This document provides an overview of the role of CNC machines in manufacturing stator bars for large turbo generators between 500-1000MW at Bharat Heavy Electricals Limited (BHEL). It discusses how CNC machines such as the Robel bar centre machine are used in BHEL's Heavy Electrical Equipment Plant to cut, bend, and transpose conductors for stator bar winding with high precision and accuracy for large generators. The document also provides background on BHEL, CNC machines, and the various sections involved in stator bar manufacturing.

1. BHARAT HEAVY ELECTRICALS LIMITED
A PROJECT REPORT
ON
Role of CNC machines in manufacturing of 500/600/800mw turbo generator
stator bars
SUBMITTED TO
BALINDRA SINGH
(ENGINEER-CIM)
PREPARED BY
NAWNEET KUMAR
B.Tech,3RD year
Electrical and electronics engineering
Anand engineering college , Agra

2. ACKNOWLEDGEMENT
“An engineer with only theoretical knowledge is not a complete engineer. Practical
knowledge is very important to develop and apply engineering skills”. It gives me a
great pleasure to have an opportunity to acknowledge and to express gratitude to
those who were associated with me during my training at BHEL, Haridwar .
Special thanks to Mr. Balinder singh for providing me with an opportunity to
undergo training under his able guidance and offering me a very deep knowledge
of practical aspects of industrial work culture...
I express my sincere thanks and gratitude to BHEL authorities for allowing me to
undergo the training in this prestigious organization. I will always remain indebted
tothem for their constant interest and excellent guidance in my training work,
moreoverfor providing me with an opportunity to work and gain experience.
NAWNEET KUMAR
Anand engineering college
Agra

3. BHEL: AN OVERVIEW
BHEL is the largest engineering and manufacturing enterprise on India in the
energy related/infrastructure sector. BHEL was established more than 40 years
ago, ushering in the indigenous Heavy Electrical Equipment industry in India, a
dream which has been more than released with a well-recognized track record of
performance. It has been earning profits continuously since 1971-72.BHEL caters
to core sectors of India economy viz. Power Generation and Transmission,
Renewable Energy, Defense etc. The wide network of BHEL’s 14 manufacturing
divisions, 4 power sector regional centers, 8 service centers, 15 regional offices
and a large number of projects sites spread all over India and abroad enables the
company to promptly serve as customer and provide them with suitable products,
systems and services- efficiently and at competitive prices.
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
9001:2000version. All the major units 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 business excellence as per the
globally recognized model of European Foundation for quality management. BHEL
is the only PSU among the 12 Indian Companies to figure in ―Forbes Asia
Fabulous 50‖ list. It has also won the ―Business standard star Public Sector
Company Award 2006‖. The company received MoU Excellence award for 2004-
2005 and Merit Certificate for MoU Excellence for 2005-2006.

4. POWER GENERATION
Power generation Sector comprises Thermal Gas, Hydrogen, Nuclear power plant
business. As of 31.3.2007. BHEL supplied sets accounts for 80,781 MW or nearly
65% of the total install capacity of 1, 25,414 MW in the country. Significantly these
sets contribute 73% of the total power generated in the country. BHEL has proven
turnkey capabilities for executing power projects from concepts to commissioning.
It possesses the technology and capability to produce Thermal sets with super
critical parameters up to 1000 MW unit rating and gas turbine generator sets of up
to300 MW units rating. Co-generating and combined cycle plants have been
introduced to achieve higher plant efficiencies. To make efficient use of the high-ash-
content coal available in India. BHEL also supplies circulating Fluidized Bed
Combustion (CFBC) boilers for thermal plants.
The company has proven expertise in plant performance improvement through
innovations,modernization upgrading of a variety of power plant equipment
besides specialized know-how of a residual life assessment health diagnostic and
life extension of plant. Overall, BHEL build thermal sets achieved the highest ever
PLH of 78.3% in 2006-2007 which is 2.5% higher than the national average .The
combined operating availability of these sets was 84.7%.
HEAVY ELECTRICAL EQUIPMENT PLANT
BHEL’S (HEEP) was set up in technical collaboration with USSR,for manufacturing
of power plant equipments,AC/DC motors of various rating with associated control
equipment and started production in January 1967. In 1976,BHEL entered into
collaboration agreement with M/s Kraftwerk union ,AG of Germany for
design,manufacturing,erection and commissioning of large steam turbine. More
than 40% of the country’s electrical energy is generated from the power
equipment supplied from BHEL,haridwar.
The products which are manufactured in HEEP, are:-steam turbine, turbo
generators, hydro turbine, gas turbine.

5. COIL AND INSULATION MANUFACTURING
SHOP(BLOCK-4)
INTRODUCTION
As a complete one piece coil is not practicable are manufactured in two parts,upper
and lower bars.Out of various blocks are mentioned away from the coil and
insulation manufacturing block is 4th .Block 4 is a feeder block for insulating
item,inding with class b bituminous insulation and sheet metal component for all
the product of block-1 that is turbo generator,hydro generators, AC and DC
machines. There are three bays in this block each bay manufacturers stator bars and
coils for different machines as given below:
BAY-1: Bar winding shop: manufacturing of stator winding bar of generator.
BAY-2: manufacturing of heavy duty generator stator bars with new CNC
machine no-3464 i.e. robel bar centre.
BAY-3: insulation detail shop: Manufacturing of hard insulation &machining of
harsh insulation part such as packing, washers , insulation box,wedges etc and CNC
tapping machine.
BAR SHOP : This is ment for manufacturing of stator winding coils of turbo
generator and hydro generator.
Why do we call it a bar??
It is quite difficult to manufacture, handle and wind in stator slot of generator of
higher generation because of it bigger size and heavy weight ,that is why we make
coil in two part. One part of coil is called lower bar and other part is called upper
bar.
Turbo generators: the manufacturing of bar of standard capacity such as 100
MW,130MW,150MW,210/235MW,210/250MW500MW.The plant has capacity
and technology to manufacture 800MW and 1000MW generators.
Types of generator: The generator may be classified based upon the cooling
system based upon the generator such as THRI,TARI,THDI,THDD,THDF,THFF
and THW.

6. T=>First letter signifies the type of generator i.e. turbo generator or hydro
generator.
H/A=>second alphabet stand for cooling media used for cooling of rotor i.e.
hydrogen gas or air.
R/D/F/I => the third alphabet signifies the cooling i.e. radial , direct, indirect,
forced.
I/D/F=>last alphabet stand for the type of cooling of stator i.e. direct cooling,
indirect cooling and forced cooling.
W=>cooling media used for stator coil e.g. water.
SECTION IN BLOCK 4
1. Assembly section :
 Mechanical assembly section:-It is equipped with small size drilling machine,
welding set and hydraulic testing equipment for testing turbo generator
mechanical assemblies.
 Close cubical assembly section.
2. Stator bar winding section:
 Conductor cutting insulation and transposition section having facilities for
transposing the bars.
 Stack consolidation section, forming lug brazing section have block type hydraulic
press ,steel forming and induction brazing insulation respectively.
 Insulation tapping sections with automatic tapping facilities in air conditioned
temperature covering maximum slot portion each over hung by both end.
 Baking and pressing section having baking mould for simultaneous curcing for
straight and overhead portion with electrical heating.
3. Armature winding ,rotor coil and stator bar section:-
Coil are diamond pull type with class-B (bitumen) and class-F(conventional or
resin rich discontinuous epoxy insulation) and class-H insulation for machines
ranging from 5 to 460KW capacity.
This section has following work centres:
 Conductors cutting, U- bending and terminal conductor cutting machines,
U- bendingmachines and terminal baths.
 Forming and Insulation of DC coils.
 Main and Interpole Winding: - It is having semi-automatic winding machine.

7.  Planking, boat pulling and diamond pulling machine.
 Insulation and pressing of AC coils: - it is equipped with hydraulic presses of
608 T.
4. Impregnation Section :-
It is equipped with impregnation tank, ovens for impregnation of DC pole coils.
5. Insulation Section :-
 Insulating details, machining is equipped with small size lathes, milling and
radialdrilling machines and jet cutting saw.
 Press Molding Section: - It has electrical ovens, hydraulic presses, shearing andcircular
saw cutting machines for manufacturing press molded components of all theelectrical
machines.
 Plastic Molding Section: - Is equipped with various presses for plastic molded parts.
 Bitumen Mica Tape Manufacture: - Is equipped with mica tape manufacturingmachine
and lathe for slitting mica tape to the required size.

8. INTRODUCTION TO CNC MACHINE

9. Numerical control for machines .tools were introduced in 1950’s by Prof.John T
Parsons. The first NC machine was built at the Massachusetts institute of
Technology in 1953 by joint efforts of US Air Force, the MIT and parson’s
cooperation. NC is control by numbers .NC is control recorded information called
part program, which is set of coded instructions given as numbers for automatic
control of am machine in a pre-determined sequence.
Numerical control can be defined as a technique of controlling a machine tool by
the direct insertion of numerical data at some point of the system .The functions that
are controlled on the machine tool are displacement of the slide members, spindle
speeds ,tool selection etc.At first ,the numerical control was used to produce
geocentrically complex parts ,but later used for added efficiency in medium batch
production of turned and milled parts presently, Numerical control is employed in
all sectors of production .
Rapid development in the field of electronics such as integrated circuit, large scale
integrated circuits and development of minicomputer lead to the development of
minicomputers based CNC systems. Further development and the electronic “chip”
revolution have ushered in the current generation “compact and powerful”
Microprocessor based CNC systems.
Development of computer numerically controlled (CNC) machines is an
outstanding contribution to the manufacturing industries. It has made possible the
automation of the machining process with flexibility to handle small to medium
batch of quantities in part production.
Initially, the CNC technology was applied on basic metal cutting machine like
lathes, milling machines, etc. Later, to increase the flexibility of the machines in
handling a variety of components and to finish them in a single setup on the same
machine, CNC machines capable of performing multiple operations were
developed. To start with, this concept was applied to develop a CNC machining
centre for machining prismatic components combining operations like milling,
drilling, boring and taping. Further, the concept of multi-operations was also
extended for machining cylindrical components, which led to the development of
turning centers.
Computer Numerical Control (CNC) is a specialized and versatile form of Soft

10. Automation and its applications cover many kinds, although it was initially
developed to control the motion and operation of machine tools.
Computer Numerical Control may be considered to be a means of operating a
machine through the use of discrete numerical values fed into the machine, where
the required 'input' technical information is stored on a kind of input media such
as floppy disk, hard disk, CD ROM, DVD, USB flash drive, or RAM card etc. The
machine follows a predetermined sequence of machining operations at the
predetermined speeds necessary to produce a workpiece of the right shape and
size and thus according to completely predictable results. A different product can
be produced through reprogramming and a low-quantity production run of
different products is justified.
ADVANTAGE OF CNC MACHINES
 Higher flexibility
 Increased productivity
 Consistent quality
 Reduced scrap rate
 Reliable operation
 Reduced non productive time
 Reduced manpower
 Shorter cycle time
 High accuracy
 Reduced lead time
 Just in time (JIT) manufacture
 Automatic material handling
 Lesser floor space
 Increased operation safety
 Machining of advanced material

11. The definition of CNC given by Electronic Industry Association (EIA) is as
follows:
“A system in which actions are controlled by the direct insertion of
numerical data at some point. The system must automatically interpret at
least some portion of this data.”
In a simple word, a CNC system receives numerical data, interpret the data and
then control the action accordingly.
CNC SYSTEMS
INTRODUCTION
Numerical control (NC) is a method employed for controlling the motions of a
machine tool slide and its auxiliary functions with input in the form of numerical
data. A computer numerical control (CNC) is a microprocessor-based system to
store and process the data for the control of slide motions and auxiliary functions
of the machine tools. The CNC system is the heart and brain of a CNC machine
which enables the operation of various machine members such as slides, spindles,
etc. as per the sequence programmed into it, depending on the machining
operations.
The main advantage of a CNC system lies in the fact that the skills of the
operator hitherto required in the operation of a conventional machine is removed
and the part production is made automatic.
The CNC systems are constructed with a NC unit integrated with a
programmable logic controller (PLC) and some times with an additional external
PLC (non-integrated). The NC controls the spindle movement and the speeds and
feeds in machining. It calculates the traversing path of the axes as defined by the
inputs. The PLC controls the peripheral actuating elements of the machine such as
solenoids, relay coils, etc. Working together, the NC and PLC enable the machine
tool to operate automatically. Positioning and part accuracy depend on the CNC
system's computer control algorithms, the system resolution and the basic
mechanical machine accuracy. Control algorithm may cause errors while

12. computing, which will reflect during contouring, but they are very negligible.
Though this does not cause point to point positioning error, but when mechanical
machine inaccuracy is present, it will result in poorer part accuracy.
Computer Numerical Control (CNC) is a specialized and versatile form of Soft
Automation and its applications cover many kinds, although it was initially
developed to control the motion and operation of machine tools.
Computer Numerical Control may be considered to be a means of operating a
machine through the use of discrete numerical values fed into the machine, where
the required 'input' technical information is stored on a kind of input media such
as floppy disk, hard disk, CD ROM, DVD, USB flash drive, or RAM card etc. The
machine follows a predetermined sequence of machining operations at the
predetermined speeds necessary to produce a work piece of the right shape and
size and thus according to completely predictable results. A different product can
be produced through reprogramming and a low-quantity production run of
different products is justified.
Applications of CNC Machines
CNC machines are widely used in the metal cutting industry and are best used to produce

13. the following types of product:
• Parts with complicated contours
• Parts requiring close tolerance and/or good repeatability
• Parts requiring expensive jigs and fixtures if produced on conventional
machines
• Parts that may have several engineering changes, such as during
the development stage of a prototype
• In cases where human errors could be extremely costly
• Parts that are needed in a hurry
• Small batch lots or short production runs
Some common types of CNC machines and instruments used in industry are as
following:
• Drilling Machine
• Lathe / Turning Centre
• Milling / Machining Centre
• Turret Press and Punching Machine
• Wire cut Electro Discharge Machine (EDM)
• Grinding Machine
• Laser Cutting Machine
• Water Jet Cutting Machine
• Electro Discharge Machine
• Coordinate Measuring Machine
• Industrial Robot

14. TYPES OF CNC MACHINES
1. ROEBEL MACHINE
2. BRAZING MACHINE
3. PRESSING
4. TAPPING
5. MICALASTIC MACHINE
ROEBEL MACHINE
It is a type of machine used for making the stator windings of various turbo generators. It facilitates the operations
involved like
1. Cutting of conductors in a specific length (depends upon type of bars).
2. Bending of conductor.
3. Transposition of conductors.
Working operation
The bars are cut in specific length and then they are submitted to manipulators and then bending is done by
manipulator. After each step the starting point for the bending of conductor advances for a certain length.after
bending process the bars are adjusted manually.
Cutting of 500 mw stator winding
No of conductors 15(u)
Length of wire 10050mm
First bending 2062mm
Transposition length 5850mm
No of conductors 20(L)
Length of wire 10200mm
First bending 2127mm
Transposition length 5848mm
Cutting for 600mw stator winding
No of conductors 21(14:7)
Length of wire 10887mm(u),11053mm(L)
First bending 2069mm(U),2149mm(L)
Transposition length 6653mm
Cutting of 800mw stator winding
No of conductors 30(25:5)
Length of wire 110077mm(u),11282(l)
First bending 2158mm(U),2257mm(L)
Transposition length 6702mm

15. BRAZING
It is a joining two copper conductors whereby a filler copper is heated above melting point and distributed between two
or more close fitting part by capillary action. The filler metal is brought slightly above its melting temperature while
protected by a suitable atmosphere usually a flux. It then flows over the base metal and is then cooled to join the work
pieces together .it is similar to soldring except the temperature used to melt the filler metal are higher for brazing.
There are two type of brazing
1. Main brazing
It consist of two operations contact sleve of top part plus bottom part
Temp can be within the range of 700 to 750 degree Celsius.
Brazer used is –lag55sh for electrical constraint and mechanical strength then the process followed by main
brazing is milling and extra conductor cutting because after brazing there may be some error in conductor size
so in order to insure error free conductor.
After each brazing process pickling is done because collection of unwanted elements on the surface of
conductor so it cleans the surface
2. Cup brazin
3. It consist of water box top part plus water box bottom part.
Temperature is 640 degree
The brazer used is –Lag 40c2

16. Again after cup brazing pickling is done in order to clean the surface of the conductor.in pickling process there
are different chemical solutions from which the conductor is passed through these solutions clean the surfaces.
TAPPING MACHINE
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. Mica filic paper is used for insulation.
S
MICALASTIC MACHINE
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.
VPI Micalastic system:
The bars already laid in closed fixture and full fixture is impregnated (dipped) in resin and then fixture with box is baked
under given temperature for given duration.
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.

17. CONCLUSION
This training has proved to be quite faithful. This gave me, a chance to have an encounter
with such heavy machines like turbo generator (TG) 800MW.The architecture of B.H.E.L. ,the
way the various units are linked and the way the working of the whole plant is controlled,
makes the student realize that engineering is not just the structural descr iption but more of
planning and management. It has provided an opportunity to learn that optimization of
technology used at proper place and time can save a lot of labour.
The training has proved to be immensely helpful as it has helped me to have an exposure of
the practical implementation of the theoretical knowledge that I have gained till date.