23677463 training report done at bhel for electrical engineering

8/6/2019 23677463 Training Report Done at BHEL for Electrical Engineering

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BRIGHTENING LIVES,

POWERING PROGRESS

INTRODUCTION --

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 aturnover of Rs 2,658 crore for the year 2007-08, showing a growth of 17 per cent over the


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previous year. Bharat Heavy Electricals Limited is countrys 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 electricalequipments.

BHEL caters to core sectors of the Indian Economy viz., Power Generation's &Transmission, Industry, Transportation, Telecommunication, Renewable Energy,

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

and ISO 14001 certification for environment management and OHSAS 18001certification 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 aspect of BHELs growth has been its

diversification .The constant reorientation of the organization to meet the varied needs intime 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 andtransportation.

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.BHELs technological excellence and turnkey capabilities have won it worldwide

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

individual equipment to complete power stations on turnkey basis

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 centers, over 150 project sites, eightservice centers 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 then 75% of the nationalgrid, interestingly a share of 45% comes from its single unit. And this is none other then

BHEL-Hardwar.


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BHEL has:-

Installed equipment for over 90,000MW of power generation--- for

utilities captive and industrial users.

Supplied over 2, 25,000 MVA transformer capacity and otherequipment operating in transmission and distribution network up to

400 kV (AC & DC).

Supplied over 25,000 motors with drive control systems to power

projects, petrochemicals, refineries, steel, aluminum, fertilizers,

cement plants etc.

Supplied Traction electrics and AC/DC locos to power over 12,000

kms railway network.

Supplied over one million valves to power plants and otherindustries.


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BHEL An Overview

BHEL today is the largest Engineering Enterprise of its kind in India with

excellent track record of performance, making profits continuously since 1971-72.

BHEL's vision is to become a world-class engineering enterprise, committed to

enhancing stakeholder value. The company is striving to give shape to its aspirations and

fulfill the expectations of the country to become a global player.

BHEL business operations cater to core sectors of Indian Economy like.

Power

Industry

Transportation

Transmission

Defenses etc.

The greatest strength of BHEL is its highly skilled and committed 42,600employees. Every employee is given an equal opportunity to develop himself and grow in

his career. Continuous training and retraining, career planning, a positive work culture

and participative style of management all these have engendered development of acommitted and motivated workforce setting new benchmarks in terms of productivity,

quality and responsiveness.

POWER SECTOR

Power generation sector comprises thermal, gas, hydro and nuclear power plantbusiness .BHEL supplied utility sets accounts to 87,646 MW 65% of the total installed

capacity of 1,38,175 MW in the country , as against nil in 1969 -70.

As part of Indias largest Solar Power-based Island Electrification Project in India, Bharat


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Heavy Electricals Limited (BHEL) has successfully commissioned two Grid-Interactive

Solar Power Plants of 100 KW each in Lakshadweep.

With this, the company has commissioned a total of eleven Solar Power Plants in theLakshadweep islands, adding over 1 MW of Solar Power to the power generating

capacity of the coral islands in the Arabian Sea.

BHEL has proven turnkey capabilities for executing power projects from

concept to commissioning and manufactures boilers, thermal turbine generatorsets and auxiliaries up to 500MW.

It possesses the technology and capability to procure thermal power generation

up to 1000MW.

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

For the efficient use of high ash content coal BHEL supplies circulating

fluidized boiler.

BHEL manufacturers 235MW nuclear sets and has also commenced production

of 500MW nuclear turbine generator sets.

Custom made hydro sets of Francis, pelton and kepian types for different head dischargecombination are also engineering and manufactured by BHEL.

In, all 700 utility sets of thermal, hydro, gas and nuclear have been placed on the

company as on date. The power plant equipment manufactured by BHEL is based on

contemporary technology comparable to the best in the world and is also internationallycompetitive.

The Company has proven expertise in Plant Performance Improvement through

renovation modernization and up rating of variety of power plant equipment besides

specialized know how of residual life assessment, health diagnostics and life extension ofplants.

POWER TRANSMISSION AND DISTRIBUTION (T&D) ---

BHEL offer wide-ranging products and systems for T & D applications Products.

manufactured include power transformers, instrument transformers, dry typetransformers, series and shunt reactor, capacitor tanks, vacuum and SF circuit

breakers gas insulated switch gears and insulators.

A strong engineering base enables the Company to undertake turnkey delivery of electric

substances up to 400 kV level series compensation systems (for increasing power transfercapacity of transmission lines and improving system stability and voltage regulation),

shunt compensation systems (for power factor and voltage improvement) and HVDC


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systems (for economic transfer of bulk power). BHEL has indigenously developed the

state-of-the-art controlled shunt reactor (for reactive power management on long

transmission lines). Presently a 400 kV Facts (Flexible AC Transmission System) projectunder execution.

INDUSTRY SECTOR

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

Cement

Petrochemicals

Fertilizers

Steel papers

Refineries

Mining and telecommunication

BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for

reactive power management on long transmission lines). Presently a 400 kV FACTS

(Flexible AC Transmission System) projects is under execution.

The range of system and equipment supplied includes:-

Captive power plants

High speed industrial drive turbines

Industrial boilers and auxiliaries

Waste heat recovery boilers

Gas turbine pump, valves, seamless steel tubes

Heat exchangers

Process control etc.

The Company is a major producer of large-size thruster devices. It also suppliesdigital distributed control systems for process industries, and control & instrumentation

systems for power plant and industrial applications. BHEL is the only company in India

with the capability to make simulators for power plants, defense and other applications.

The Company has commenced manufacture of large desalination plants to help

augment the supply of drinking water to people.

TRANSPORTATION


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BHEL is involved in the development design, engineering, marketing, production,

installation, and maintenance and after-sales service of Rolling Stock and traction

propulsion systems. In the area of rolling stock, BHEL manufactures electric locomotivesup to 5000 HP, diesel-electric locomotives from 350 HP to 3100 HP, both for mainline

and shunting duly applications. BHEL is also producing rolling stock for special

applications viz., overhead equipment cars, Special well wagons, Rail-cum-road vehicleetc., Besides traction propulsion systems for in-house use, BHEL manufactures traction

propulsion systems for other rolling stock producers of electric locomotives, diesel-

electric locomotives, electrical multiple units and metro cars. The electric and dieseltraction equipment on India Railways are largely powered by electrical propulsion

systems produced by BHEL. The company also undertakes retooling and overhauling of

rolling stock in the area of urban transportation systems. BHEL is geared up to turnkey

execution of electric trolley bus systems, light rail systems etc. BHEL is also diversifyingin the area of port handing equipment and pipelines transportation systems.

TELECOMMUNICATION---

BHEL also caters to telecommunication sector by way of small, medium and

large switching system.

HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP)

At Hardwar, against the picturesque background of Shivalik Hills, 2 importantmanufacturing units of BHEL are located viz. Heavy Electrical Equipment Plant


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(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 in 1959,

BHELs prestigious unit, Heavy Electrical Equipment plant (HEEP), was established in

October, 1963, at Hardwar. It started manufacturing thermal sets in 1967 and nowthermal 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 MW. HEEP-manufactured gas turbines, hydro

turbines and generators, etc., are not only successfully generating electrical energy withinand 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 ambitions 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.


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Integrity and fairness in all matters.

ESTABLISHMENT AND DEVELOPMENT STAGES:

Established in 1960s under the Indo-Soviet Agreements of 1959 and 1960 in thearea 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, extensible

to 1000/1300 MW unit sizes with marginal addition in facilities with the

collaboration of M/s KWU-Siemens, Germany.

Motor manufacturing technology updated with Siemens collaboration during

1984-87.

Facilities being modernized continually through Replacements / Reconditioning-Retrofitting, Technological / operational balancing.

CLIMATIC AND GEOGRAPHICAL CONDITIONS:

Hardwar is in extreme weather zone of the Western Uttar Pradesh of India andtemperature varies from 2oC in Winter (December to January) to 45oC in Summer

(April-June); Relative humidity 20% during dry season to 95-96% during rainyseason.

Longitude 78o3' East, Latitude 29 o55'5" North.

Height above Mean Sea Level = 275 meters.

Situated within 60 to 100 KMs of Foot-hills of the Central Himalayan Ranges;


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Ganges flows down within 7 KMs from the Factory area.

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

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.

Facilities (Plant Premises)


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ELECTRICAL MACHINES BLOCK (BLOCK-I)

INTRODUCTION---

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

large and medium size AC and DC Electrical machines.

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

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 the

products 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 :

BAY

1

ROTOR

SHAFTMACHINING

ROTOR SHAFT

SLOTTING

ROTOR

WINDING

OVER SPEED

ANDBALANCING

TUNNEL

LARGE SIZE

TURBOGENERATOR

BAY

2

EXCITERSHAFT

MACHINING

STATOR BODYMACHINING

STATORWINDING

TOTALIMPREGNATION

TEST BED

BAY-

-3

ROTOR

SUPPORT

BEARING

SHAFT SEAL

BODY

DC

MOTOR

WINDING(EARLIER)

BAY-

-4

COOLING

FANSMACHINING

ARRANGEMEN

T AND OTHERPARTS


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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.

TURBO GENERATOR

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

principles ofELECTROMAGNETIC INDUCTION. In them the standard constructionconsists of armature winding mounted on stationary element calledstatorand fieldwindings 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 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.fand 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.

SYNOPSIS OF THE FUNCTION OF T.G.:

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

2. 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.


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

generator rotor.

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

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

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

feedback from main generator terminal voltage, to control exciter field variationby automatic voltage regulator. The rectified DC supply out of exciter is suppliedto turbo generator rotor winding either through brushes or central which will be

directly connected to turbo generator. This depends on the type of exciter viz. DC

commutator machines or brushes exciter.7. The main A.C. voltage is finally available at the stator of Turbo Generator.

LSTG AREA

LARGE SIZE TURBO GENERATOR (LSTG)


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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. THDI4. THDD

5. THDF

6. THFF

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

COMPONENTS OF T.G. :-

STATOR


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1. Stator frame

2. Stator core

3. Stator winding

4. End covers.

ROTOR

1. Rotor shaft

2. Rotor windings

3. Rotor retaining rings

BEARINGS

COOLING SYSTEM

EXCITATION SYSTEM

STATOR

The generator stator is a tight construction supporting and enclosing statorwinding, 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 directcoupled steam turbine at the speed of 3000 rpm.

The generator is designed for continuous rated output. Temperature detector orother devices installed or connected within the machine, permits the winding core and

hydrogen temperature, pressure and purity in machine.

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 the statorwinding.


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The fabricated inner cage is inserted in the outer frame after the stator has been

constructed and the winding completed.

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 ofindividual sections. The 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.

STATOR WINDING:-


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Each conductor must be capable of carrying rated current without over heating.

The stator winding consists of two layers made up of individual bars. Windings for thestators 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. The transposition

provides for mutual neutralization of the voltage induced in the individual strands due toslot 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 hollow strand and two solid strands ensuresoptimum 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 dueto 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 thecorona 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 fromthe slot to end winding. The bars consist of a large no. of separately insulated strands

which are transposed to reduce the skin effect.


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INSULATION OF BARS:-

A. Vacuum pressed impregnated micaclastic high voltage insulation:-

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

thermo setting epoxy system. Several half overlapped continuous layer of resin poor

mica tape are applied over the bars. The number of layers or thickness of insulationdepends on the machine voltage. To minimize the effect of radial forces windings

hold and insulated rings are used to support the overhang.


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B. Corona Protection:-

To prevent the potential difference and possible corona discharge between the slot

wall and the insulation, the section of bars are provided with outer corona protection.The protection consists of polyester fluce tape impregnated in epoxy resin with

carbon and graphite as fillers. At the transition from the slot to the end winding

portion of the stator bars a semiconductor tape is impregnated.

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 corelonger, 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 thewinding 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 isbased on the prime factor that the electric resistance of metallic conductor varies

linearly with temperature

END COVERS:-

The end covers are made up of fabricated steel or aluminum castings. They are

employed with guide vans on inner side for ensuring uniform distribution of air orgas.


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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.

Iron Assembly Section:-

In BAY-2 this section has facilities for stator core assembly ofTurbo-generators

and Heavy Electric Motors.


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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.

Bar Preparation Section:-

This section is present in BAY-1. This section consists of milling machine forlong preparation, installation for insulation of tension bolts for stator and preparation of

stator winding before assembly. The three phase winding is afractional pitch two layer

type consisting of individual bars.

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.

Cooling:-

Heat losses arising in the generator are dissipated through hydrogen. The heatdissipating capacity of hydrogen is eight times to that of air.

ROTOR

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 turbo generators. It

is coiled heavily (field coils) as it has to support large amount of current and voltage.

Rotor revolves in most generators at a speed of 3000rpm. Field coils are wound over it tomake 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. Withgood design and great care this problem can be solved.


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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.

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 ithandles 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 thenagain slotting of that portion is done. It is done in diametrically opposite ends so as to

prevent bristling of slot due to mechanical vibrations.

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. The coil doesnt deform even at high temperatures as

on adding silver the thermal stresses are eliminated. Rotor winding is also known asfield

windingwhich is wound in longitudinal slots in rotor.

ROTOR SLOT WEDGES :-

To protect the rotor windings against the effects of centrifugal forces, the windingsare secured in slots with wedges.

Slot wedges are made of copper-nickel-silicon alloy featuring high temperature

resistance and high strength.

There is retaining ring, which protects the rotor from the impact of centrifugal

force on end windings.

Comprehensive tests such as ultrasonic examination and liquid penetration

examination are carried out in the coils.


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To ensure low contact resistance, retaining rings are coated with nickel, aluminum

and silver by three step flame-spraying process.

ROTOR WINDING:-

The winding consist of several coils inserted into the slots and the series

connected such that two coils group to form one pole. Each coil consist of several series

connected turns each of which consist of two half turns connected by brazing in endsection. The individual turn of coil are insulated against each other by interlayer

insulation. L-shaped strip of laminated epoxy glass fiber with nomex filter are used forslot insulation.

The slot wedges are made up of high electrical conductivity material and thus act

as damper winding. At their ends, the slots wedges are short circuited through the rotorbody. When rotor is rotating at high speed, the centrifugal forces tries to lift the winding

out of slots, they are contained by wedges.

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 fieldwinding.


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Depending upon the type of cooling there are 8 solid and 6 hollow strips in each

half of the coil.

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.

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 and115*c temperature.

Then for 45 minutes it is heated at temperature of about 130*c and 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 coilsare 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


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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 acrossall the conductors.

The insulation is molding 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 nowater 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 ofstator and not used in rotors of any of the generators being used in the power plants

nowadays.

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.

Conductor material:-

The conductors are made up of copper with silver content of approx. 0.1%. As

compared to electrolytic copper silver alloyed copper features high strength properties at

high temperature so that coil deformations due to thermal stresses are eliminated.

Insulation:-

The insulation between the individual turns is made up of layer of glass fiberlaminate the coils are insulated from the rotor body with L-shaped strip of glass fiber

laminate with nomex interlines to obtain the required leakage path between the coil and

rotor body, thick top strips of glass fiber laminate are inserted below wedge. The topstrip are provided with axial slots of same cross-section and spacing and used on the rotor

winding.


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ROTOR RETAINING RINGS

The centrifugal forces of the end windings are contained by piece rotor retainingrings. 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 ringswithstand 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 end winding without contact on the

rotor shaft. This ensures unobstructed shaft deflection at end windings. The shrunk onhub 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, therings are made up of non-magnetic cold worked material.

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 havethreaded roots for screwed into the rotor shaft. Blades are drop forged from aluminum

alloy. Threaded root fastenings permit angle to be changed. Each blade is screwed at its

root with a threaded pin.

BEARINGS

The turbo generators are provided with pressure lubricated self aligning typebearing 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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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.

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 ROTORASSEMBLY SECTIONpresent 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 retainingrings.

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 Lathesand Vertical Boring, Horizontal Boring machine, Rotor slot milling and Radial drilling

machines for machining stator body, rotor shaft End shields, Bearing etc for Turbo-

generators. Same section is present in Bay-3 (Medium size motors) equipped withMedium size machine tools for machining components for medium size AC and DC

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


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VENTILLATION AND COOLING SYSTEM:-

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 andis intensively cooled through special ventilation system. Design of special ventilation is

to ensure almost uniform temperature of rotor windings and stator core.

COOLING SYSTEM

STATOR COOLING SYSTEM

The stator winding is cooled by distillate water which is fed from one end of themachine 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 ofstator 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 withany 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.

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 theventilating 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 thehot 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 hasan inherent of eliminating the deformation of copper due to varying temperature.


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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 iscapable of performing following system

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 vapors that may be present in it

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

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.


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BLK-I

EXCITATION SYSTEM:-

EXCITER:-

EXCITER ROTOR

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 shaftwhich generates electricity and that is fed to yoke of main exciter. This exciter generates

electricity and this is of AC in nature. 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 themagnitude 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


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

rotor as per requirement.

The brushless exciter mainly consists of:-

1. rectifier wheels

2. three phase main exciter

3. three phase pilot exciter

4. Metering and supervisory equipment.

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 inducedto 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 thegenerator rotates at the rated speed, the PMG generates 220 V at 50 hertz to providepower supply to automatic voltage regulator.

A common shaft carries the rectifier wheels the rotor of main exciter and thepermanent magnet rotor of pilot exciter. The shaft is rigidly coupled to generator rotor

and exciter rotors are than supported on these bearings.


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BAY IV (SMALL AND MISCELLANEOUS COMPONENTS)

Facilities available in the various sections are as follows:-

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 and

Motors are machined in this section.

POLE COIL SECTION

COILING SECTION


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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 installation and hydraulic press (800 Ton capacity ) formanufacturing 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-

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.

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

bending.


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2. BRAZING:-

Braze the joint with brazing alloy Ag40Cd.

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

turns for preparation of end-half turns.

3. Carry out bright annealing of the coil. Take out the coil from the oven afterannealing.

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

Take out the coil from press.

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.

6. SEPARATION:-

Remove the buckling of each coil manually.

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

grinder.


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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 as in pt.5 & take out the coil from the press.

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.

8. Prepare end half turn as per drawing with template.

9. 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.

10. 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.

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

12. INSULATION:-


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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 3to 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

13. 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 +/-5o 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 +/- 5oC , 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 50o C, and

taking out the coil from the press.

14.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 tons in 5minutes.

15. Coat the coil with two layers of epoxy red gel.

TURBO ROTOR COIL SECTION:-


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This section is equipped with copper straightening and cutting machines, edgebending 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.

IMPREGNATION SECTION:-

This section is equipped with electric drying ovens, Air drying booths, Bath forarmature / rotor impregnation. Rotors / armatures of AC and DC motors are impregnated

in this section.

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

babbitting machines, Babbitting of bearing liners for Turbo generators, Turbines, Hydrogenerators, AC motors and DC motors is carried out in this section.

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,


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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 typetesting of motors. Data logging equipment is also available.

LARGE SIZE TURBO GENERATOR TEST STAND (LSTG):-

It is equipped with a 12 MW drive motor and two number test pits. Opencircuit ,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 auxiliarysystems), Turbo-generators of unit size up to1000 MW can be tested.

HELIUM LEAK TEST

PURPOSE

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 AND PNEUMATIC 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.The pneumatic testing involves filling of hydrogen in the sealed stator frame and thensoap water is used to check the leakage of welding.


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TRAINING

REPORT

TRAINING TAKEN AT -

BHARAT HEAVY ELECTRICALS LIMITED

(BHEL, HARDWAR).

SESSION

2009-10.

SUBMITTED BY

HIMANSHU BHINDA.

SUBMITTED TO

DEPARTMENT OF ELECTRICAL ENGINEERING,MNIT (JAIPUR).


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ACKNOWLEDGEMENT

It is a matter of great pleasure and privilege for me to present the report on the

practical training of 60 days on the basis of practical knowledge gained by me during the

practical training at BHARAT HEAVY ELECRTICALS LIMITED, HARIDWAR from12th may to 11th July 2009.


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CONTENTS-

1. INTRODUCTION.

2. BHEL A Brief Profile.

3. BHEL An Overview.

4. HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP).

5. ELECTRICAL MACHINES (BLOCK 1)

I. TURBO-GENERATOR.

II. LARGE SIZE TURBO-GENERATOR.

III. COMPONENTS OF TURBO-GENERATOR.

a) STATOR

1) STATOR CORE.

2) STATOR WINDING.

3) END COVERS.

b) ROTOR

1) STEPS IN ROTOR MACHINING.

IV. VENTILLATION AND COOLING SYSTEMS.

V. EXCITATION SYSTEM.

a) EXCITER.

VI. BAY-4 (SMALL AND MISCALLANEOUS COMPONENTS)

VII. TEST STANDS.


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VIII. LSTG TEST STANDS.

IX. TESTING.

a) HELIUM LEAK TESTS

b) HYDROGEN TESTING AND PNEUMATIC TESTING.

CONCLUSION

The Vocational training at BHEL Hardwar helped me in improving mypractical 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 thepower generation.

Here I learnt about how the electrical equipments are being manufactured and how theytackle the various problems under different circumstances. At least I could say that the

training at BHEL Hardwar is great experience for me and it really helped me in making

or developing my knowledge about turbo generator and other equipment used in powergeneration.

REFERENCES

1. Material provided by the training Incharge.

2. Internet

23677463 training report done at bhel for electrical engineering

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