bhel1

ELECTRICAL MACHINES MANUFACTURING (TURBO ALTERNATORS)

AN IT REPORT SUBMITTED TOWARDS THE PARTIAL FULFILLMENT OF

THE REQUIREMENTS OF THE AWARD OF DEGREE OF

BACHELOR OF ENGINEERING

IN

ELECTRICAL ENGINEERING

SUBMITTED BY

AKSHAY DHAR

C.R.NO 377/07

U.R.NO. 725/07

DEPARTMENT OF ELECTRICAL ENGINEERING

MAHANT BACHITTAR SINGH COLLEGE OF ENGINEERING & TECHNOLOGY.

UNIVERSITY OF JAMMU

YEAR 2010

I

ACKNOWLEDGEMENT

With a sense of great pleasure and satisfaction I present this industrial training report

entitled as “ELECTRICAL MACHINES MANUFACTURING (TURBO

ALTERNATORS). Completion of this report is no doubt a product of invaluable support

and contribution of a number of people.

I present my sincere gratitude to Mr. P.S Jangpangi (Sr.DGM), Mr. U.K.Singh

(MGR), Mr. Rahul Kumar (Engineer stator winding section) Mr. R.K Dhiman (Engineer

Exciter Winding Section) & Mr. U.K Kamila (Mgr. 500MW Rotor/Stator Winding section)

of BHEL for being a constant guide and inspiration.

I would also like to thank Mr. Ajay Sharma (HOD EE Deptt.) & Ms. Damandeep

Kour (Lect. EE Department) for providing us timely valuable guidance and suggestions.

It is heartening to have a comradeship of my sincere friends namely: Mr. Sachin

Kangotra (354/07) Mr. Manpreet Singh (402/07) Mr. Deepak Kumar Verma (350/07) Mr.

SorabAttri (362/07) who equally stood like the rock of gibraltar for the formulation and

compilation of the text and allied jobs. Without their support this would not have been

possible.

Akshay Dhar

C.R.NO 377/07

U.R.NO. 725/07

II

DECLARATION

I hereby declare that the IT report entitled “ELECTRICAL MACHINES MANUFACTURING

(TURBO ALTERNATORS)” is an authentic record of my own work carried out as the partial

fulfillment of the requirements for the award of degree of B.E (electrical engineering) at M.B.S.

College of engineering and technology, Jammu during June - July 2010

Akshay Dhar

C.R.NO 377/07

U.R.NO. 725/07

Date:

Certified that the above statement made by the student is correct to the best of my knowledge and

belief.

Ms. Damandeep Kour

(Lecturer EE Deptt.)

I.T. Coordinator

Countersigned by

Mr. Ajay Sharma

HOD EE Deptt.

III

ABSTRACT

Practical knowledge means the visualization of the knowledge, which we read in our books.

For this, we perform experiments and get observations. Practical knowledge is very important

in every field. One must be familiar with the problems related to that field so that he may solve

them and become a successful person. After achieving the proper goal in life, an engineer has

to enter in professional sector or self-own. For the efficient work in the field, he must be well

aware of the practical knowledge as well as theoretical knowledge. To be a good engineer, one

must be aware of the industrial environment and must know about management, working in the

industry, labour problems etc. so he can tackle them successfully.

Due to all the above reasons and to bridge the gap between theory and practical,our

engineering curriculum provides a practical training of 30 days. During this period, a student

works in the industry and gets all type of experience and knowledge about the working and

maintenance of various types of machinery.

I have undergone my summer training (after 3rd yr.) at BHARAT HEAVY

ELECTRICALS LIMITED.This report is based on the knowledge, which I acquired

during my training period at the plant.

IV

V

CONTENTS

1. Introduction to B.H.E.L Page No.

1.1 Establishment 1

1.2 BHEL – A Brief Profile 2

1.3 BHEL–An Overview 2

2. Heavy Electrical Equipments Plant (HEEP)

2.1 Brief Profile 6

2.2 Establishment & Development Stages 7

2.3 Climatic & Geographical Conditions 8

2.4 Power & Water supply system 8

2.5 Electrical Machines Block (BLOCK-I) 9

2.6 Basic Training Departments 11

3. Turbo Generators

3.1 Introduction 12

3.2 Synopsis of the Function of T.G 13

3.3 Large Sized Turbo Generator 13

4. Stator

4.1 Introduction 17

4.2 Stator Frame 17

4.3 Stator Core 18

4.4 Stator Winding 19

4.5 Insulation of Bars 20

4.6 End Cover 21

4.7 Manufacturing of various parts of stator 22

5. Rotor

5.1 Introduction 26

5.2 Rotor Shaft 27

5.3 Various Steps Involved In Rotor Machining 28

5.4 Rotor Winding 30

5.5 Construction of field winding 31

5.6 Conductor Material 33

5.7 Insulation 33

5.8 Rotor Slot wedges 35

5.9 Rotor Retaining Rings 36

5.10 Rotor Fans 37

5.11 Bearings 37

5.12 Field Current lead in shaft base 38

5.13 Rotor Assembly 38

5.14 Machine section 38

VI

6. Ventilation & Cooling System

6.1 Ventilation System 40

6.2 Stator cooling system 40

6.3 Rotor cooling system 40

6.4 Hydrogen cooling system 41

6.5 Generator sealing system 42

7. Excitation System

7.1 Exciter 43

7.2 Main Components 44

7.3 Automatic Voltage Regulator (AVR) 46

8. Small & Miscellaneous components (BAY-IV)

8.1 Machine Section 47

8.2 Pole coil section 47

8.2.1 Annealing Process 48

8.2.2 Winding process 48

8.2.3 Brazing 48

8.2.4 Pressing 48

8.2.5 Fixing 49

8.2.6 Separation 49

8.2.7 Pickling 49

8.2.8 Finishing 49

8.2.9 Insulation 50

8.2.10 Baking& Pressing of coil 50

8.2.11 Cleaning & Drying 50

8.2.12 Turbo Rotor coil section 50

8.2.13 Impregnation section 51

8.2.14 Babbiting section 51

8.3 Test Strands 51

8.4 Large size turbo generator test stand (LSTG) 51

8.5 Helium Leak Test 51

9. Conclusion 52

BIBILIOGRAPHY

VII

LIST OF FIGURES

S.No Fig.No. Name of Figure Page No.

1. 1.1 Entrance to the Heavy Electrical 1

Equipments Plant (HEEP)

2. 2.1 Electrical Machines Block-1 6

3. 3.1 Hydrogen-cooled turbogenerator of the

500 MVA class in standard steam

turbine arrangement 12

4. 3.2 A Turbo generator in action 14

5. 3.3 Cut Section of a Turbo alternator 15

5. 4.1 Stator Frame 17

6. 4.2 Stator core 18

7. 4.3 Stator Windings in a T.G. 19

8. 4.4 End Cover of a T.G. 21

9. 4.5 Stator Core under fabrication process 22

10 4.6 Stator Core Assembly Section 23

11 4.7 Milling Machine 24

12 4.8 Hydrogen Cooling System of a T.G. 25

13 5.1 A fully completed T.G. Rotor 26

14. 5.2 A Rotor Mounted on a Slotting Machine 27

15. 5.3 Rotor Shaft mounted on a Central

Lathe Machine 28

16. 5.4 A completely slotted Rotor 29

17. 5.5 Rotor Winding in a T.G. 30

18. 5.6 TG Rotor alongwith field windings 31

19. 5.7 Rotor Windings/conductors 33

20. 5.8 Nomex Fibres for Rotor Slot Insulation 34

21. 5.9 Rotor Damber Bars/Wedges 35

22. 5.10 Rotor Retaining Rings 36

23. 5.11 Rotor Blades 37

24. 5.12 A Fully Assembled T.G. 38

25. 5.13 Lathe Machine 39

26. 6.1 Hydrogen Cooler of a T.G. 41

VIII

27. 6.2 T.G. Testing Section 42

28. 7.1 Exciter Winding Section 43

29. 7.2 Diode/Rectifier Wheel 44

30. 7.3 Exciter of a Turbo Generator

alongwith Diodes set 45

31. 7.4 Internal Circuitry of an AVR 46

32. 8.1 Bay- IV 47

IX

LIST OF TABLES

S.No Name of Table Page No.

1. Various blocks at Heavy Electrical 8

Equipments Plant along with the

major facilities and the

products manufactured.

2. Shows the various bays in Block-I 10

along with their respective jobs.

1

CHAPTER 1.

INTRODUCTION TO B.H.E.L

1.1 ESTABLISHMENT

Fig 1.1 Entrance to the Heavy Electrical Equipments Plant (HEEP)

BHEL was established more than 50 years ago when its first plant was setup in Bhopal ushering in

the indigenous Heavy Electrical Equipment Industry in India. A dream which has been more than

realized with a well-recognized track record of performance it has been earning profits

continuously since 1971-72 and achieved a turnover of Rs 2,658 crore for the year 2007-08,

showing a growth of 17 per cent over the previous year. Bharat Heavy Electricals Limited is

country‟s „Navratna‟ company and has earned its place among very prestigious national and

international companies. It finds place among the top class companies of the world for manufacture

of electrical equipments.BHEL caters to core sectors of the Indian Economy viz., Power

Generation's & Transmission, Industry, Transportation, Telecommunication, Renewable Energy,

Defence, etc. BHEL has already attained ISO 9000 certification for quality management, and ISO

14001 certification for environment management and OHSAS – 18001 certification for

Occupational Health and Safety Management Systems. The Company today enjoys national and

international presence featuring in the “Fortune International-500” and is ranked among the top 10

companies in the world, manufacturing power generation equipment. BHEL is the only PSU among

the 12 Indian companies to figurein “Forbes Asia Fabulous 50” list.Probably the most significant

2

aspect of BHEL‟s growth has been its diversification .The constant re-orientation of the

organization to meet the varied needs in time with a philosophy that has led to total development of

a total capability from concepts to commissioning not only in the field of energy but also in

industry and transportation. In the world power scene BHEL ranks among the top ten

manufacturers of power plant equipments not only in spectrum of products and services offered, it

is right on top. BHEL‟s technological excellence and turn key capabilities have won it world wide

recognition. Over 40 countries in world over have placed orders with BHEL covering individual

equipment to complete power stations on turn key basis

1.2 BHEL – A BRIEF PROFILE

BHEL is the largest engineering and manufacturing enterprise in India in the energy related

infrastructure sector today. The wide network of BHEL's 14 manufacturing division, four power

Sector regional centres, over 150 project sites, eight service centres and 18 regional offices, enables

the Company to promptly serve its customers and provide them with suitable products, systems and

services efficiently and at competitive prices. While the company contributes more than 75% of

the national grid, interestingly a share of 45% comes from its single unit. And this is none other

than BHEL-Haridwar.

BHEL has:-

1) Installed equipment for over 90,000MW of power generation for utilities captive and industrial

users.

2)Supplied over 2, 25,000 MVA transformer capacity and other equipment operating in

transmission and distribution network up to400 kV (AC & DC).

3)Supplied over 25,000 motors with drive control systems to power projects, petrochemicals,

refineries, steel, aluminium, fertilizers, cement plants etc.

4)Supplied Traction electrics and AC/DC locos to power over 12,000 kms railway network.

5)Supplied over one million valves to power plants and other industries.

1.3 BHEL-AN OVERVIEW

The first plant of what is today known as BHEL was established nearly 40 years ago at Bhopal &

was the genesis of the Heavy Electrical Equipment industry in India.BHEL is today the largest

3

Engineering Enterprise of its kind in India with excellent track record of performance, making

profits continuously since 1971-72. BHEL business operations cater to core sectors of the Indian

Economy like:-Power, Industry, Transportation, Transmission, Defences etc..

Today BHEL has

14 Manufacturing Divisions

9 Service Centres

4 Power Sector Regional Centres

150 Project sites

BHEL vision is to world-class engineering enterprise, committed to enhancing stakeholder value.

The greatest strength of BHEL is its highly skilled and committed 44,000 employees.Spread all

over India & abroad to provide prompt and effective service to customers.

BUSINESS SECTOR

BHEL operations are organized around business sectors to provide a strong market orientation.

These business sectors are Power Indus and International operations.

POWER SECTOR

Power sector comprises of thermal, nuclear, gas and hydro business. Today BHEL supplied

sets account for nearly 65% of the total installed capacity in the country as against nil till

1969-70.

BHEL has proven turnkey capabilities for executing power projects from concept to

commissioning and manufactures boilers, thermal turbine generator set & auxiliaries up to

500MW.

It possesses the technology and capability to procure thermal power generation equipment

up to 1000MW.

4

Co-generation and combined cycle plants have also been introduced.

For efficient use of the high ash content coal-BHEL supplies circulating fluidized boiler.

BHEL manufactures 235MW nuclear sets & has also commenced production of 500MW

nuclear set.

Custom-made huge hydro sets of Francis, Pelton and Kaplan types for different head

discharge

Combinations are also engineered and manufactured by BHEL.

INDUSTRY SECTOR

BHEL is a major contributor of equipment and system to important industries like:

Cement

Petrochemicals

Fertilizers

Steel paper

Refineries

Mining and Telecommunication

The range of system and equipment supplied including captive power stations

High speed industrial drive turbines

Industrial boilers and auxiliaries

Waste heat recovery boilers

Gas turbines pump, valves, seamless steel tubes

5

Heat exchangers

Process control etc.

TRANSPORTATION

BHEL supplies a wide equipment and system to Indian Railways.

Electric locomotive

Traction electric and traction control equipment

TELECOMMUNICATION

BHEL also caters to Telecommunication sector by way of small, medium and large switching

system.BHEL manufactures telecom switching equipment based on C-DOT technology, the major

products being MAX-XL of up to 40,000 lines capacity and Single Base Module RAX for rural

applications.

RENEWABLE ENERGY

Technologies have been developed and commercialised for exploiting non-conventional and

renewable sources of energy. These include photovoltaic cells and modules, solar lanterns, grid-

interactive PV Power Plants and solar heating systems. BHEL has emerged as a major

manufacturer of wind electric generators of up to 250 kW unit size. The Company has set up its

own wind farms of 3000 kW capacity (12x250 kW) at Ramgiri (A.P.) and another of 4000 kW

capacity (16x250 kW) at Kadavakkallu (A.P.).

6

CHAPTER 2.

HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP)

2.1 BRIEF PROFILE

Fig 2.1 Electrical Machines Block-1

At Haridwar, against the picturesque background of Shivalik Hills, two important manufacturing

units of BHEL are located viz. Heavy Electrical Equipment Plant (HEEP) & Central Foundry Forge

Plant (CFFP). The hum of the construction machinery working started under Shivalik Hills during

early 60s and sowed the seeds of one of the greatest symbol of Indo Soviet Collaboration – Heavy

Electrical Equipment Plant. Consequent upon the technical collaboration between India and USSR

in1959, BHEL‟s prestigious unit, Heavy Electrical Equipment plant (HEEP), was established in

October 1963, at Haridwar. It started manufacturing thermal sets in 1967 and now thermal sets of

210, 250 and 500 MW, including steam turbines, turbo-generators, condensers and all associated

equipments, are being manufactured. This unit is capable of manufacturing thermal sets up to 1000

7

MW. HEEP manufactured gas turbines, hydro turbines and generators, etc., are not only

successfully generating electrical energy within and outside the country, but have also achieved a

historic record of the best operational availability and plant load factor. The Company is embarking

upon an ambitious growth path through clear vision, mission and committed values to sustain and

augment its image as a world class enterprise.

VISION

World-class, innovative, competitive and profitable engineering enterprise providing total business

solutions.

MISSION

The leading Indian engineering enterprise providing quality products systems and services in the

fields of energy, transportation, infrastructure and other potential areas.

VALUES

Meeting commitments made to external and internal customers.

Foster learning creativity and speed of response.

Respect for dignity and potential of individuals.

Loyalty and pride in the company.

Team playing

Zeal to excel.

Integrity and fairness in all matters.

2.2 ESTABLISHMENT AND DEVELOPMENT STAGES

Established in 1960s under the Indo-Soviet Agreements of 1959 and 1960 in the area of

Scientific, Technical and Industrial Cooperation.

DRR – prepared in 1963-64, construction started from October '63

Initial production of Electric started from January, 1967.

Major construction / erection / commissioning completed by 1971-72 as per original DPR

scope.

Stamping Unit added later during 1968 to 1972.

Annual Manufacturing capacity for Thermal sets was expanded from 1500 MW to3500

MW under LSTG. Project during 1979-85 (Sets up to 500 MW, extensibleto 1000/1300

8

MW unit sizes) with marginal addition in facilities with the collaboration of M/s KWU-

Siemens, Germany.

Motor manufacturing technology updated with Siemens collaboration during1984-87.

Facilities being modernized continually through Replacements / Reconditioning-

Retrofitting, Technological / operational balancing.

2.3 CLIMATIC AND GEOGRAPHICAL CONDITIONS

Haridwar is in extreme weather zone of the Western Uttar Pradesh of India and temperature

varies from 2°C in Winter (December to January) to 45°C in Summer(April-June); Relative

humidity 20% during dry season to 95-96% during rainy season.

Longitude 78°3' East, Latitude 29 °55'5" North.

Height above Mean Sea Level = 275 meters.Situated within 60 to 100 KMs of Foot-hills of

the Central Himalayan Ranges;

Ganges flows down within 7 KMs from the Factory area.

HEEP is located around 7 KMs on the Western side of Haridwar city.

2.4 POWER & WATER SUPPLY SYSTEM

40 MVA sanctioned Electric Power connection from UP Grid (132 KV / 11KV /6.6 KV)

(Connected load – around 185 MVA)

26 deep submersible Tube Wells with O.H. Tanks for water supply.

A 12 MW captive thermal power station is located in the factory premises.

Table No. 1; Shows the various blocks at Heavy Electrical Equipments Plant along with the major

facilities and the products manufactured.

S.No. Area/ Block Major Facilities Products

1

Block –I

(Electrical

Machines)

Machine Shop., Windings bar

preparation assembling, painting

section, packing& preservation,

over speed balancing, test bed test

stand, babbiting, micalastic

impregnation etc.

Turbo

Generator,Hydro

Generators,

Generator exciters,

motors (AC& DC)

9

2

Block – II

(Fabrication

Block)

Markings, welding ,Cutting,

straightening, gas cutting press, ,

grinding, assembly, heat treatment,

cleaning & Shot blasting,

machining, fabrication of pipe

coolers, painting

Large size fabricated

assemblies/

components for power

equipments

3

Block –III

(Turbines &

Auxiliary

Block)

Machining, facing wax melting,

broaching, assembly preservation

& packing, test stands/ station,

painting grinding, milling,

polishing etc.

Steam turbines, hydro

turbines, gas turbines,

turbine bladders,

special tooling.

4

Block –IV

(Feeder Block)

Bar winding, mechanical

assembly, armature winding,

sheet metal working marching,

copper profile drawing

electroplating, impregnation,

machining & preparation of

insulating components plastic

moulding, press moulding

Windings for turbo

generators, hydro

generators insulation

for AC & DC motors,

insulating components

for TG, HG & Motors

control panel, contact

relays master control

etc

5

Block – V

Fabrication, pneumatic hammer

for forgings, gas fired furnaces,

hydraulic manipulators

Fabricated parts of

steam turbine, water

box, storage tank

2.5 ELECTRICAL MACHINES BLOCK (BLOCK-I)

Block-I is designed to manufacturing Turbo Generators, Hydro generators and large and

medium size AC and DC Electrical machines.

10

The Block consist of 4 bays: Bay-1 (36*482 meters), Bay-2 (36*360 meters) &Bay-3 and

Bay-4 of size 24 *360 meters each. For handling and transporting thevarious components

over-head Crane facilities are available, depending upon theproducts manufactured in each

Bay. There are also a number of self-propelledelectrically-driven transfer trolleys for the

inter-bay movement of components/assemblies.

Conventional bay -wise broad distribution of products is as follows :

Table No. 2; Shows the various bays in the Block-I along with their respective jobs.

BAY

–1

ROTOR

SHAFT

MACHININ

G

ROTOR

SHAFT

SLOTTING

ROTOR

WINDING

OVER SPEED

AND

BALANCING

TUNNEL

LARGE SIZE

TURBOGENE

RATORS

BAY

–2

EXCITER

SHAFT

MACHINING

STATOR

BODY

MACHINING

EXCITER

MOTOR

STARTER

WINDING

TOTAL

IMPREGNATIO

N

TEST BED

BAY

–3

ROTOR

SUPPORT

BEARING

SHAFT SEAL

BODY

DC

MOTOR

WINDING

(EARLIER)

&

DETAIL

ASSEMBLY

MOTOR

BALANCING

PAINTING

SECTION

BUS BAR &

FILLING

SECTION

MACHINE

TEST STAND

BAY

–4

COOLING

FANS

MACHINING

T.R.C

IMPREGNATI

ON

CNC

MACHINE

HALL

11

2.6 BASIC TRAINING DEPARTMENTS

MACHINE SHOP.

T/G ROTOR WINDING.

H/G IRON ASSEMBLY.

EXCITER.

T/G STATOR WINDING.

TOTAL IMPREGNATION TECHNIQUE.

T/G IRON ASSEMBLY.

T/G MAIN ASSEMBLY.

L.S.T.G ROTOR WINDING.

L.S.T.G STATOR WINDING.

L.S.T.G MAIN ASSEMBLY.

TEST BED.

12

CHAPTER 3.

TURBO GENERATOR

3.1 INTRODUCTION

Turbo generator or A.C. generators or alternators operates on the fundamental principles of

ELECTROMAGNETIC INDUCTION. In them the standard construction consists of armature

winding mounted on stationary element called stator and field windings on rotating element called

rotor. The stator consists of a cast-iron frame, which supports the armature core , having slots on its

inner periphery for housing the armature conductors. The rotor is like a flywheel having alternating

Fig. 3.1Hydrogen-cooled turbogenerator of the 500 MVA class in standard

steam turbine arrangement

north and south poles fixed toits outer rim. The magnetic poles are excited with the help of an

exciter mounted on the shaft of alternator itself. Because the field magnets are rotating the current

is supplied through two slip rings. As magnetic poles are alternately N and S, they induce an e.m.f

and hence current in armature conductors. The frequency of e.m.f depends upon the no. of N and S

poles moving past a conductor in 1 second and whose direction is given by Fleming ‟s right hand

rule.

13

3.2 SYNOPSIS OF THE FUNCTION OF T.G.

The generator is driven by a prime mover which is steam turbine in this case.

The other side of generator is provided by a rotating armature of an exciter which produces

A.C. voltage. This is rectified to D.C. by using a rotating diode wheel.

The rear end of above exciter armature is mounted by a permanent magnet generator rotor.

As the above system is put into operation, the PMG produces A.C. voltage.

The voltage is rectified by thyristor circuit to D.C.

This supply is given to exciter field. This field is also controlled by taking feedback from

main generator terminal voltage, to control exciter field variation by automatic voltage

regulator. The rectified DC supply out of exciter is supplied to turbo generator rotor

winding either through brushes or central which will bedirectly connected to turbo

generator. This depends on the type of exciter viz. DC commutator machines or brushes

exciter.

The main A.C. voltage is finally available at the stator of Turbo Generator

3.3 LARGE SIZE TURBO GENERATOR (LSTG)

In these types of generators steam turbine does the function of prime mover which rotates the rotor

of LSTG and the field winding is supplied D.C. by an exciter.

Main types of T.G. are:-

1. THRI

2. TARI

3. THDI

4. THDD

5. THDF

6. THFF

14

Fig 3.2 A Turbo generator in action

1st LETTER = (here-T) = 3-phase turbo generator

2nd

LETTER = (here H or A) =Medium present for generator cooling (H= hydrogen, A or L=air)

3rd

LETTER =type of rotor cooling employed

R= radial,

F= direct water cooling

D= direct axial gas cooling)

4th

LETTER = type of as used for stator winding cooling

I= indirect gas cooling

D= direct gas cooling

F= direct water cooling

15

Fig 3.2 CUT SECTION OF A TURBOALTERNATOR

1. DE bearing

2. Shaft

3. DE seal

4. Closing of DE endshield/frame

5. Internal DE fan

6. Stator winding

7. DE endshield

8. Stator winding

9. DE fan cover

10. Rotor core

11. Stator core

12. Frame

13. Equalizer winding

14. NDE fan cover

15. NDE endshield

16. Internal NDE fan

17. Closing of NDE endshield/frame

16

18. NDE seal

19. Exciter fan

20. Pilot exciter (PMG)

21. Exciter compartment

22. Main exciter

23. Rotary rectifier set

24. Exciter cover

25. Anchor plate set

26. Accessory terminal box

27. Intermediate base

28. Alignment cap screws

29. Anchor bolts

17

CHAPTER 4.

STATOR

4.1 INTRODUCTION

The generator stator is a tight construction supporting and enclosing stator winding, core and

hydrogen cooling medium. Hydrogen is contained within the frame and circulated by fans mounted

at either end of rotor. The generator is driven by a direct coupled steam turbine at the speed of 3000

rpm. The generator is designed for continuous rated output. Temperature detector or other devices

installed or connected within the machine, permits the winding core and hydrogen temperature,

pressure and purity in machine.

4.2 STATOR FRAME

Fig 4.1. Stator Frame

The stator frame is used for housing armature conductors. It is made of cylindrical section with two

end shields which are gas tight and pressure resistant. The stator frame accommodates the

electrically active parts of stator i.e. the stator core and stator winding.The fabricated inner cage is

inserted in the outer frame after the stator has been constructed and the winding completed.

18

4.3 STATOR CORE

The stator core is stacked from the insulated electrical sheet steel lamination and mounted in

supporting rings over the insulated dovetail guide bars. In order to minimize eddy current losses

core is made of thin laminations. Each lamination layer is made of individual sections. The

Fig 4.2.Stator Core

ventilation ducts are imposed so as to distribute the gas accurately over the core and in particularly

to give adequate support to the teeth. The main features of core are:

1. To provide mechanical support.

2. To carry efficiently electric, magnetic flux.

3. To ensure the perfect link between the core and rotor.

19

4.4 STATOR WINDING

Each conductor must be capable of carrying rated current without overheating. The stator winding

consists of two layers made up of individual bars. Windings for the stators are made of copper

strips wound with insulated tape which is impregnated with varnish, dried under vacuum and hot

pressed to form a solid insulation bar. These bars are then placed in the stator slots and held in with

wedges to form the end turns.These end turns are rigidly placed and packed with blocks of

insulation material to withstand heavy pressure. The stator bar consists of hollow (in case of 500

MW generators) solid strands distributed over the entire bar cross-section, so that good heat

dissipation is ensured. In the straight slot portion the strands are transposed by 540 degrees.

Fig 4.3.Stator Windings in a T.G.

The transposition provides for mutual neutralization of the voltage induced in the individual strands

due to slot cross field and end winding flux leakage and ensure that minimum circulating current

exists. The current flowing through the conductors is thus uniformly distributed over the entire

cross section so that the current dependent losses will be reduced. The alternate arrangement of one

20

hollow strand and two solid strands ensures optimum heat removal capacity and minimum losses.

The electrical connection between top and bottom bars is made by connecting sleeve. Class “F”

insulation is used. The no. of layer of insulation depends on machine voltage. The bars are brought

under vacuum and impregnated with epoxy resin, which has very good penetration property due to

low viscosity. After impregnation bars are subjected to pressure with nitrogen being used as

pressurizing medium (VPI process). The impregnated bars are formed to the required shape on

moulds and cured in an oven at high temperature to minimize the corona discharge between the

insulation and slot wall a final coat of semiconducting varnish is applied to the surface of all bars

within the slot range. In addition all bars are provided with an end corona protection to control the

electric field at the transition from the slot to end winding. The bars consist of a large no. of

separately insulated strands which are transposed to reduce the skin effect.

4.5 INSULATION OF BARS

a) Vacuum pressed impregnated micalastic high voltage insulation:

The high voltage insulation is provided according to the proven resin poor mica base of

thermosetting epoxy system. Several half overlapped continuous layer of resin poor mica

type are applied over the bars. The number of layers or thickness of insulation depends on

machine voltage.

The bars are inserted into the slots with very small lateral clearance and wedged with

packers. To prevent moment of end windings in circumferential direction, spacer blocks are

arranged between the bars and firmly with treated glass tapes. To minimize the effect of

radial forces, winding holders and insulated rings are used to support the overhang.

The stator is impregnated in a tank under vacuum and pressure with low viscosity epoxy

resin that penetrates the winding thoroughly. After impregnation, the stator is cured at at

appropriate temperature in an oven.

The high voltage insulation thus obtained is characterized by its excellent electrical,

mechanical and thermal properties. Its moisture absorption is extremely low and it is oil

resistant. The behavior of the insulation is far superior to any other conventional mica tape

insulation system.

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b) Corona Protection

To prevent a potential difference and possible corona discharges between the insulation and

slot wall, the slot sections of bars are provided with an outer corona protection. This

protection consists of polyester fleece tape impregnated in epoxy resin with carbon and

graphite as filters.

At the transition from slot to the end winding portion of stator bars a semi-conductive tape

made of polyester fleece is impregnated with silicon carbide as filler is applied for a specific

length. This ensures uniform control of the electric field and prevents the formation of

corona discharge during operation and performance of HV tests.

c) Resistance Temperature Detector

The stator slots are provided with platinum resistant thermometer to record and watch the

temperature of stator core and tooth region and between the coil sides of machine in

operation. All AC machines rated for more than 5 MVA or with armature core longer, the

machine is to be provided with at least 6 resistance thermometers. The thermometer should

be fixed in the slot but outside the coil insulation. When the winding has more than one coil

side per slot, the thermometer is to be placed between the insulated coil sides. The length of

resistance thermometer depends upon the length of armature. The leads from the detector

are brought out and connected to the terminal board for connection onto temperature meter

or relays. Operation of RTD is based on the prime factor that the “electric resistance of

metallic conductor varies linearly with temperature”

4.6 ENDCOVERS

The end covers are made up of

fabricated steel or aluminium

castings. They are employed

with guide vans on inner side for

ensuring uniform distribution of

air or gas. Incase of 1500 rpm

generators, end windings are

first enclosed in glass epoxy

Fig 4.4. End Cover of a T.G.

22

moulded end covers and an overall steel outer cover is provided over the stator.

4.7 MANUFACTURING OF VARIOUS PARTS OF STATOR

Stator Core Assembly Section

This section is present in BAY-1. Two no. core pits with core building and pressing facilities are

available in this section. The section is also equipped with optical centering device, core heating

installation and core loss testing facilities.

Fig 4.5. Stator Core under fabrication process

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Iron Assembly Section

In BAY-2 this section has facilities for stator core assembly of Turbo-generators and Heavy

Electric Motors.

Stator Winding Section

This section is present in BAY-1. The section is located in a dust-proof enclosure with one no.

winding. Platform with two no. rotating installation for assembly of winding. Resistance brazing

machines and high voltage transformers are also available inthis section.

Fig 4.6. Stator Core Assembly Section

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Bar Preparation Section

This section is present in BAY-1. This section consists of milling machine for long preparation,

installation for insulation of tension bolts for stator and preparation of stator winding before

assembly. The three phase winding is a fractional pitch two layer type consisting of individual bars.

Fig 4.7. Milling Machine

Armature Section

This section is equipped with installations like bandaging machines, tensioning devices, Magnetic

putty application machine and 45 KW MF brazing machines for laying windings in large size DC

armatures.

25

Cooling

Heat losses arising in the generator are dissipated through hydrogen. The heat dissipating capacity

of hydrogen is eight times to that of air.

Fig 4.8.Hydrogen Cooling System of a T.G.

26

CHAPTER 5.

ROTOR

5.1 INTRODUCTION

The moving or rotating part of generator is known as rotor. The axial length of shaft of the rotor is

very large as compared to its diameter in case of turbogenerators. Itis coiled heavily (field coils) as

it has to support large amount of current and voltage.Rotor revolves in most generators at a speed

of 3000 RPM. Field coils are wound over it to make the magnetic poles and to maintain magnetic

strength the winding must carry a very high current. As current flows heat is generated, but the

temperature has to be maintained because as temperature raises problems with insulation becomes

more pronounced. With good design & great care this problem can be solved. Solid rotors are

manufactured from forged alloy steel with suitable alloying elements to achieve very high

mechanical and magnetic properties. Rectangular or trapezoidal rotors slots are accurately

machined to close tolerances on slot milling machine. For indirectly cooled generator rotors,

ventilation slots are machined in the teeth. For directly cooled rotors, Sub slots are provided for

cooling Generators rotors of 1500 RPM are of round laminated construction. Punched and

varnished laminations of high tensile steel are mounted over machined shaft are firmly clamped by

end clamping plates.

Fig 5.1 A fully completed T.G. Rotor

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5.2 ROTOR SHAFT

The rotor shaft is cold rolled forging 26N1 or MOV116 grade and it is imported from Japan and

Italy.Rotor shaft is a single piece. The longitudinal slots are distributed over its circumference.After

completion, the rotor is balanced in the various planes and different speed and then subjected to an

over speed test at 120% of rotor speed. The rotor consists of electrically active portion and two

shaft ends approximately 60 % of rotor body circumference have longitudinal slots which hold the

field winding. Slots pitch is selected so that the twosolid poles are displaced by 180 degree the rotor

wedges act as damper winding within the range of winding slots. The rotor teeth at the rotor

Fig. 5.2 A Rotor Shaft Mounted on a Slotting Machine

body are provided in radial and axial poles enabling cooling air to be discharged. Rotor shaft is a

single piece solid forming manufactured form a vacuum casting. It is forged from a vacuum cast

steel ingot. Slots for insertion or the field winding are milled into rotor body. The longitudinal slots

are disturbed over the circumference such that two solid poles are obtained. To ensure that only a

28

high quality product is obtained, strength tests, material analysis and ultrasonic tests are performed

during the manufacture of rotor. The high mechanical stresses resulting from the centrifugal forces

and short circuit torque call for a high specified mechanical and magnetic properties as well as

homogeneous forging. After completion, the rotor is balanced in various planes at different speeds

and then subjected the rotor is balanced in various planes at different speeds and then subjected to

an over speed test at 120% of the rated speed for two minutes.

5.3 VARIOUS STEPS INVOLVED IN ROTOR MACHINING

1. SHAFT MACHINING

It involves finishing of shaft by machining it with a central lathe machine. It is done in

accordance to the engineering drawing design. Special care is taken to maintain the

tolerance level.

Fig. 5.3 Rotor Shaft mounted on a Central Lathe Machine

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2. SLOTTING

Two types of machines do slotting, air cooled and liquid cooled. Slotting is done

diametrically. First the shaft is made to rest on two horizontal plates and is firmly attached

to them with the help of chains which exerts load and with the help of jack so that it handles

the vibrations produced during the slotting process. Now the centre is marked and slotting is

done. After slotting is done through one side the shaft is rotated to the diametrically

opposite end of the slotted portion and then again slotting of that portion is done. It is done

in diametrically opposite ends so as to prevent bristling of slot due to mechanical vibrations.

Fig 5.4. A completely slotted Rotor

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5.4 ROTOR WINDING

Rotor winding involves coiling of rotor. It is a two pole rotor.Rotor coils are made of pure copper +

0.2% silver, which has high tensile as well as temperature bearing properties.

Fig 5.5 Rotor Winding in a TG

The coil doesn‟t deform even at high temperatures as on adding silver the thermal stresses are

eliminated. Rotor winding is also known as field winding which is wound in longitudinal slots in

rotor.The windings consist of several coils inserted into the slots and series connected such that two

coil groups form one pole. Each coil consists of several series connected turns, each of which

consists of two half turns connected by brazing in the end section. The rotor bearing is made of

silver bearing copper ensuring an increased thermal stability. The individual turns of coils are

insulated against each other by interlayer insulation.

The slot wedges are made of high electrical conductivity material and thus act as damper windings.

At their ends the slot wedges are short circuited through the rotor body. When rotor is rotating at

high speed, the centrifugal forces tries to lift the winding out of slots, they are contained by wedges.

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5.5 CONSTRUCTION OF FIELD WINDINGS

The field winding consists of several series connected coils into the longitudinal slots of body. The

coils are wound so that two poles are obtained. The solid conductors have a rectangular cross-

section. These coils are formed arranging together the 14 no. of strips which makes a half of the

coil which means that total 28 strips are used to make single coil of the field winding.Depending

upon the type of cooling there are 8 solid and 6 hollow strips in each half of the coil.

Fig 5.6 TG Rotor alongwith field windings

Let us understand it with help of the flow chart:

Coils placed together.

Then Teflon insulation is done on them.

A total of 13 layers are wrapped.

Then epoxy glass tape is wrapped around.

A card board of paper thickness is placed to keep the coils separated.

32

Then a varnish of 7556 is wrapped on it.

Then kept free heating of about 6 hrs is done.

Then a free heating of about 1.5 hr is done at low pressure of about 30 kg and 115˚C

temperature.

Then for 45 minutes it is heated at temperature of about 130˚C & pressure is increased to

200 kg.

Then keeping the pressure constant the temperature is raised to around 160 ˚C and coils are

heated for around 3 hrs.

Then the coils are removed off the pressure gradually and cooled by spraying water so now

the temperature reaches 60 ˚C then left to cool slowly and the coils are ready to be wedged

in the slots.

Then the coils placed in the slots and tighten up to prevent the loosening by tightening

rings.There are 7 turns per pole per pitch and rotor of 210 MW is ready to test.There is a

slight difference in formation of coils 500 MW turbo-generators.

In those generators the coils are arranged in the following manner.

Firstly they alternate hollow and solid conductors.

There are two solid conductors for every hollow strip and they are marked as

A---- Which has 7 conductors.

B---G where they have 9 conductors each coil.

They are transposed by 540* as it removes air gap and improves cross over insulation.

It increases mechanical strength and help in producing equal E.M.F across all the

conductors.

The insulation is moulding mica mite.

Testing involving the coils are thermal shock testing hot and cold.

This testing is done to check the strength of brazing so that there is no water leakage and as

a result it can bear thermal stresses easily. Nitrogen test is also performed for cleaning and

leakage purposes and finally impregnating it through vacuum impregnation technique.

The vacuum impregnation technique is the latest technique to insulate the windings of stator and

not used in rotors of any of the generators being used in the power plants now a days. The process

above is discussed is also known as transposition, which involves the bending of the strips used in

forming the coil of either rotor or stator.

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5.6 CONDUCTOR MATERIAL

The conductors are made of copper with a silver content of approximately 0.1%. As compared to

electrolytic copper, silver alloyed copper features high strength properties at high temperatures so

that coil deformations due to thermal stresses are eliminated.

Fig 5.7. Rotor Windings/conductors

5.7 INSULATION

The insulation between the individual turns is made of layer of glass fiber laminate. The coils are

insulated from the rotor body with L- shaped strips of glass fiber laminate with nomex interlines.

To obtain the required leakage paths between the coil and rotor body thick top strips of glass fiber

laminate are inserted below top wedges. The top strips are provided with axial slots of the same

cross section and spacing as used on the rotor winding.

34

Fig 5.8.Nomex Fibres for Rotor Slot Insulation

Requirements for a filler material to be used in high voltage insulation are:

High thermal conductivity

High electrical insulating capability

High partial discharge resistance

Compatibility with the binder and impregnating resin

Chemical stability and low toxicity

Availability in consistent quality

Practical cost

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5.8 ROTOR SLOT WEDGES

To protect the winding against the effects of centrifugal forces, the winding is secured in the slots

with wedges. The slot wedges are made of copper alloy featuring high strength and good electrical

Fig 5.9. Rotor Damber Bars/Wedges

conductivity. They are also used as damper winding bars. The slot wedges extend beyond the

shrink seats of retaining rings. The wedge and retaining rings act on the damper winding in the

event of abnormal operations. The rings act as a short circuit rings in the damper windings.

36

5.9 ROTOR RETAINING RINGS

The centrifugal forces of the end windings are contained by piece rotor retaining rings. Retaining

rings are made up of non-magnetic high strength steel in order to reduce the stray losses. Ring so

inserted is shrunk on the rotor is an over hang position. The retaining ring is secured in the axial

position by snap rings. The rotor retaining rings withstand the centrifugal forces due to end

winding. One end of each ring is shrunk fitted on the rotor body while the other hand overhangs the

Fig 5.10. Rotor Retaining Rings

end winding without contact on the rotor shaft. This ensures unobstructed shaft deflection at end

windings. The shrunk on hub on the end of the retaining ring serves to reinforce the retaining ring

and serves the end winding in the axial direction. At the same time, a snap ring is provided against

axial displacement of retaining ring. To reduce the stray losses and have high strength, the rings are

made up of non-magnetic cold worked material.

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5.10 ROTOR FANS

The cooling air in generator is cold by two axial flow fans located at the rotor shaft one at each end

augment the cooling of the winding. The blades of fan have threaded roots for screwed into the

rotor shaft. Blades are drop forged from aluminium alloy. Threaded root fastenings permit angle to

be changed. Each blade is screwed at its root with a threaded pin.

Fig 5.11.Rotor Blades

5.11 BEARINGS

The turbo generators are provided with pressure lubricated self-aligning type bearing to ensure

higher mechanical stability and reduced vibration in operation. The bearings are provided with

suitable temperature element to monitor bearing metal temperature in operation. The temperature of

each bearing monitored with two RTDs (resistance thermo detector) embedded in the bearing

sleeve such that the measuring point is located directly below Babbitt. Bearing have provision for

vibration pickup to monitor shaft vibration. To prevent damage to the journal due to shaft current,

bearings and coil piping on either side of the non-drive and bearings are insulated from the

foundation frame.

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5.12 FIELD CURRENT LEAD IN SHAFT BASE

Leads are run in axial direction from the radial bolt of the exciter coupling. They consist of low

semi-circular conductors insulated from each other and from the shaft by a tube.The field current

leads are coupled with exciter leads through a multi contact plug in which allows unobstructed

thermal expansion of field current.

5.13 ROTOR ASSEMBLY

Rotor winding assembly and rotor assembly and rotor assembly like rotor retaining ring fitting. All

these four assemblies are carried out in a

ROTOR ASSEMBLY SECTION present in

BAY 1. This section is also in a dust-proof

enclosure with no. of rotators, rotor bars

laying facilities and MI heating and mounting

of retaining rings.

Fig 5.12. A Fully Assembled TG

5.14 MACHINE SECTION

This section is present in BAY-2 (Turbo- Generators and Heavy Motors). This section is equipped

with large size CNC and conventional machine tools such as Lathes and Vertical boring, Horizontal

boring machine, Rotor slot milling and Radial drilling machines for machining stator body, rotor

shaft , End shields, Bearing etc. for Turbogenerators. Same section is present in Bay-3 (Medium

size motors) equipped with medium size machine tools for machining components for medium size

AC and DC machines and smaller components of Turbo-generators and Hydro generators.

39

Fig 5.13. Lathe Machine

Fig 5.14 Central Lathe Machine

40

CHAPTER 6.

VENTILATION AND COOLING SYSTEM

6.1 VENTILATION SYSTEM

The machine is designed with ventilation system having rated pressure. The axial fans mounted on

either side of rotor ensure circulation of hydrogen gas. The rotor is designed for radial ventilation

by stem. The end stator is packets and core clamping and is intensively cooled through special

ventilation system. Design of special ventilation is to ensure almost uniform temperature of rotor

windings and stator core.

6.2 STATOR COOLING SYSTEM

The stator winding is cooled by distillate water which is fed from one end of the machine by Teflon

tube and flows through the upper bar and returns back through the lower bar of a slot. Turbo

generator requires water cooling arrangement over and above the usual hydrogen cooling

arrangement. The stator is cooled in this system by circulating demineralized water trough hollow

conductors. The cooling was used for cooling of stator winding and for the use of very high quality

of cooling water. For this purpose DM water of proper specifying resistance is selected. Generator

is to be loaded within a very short period. If the specific resistance of cooling DM water goes

beyond preset value. The system is designed to maintain a constant rate of cooling water flow

through the stator winding at a nominal inlet with temperature of 40 degree centigrade, the cooling

water is again cooled by water which is also demineralized to avoid contamination with any impure

water in case of cooler tube leakage, the secondary DM cooling water is in turn cooled by clarified

water taken from clarified water header.

6.3 ROTOR COOLING SYSTEM

The rotor is cooled by means of gap pickup cooling, where the hydrogen gas in the air gap is

sucked through the scoops on the rotor and is directed to flow along the ventilating canals milled on

the sides of the rotor coil, to the bottom of slot where it takes a turn and comes out on the similar

canal milled on the other side of the rotor coil to the hot zone of the rotor, Due to the rotation of the

rotor, a positive section as well as discharge is created due to which a certain quantity of a gas

flows and cools the rotor. The method of cooling gives uniform distribution of temperature. Also

this method has an inherent of eliminating the deformation of copper due to varying temperature.

41

6.4 HYDROGEN COOLING SYSTEM

Hydrogen is used as a cooling medium in large capacity generators in views of highest carrying

capacity and low density. Also in order to prevent used hydrogen from generators, casing and

sealing system is used to provide oil sealing. The system is capable of performing following system

Fig 6.1. Hydrogen Cooler of a T.G.

42

Filing in and purging of hydrogen safely without bringing in contact with air.

Maintaining the gas pressure inside the machine at desired value at all the times.

Providing indication to the operator about the condition of the gas inside the machine i.e.

the pressure, temperature and purity.

Continuous circulation of gas inside the machine through a drier in order to remove any

water vapours that may be present in it

Indication of liquid level in the generator and alarm in case of high level.

6.5 GENERATOR SEALING SYSTEM

Seals are employed to prevent the leakage of hydrogen from the stator at the point of rotor exit. A

continuous film between a rotor collar and the seal liner is maintained by measurement of the oil at

pressure above the casing hydrogen gas pressure.

Fig 6.2. T.G. Testing Section

43

CHAPTER 7.

EXCITATION SYSTEM

7.1 EXCITER

The basic use of given exciter system is to produce necessary DC for turbo generator system.

Principal behind this is that PMG is mounted on the common shaft which generates electricity and

that is fed to yoke of main exciter. This exciter generates electricity and this is of AC in nature.

Fig 7.1. Exciter Winding Section

This AC is that converted into DC and is that fed to turbo generator via C/C bolt. For rectifying

purpose we have RC block and diode circuit. The most beautiful feature is of this type of exciter is

that is automatically divides the magnitude of current to be circulated in rotor circuit. This happens

with the help of AVR regulator which means automatic voltage regulator. A feedback path is given

to this system which compares theoretical value to predetermine and then it sends the current to

rotor as per requirement.

44

7.2 COMPONENTS

The brushless exciter mainly consists of:-

1. rectifier wheels

2. three phase main exciter

3. three phase pilot exciter

4. Metering and supervisory equipment.

Fig 7.2. Diode/Rectifier Wheel

The brushes exciter is an AC exciter with rotating armature and stationery field. The armature is

connected to rotating rectifier bridges for rectifying AC voltage induced to armature to DC voltage.

The pilot exciter is a PMG (permanent magnet generator). The PMG is also an AC machine with

stationery armature and rotating field. When the generator rotates at the rated speed, the PMG

generates 220 V at 50 hertz to provide power supply to automatic voltage regulator. A common

45

shaft carries the rectifier wheels the rotor of main exciter and the permanent magnet rotor of pilot

exciter. The shaft is rigidly coupled to generator rotor and exciter rotors are than supported on these

bearings.

Fig 7.3.Exciter of a Turbo Generator alongwith Diodes set

1. Pilot exciter with permanent magnets (PMG)

2. Fan

3. Stator of auxiliary exciter

4. Rotor of main exciter

5. Stator of main exciter

6. Exciter housing

7. NDE endshield of the exciter

8. Diodes set

9. Heat sink

10. Varistor wiring bridge

11. Varistor

12. Diode

46

13. Heat sink

14. Stranded cable

7.3 AUTOMATIC VOLTAGE REGULATOR (AVR)

Automatic Voltage Regulator (AVR) forms a part of the excitation system for a brush-less

generator. The AVR is connected in series to the pilot exciter.In addition to regulating the generator

voltage, the AVR circuitry includes under-speed and sensing loss protection features. Excitation

power is derived directly from the generator terminals. Positive voltage build up from residual

levels is ensured by the use of efficient semiconductors in the power circuitry of the AVR. The

AVR is linked with the main stator windings and the exciter field windings to provide closed loop

control of the output voltage with load regulation of +/- 1.0%. In addition to being powered from

the main stator, the AVR also derives a sample voltage from the output windings for voltage

control purposes. In response to this sample voltage, the AVR controls the power fed to the exciter

field, and hence the main field, to maintain the machine output voltage within the specified limits,

compensating for load,speed, temperature and power factor of the generator. A frequency

measuring circuit continually monitors the generator output and provides output under-speed

protection of the excitation system, by reducing the output voltage proportionally with speed below

a pre-settable threshold.

Fig 7.4. Internal Circuitry of an AVR

47

CHAPTER 8.

BAY IV (SMALL AND MISCELLANEOUS COMPONENTS)

8.1 MACHINE SECTION

The machine section of Bay-4 is equipped with small and medium size CNC & conventional

machine tools like centre lathes, milling, radial drilling, cylindrical grinding, slotting, copy turning

lathe, internal grinding and surface grinding machines. Small-size and miscellaneous components

for Turbo-generators, Hydro generators.Motors are machined in this section.

8.2 POLE COIL SECTION

This section is equipped with baking oven , pneumatic shearing machines , semi-automatic winding

machines , pole straightening installations , electric furnace for bright annealing of copper , tinning

Fig 8.1 Bay–IV

installation and hydraulic press (800 Ton capacity ) for manufacturing pole coils of DC motors ,

AC synchronous motors and hydro generators.Pole assembly is also carried out in this

section.Manufacturing of coils (hydro generators) taken in this section. German copper coils are

initially in the form of rolls. These rolls are then undergoes following processes to change into

copper coils which are then mounted with poles.

48

8.2.1 ANNEALING PROCESS

This is the process of hardening or softening any metal.

Initially copper rolls are hard & if it undergoes annealing then it may breaks so firstly to

make it soft so that it can easily change to winding.

This process is carried out in the annealing furnace.

8.2.2 WINDING PROCESS

This process undergo following steps:-

Take out the softened copper rolls for pole coil winding.

Winding is done with the help of change plate & winding template so ensure major working

dimensions of change plate & winding template with respect to tool drawing.

Adjust & set the winding machine as per the product standards using gear rack,change plate

& winding template. Ensure parallelity of winding template with respect to machine

platform. Maintain height of winding template with platform.Wind the coil in anticlockwise

direction.

NOTE:

The joint in the copper coil shall be located in the straight part of longer side.

If required heating by gas torch of copper profile at corner zone at temperature between

100-150 degree centigrade is allowed. This is to make bending easier.

8.2.3 BRAZING

Braze the joint with brazing alloy Ag 40Cd.

Remove the coil with machine with 2 to 3 turns extra than the actual number of turns for

preparation of end-half turns.

Carry out bright annealing of the coil. Take out the coil from the oven after annealing.

8.2.4 PRESSING

Pressing of coil is done by hydraulic pressure of 800 tons.

This process is carried out in order to remove wrinkles from the coil.

This process is carried out after every process. In this process, set the coil on the mandrel

for pressing then slide the coil under press and press the coil.

49

Take out the coil from press.

8.2.5 FIXING

Fix the accessory on the stretching machine.

Put the coil on the stretching machine & pull the coil to the drawing dimensions.

Dress the conductors along periphery & take out the coil.

Check window dimensions as per drawing.

8.2.6 SEPARATION

Remove the buckling of each coil manually.

Grind the bulging of the copper at place of binding (inner side) with pneumatic grinder.

Check the thickness of the profiled copper with the gauge. Grinding shall be uniform & of

smooth finish.

Round of sharp edges.

Again press the coil & take out the coil from the press.

8.2.7 PICKLING

Send the coil for pickling to block 4 & check the quality of pickling.

Press the coil again after pickling then remove pressure and take out the coil.

Prepare end half turn as per drawing with template.

Braze item 2 & 3 corresponding to the variant with end half turn with brazing alloy Ag 40

Cd.

Remove extra material, clean and check with gauge.

Adjust the end half turn with top & bottom turn of coil braze the joint.

Remove extra material and check thickness of the gauge.

Check the distance from center axis of pole coil as per drawing.

8.2.8 FINISHING

Hang the coil on stand and separate out turns

Remove black spots, burrs the sharp edges and clean the coil turns with cotton dipped in

thinner.

Press the coil again and check the height of the coil under press to check dimensions as per

drawing.

Take out the coil from the press and send for insulation.

50

8.2.9 INSULATION

Hang the coil on stand and separate out the turn.

Clean each turn with cotton dipped in thinner.

Apply Epoxy varnish on both sides of each turn with brush uniformly all over the leaving

top & bottom turn.

Cut strips of Nomax paper as per contour of coil with technological allowance 3 to 5 mm on

either side.

Stick two layers of Nomax strips between each turn.

Coat varnish layer between two layers of Nomax also.

Let the excess varnish to flow out some time

8.2.10 BAKING AND PRESSING OF COIL

Place the coil on mandrel putting technological washer at top & bottom of the coil.

Heat the coil by DC up to 100 +/-50˚C, and maintain for 30 to 40 minutes.

Switch off the supply and elongate the coil and tight the pressing blocks from sides.

Start heating coil again and raise temperature gradually in steps up to 130 +/- 50˚C, with in

10 +/- 10 minutes.

Apply 110 tones pressure and maintain for 20 to 30 minutes. Then after every half an hour,

increases the pressure and temperature according to product requirement.

Stop heating and then allow cooling the coil under pressure below 50˚C, and taking out the

coil from the press.

8.2.11 CLEANING AND DRYING

Clean outer and inner surface of projected insulation by means of shop made scrubber.

Flow dry compressed air after cleaning.

Check height and window dimensions as per drawing.

Check no gap between the turns.

Test the coil from inter turn test at 116 volts AC at a pressure of 480 tonnes in 5 minutes.

Coat the coil with two layers of epoxy red gel.

8.2.12 TURBO ROTOR COIL SECTION

This section is equipped with copper straightening and cutting machines, edge bending machines,

installation for forming and brazing, 10-block hydraulic press and installation for insulation filling.

Rotor coils for water cooled generators (210 /235 MW) are manufactured in this section.

51

8.2.13 IMPREGNATION SECTION

This section is equipped with electric drying ovens, Air drying booths, Bath for armature / rotor

impregnation. Rotors / armatures of AC and DC motors are impregnated in this section.

8.2.14 BABBITING SECTION

This section is equipped with alkaline degreasing baths, hot and cold rinsing baths, pickling baths,

tinning bath, and electric furnaces and centrifugal shot blasting babbiting machines, babbiting of

bearing liners for Turbo generators, Turbines, Hydro generators, AC motors and DC motors is

carried out in this section.

8.4 TEST STANDS

Turbo-generators Test Bed -The Test Bed for Turbo-generators and Heavy motors is equipped with

one no. 6 MW drive motor and a test pit for carrying out testing of Turbo-generators and Heavy

motors. Open circuit, short circuit, temperature rise, hydraulic and hydrogen leakage test etc., are

carried out here for Turbo-generators. AC motors up to 11 MVA capacity and DC machines up to

5000 amps and 850 volt can also be tested. Two DC drive motors of 2200 KW and one of 1500

KW are available for type testing of motors. Data logging equipment is also available.

8.5 LARGE SIZE TURBO GENERATOR TEST STAND (LSTG)

It is equipped with a 12 MW drive motor and two number test pits. Open circuit ,short circuit ,

sudden short circuit , temperature rise , hydraulic & hydrogen leakage tests are carried out here

Large size Turbo-generators. This test bed can presently test TGs of unit capacity up to 500 MW.

With certain addition in facilities (Higher capacity Drive motor and EOT cranes and modification

in controls and auxiliary systems), Turbo-generators of unit size up to1000 MW can be tested.

8.6 HELIUM LEAK TEST

It is used to check any leakage of gas from stator and rotor as if there is any leakage of gas used for

cooling such as hydrogen then it may cause an explosion. Testing of stator frame involves two

types of testing:-

HYDRAULIC TESTING :-Hydraulic testing involves in empty stator frame with attached end

shields and terminal box is subjected to a hydraulic test at 10 bar to ensure that it will be capable of

withstanding maximum explosion pressure.

PNEUMATIC TESTING:-The pneumatic testing involves filling of hydrogen in the sealed

stator frame and then soap water is used to check the leakage of welding.

52

CHAPTER 9.

CONCLUSION

The Vocational training at BHEL Haridwar helped me in improving my practical knowledge and

awareness regarding Turbo Generator to a large extent. Here I came to know about the technology

and material used in manufacturing of turbo generators. Besides this, I also visualized the parts

involved or equipments used in the power generation.Here I learnt about how the electrical

equipments are being manufactured and how they tackle the various problems under different

circumstances. At least I could say that the training at BHEL Haridwar is great experience for me

and it really helped me in making or developing my knowledge about turbo generator and other

equipment used in power generation. It has allowed us an opportunity to get an exposure of the

practical implementation of theoretical fundamentals.

53

BIBILIOGRAPHY

http://www.bhelhwr.co.in

http://en.wikipedia.org/wiki/Turbo_generator

http://books.google.co.in/books?id=IBg_ktPm1foC&pg=PA49&dq=turbogenerators&hl=en

&ei=eUm8TMa1Dor5cenAzcIM&sa=X&oi=book_result&ct=result&resnum=2&ved=0CC

4Q6AEwAQ#v=onepage&q=turbogenerators&f=false

http://www.ansaldoenergia.com/PDF/Turbo.pdf

http://www.weg.net/files/products/WEG-turbogenerator-687-brochure-english.pdf

http://www.energy.siemens.com/us/pool/hq/power-generation/power-plants/gas-fired-

power-plants/combined-cycle-powerplants/scc5-4000f-1s/A96001-S90-A130-V3-4A00.pdf

http://www.bhelhyderabad.com/qualityturbogenarators.html

http://www.converteam.com/majic/dl/4/doc/Core_Components/Motors_and_Generators/SA

155R_2_Pole_turbine_Generators_Rotor_Construction.pdf