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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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