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

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

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.

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.

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 4 th .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.

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.

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.

INTRODUCTION TO CNC MACHINE

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

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

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

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

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

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

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

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.

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 description 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.