19 H.V. & Tan Delta Test 21
3.20 Baroscopic & ECP Coating 22
3.21 Packing & Shipment of Bars 22
CHAPTER 4 - Manufacturing of Insulation (Bay III) 23
4.1 Introduction 23
CHAPTER 5 - Summary 25
CHAPTER 6
6.1 Conclusion 26
6.2 References 26

4. 4
CHAPTER-1
1.1 Introduction
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 core sectors of the
economy, viz. Power, Transmission, Industry, Transportation (Railways),
Renewable Energy, Oil & Gas, Water and Defence with over 180 products
offerings to meet the needs of these sectors. BHEL has been the bedrock of
India's Heavy Electrical Equipment industry since its incorporation in 1964.
BHEL's growth has been synchronous with achieving self-sufficiency in the
indigenous manufacturing of heavy electrical equipment. Out of the available
35,000 MW per annum capacity for power plant equipment manufacturing in
the country, BHEL alone constitutes a mammoth 20,000 MW per annum
capacity. A widespread network of 17 Manufacturing Divisions, 2 Repair Units,
4 Regional Offices, 8 Service Centres, 6 Overseas Offices, 6 Joint Ventures, 15
Regional Marketing Centres and current project execution at more than 150
project sites across India and abroad corroborates the humungous scale and size
of its operations.
BHEL also has a widespread overseas footprint in 80 countries with cumulative
overseas installed capacity of BHEL manufactured power plants nearing 10,000
MW including Belarus, Bhutan, Egypt, Indonesia, Iraq, Kazakhstan, Malaysia,
New Zealand, Oman, Rwanda, Sudan, Tajikistan and UAE.
BHEL places strong emphasis on innovation and creative development. The
R&D efforts of the company are aimed not only at improving the performance
and efficiency of existing products, but also developing new products using
state-of-the-art technologies and processes. With its innovation-led growth
strategy, BHEL continues to rank among the highest R&D spenders in the
country in the engineering and manufacturing segment. 477 patents and
copyrights were filed during the year 2015-16, enhancing the company's
intellectual capital to 3,441.

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Fig 1.a – Rotor of Turbo Generator
1.2 Heavy Electrical Equipment Plant
BHEL's Heavy Electrical Equipment Plant (HEEP) was set up in
technical collaboration with USSR, for the manufacturing of power plant
equipment, AC/DC motors of various rating with associated control equipment
and started production in January 1967. In 1976, BHEL entered into a
collaboration agreement with M/s Kraftwerk Union, AG of Germany for design,
manufacturing, erection and commissioning of large size steam turbines. More
than 40 per cent of the country's electrical energy is generated from the power
equipment supplied by BHEL, Haridwar. Products manufactured include power
transformers, instrument transformers, dry type transformers, series — and stunt
reactor, capacitor tanks, vacuum — and SF circuit breakers gas insulated switch
gears and insulators. The products, which are manufactured in HEEP, are: -
Steam Turbines, Turbo Generators, hydro turbines, Gas turbines, etc.

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. (1.b) -TG Stator (1.c) - Internal of stator (Front view)
(1.d)- Block-1 (1.e)- Rotor on Lathe M/c
**FACTS**
The generator may be classified based upon the cooling system used in
them such as: THRI, TARI, THDI, THDD, THDF, THFF and THW.
T(First alphabet) >>> Type of generator i.e. Turbo-generator or Hydro-
generator.
H/A(Second alphabet) >>> Cooling media used for the cooling of rotor i.e.
Hydrogen gas or Air.
R/D/F/I(Third alphabet) >>> Type of cooling of rotor e.g. Radial, Indirect,
Forced and Direct.
I/D/F(Fourth alphabet) >>> Type of cooling of stator e.g. Indirect, Direct and
Forced.
W >>> Cooling media used for cooling of stator coil e.g. water.

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CHAPTER-2
Coil & Insulation Manufacturing (CIM)
(Block-IV)
2.1 Introduction
Coil & Insulation manufacturing Block is a feeder block for insulating
items, winding with class-B Bituminous insulation and sheet metal components
for all the products of Block-1 i.e. Turbo-generators, Hydro-generators, A.C.
and D.C. machines.
. (2.a) (2.b)
Fig. (2.a) - Layout of CIM Block –IV; (2.b) - Main Products of CIM block
There are four BAYS in this block each bay manufactures stator bars and coils
for different machines i.e. BAY-0, BAY-I, BAY-II, BAY-III.

8. 8
2.2 Flow Chart
800 MW STATOR BAR PROCESS FLOW CHART
NOT OK
NOT OK
NOT OK
NEXT PAGE
Conductor Drawn
From Store
Conductor Cutting For
Transposition
First Pressing
Final Pressing
Radius Milling
I.S.T
Water Flow
I.S.T Repair
Forming
Pickling &End Cutting
Crossover Insulation
Inter Strand
Test (I.S.T)

9. 9
NOT OK
NOT OK
NOT OK
NEXT PAGE
Contact Sleeve &
Bottom Mounting
TIG Welding Of Tubes
With Sheet
(Automatic)
Main Brazing
Water Box- Top Part
Welding (TIG)
Nitrogen
Test
Die Penetration Test
Thermal Shock
Mat Filling
Helium Leak Test
Inner Corona
Protection (ICP)
Main Body
Insulation
Impregnation

10. 10
Impregnation
Wagon Setting &
Pressing Of Bar
Curing
Surface Finishing &
Calibration
Outer Corona Protection
Marking & End Corona
Protection Coating
(ECP)
Borescope
High Voltage & Tan
Delta Preparation
Protection Warping Of
ECP
Conductive Wrapping
of Slot
Packing Of Bar
Send the Bar to
Block 1
H.V. & Tan
Delta Test
Inter Corona
Protection (ICP)

11. 11
CHAPTER 3
Manufacturing Process of 800 MW Bars
(Bay I & II)
3.1 Conductor Drawn From Store & Insulation Check
For the manufacturing of stator bars, insulated solid
Copper conductors are brought from Bangalore and hollow Steel conductors are
brought from GermanyEngland.
 Hollow Steel conductors use for both conduction as well as to facilitate
the flow of coolant (e.g. Water).
 Insulating materials and the conductors are ensured to be certified.
 The insulation is checked by the respective agencies.
3.2 Conductor cutting for Transposition
This process is done by automatic CNC machine (Roebel
Machine). In this process the pre-insulated copper conductor is cut into number
of pieces of required length (length given in drawing as per design) insulation is
removed from both ends of the copper conductor.
**FACT**
Why do we call it bar?
It is quite difficult (rather impossible) to manufacture, handle and wind in the stator
slot of generator of higher generation capacity because of its bigger size and heavy
weight. That is why we make coil in two parts. One part its bottom part of coil
called bottom or lower bar and other part of coil is called top bar or upper bar.

12. 12
Upper Bar:-
Type of
conductor
Conductor Size
(mm)
Length (mm) Number of
conductor
Solid Copper 14
*
1.8 11282 50
Hollow
hollow
14
*
4 11282 10
Lower Bar:-
Type of
conductor
Conductor
Size (mm)
Length (mm) Number of
conductor
Solid Copper 14
*
1.8 11077 50
Hollow hollow 14
*
4 11077 10
Transposition means changing/shifting of position of each conductor in active
core (slot) part.
Here Roebel CNC Machine (3-464) automatic cut the conductor of required
length and also clean the ends of conductor by vertical and horizontal brushes.
Each conductor pick by the manipulator (having sensor) of machine and bends
are given with the help of bending die at required distance by the machine.
After bends are given, machine automatically arrange the conductors (i.e. for
800MW 2-solid then 1- hollow steel followed by 5- solid then 1-hollow steel so
on). Then the arranged conductors are taken out from magazine 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 an insulating spacer (mica) is placed
between the two halves.
. (3.2.a) (3.2.b)

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. (3.2.c) (3.2.d)
Fig - (3.a) & (3.b)-Roebel Machine, (3.c)-Bends in Bar, (3.d)-Transposition
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.
I. To reduce eddy current losses.
II. Equalize the voltage generator & prevent current circulation.
III. To minimize skin effect of ac current, small cross section of conductor
is used and also hollow conductors are used to effect cooling by water.
3.3 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.
3.4 Hydraulic 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

14. 14
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/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/cm2
vertically and
70±10 kg/cm2
horizontally.
Then the bars are cooled and both ends of bars are cleaned with rectified spirit
and sand paper for the inter strand test.
3.5 Radius Milling
After hydraulic pressing of bar, the bar is brought for
radius milling. Due to hydraulic pressing, the bar’s edges become sharp. In this
process the sharp end of bar is grinded to give a smooth finish of uniform
radius.
3.6 Inter Strand Test (IST)
The pressed bar 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 which
damage the side conductor and its insulation thus damage whole bar when it
place in stator. For this test all the bare conductors at both the ends are separated
from each other by putting them in comb so that they do not short circuit.
Then testing knob is connect to an adjacent conductor and check for whether it
is short or not by glow of bulb (which is series connected).Same is done for up-
down conductors. 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.
3.7 Water Test
Water test is performed so that there not any blockage in
the hollow steel conductor. In this test water is supplied from one side of the bar

15. 15
and water profile is checked at other end. Profile must be same for every hollow
conductor.
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 or profile is
disturbed so the bar is assumed to be chocked. Then chocked conductors are
repaired and water test is again performed to check the flow of water.
3.8 Forming
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 tools (e.g. mallet, clamper etc.) from both the ends.
While forming, the bars are assumed to get loosen. 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.
3.9 Pickling & End Cutting of Conductors
After giving a required shape through forming process the
bars are marked up to required length. Only solid conductors are clip out with
the help of Top Cutting Plier.
Due to forming, cutting of the bar and 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, pickling process is performed.
The solution used for this are constituents of Sulphuric acid (10%), Phosphoric
acid (5%), Hydrogen peroxide (5%) and Water.
The end of the bar is dipped in thinner to remove the dust or oil particles then
dried with the help of N2 gas. After that the bar end is dipped in pickling
solution for 5 to 10 minutes followed by dipping in water. Then the bar is

16. 16
dipped in rectified spirit to make the water contents evaporate as soon as
possible also dried with N2 gas.
3.10 Contact Sleeve & Bottom Mounting
After the pickling process and end cutting is done, contact
sleeve and water box bottom parts are mounted on both the ends of the bar.
Contact sleeve - 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 remaining hollow Steel conductors are cut after the contact sleeve is
fitted leaving 2 mm for TIG welding (automatic).
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.
3.11 Brazing & TIG Welding
The water box bottom part is welded on contact sleeve
through TIG welding using Helium as shielding gas. 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.
The contact sleeve (coil lug) which house conductors of bar is brazed through
the process of Brazing (Induction Brazing).
Fig (3.11.a) – Brazing Process
Brazing is a metal-joining process in which two or more metal items are joined
together by melting and flowing a filler metal into the joint, the filler metal
having a lower melting point than the adjoining metal.
The two types of brazing processes are:-
 Thermal brazing (using LPG)
 Induction brazing

17. 17
As induction brazing is more beneficial than thermal brazing as it does not
requires any inflammable gas for heating. So in BHEL, induction brazing
process is used. 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 750°C, the brazing material (alloy
of Ag+Cu+Au+Brass) is then pushed to fill the air gaps and to consolidate the
contact sleeve on the bar. It is then allowed to cool.
The hollow Steel conductors are welded with water box
bottom part through process of TIG welding. This is done by CNC Machine.
Before welding, the opening hole of conductors are adjust with help of chisel.
Heat generated by Tungsten melt down the hollow steel conductor (2mm) and
water box bottom part, due to this both join to each other, thus no filler material
use here.
Voltage (V) Current (Amp) Feed (mm/min) Time (sec)
8-9 55-70 102 20-30
Table 3.9.a – TIG welding of tubes with water box bottom part.
The top water box is also welded on water box bottom part through the method
of TIG welding. For this it should be kept in mind that water box bottom part
should have same material as that of water box top part. Shielding gas use here
is Argon gas and filler material use here is stainless steel.
Tungsten Inert Gas (TIG) welding, is an arc welding process that uses a non-
consumable tungsten electrode to produce the weld. The weld area is protected
from atmospheric contamination by an inert shielding gas (Ar & He), and a
filler metal is normally used.
(3. 9.a)
Fig. (3.9.a) - TIG Welding

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3.12 Nitrogen Test & Dye Penetration Test
This test is performed to check any leakage in bar i.e. to
check the TIG welding. 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, this test is performed with the help of Nitrogen gas.
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. If bubbles appear then welding
is done again and same test is performed to ensure TIG welding of water box
top and bottom part is done properly.
Dye Penetration Test used to locate surface-breaking defects in all non-porous
materials. Liquid with certain dye is applied on water box and check for breaks
on surface.
3.13 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.
Thermal shock test consist of series of hot water & cold water cycles
alternatively. So firstly hot water at temperature of about 80-90°C is passed
through the bar and then cold water at about room temperature 25-30°C approx.
is flowed inside the bar alternatively. This process is repeated again and again.
This process is repeated for about 6 times i.e. it has 6 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.

19. 19
.Fig(3.13.a) – Layout for thermal shock of bar.
3.14 Helium Leakage Test
Helium test is the most important test of all, because this
test is performed to check any minute leakage within the bar and at the welded
portion. Any minute leakage which couldn't be checked by water test can easily
be observed by Helium test because Helium is one of the lightest gases.
In this test, end of the bar is wrapped in the polythene. 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.
If the test is failed then the bar again go under the welding process and whole
process.
3.15 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 do the forming process again.
3.16 Main Body Insulation & Impregnation
The bar is insulated with the specific number of layers to
build the wall thickness of insulation subjected to the generating voltage of the

20. 20
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.
The bar is provided with many layers of insulation which is done by machine
called CNC TAPPING MACHINE.
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 eliminates all voids.
 Impregnation:
The impregnation resin mixture is to be heated in the
working tank, to (60±3) °C. At a temperature of 50°C, 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.
3.17 Pressing Of Bar & Curing
After impregnation under vacuum, the impregnated bars
then brought to the required dimensions in moulds and cured in an oven at a
high temperature.
 Pressing: The bars are pressed to bring them back to the original
dimensions.

21. 21
 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.
 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) °C for minimum 8 hours.
3.18 Surface Finishing & OCP
The baked and dimensionally correct bars are sanded-off
to smoothen the edges and the surface is calibrated as per requirement of the
dimension.
OCP (Outer Corona Protection) Coating: - The black semi-conducting varnish
coating is applied on the bar surface on the core length.
3.19 H.V. & Tan Delta Test
When the bar is dried it is wrapped with aluminium 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.
 Tan δ 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 Schering Bridge which works on the principle of wheat-stone bridge is
used to find the unknown capacitance of the bar.
When the bar wrapped with aluminium there are two conducting material i.e.
the aluminium sheet and the conductors of the bar, which act as two plates of
the capacitor and the insulation on the bar act as dielectric medium for the

22. 22
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 * 104 = tan δ
 H.V. (High Voltages 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 three times the working voltage of the
bar. If the insulation is weak the bar will puncture at the place of weaker
insulation.
The bar is tested to three times the rated voltage. If any of the bar fails this test
i.e. bar is punctured at any point then the bar is sent back for ICP and along with
re-insulation all the processes are repeated again.
3.20 Baroscopic & ECP Coating
This test is performed to check the impurities or foreign
material inside the bar (hollow conductors). To look inside with naked eye is
not possible so we use baroscopic for this purpose.
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
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
they are removed.
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.
Packing & Shipment of Bars
When the bars under goes all the previous step
successfully then they are packed and ready for shipment i.e. sending of the bars
to BLOCK -1. There they are going to place in stator core of Turbo Generator.

23. 23
CHAPTER 4
Manufacturing of Insulation
(Bay III)
4.1 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
 Perspex 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 high, then 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.

24. 24
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.

25. 25
CHAPTER 5
SUMMARY
 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.
 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.

26. 26
CHAPTER 6
6.1 Conclusion
I would like to say that this training program is an excellent opportunity for us
to get to the ground level and experience the things that we would have never
gained through going straight into a written material.
The main objective of the industrial training is to provide an opportunity to
undergraduates to identify, observe and practice how engineering is applicable
in the real industry.
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 proved an opportunity for encounter with such huge machines with their
working. Overall this training is totally satisfactory for me.
6.2 References
 Bharat Heavy Electricals Limited (2016). About BHEL
http://www.bhel.com/about.php
 Bharat Heavy Electricals Limited (2016). About Research & Development
http://www.bhel.com/about_rd.php
 Wikipedia, the free encyclopaedia (2016). About TIG welding, Brazing etc.
https://en.wikipedia.org
 Google Images (2016). Various Pictures https://www.google.co.in
 Machine operators (Dec-2016). Provide visiting diary notes.