MANUFACTURING

PROCESS OF

TURBO GENERATORS

MANUFACTURING PROCESS OF TURBO GENERATORS

A Mini Project Work

Submitted in partial fulfilment of the

Requirements for the award of degree of

BACHELOR OF TECHNOLOGY

In

ELECTRICAL ENGINEERING

By

NITIN GUPTA (2008UEE129)

Under the guidance of

Mr.C.M.ARORA & Mr. V.K.JAIN

Dept. of Electrical Engineering

MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY

2011-2012

ACKNOWLEDGEMENT

“An engineer with only theoretical knowledge is not a complete engineer. Practical

knowledge is very important to develop and apply engineering skills”. It gives me a great

pleasure to have an opportunity to acknowledge and to express gratitude to those who

were associated with me during my training at BHEL.

Special thanks to Mr.P.S.Jangpangi for providing me with an opportunity to undergo

training under his able guidance.

I am very great full to our training and placement officer Mr. ROHIT GOYAL for his

support.

I express my sincere thanks and gratitude to BHEL authorities for allowing me to

undergo the training in this prestigious organization. I will always remain indebted to

them for their constant interest and excellent guidance in my training work, moreover

for providing me with an opportunity to work and gain experience.

INDEX

1. BHEL-An Overview

2. Introduction

3. Stator

4. Rotor

5. Excitation System

6. Cooling system

7. Generator Technical Data

8. Testing Of Turbo Generator

9. Conclusion

10. References

CHAPTER 1

BHEL-AN OVERVIEW

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 Equipment industry in India.

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

track record of performance, making profits continuously since 1971-1972

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

Power

Industry

Transportation

Transmission etc.

BHEL has 14 units spread all over India manufacturing boilers, turbines,

generators, transformers, motors etc. Besides 14 manufacturing divisions the

company has 4 power sector regional centres, 8 service centres and 18 regional

offices and a large number of project sites thus enable the Company to promptly

serve its customers and provide them with suitable products, systems and

services efficiently and at competitive prices. The high level of quality & reliability

of its products is due to the emphasis on design, engineering and manufacturing

to international standards by acquiring and adapting some of the best

technologies from leading companies in the world, together with technologies

developed in its own R&D centres.

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

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

aspirations and fulfil the expectations of the country to become a global player.

BHEL, HARIDWAR

Against the picturesque Shivalik foot hill of the Himalayas and on the banks of the

holy Ganga in Ranipur near Hardwar are located the two manufacturing plants of

BHEL: Heavy Electrical Equipment Plant (HEEP) and Central Foundry Forge Plant

(CFFP) employing about 10000 people.

Heavy Electrical Equipment Plant is equipped to produce Steam and Hydro

Turbines with matching Generators, Industrial Manufacturing Thermal sets up to

1000 MW capacity.

Located immediately south of HEEP is the Central Foundry Forge Plant setup.

The Heavy Electrical Equipment Plant was set up in technical collaboration with

M/s Prommash-export of USSR. The construction of the plant commenced in

1962 and the production of equipment was initiated in early 1967. In 1976, BHEL

entered into a collaboration agreement with M/s Kraftwerk Union A.G. of West

Germany for design, manufacture, erection and commissioning of large size steam

turbines and turbo generators of unit rating up to 1000MW.

The BHEL plants in Haridwar have earned the ISO-9001 AND 9002 certificates for

its high quality and maintenance. These two units have also earned the ISO-14001

certificates.

CHART SHOWING DIFFERENT BLOCKS OF BHEL, HARIDWAR

BHARAT HEAVY ELECTRICALS LTD.

HARIDWAR

HARDWAR

HEEP (HEAVYEL ECTRICAL

EQUIPMENT PLANT)

CFFP (CENTRAL FOUNDARY

FORGED PLANT)

BLOCK-2: HEAVY FABRICATION SHOP

BLOCK-3: TURBINE MANUFACTURING BLOCK

BLOCK-4: CIM (COILS & INSULATION MANUFACTURING)

BLOCK

FACTURING) BLOCK BLOCK-5: CONDENCER FABRICATION & FORGR BLOCK

BLOCK-6: FABRICATION SHOP, DIE SHOP

STAMPING SHOP)

BLOCK-7: CARPANTARY SHOP

BLOCK-8: HEAT EXCHANGER SHOP

BLOCK-1: ELECTRICAL MACHINE SHOP

CHAPTER 2

INTRODUCTION

2. INTRODUCTION

2.1 TURBOGENERATOR:

A turbo generator is a turbine directly connected to electric generator for the

generation of electricity. They are mostly used as large capacity generator driven

by steam/gas turbine.

2.2 PRINCIPLE OF OPERATION:

In case of turbo generator, Rotor winding is supplied with DC current (through

slip rings or brushless exciter) which produces constant magnetic field.

3 phase stator winding is laid in stator core.

When generator rotor is rotated (by a turbine) magnetic flux produced by

rotor winding also rotates.

Voltage is induced in stator winding according to Faraday’s law*.

3 phase stator winding also produces magnetic flux revolving at synchronous

speed (=120*f/2p). Rotor also rotates at synchronous speed. Both the

magnetic fields are locked and rotate together.

*Faraday’s Law:

E.M.F. (Voltage) is induced in a closed path due to change of flux linkages and is

proportional to rate of change of flux linkages. The change in flux linkages can be

caused by change in flux in a stationary coil or by motion of coil with constant flux

or both.

E = −N dϕ/dt

2.3 SIZING OF GENERATOR MODULE:

Basic equation for sizing of electrical machines

P=K.As.Bδ.D2 L .ns

It can also be written as

D2L=P/ (K.As. Bδ .ns)

Here

P = MW output

As = Electric Loading (Amp.cond/cm)

Bδ = Magnetic Loading (gauss)

D = Stator bore diameter (cm)

L = Stator core length (cm)

ns = Rated speed

D2L = Volume of Rotor or Size of the Machine

MW Rating:

Size of machine (D2L) is directly proportional to its output (MW)

Speed:

Size of machine (D2L) is inversely proportional to its speed

Synchronous Speed = 120*F/ P

2.4 SYNCHRONOUS GENERATOR CLASSIFICATION BASED ON THE

MEDIUM USED FOR GENERATION:

Turbo generators in Thermal, nuclear, Gas station

High speed – 3000 rpm

No. of poles – 2 poles

Horizontal construction

Cylindrical rotor

Hydro generators in hydel plants

Low speed – 500 to 1000 rpm

No. of poles – 6 or more

Vertical construction

Salient type of rotor

2.5 GENERATOR MODULE NOMENCLATURE:

2.6 GENERATOR MODULES:

TARI: Air Cooled Turbo generator

Stator Winding: Indirectly Air Cooled

Rotor Winding/ Stator Core: Directly Air Cooled

THRI: Hydrogen Cooled Turbo generator

Stator Winding: Indirectly Hydrogen Cooled

Rotor Winding/ Stator Core: Directly Hydrogen Cooled

THDF: Hydrogen/Water Cooled Turbo generator

Stator Winding: Directly Water Cooled

Rotor Winding/ Stator Core: Directly Hydrogen Cooled

2.7 COMPONENTS USED IN TURBO GENERATOR:

2.7.1 STATOR

Stator frame

Stator core

Stator winding

End cover

Bushings

Generator terminal box

2.7.2 ROTOR

Rotor shaft

Rotor winding

Rotor retaining ring

Field connection

2.7.3 EXCITATION SYSTEM:

Pilot exciter

Main exciter

Diode wheel

The following auxiliaries are required for operation:

Bearings

Cooling system

Oil Supply System

CHAPTER 3

STATOR

STATOR

3. STATOR

The stator consists of following parts:

1. Stator frame

2. Stator core

3. Stator winding

4. Stator end cover

5. Bushings

6. Generator terminal box

3.1 Stator frame:

Rigid fabricated cylindrical frame and is the heaviest section in the generator

Withstands weight of core & winding, forces & torques during operation

Provisions for H2/CO2 filling

Provision for temperature measurements

Foot plates for supporting on foundation

Provision for H2 coolers

3.2 Stator core:

The stator core is made from the insulated electrical sheet lamination to minimize

eddy current losses. Each lamination layer is made of individual sections.

The main features of core are:

1. To carry electric & magnetic flux efficiently.

2. To provide mechanical support.

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

Fig: stator core

3.2.1 THE PURPOSE OF STATOR CORE:

Support the stator winding

To carry the magnetic flux generated by rotor winding.

Therefore the selection of material for building up of core is very important. In

selection of material the losses in the core are considered. There are basically two

types of losses.

Hysteresis losses: Due to the residual magnetic flux in the core material.

Hysteresis loss is given by

Wh α Kh . βmax1.6

Eddy Current losses: Due to the e.m.f induced in the core eddy currents are

produced and produce losses. Eddy current loss is given by

We α βmax2 . t2

For the reduction of hysteresis loss, silicon alloyed steel is used since it has low

value of hysteresis coefficient (Kh) for the manufacture of core. The composition

of silicon steel is

Steel-95.8%

Silicon-4.0%

Impurities-0.2%

Since the eddy current loss depends on the square of thickness of the lamination.

Hence to reduce eddy current loss core is made up from thin laminations which

are insulated from each other. The thickness of lamination is about 0.5mm.

3.3 LAMINATION PREPARATION:

The core is built up of 6 sectors, each of 600. The insulation used between the

lamination is ALKYD PHENOLIC VARNISH dried at suitable temperature. The

laminations are passes through a conveyor, which has an arrangement to sprinkle

the varnish. The sheets are dried at a temperature around 300o-400oC. Two

coatings of varnish are done. The thickness of varnish should be around 8-10

microns. Each lamination should be dried for around 90 sec at constant speed.

3.4 ASSEMBLY OF CORE:

The stator laminations are assembled as separate cage without stator frame. The

entire core length is made in the form of packets separate by radial ducts to

provide ventilating passage for the cooling of core. The thickness of lamination is

about 0.5mm and the thickness of lamination separating the packets is about

1mm. The segments are staggered from layer to layer so that a core of high

mechanical strength and uniform permeability of magnetic flux is obtained.

Fig: assembly of core

To obtain the maximum compression and eliminate under setting during

operation, the laminations are hydraulically compressed and heated during the

stacking procedure when certain heights of stack is reached. The complete stack

is kept under pressure and located in stator frame by means of clamping bolts and

pressure plates.

Fig .Compression of Core

3.5 STATOR WINDING:

The stator winding of Turbo Generator is three phase two layer lap winding with

the pitch of winding so adjusted as to reduce the 5th and 7th harmonics. The

number of slots for generation of three phase power must be a multiple of 3 or 6.

Each stator slot accommodates two stator bars.

3.5.1 CONDUCTOR CONSTRUCTION:

The bar consists of a large number of separately insulated strands which are

transposed to reduce the skin effect losses.

The strands of small rectangular cross-section are provided with braided glass

insulation and arranged side by side over the slot width. The individual layers are

insulated by vertical separator. In the straight slot portion the strands are

transposed by 540o.

The transposition provides for a mutual neutralization of the voltages induced in

the individual strands due to the slot cross-field and end winding flux leakage and

ensures that minimum circulation current exist. The current flowing through the

conductor is thus uniformly distributed over the entire cross-section so that the

current-dependent losses will be reduced

Fig. Transposition of bars

3.5.2 THDF BAR CONSTRUCTION:

The bar consists of hollow and solid strands distributed over the entire bar cross-

section so that good heat dissipation is ensured. At the bar ends, all the solid

strands are jointly brazed into a connecting sleeve and the hollow strands into a

water box from which the cooling water enters and exists via Teflon insulating

hoses. The strands are transposed by 540o in the slot portion.

fig. Stator bar of THDF

3.5.3 INSULATION:

Insulation is basically done to prevent any kind of short circuit between the bar

and the stator core when the bar is assembled in the stator of the machine. The

stator bars are insulated with Micalastic (trade name) insulation.

Advantages of Micalastic insulation are as follows:

Good conductor of heat

Low inflamability

High resistance to moisture and chemical action

Retains properties even after years of operation

3.6 STATOR END COVER:

The ends of the stator frame are closed by pressure containing end shields .The

end covers are made up of non-magnetic material (Aluminium castings) to reduce

stray load and eddy current losses. The end shields feature a high stiffness and

accommodates generator bearings, hydrogen coolers etc. The end shields are

horizontally split to allow for assembly. The end shield used at the turbine end

and exciter end side is different in construction for 500MW. The end cover used in

250 MW is similar in construction.

EXCITER END SIDE (500MW) TURBINE END SIDE (500MW)

3.7 BUSHINGS:

The beginning and ends of the three phase windings are brought out from the

stator frame through bushings, which provides for high voltage insulation. The

bushings are bolted to the stator frame at the exciter end.

Fig. Bushings

3.8 GENERATOR TERMINAL BOX:

The phase and neutral leads of the three phase stator windings are brought out of

the generator through six bushings located in the generator terminal box at the

exciter end of the generator.

Terminal box Bushing

Fig. Generator terminal box

CHAPTER 4

ROTOR

4. ROTOR

1. Rotating part of turbo generator

2. A high strength alloy steel single forging prepared by vacuum cast steel.

3. Longitudinal slots for housing field winding

4. Damper winding is provided which safeguards the asymmetrical and

asynchronous operative conditions.

5. Rotor of cylindrical type used in turbo generator.

6. Supported on two journal bearings.

7. Provision of axial fan for forced ventilation.

Fig. Rotor

Approximately 60% of the rotor circumference is provided with longitudinally

slots which hold the field windings. The slot pitch is selected so that two solid

poles are obtained with a displacement of 180 degrees.

Due to the non uniform slot distribution is on the circumference, different

moments of inertia are obtained in the main axis of rotor. This in turn causes

vibration. These vibrations are reduced by transverse slotting of the poles.

The rotor winding is provided with a lateral gap pick up system of cooling in the

slot portion, ensuring uniform temperature distribution of the winding.

4.1 MAIN PARTS OF ROTOR

Fig. Main parts of rotor

4.2 ROTOR WINDING:

The rotor of turbo generator accommodates field winding. Turbo generator is a

two pole machine rotating at a speed of 3000 R.P.M. There are 28 slots cut on

two-third of the periphery which support field winding. The field winding consists

of several series connected coils inserted into the longitudinal slots of rotor body.

The coils are wound so that two poles are obtained. The conductors are made up

of copper with a silver content of approximately of 0.1%. The solid conductors

have a rectangular cross section and are provided with axial slots for radial

discharge.

Fig. Rotor bar

The individual bars are bent to obtain half turns. After insertion into the rotor

slots, these turns are brazed to obtain full turns. The series connected turns of

one slot constitute one coil. The individual coils are connected in a way that north

and south poles are obtained.

Fig.Rotor winding

4.3 INSULATION:

The insulation between the individual turns is made of layer of glass fibre

laminate. The coils are insulated from the rotor body with L-shaped strips of glass

fibre laminate with nomex interlines. Insulation between overhang is done by

blocks mad of HGL.

4.4 ROTOR SLOT WEDGES:

The rotor of turbo generator is rotating at a very high speed therefore to protect

the winding against the effects from centrifugal forces they are secured firmly by

rotor slot wedges. The slots wedges are made of copper alloy. They are also use

ad damper winding bars. The wedge and retaining ring act as damper winding in

case of asymmetrical and asynchronous operation. The ring is coated with silver

which acts as short circuit rings in damper windings.

Fig. Rotor slot wedge

4.5 ROTOR RETAINING RING:

To protect end winding of rotor from flying out from the rotor due to centrifugal

forces rotor retaining ring is used. Retaining rings are made from high tensile non-

magnetic alloy steel forgings in order to reduce stray losses. These act as short

circuit rings to the induced current to the damper system. To ensure low contact

resistance retaining rings are coated with nickel, aluminium, silver.

Fig. Retaining ring

4.6 FIELD CONNECTION:

The field current is supplied to the rotor winding through radial terminal bolts and

two semicircular conductors located in the hollow bores of the exciter and rotor

shafts. The field connection provides electrical connection between the rotor

winding and exciter.

4.6.1 TERMINAL LUG:

The terminal lug is a copper conductor of rectangular cross section. One end of

terminal lug is braced to the rotor winding while the other end is screwed to the

radial bolt.

4.6.2 RADIAL BOLT:

The field current leads located in the shaft bore is connected to the terminal lug

at the end winding through a radial bolt.

4.6.3 FIELD CURRENT LEAD:

The leads are run in the axial directions from the radial bolt to the end of rotor.

They consist of two semicircular conductors insulated from each other by an

intermediate plate and from the shaft by tube.

Fig. Field current lead

4.7 ROTOR FAN:

The cooling air in generator is circulated by axial fans located on the rotor shaft. In

250 MW rotor two axial flow fans are located on both turbine as well as exciter

end side whereas in 500 MW axial fans are located on turbine end side only.

Fig. Rotor fan

CHAPTER 5

EXCITATION SYSTEM

5. EXCITATION SYSTEM

5.1 Brushless Excitation:

The main parts of brushless excitation system are as follows:

1. Pilot exciter

2. Main exciter

3. Rectifier wheel

4. Automatic voltage regulator

The three phase pilot exciter has a revolving field with permanent magnet poles.

The armature winding is housed on the stator. The three phase a.c. generated by

the pilot exciter is rectified and controlled by automatic voltage regulator to

provide variable D.C. for exciting the main exciter. The three phase main exciter

has stationary field with revolving armature. Thus three phase a.c. power is

produced in main exciter which is rectified by rotating rectifier bridge and is fed to

the field winding of the rotor (turbo generator) through dc leads.

Permanent magnet fan main exciter rectifier wheel

generator

5.2 Pilot Exciter:

Three phase pilot exciter is 16 pole revolving field units. The stator accommodates

three phase armature winding and magnetic poles are placed on the rotor. Thus

rotating flux is produced which cuts the stationary armature conductors and three

phase a.c. is generated.

PMG ROTOR AND FAN

5.3 Main Exciter:

The three phase main exciter is a 6 pole armature type unit. The stator frame

accommodates the field winding. The field winding is placed on the magnetic

poles. The armature consists of stacked lamination and the three phase winding is

inserted into the slots of the laminated armature.

Stator core

Stator Frame magnetic pole damper winding

Fig. main exciter

5.4 Rectifier wheel:

Components in the rectifier wheel are as follows:

1. Silicon diodes

2. Aluminium heat sink

3. Fuses

4. RC circuit

DC leads heat sink Diodes rectifier

wheel

Fig. rectifier wheel

The main component in the rectifier wheel is silicon diodes which are arranged in

rectifier wheel in three phase bridge circuit. The direct current from rectifier

wheel is fed to DC leads and then to the field winding of the rotor.

5.5 Flowchart of Brushless Excitation:

Pilot exciter Main Exciter

5.6 Advantages of Brushless Excitation:

Eliminates slip rings and brushes

Eliminates all problems associated with transfer of current via sliding contacts

Eliminates the hazard of changing brushes on load

Brush losses are eliminated

Minimum operating and maintenance cost

High response excitation with fast acting AVR

Rotor Earth Fault Measurement through provision of Instrument Slip Rings

Permanent magnet field on

rotor, Armature on stator

Armature on rotor, field

winding on stator

Silicon Diode bridge on

shaft

To alternator field

Output from alternator Regulator

Thyristor Controlled

Bridge

CHAPTER 6

COOLING SYSTEM

6. COOLING SYSTEM

Power output of electrical machine is given by

P=K.As.Bδ.D2 L .ns

It can also be written as

D2L=P/ (K.As. Bδ .ns)

Machine Size is a critical and important aspect of design of very Large Capacity

Machines from handling, transportation point of view.

From Output Equation, Machine Size is inversely proportional to ‘As’.

Electrical loading ‘As’ is indicative of Winding Losses.

Higher the losses are allowed, more Output Power can be obtained from the

Machine.

Winding temperature increases with increase in Losses.

Size can only be limited with very high ‘As’. This can be achieved by efficient

cooling system since higher value of ‘As’ means higher losses.

6.1 COOLING METHODS FOR TURBOGENERATOR:

STATOR WINDING: Indirectly Air Cooled

ROTOR WINDING: Directly Air Cooled

STATOR WINDING: Indirectly Hydrogen Cooled

ROTOR WINDING: Directly Hydrogen Cooled

STATOR WINDING: Directly Water Cooled

ROTOR WINDING: Directly Hydrogen Cooled

6.2 AIR COOLED TURBO GENERATOR:

In Air Cooled Turbo generator stator winding is indirectly air cooled whereas the

rotor winding and stator core is directly air cooled. This type of cooling is

applicable for rating of 30 MW- 60 MW generators. In this type of turbo generator

there are vertically side mounted cooler in a separate housing.

fig. Cooling of rotor and stator

Hot air

Cold air

6.3 HYDROGEN COOLING AND HYDROGEN COOLED T.G. (THRI):

When the problem of increasing generator rating was talked in it became clear

that the air cooled machine did not provide the necessary scope for progress. Not

only in circulating the requisite of air through the machine but also because high

fan power required to circulate. Evidently to push up generator ratings hydrogen

is used as cooling medium.

Advantages of Hydrogen as Cooling Medium:

a) Increased efficiency: The density of H2 is only 0.07 times the density of air and

therefore the power required to circulate H2 is less than that required in air.

b) Increase in rating: H2 has a heat transfer coefficient 1.5 times and its thermal

conductivity is 7 times that of air. Consequently when H2 is used as a coolant,

the heat is more rapidly taken up from the machine parts and dissipated.

c) Elimination of fire hazard: The outbreak of fire inside the machine is

impossible as H2 does not support combustion.

d) Smaller size of coolers: The size of cooler required is smaller in size.

Cooler Stator core Stator Rotor Bushings

fig. Cooling of rotor and stator

6.4 HYDROGEN/WATER COOLED T.G. (THDF):

In large rating machines, hydrogen cooling is not sufficient to remove the entire

heat generated. For additional cooling, a Primary Water (PW) cooling system with

demineralised water flowing through the hollow stator conductors is used. The

rotor conductors are hydrogen cooled.

Cooler water box stator core rotor

fig. Cooling of rotor and stator

CHAPTER 7

GENERATOR TECHNICAL

DATA

7. GENERATOR TECHNICAL DATA

Chapter 8

TESTING OF TURBO

GENERATOR

8. TESTING OF TURBO GENERATOR:

To ensure that all functional requirements are fulfilled, and to estimate the

performance of generator, the TURBO GENERATORS are required to undergo

some tests.

8.1 SHORT CIRCUIT TEST:

The machine is run at rated speed and drive motor input voltage and current are

noted and excitation is gradually increased in steps, at 20, 40, 60, 80, 100% rated

current of machine. The short circuit characteristics is plotted from short circuit

results by selecting X-axis as field current and Y-axis as % rated current.

From the Short Circuit test, we will get copper losses.

8.2 OPEN CIRCUIT TEST:

The machine is run at rated speed and the motor input voltage and current are

noted and excitation is gradually increased in steps, at 20, 40, 60, 80, 90, 95, 100,

105, 110 and 120 % of rated voltage of machine. The open circuit characteristics is

plotted from open circuit results by selecting X-axis as field current and Y-axis as

% rated voltage.

From the open circuit test, we will get Iron Losses.

8.3 INTER STRAND TEST:

This testing is basically done to check any short circuit between ant two

consecutive conductors of a bar. For this test all the bare conductors at both the

ends are separated from each other so that they do not short circuit. Then a live

wire is connected to a conductor and received from it consecutive conductor to

light a lamp. Hence if the lamp lights up it shows short circuit between the two

conductors due to improper insulation between them.

It shows insulation failure between the conductors, these conductors are then

replaced and bar is followed through all the previous processes. Similarly all the

conductors are checked for any short circuit.

8.4 HIGH VOLTAGE TEST ON ROTOR AND STATOR WINDING

(MACHINE AT REST):

The High Voltage is applied to windings by increasing gradually to required value

and maintained for one minute and reduced gradually to minimum. The

transformer is switched off and winding is discharged to earth by shorting the

terminal to earth using earthing rod connected to earthen wire. The test is

conducted on all the phases and rotor winding separately. When High Voltage

test is done on one phase winding, all other phase windings, rotor winding,

instrumentation cables and stator body is earthed. This test is done to check the

insulation of the winding and hence it is also known as insulation test.

High Voltage test levels:

Stator winding = (2 Ut +1) KV

Rotor winding = (10 * Up) V

Here,

Ut = Rated voltage of the machine under test

Up = Excitation voltage

8.5 HELIUM TEST:

Helium test is done to check leakage within the bar and at the brazed portions.

Any minute leakage which couldn’t be checked by water test can easily be

observed by helium test because helium is one of the lightest gas.

In helium test, whole of the bar is wrapped in the polythene excluding the end

points. The helium gas at pressure of 11Kg/Cm2 is passed through the bar and a

probe connected to the gauge is inserted inside the polythene at different places.

The gauge will show deflection if there is any helium atom present. Gauge will

show reading even if 1 helium atom in 100000 atoms is present.

CHAPTER 9

CONCLUSION

CONCLUSION

The Vocational training at BHEL Haridwar helped us in improving our practical

knowledge and awareness regarding Turbo Generator to a large extent. Here we

came to know about the technology and material used in manufacturing of turbo

generators. Besides this, we also visualized the parts involved or equipments used

in the power generation.

Here we learnt about how the electrical equipments are being manufactured and

how they tackle the various problems under different circumstances. At least we

could say that the training at BHEL Haridwar is great experience for us and it really

helped us in making or developing our knowledge about turbo generator and

other equipment used in power generation.

REFERENCES

http://www.bhel.com/about_publication.php

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

http://en.wikipedia.org/wiki/Hydrogen-cooled_turbogenerator

A text book of electrical machines by P.S.BIMBRA

A text book of electrical technology by B.L.THERAJA

BHEL Internal material