PRESENTATION ON COIL INSULATION MANUFACTURING (CIM)

1. MANUFACTURING PROCESS OF 660 MW
TURBO GENERTOR STATOR WINDING
BAR
ABHISHEK SINGH
12ERDME004
AT BHEL HARIDWAR

2. INTRODUCTION
In 1956 India took a major step towards the establishment of its
heavy engineering industry when BHEL, the first heavy electrical
Manufacturing unit of the country was set up at Bhopal.
BHEL's Heavy Electrical Equipment Plant (HEEP) was set up
in technical collaboration with USSR, for the manufacturing of
power plant equipment.
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 percent of the country's electrical energy is
generated from the power equipment supplied by BHEL,
Haridwar.

3. MANUFACTURING BLOCKS:
.
BLOCK I: ELECTRICAL MACHINE BLOCK, IS DESIGNED TO
MANUFACTURING OF TURBOGENERATORS
BLOCK II: FABRICATION BLOCK
BLOCK III: TURBINE BLADE BLOCK
BLOCK IV: COIL & INSULATION MANUFACTURING &
APPARATUS & CONTROL GEAR MANUFACTURING
BLOCK
BLOCK V: FEEDER BLOCK AND KNOWN AS FABRICATION
AND FORGE BLOCK
BLOCK VI: STAMPING AND DIES MANUFACTURING BLOCK
BLOCK VII: WOODWORKING BLOCK
BLOCK VIII: HEAT EXCHANGER BLOCK, IS DESIGNED TO
MANUFACTURE HEAT EXCHANGER UNIT FOR
STEAM TURBINES.

4. COIL & INSULATION MANUFACTURING
SHOP (BLOCK-IV)
Block-4 is designed to manufacture stator winding
bars of Turbo & Hydro generator and coil like DC
Armature coil ,main pole coil , equalizer coil etc.
There are three BAYS in this block each bay
manufactures stator bars and coils for different
machines

5. BAY-I: Bar winding shop: manufacturing of stator winding
bars of generator
BAY-II: Manufacturing of heavy duty generator stator bars
with New CNC M/c
BAY-III: Insulation detail shop: Manufacturing of hard
insulation & machining of hares insulation part (Glass Textolite)
such as packing, washer, insulation box, wedges etc
Bar Shop: This shop is meant for manufacturing of stator
winding coils of turbo-generator and hydro generator

6. Layout of CIM, Block-IV

7. 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.
Why do we call it bar?

8. Manufacturing Process
• For the manufacturing of stator bars insulated
copper conductors are brought from Bangalore,
it’s of two type’s i.e. solid copper conductor &
hollow copper conductors which are used in
water cooled stator layer glass insulation.
• solid bar for 600/660/700 MW
volume - 9.5X1.2
• Hollow copper for 600/660/700
Volume – 8.0x 4.6x1.3

9. Cutting
This process is done by automatic 3-444CNC machine. In
this process the pre insulated copper conductor is cut into
number of required length. Insulation is removed from both
ends of the conductor cut.

10. 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 conductor are taken out from the comb & die
and placed with their ends in a line and transposition is
carried out.
Need of transposition.
1. To reduce eddy current losses.
2. Equalize the voltage generator.
3. To minimize skin effect of ac current

11. Cross Over 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 or
moulding micanite) is provided along the height of the bar to
maintain the rectangular shape and to cover the difference of
level of conductors.

12. Stack Pressing
• The core part of bar stack is pressed in under the pressure b/w
70kg to 80 kg and Temperature b/w 90 C to160 C for given
period. Four bar is pressed in one time and six to eight plate
are used for pressing .after that the consolidated stack is
withdraw from the press.
Inter Stand Short Test
The consolidated 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.(300 A/C supply)

13. Forming
• 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. The straight bar stack is formed as per overhang
profile (as per design), The overhang portion is consolidated
after forming.
. 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 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.

14. 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. it is a rectangular sleeve
which is used to make contact between upper and
lower bars . All the solid conductors are cut from
the ends of the bar after the contact sleeve except
the outer solid conductors. 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.

15. • Brazing is basically the process of fixation of
both the contact sleeve and water box.
• Brazing is suitable for small parts , when high
joint strength is required.In brazing alloy is
mixed with water.
Brazing

16. • 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.
Nitrogen test

17. 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.

18. Helium Leakage Test
• After thermal shock test bar is tested for any leakage with
help of Helium gas. 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. because
helium is one of the lightest gases.

19. Reforming
• After all the previous processes which had undergone on the
bar. 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 .
Insulation
• The stator bars are insulated with Micalastic (trade name)
insulation.
• 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

20. Impregnation and Baking
• 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.
• After impregnation the bars are pressed to bring them
back to the original dimensions.

21. HIGH VOLTAGE TEST
•When the bar is dried it is wrapped with aluminum sheet to make
outer surface of the bar conducting so that H.V. (High voltage
test) can be performed. After this tests the coating of red gel is
applied at both the ends of the bar.
•In this test the bar which is already wrapped with aluminum 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.
•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

22. Finishing
• The baked and dimensionally correct bars are
sanded-off to smoothen the edges and the
surface is calibrated, if required, for the
dimension.
Dispatched for winding
• The bars preserved with polythene sleeves to
protect from dust, dirt, oil, rain etc are send to Block-I
(Electric Machines Production Block - I, Turbo
Generators and Hydro Generators) for winding

23. Picture Of Bars

24. THANK YOU