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Jaipur national university

BHARAT HEAVY ELECTRICAL LTD. [BHEL],

RANIPUR (HARIDWAR). A

PRACTICAL TRAINING REPORT

ON

“MANUFACTURING OF TURBO-GENERATORS ”

Submitted by:- Submitted to:-

Mohan Lal Meena

B-Tech third year Head of Dept. in Electrical Engg.Electrical Engineering jnu, Jaipur jnu, Jaipur

Department of Electrical Engg.

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ACKNOWLEDGEMENT

I am thankful to Mr. P Jagpangi-SDGM Block-1 BHEL, Sr. Engg Rahul kumar for giving me full guidance and support during the course of my 1 month training.

I wish to express my profound sense of gratitude to all the faculty members of Electrical engineering Branch & HOD sir- School Of Engineering & Technology(jnu), Jaipur for their delightful guidance and constant encouragement throughout the process; they have always been a great inspirational motivator for me.

I take this as my opportunity to express my whole hearted thanks to all other persons involved in the process who made it possible to achieve the completion of summer training with success.

Date:…………… Mohan Lal Meena

B.TECH. third year (2010-11)

Electrical ENGG.


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PREFACE

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 life. According to this life, he has to serve an industry, may be public or private 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, labor 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 30 days training (after 3rd yr.) at BHARAT HEAVY ELECTRICALS LIMITED. This report is based on the knowledge, which I acquired during my 30 days training period at the plant.


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CONTENTS

Chapter Page No.

Chapter 1:- Introduction 6

Chapter 2:- BHEL-A Brief Profile 8

1. Achievements of BHEL 8

Chapter 3:- BHEL An overview 9

1. Parts of BHEL 9 2. Sectors of BHEL 10 3. Transportation 11 4. Telecommunication 11 5. Blocks of BHEL 11 6. Manufacturing divisions 12

Chapter 4:- HEEP: An overview 15

1. Vision, Mission & Values 16

Chapter 5: - Electrical machines block (bl-1) 17

1. Introduction to block 1 18 2. Bays in block 1

19

Chapter 6:- Manufacturing profile 21

1. Generators 21 2. Generator series 23 3. Types of generators manufactured by BHEL 23 4. Technical data 25 5. Important weights 25


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Chapter 7:- Manufacturing process of turbogenerators 29

1. Basis of operation 29 2. Fundamental laws 29 3. Faradays’ laws of induction

30 4. Kirchhoff’s law of electric circuit 30

5. Amperes law 30 6. Turbo-generators 31 7. Parts of Turbo-generators 39 8. Cooling system

39 9. Parts of stator 39 10. Pipe connections 42 11. Terminal box 42 12. Constructional feature of core 44 13. Rotor

58 14. Rotor windings & connections 65 15. Exciters 68

Chapter 8:- Micalastic impregnation 72

1. Definitions 72 2. Resin tanks 74 3. Advantages 75

Chapter 9:- Testing of Turbo generators 76

1. Mechanical tests 76 2. Electrical tests 76

Chapter 10:- Conclusion 82

Chapter 11:- Bibliography 83


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CHAPTER - 1: - INTRODUCTION

In 1956, India took a major step towards the establishment of its heavy engineering industry when Bharat Heavy Electrical Ltd., the first heavy electrical manufacturing unit of the country was setup at Bhopal. It progressed rapidly and three

more factories went into production in 1965. The main aim of


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establishing BHEL was to meet the growing power requirement of the country.

B.H.E.L appeared on the power map of India in 1969 when the first unit supplied by it was commissioned at the Basin Bridge Thermal Power Station in Tamil Nadu. Within a decade, BHEL had commissioned the 100th unit at Santaldih. West Bengal. BHEL had taken India from a near total dependence on imports to complete self-reliance in this vital area of power plant equipment BHEL has supplied 97% of the power generating equipment.

BHEL has already supplied generating equipment to

various utilities capable of generating over 18000 MW power. Today BHEL can produce annually; equipment capable of generating 6000MW. This will grow further to enable BHEL to meet all of India’s power project equipment requirement. As well as sizeable portion of export targets. Probably the most significant aspect of BHEL has been its diversification. The constant reorientation of the organization to meet the varied needs in time with time a philosophy that has led to the 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 manufactures of power plant equipment and in terms of the spectrum o0f products and services offered, it is right on top.

BHEL’s technological excellence and turnkey capability have won it world wide recognition. Over 40 countries in the world over have placed orders with BHEL covering individual equipment to complete power stations on a turnkey basis. In 1978-79 export earnings reached Rs. 122 crores, the highest for any one- year. BHEL has its


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headquarters at New Delhi. Its operations are spread over 11 manufacturing plants and number of engineering and service divisions located across the country. The service divisions includes a network of regional branch offices throughout India.


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CHAPTER 2 : - BHEL-A Brief Profile

BHEL is the largest engineering and manufacturing enterprise in India in the energy-related/infrastructure sector, today. BHEL is ushering in the indigenous Heavy Electrical Equipment industry in India-a dream that has been more than realized with a well-recognized track record of Performa .

A widespread network comprising of 14

manufacturing companies, which have international recognition for its commitment towards quality. With an export presence in more than 60 countries, BHEL is truly INDIA’S INDUSTRIAL AMBASSADOR TO THE WORLD.

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

BHEL has:-

Installed equipment for over 90,000MW of power

generation for Utilities, captive and Industrial users.

Supplied over 25000 Motors with Drive Control System to power projects, Petrochemicals Refineries, Steel, Aluminum, Fertilizer, Cement plant, etc.

Supplied Traction electrics and AC/DC locos over 12000 kms Railway network.

Supplied over one million Values to Power Plants and other Industries.


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CHAPTER- 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 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 Defenses etc...

Today BHEL has:-

14 Manufacturing Divisions 9 Service Centers 4 Power Sector Regional Centers 150 Project sites

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


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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 and auxiliaries up to 500MW.

It possesses the technology and capability to procure thermal power generation equipment up to 1000MW.

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 and has also commenced production of 500MW nuclear set.

Custom-made huge hydro sets of Francis, Elton 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 :-


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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 Heat exchangers Process control etc.

TRANSPORATION:- 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 has been divided into eight blocks:-

1). Block-1:-

In block one turbo generator, generator, exciter


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motors (A.C&D.C) are Manufactured & assembled.2). Block-2:-

In block-2 large size fabricated assemblies\component for power equipment are manufactured & assembled.

3). Block-3:- In block -3 steam turbine, hydro turbines, and gas turbines, turbines blade are manufactured & assembled. 4). Block-4:-

In block -4 winding for turbo generator, hydro generator, insulation of A.C&D.C motors insulating component for turbo generator, hydro generator motors are manufactured & assembled.

5). Block-5:-

In block-5 fabricated parts of steam turbine water box, hydro turbine turbines parts are manufactured & assembled.

6). Block-6:-

In block -6 fabricated oil tanks hollow guide blades, rings, stator frames rotor spiders are manufactured & assembled. 7). Block-7:-

In block -7 stamping dies, stamping for generators & motors are manufactured & assembled.

8) .Block-8:-

In block -8 LP heaters, ejectors, steam coolers,oil


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coolers, ACG coolers, oil tanks are manufactured & assembled.

MANUFACTURING DIVISIONS :-

Heavy Electricals Plant, Piplani, Bhopal (M.P)

Electricals Machines Repair Plant (EMRP), Mumbai

Transformer Plant P.O. BHEL, Jhansi.

Bharat Heavy Electricals Limited : Heavy Electricals Equipment Plant (HEEP), Central Foundry Forge Plant., Ranipur,


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Basic structure of BHEL,haridwar

Heavy Equipment Repair Plant, Varanasi.

Insulator Plant, Jagdishpur, Distt. Sultanpur.

Heavy Power Equipment Plant, Ramachandra Puram, Hyderabad

High Pressure Boiler Plant & Seamless Steel Tube Plant, Tiruchirappalli.

Boiler Auxiliaries Plant, Indira Gandhi Industrial Complex, Ranipet.

Industrial Valves Plant, Goindwal.

Electronics Division : Amorphous Silicon Solar Cell Plant (ASSCP). Electro porcelains Division. Industrial Systems Group. Electronics Systems Division.

. Component Fabrication Plant, Rudrapur.

Piping Centre, Chennai.

Regional Operations Division, New Delhi


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CHAPTER 4:- HEEP: AN OVERVIEW

Over the years, Bharat Heavy Electrical Limited has emerged as world class engineering and Industrial giant, the best of its kind in entire South East Asia. Its business profile cuts across various sectors of engineering/power utilities and industry. The company today enjoys national and international presence featuring in the "Fortune International-500” and is ranked among top 12 companies in the world manufacturing power generation equipment.

BHEL has now 14 manufacturing division, 8 service centers and 4power power sectors regional centers besides a large number of project sites spread over India and abroad.

The company is embarking upon an ambitious


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growth path through clear vision, mission and committed values to sustain and augment its image as a world-class enterprise.

Vision

A world-class innovating, competitive and profitable engineering enterprise providing total business solution.

Mission

To be the leading Indian engineering enterprise providing quality products system and services in the field of energy, transportation, infrastructure and other potential areas.

Values

Meeting commitments made to external & internal customers.

Foster learning creative and speed of response.

Respect for dignity and potential of individual

Loyalty and pride in the company.

Team playing.


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CHAPTER 5 :-

ELECTRICAL MACHINES BLOCK (BL-1)

Introduction

1. Block-1 is designed to manufacture hydrogenerators and large and medium size AC and DC Electrical machines. 2. The Block consists of 3 Bays:

Bay-1 (36*482 meters),

Bay-2 , (36*360 meters) and

Bay-3 of size (24*360) meters each.

For handling and transporting the various components over-head crane facilities are available, depending upon the products manufactured in each bay.

There are also a number of self propelled electrically driven transfer trolleys for the inter-bay movements of components/assemblies

3. Conventional Bay-wise broad distribution of products is as Follows: (LSTG Area --large size turbo generators)


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BAY-1 Hydro generators, their exciters; PMG and Large size Turbo- Generators.

BAY-2 Turbo-generators, their exciters and Heavy Electrical Motors.

BAY-3 Medium size Electrical Motors.

4. Testing facilities for turbo generators and heavy motors are available in bay-2 and for medium size motors in bay-3 .

5. There is a special test bed for testing of T.G. of capacity of 500 MW units sizes and above.

There are three BAY in BLOCK 1 BAY-I [Hydro Generator ]

Machine Section Assembly Section Stator winding

BAY-II [Turbo Generator]

Machine Section

Iron Assembly

Heavy Rotor Assembly Section

Stator winding Section

Armature/Rotor Section


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Armature/Rotor Impregnation Section

General Assembly Section

Test Stands

BAY-III [Medium Size Motors] Machine Section

Iron Assembly Section

Commutator Section

Pole Core Section

Painting Section

Bus bar & filling Section

Winding Section

General Assembly Section Test Stand

Bay-1 (A) LARGE SIZE TURBO GENERATORS (LSTG AREA)

Following facilities are available in different sections of this area:- a. Stators core assembly section: - Two Number core pits with core building and pressing facilities are


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available in this section. The section is also equipped with optical centering device, core heating installation and core loss testing facilities.

b. Stator winding section: - The section is located in dust-proof enclosure and equipped with one number-winding platform with two number rotating installations for assembly of winding. Resistance brazing machines and high voltage transformer are also available in this section.

c. Rotor assembly section: - This section is also in a dust-proof enclosure with number of rotators, rotors bar laying facilities

and MI heating and mounting of retaining rings, rotor winding assembly and rotor assembly like retaining ring fitting, four assemblies are carried out in this section.

d. Bar preparation section:- This section consist of milling machine for long preparation, installation for insulation of tension bolts for stator and preparation of stator winding before assembly.

e. Test bed section:- This section this section is equipped with bedplates, height blocks, supporting blocks and 12MW drive motors. Large size turbo generators and exciters are assembled and tested in this section.


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CHAPTER 6:- MANUFACTURING PROFILE

Generator- 1. Russian 2. Kraft Work Union- i) THDF ii) THRI iii) TARI

TARI: Capacity 500 MW

Cooling is done by air.

THRI :

Capacity 130-400 MW.

Water is the cooling medium.

Stator is indirectly cooled while Rotor is radially cooled.


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Table 6.1 GENERATOR SERIES

T - Turbo Generator A - Air Cooling

R - Direct RadialCooling with Gas I -Indirect Cooling

H - Hydrogen cooling

D - Direct Axial Cooling with Gas

D- Direct Cooling

F - Direct Axial Cooling with water

F- Direct cooling with water


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Type of Product

Cooling b/w

Rotor & Stator

Cooling of Stator

Cooling of rotor

T A R I

T H R I

T H D I

T H D F

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TYPES OF TURBOGENERATOR MANUFACTURED BY HEEP-HARIDWAR

TARI : Turbo generator with Air-cooled radially indirect cooling.

THW : Turbo generator with Hydrogen and Water cooling.

THRI : Turbo generator with Hydrogen radially indirect cooling.

THDF : Turbo generator with Hydrogen and Water direct cooling TURBO GENERATORS

(a) Air Cooled Generators Upto 200 Mw Range (Type: TARI) :-

Salient Design Features

Stator core and rotor winding direct

air-cooled (b)TARI 108/41 GAS TURBINE


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GENERATOR FOR FARIDABAD CCPP

Indirect cooling of stator winding

Horizontally split casing design of

stator

Vertically side mounted coolers in aSeperste housing.

Micalastic bar type insulation system

Separately assembled stator core and

winding for reducing the manufacturing cycle

Brushless/static excitation system

Hydrogen Cooled Turbo generators of 140-260 Mw Range (Type: Thri) Salient

Design Features :-

Stator core and rotor winding directly hydrogen cooled

Indirect cooling of stator winding

Rigid core bar mounting


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Micalastic insulation system

End shield mounted bearings

Top ripple springs in stator slots

Ring type shaft seals

Symmetrical ventilation.


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Salient Technical Data: -

Rated output : 588 MVA, 500 MW

Terminal voltage : 21 KV

Rated stator current : 16 KA

Rated frequency : 50 Hz

Rated power factor : 0.85 Lag

Efficiency : 98.55%

Important Weights :

Heaviest lift of generator stator : 255 Tons

Rotor weight : 68 Tons

Total weight of turbo generator : 428 Tons


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HYDROGENERATORS:- Following facilities are available in this section:- (a) Machine section : - This section is equipped with large size rotor slot milling machine, lathe, conventional as well as CNC vertical boring, CNC horizontal boring m/c, drilling and double column planning machines. Small size milling, slotting machines and shapers are also available for manufacturing small components.

The major components machined in this section are stator frames, upper and lower bracket, rotor spider, rotor shafts, pole end plates, thrust bearing disc collar of hydro generators and rotor shafts of large size turbo-generators.

(b.) Iron assembly section: - This section is equipped with two centering columns sets of welding machines for carrying out iron assembly of hydro generator stators.

(c.) Stator winding section: - Two truck-mounted installations are available in this section for resistance brazing if bar heads joints of stator winding bars of hydro generators. (d.) Painting section: - This section is equipped with a paint spray booth with suitable exhaust for painting the various components.

(e.) Packing and preservation: - This section is equipped with wood working machines like band saw, circular saw and pendulum crosscut saw for final packing of all the products manufactured in block-1. (f.) Over speed balancing installation: -


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The dynamic balancing of turbo generators rotor is done on this installation. (g.) Rotor winding section: - This section is equipped with rotors, hydraulic presses and wedge driving assembly of rotor of turbo generators. (h.) Rotor assembly section: - This section is equipped with bedplates and induction heating facilities for assembly of rotors of turbo generators. Assembly of retaining ring is carried out in this section.

Bay-2 Heavy Electrical Motors:- The following are the main sections:- (a.) Machine section: - 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 turbo-generators. (b.) Iron assembly section: - This section has facilities for stator core assembly of turbo-generators and heavy electrical motors. 1000T and 250T umbrella type presses for pressing the cores and transformers for induction heating of the armature core of large size electric motor are available in this section. (c.) Armature section: - This section is equipped with installations like bandaging m//c, tensioning devices, and magnetic putty application machine and 45KW MF brazing m/c for laying windows in large size DC armatures. (d.) General assembly section: - General assembly of large size AC and DC motors is carried out in


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this section.


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Bay-3 MEDIUM SIZE AC MOTORS:- The salient features of AC Machines are:-

Very high efficiency.

Torsionally rigid, rugged housing and end shields made of cast iron.

External and internal ribbing on slip ring enclosure and servicing cover.

MICALASTIC insulation using VPI technology. ?

Proven anti-friction bearing concept.

Compact dimensions.

Technical Data

Ratings: -200 to 2500 kW

Voltage range: - 3.3 to 11 kV, 50 Hz.

Number of poles: -4 to 12

Shaft heights (in mm.):- 355, 400, 450, 500 and 560


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CHAPTER -7:- Manufacturing Process Of Turbo Generators

ROTATING MACHINES: BASIS OF OPERATION:

All electric machines operate on the same basic principles and only a few fundamental laws govern the behavior of these machines. A through understanding of these fundamental laws is essential for the study of electrical machines. These laws are listed below:

THE FUNDAMENTAL LAWS:

FARADAY'S LAW OF INDUCTION

KIRCHOFF'S LAW OF ELECTRIC CIRCUIT

CIRCUITAL LAW OF THE ELECTRIC FIELD (AMPERE'S LAW)

LAW OF FORCE ON THE CONDUCTOR IN A MAGNETIC FIELD (BIOT SAVART'S LAW)

1. FARADAY'S LAW OF INDUCTION:

If a magnetic flux linking a closed conducting circuit is changing an electromotive force is induced in the circuit.

If represents the flux linking the circuit and d the change in flux during the time dt, then the magnitude of the induced emf is proportional to the rate of change of flux,d /dt


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e = n d /dt

The direction of the induced emf is determined by Lenz's law,which states that the induced emf opposes the change in flux.

2. KIRCHOFF'S LAW OF ELECTRIC CIRCUIT:

A. KIRCHOFF'S MESH LAW: Around any closed loop(or mesh) in a network ,the algebraic sum of all emf's and potential drops is equal to zero.

B. KIRCHOFF'S CURRENT LAW: At any node (or junction),the total current entering the node is equal to the total current leaving the node.Alternatively the algebraic sum of all the currents at a node (or junction) is zero.

3. CIRCUITAL LAW OF THE ELECTRIC FIELD (AMPERE'S LAW):

The line integral of the magnetic field strength along a closed path is equal to the sum of the ampere-turns with which this path is linked.


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TURBO GENERATORS

INTRODUCTION TO TURBO GENERATORS:-

The growing use of electrical in the world leads to new problems concerning the generation of electrical energy. The most frequently used machines, for the generation of electrical power are the synchronous machines.

Faraday's law of electromagnetic induction states that the induced voltage is proportional to the rate of change of the linkage of the magnetic lines of force. In the case of electrical rotating machinery the part of the machine, in which the voltage is induced is called the armature.

The component part of the electrical machine which carries the excited or field winding for the production of the required magnetic lines of force is called the field system.


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If the field is so provided that the of force after a particular distance change their direction, the field system is said to posses alternating poles. Alternating poles mean that the poles are alternatively north and south poles.

The change of flux is caused when the armature moves in a flux set by alternating poles. It is naturally just the same whether the poles moves and the armature winding remains stationary or the poles remains stationary and the armature moves. Almost all alternating current generators are now a days designed with rotating field system.

This arrangement is the natural order of things for a few very good reasons:-

The high voltage, high current and therefore high-power handling element is the armature on any AC or DC rotating electrical machine. Armature coils are therefore larger than field coils.

Since no alternate switching of coil polarities is needed on an AC machine, no commutator function is needed. Thus, the high power windings may be made stationary for direct connection. The universal motor is an exception to this condition.

The field structure and coils are not ordinarily required to handle more than a fraction of the total power. Thus, their rotating electrical connection may be made smaller. Since no polarity switching is required, collector are usually used.


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The armature and field coils are both placed in slots in the punched magnetic structure, but the stationary armature can be conveniently made to with deeper to handle the required larger coils.

It is easier to cool the stator than the rotor which is an advantage of the normal AC construction.

The main reason for designing the alternating generator with rotating field system is that AC generators are designed for high voltages(4-33kV),which are difficult to be tapped from slip rings incase of rotating armature type. For smaller voltages the rotating armature type may be cheaper but in order to achieve uniformity all AC generators are designed with rotating fields.

It is economical to have armature winding on the stator and field winding on the rotor. In order to illustrate this:-

Consider a 3-phase, star-connected, 200MVA, 11kV, synchronous machine. Its line current is 10,500 A. If the armature winding is placed on the rotor, three slip rings each capable of handling10,500 A would be required. Further each slip ring must be properly insulated from the shaft for a voltage of 11/1.732,i.e.6.35 kV. The star-point of the 3 phase winding must also be brought out through fourth slip-ring, in order to connect it to a grounded metal plate through a resistance.

Assume now that low-power required for the field winding is 1 MW at 500 volts. Then the exciting or field current is 1000/0.5=2000A.Only two slip rings, each capable of handling 2000A,are required. Also each slip ring


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should be insulated from the shaft for a voltage of 500 volts only. This shows that it is cheaper to have field winding on the rotor rather than the armature winding. Thus the construction of synchronous machine with armature winding on the rotor is much more economical.

In addition, a synchronous machine with armature winding on the stator and field winding on the rotor has reduced slip ring losses and is therefore more efficient.

Stationary armature windings can be insulated satisfactorily for higher voltages, allowing the construction of high-voltage, say 33kV, synchronous machines.

Low-power field winding on the rotor gives a lighter rotor and therefore, low centrifugal forces. In view of this ,higher rotor speeds are permissible, thus increasing the synchronous machine output for given dimensions.

The type of construction used for a synchronous generator depends upon the type of prime mover.

Three different types of prime movers very commonly used these days. These are:

STEAM TURBINES

HYDRAULIC TURBINES

DIESEL TURBINES


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1. STEAM TURBINES: -

Steam turbines have efficiency at large speeds and hence synchronous machines driven by steam turbines are high speed.

We know that

NS=120f/P

For a standard frequency 50 cycles/second and with the minimum possible number of poles to, the maximum operational speed of a synchronous machine by turbine alternators is 3000 revolution/minute. In America, however, the maximum operational speed of such generators is 3600 revolution/minute, as the frequency is 60 cycles/second. Such high speeds call for horizontal shaft of the machine and have to be designed with rather lower values of the diameter of the rotor.

The peripheral speed of machine is given by:

vp

=DN/60 Where D is the diameter of the rotor in meters and N is the speed of the rotor in revolutions per minute. Since the peripheral speed increases proportionally with the diameter and with the increase in peripheral speed


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the much forces acting on the rotor increase, the diameters are kept low and the rotors have cylindrical shapes.

2. HYDRAULIC TURBINES:-

Hydraulic turbines have different forms. The type of hydraulic turbine used as a prime mover for the generator, depends upon the water head available. If the water head available is high, a pelton wheel is used as a hydraulic turbine. In such a case the hydraulic turbine has a high speed and both the turbine and generator may either be vertical or horizontal, the horizontal type being more frequent. Pelton wheels are used for water heads 400 m and above.

Upto a water head of 380 m Francis turbines are used and in water heads upto 50 m Kaplan turbines , the turbine and the generator are of the vertical type. Since the water head is not high, the speed of such a prime mover varies from 50 rpm. The types of synchronous machine used with the hydraulic turbines are the salient pole synchronous machine, i.e. synchronous machines with projected poles.

3. DIESEL ENGINES:

Diesel engines, as prime movers are these days used in low rating synchronous machines. They are universally manufactured as horizontal type and therefore both the prime mover and the generator are of horizontal construction . Because of the slow speeds of the diesel engines, the synchronous generator used this type of prime movers are salient pole synchronous machines when driven by a diesel engine. Synchronous machines are very sensitive to the torque variations or swings of the diesel engines.


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The report describes the operation and maintenance aspects of turbo generators and its auxiliaries along with their constructional features.

The machine being developed on the proven line Skoda design under collaboration with Czechoslovakia, the operation and the maintenance procedures are developed based on the manufactures and his collaborators experienced in the field of Turbo Machines.

SYNOPSIS OF THE FUNCTION OF TURBO GENERATORS:

The generator rotor is driven by a prime mover and on driver side gas/diesel/steam /hydro , depending on the equipment to which it is meant for.

The non-drive side of the rotor is equipped with a rotating side armature, which produces AC voltage. This is rectified to DC by using a DC commutator/rotating diode wheel depending upon the type of exciter.

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

As the above rotating system is put into operation, the PMC stator produces AC voltage.

This voltage is rectified by thyristor circuit to DC.

This supply is given to exciter field. the field is also controlled by taking feedback from main generator terminal voltage, to control external field variations required by automatic voltage regulator.


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The rectified DC supply out of exciter is supplied to turbo generator rotor winding either through brushes or central lead which will be directly connected to turbo generator rotor winding. This depends on type of the exciter viz., DC commutator machine or brushless exciter.

The main AC voltage of generator is finally available at turbo generator stator.

LARGE SIZE TURBO-GENERATORS (LSTG):

These type of generators are those which has steam turbines as their prime mover and current is supplied by exciter system.

There main types are:

T H R I

T A R I

T H D I

T H D D

T H D F

T H F F

Here basic terms are;


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T = Turbo generator

A = Air cooled

H = Hydrogen cooled

R = Direct radial cooling with gas

D = Direct axial cooling with gas

F = Direct axial cooling with water

I = Indirect cooling

MAIN PARTS OF LSTG:-

The main parts of Turbo generator are:-

STATOR

ROTOR

COOLING SYSTEM

EXCITERS

STATOR:-

It includes stator frame, stator core, stator winding, generator coolers, stators end covers, temperature measuring device.

ROTOR:-

It includes rotor winding, rotor shaft, field connections, rotor retaining rings, fans and bearings.


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COOLING SYSTEM:-

It includes the cooling circuits required for the effective cooling of the generator. There are mainly 4 types of cooling system depending upon the rating of the generator:-

Air cooling system(60MW)

Hydrogen cooling(100MW)

Water cooling(500MW)

Water and hydrogen cooling(1000MW)

EXCITERS:-

Small generators which are coupled to main generators. The purpose of this is to provide the necessary excitation current.


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STATOR

CONSTRUCTIONAL FEATURE OF STATOR BODY:-

STATOR FRAME:-

The stator frame consists of a casting of welded plate construction reinforced internally in the radial and axial direction by web plates making the entire frame perfectly rigid to minimize core vibrations and suitably designed to ensure efficient cooling. Wedge shaped steel guide bars welded to the frame directly support the stator core.


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* Stator Frame Of 210MW Turbo Generators .*

End covers, which are made of Aluminium alloy, are bolted to the ends of the frame. In the end covers, are located

suction ducts with specially designed guide vanes, to ensure uniformity in fanning suction all around. Ingress of oil vapours into the machine is minimized, by sealing around the rotor and at the dividing planes of the end covers.

PIPE CONNECTION:-

To attain a good aesthetic look the water connection to gas coolers is done by routing stainless steel


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pipes inside the stator body which emanate from bottom and emerge out of wall.

From sidewalls these are connected to gas coolers by means of U-tubes outside the stator body. For filling the generator with hydrogen, a perforated manifold is provided at the top inside the stator body. Before filling hydrogen, carbondioxide is filled as hydrogen react to air result in explosive mixture. Thus carbondioxide displace air and later it is replaced by hydrogen. Same procedure is adopted when it is required to shut T.G.

TERMINAL BOX:-

The bearing and ends of three phases of stator winding are brought out to the slip-ring end of the stator body through terminal bushing in a terminal box. The terminal box is welded construction of (non-magnetic)austenitic steel plates. This material eliminates chances of stray losses due to eddy current, which may result into excessive heating.


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CONSTRUCTIONAL FEATURE OF STATOR

CORE:-

The main features of core are:-


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To provide the mechanical support (holding the windings).

To carry effectively the electromagnetic flux generated by the rotor winding.

To ensure the perfect linkage between core and rotor.

* Layout of stator core *

Stator core is made up of following components:-

End Plates………………………(2 no’s/generator)

End Packets


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Ventilation stampings

Insulating stampings……….(b/w the cores)

Insulating studs………………(b/w the sheets)

Core bars

Baskets…………………………..(3 no’s/ generator)

Compressing ring

Hydraulic press

Heating units

Pressing fixtures.

Stator cores are never made up of a single iron piece instead of they are made up of laminated sheets in order to reduce the EDDY CURRENT LOSSES.

In order to minimize the hysteresis and eddy current losses of the rotating magnetic flux, which interacts with the core, the entire stator core is made up of segmental, annealed insulated punching of hot rolled high quality silicon steel. These punchings are assembled in an interleaved manner on the machine guide bars and separate into packets of approximately 50mm thick between which are the ventilation ducts. Between two packets one layer of ventilation is provided. Steel spacer are spot welded on stampings.

The spacers from ventilating ducts where the cold hydrogen from gas coolers enter the core radially inwards there by taking away the heat generated due to eddy current losses.

The punchings are stamped from thin sheets of 0.5mm thick and contain open-end slots for the stator bars


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with dovetail slots for wedges to hold the stator bars in place .Other dovetail slots at the back of the punching are for assembly and locking of the segments on the guide bars. The assembled punchings are clamped into a stiff cylindrical core by pressure applied through steel and clamping plate. Pressure is applied to the teeth by non-magnetic pressuring fingers, which are bolted to the end clamping plates. In order to reduce end heating from end leakage flux and its associated electrical losses that are occurring at the ends of the stator core, the packets of punchings are stepped back to increase the gap between the punchings and rotor.

The insulation is a thermo-setting varnish, which maintains its insulating value at temperatures above the normal temperature range.

OPERATIONS:-

The Cold Rolled Non Grain Oriented (C.R.N.G.O) steel sheets in the required shapes according to the size of the laminations and then fed into the shearing press for punching and dovetail shaped stator laminations segments.

BLANKING AND NOTCHING:-

The holes and slots are made on segments. Nearly 500 tones crank press is used for this purpose.

DEBURRING OPERATIONS:-

In this operation the burns in the sheet due to punching are debarred. There are chances of short circuit with in the laminations if the burns are not removed. The permissible limit is about 5 micrometers. For debarring


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punched sheets are passed under rollers (with required clearance) to remove the sharp burns or edges.

VARNISH:

The laminations are now varnished to provide insulation.

Alkyl phenolic varnish is used to provide the insulation between the laminations then it is passed through furnace so that it may get consolated.

Constructional Feature Of Stator Windings:

The double layer stator winding is of the involutes type and is manufactured from electrolytic copper. It is located in open slots. The coils are pre formed from copper strips as half coils. The winding is composed of insulated half coil bars assembled in the stator slots in two layers and are brazed together at each end to form coils. They are in turn suitably grouped into proper phases, using bus type connector rings supported on end brackets. The stator bars are composed of insulated copper strands transposed by rouble method so that the eddy current losses are reduced and to ensure proper distribution of flux. A further partial transposition is carried out in the end windings. These arrangement s avoid circulating current losses which would otherwise be present under load conditions due to distribution of magnetic flux in the slot.


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The bars are insulated with mica based insulation. This insulation has excellent electrical properties, and does not require impregnation. Its moisture observation is extremely low. And outer covering of asbestos tape is applied to protect the abrasion in the slot. In order to minimize the effect of Corona slightly conductive coating (containing graphite) is then applied to the bar in the slot portion and semi conductive coating is applied to a certain length on the overhang portion of bars. An advantage of the involutes coil winding is that end winding is at an angle to the stator core end thus minimizing the stray losses in the stator core supporters.

END WINDING:-

The end winding i.e. the overhang portion has being thoroughly reinforce against the short circuit forces with epoxy glass laminated spacers and by further binding on to the

fastener blocks-which in turn are screwed to the non-magnetic damper ring bolted to the stator frame. This solid copper damper ring one on either side considerably reduces heating on the end iron.


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RESISTANCE TEMPERATURE DETECTORS:-

The stator slots are provided with platinum resistance thermometers to record and watch the temperature of the stator core, tooth region and between coil sides of machine in operation. According to VDE 05 30/7,55 all AC machines rated for more than 5 MVA or with armature cores longer than 1 metre is to be provided with at least 6 resistance thermometers or thermocouples, which shall be built inside the stator, suitably distributed around the circumference at the likely hottest points. In the case of longer lengths it is to recommended by the specification to distribute the resistance thermometers along the length. The thermometer should be fitted 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 two insulated coil sides. According to the same specifications the length of the resistance thermometers depends upon the length of the core of the armature.

LENGTH OF THE LENGTH OF THE


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CORE METER RESISTANCE

(IN METER) THERMOMETER (IN CM)

Upto 0.5 12.5

Over 0.5 to 1.0 25.0

Over 1.0 50.0

The leads from the detectors are brought out and connected to the terminal board for connection to temperature meters or relays.

The resistance temperature (RTD) is a resistance element. Operation of the RTD is based on the principle that the electrical resistance of a metallic conductor varies linearly with its temperature. The resistance wire of these detectors are molded into a fiber glass strip approximately 2 mm thick and trimmed to slot width. All molded strip detectors are non-inductively wound to cancel the extraneous voltage induced in them. Thus, by measuring resistance (usually incorporating quick and fairly accurate Whetstone’s bridge) temperature can be computed from calibration curve supplied with the test report.

Thermometers for the remote measurement of temperatures of air at inlet and outlet (i.e. cold and hot) have also being provided with in the stator frame.

DESIGN FEATURE OF STATOR:-

Overhang portion genuinely shifts to support rings, where it rests.

End packet of core stampings are put in steps.


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Simultaneously a cut is provided on these stamping. The main motto behind this is to reduce eddy current losses as at ends leakage flux is maximum.

Forming angles of all stator bars are different. Thus it is possible to connect them in given particular fashion. End bars have got different lug to take phase connection out it.

One design factor is chording of the pole windings. If in the 36-slot,4-pole machine, an individual coil enters slot 1 and comes in slot 10,it will have spanned 90 mechanical

degrees of the stator circular structure. In this case 90 mechanical degrees is 180 electrical. Thus the two sides of the coil are in the same relative position on the adjacent north and south pole positions. This is a full-pitch coil construction.

The more usual AC machine coil will cover less of the periphery of the machine and is then said to be fractional pitch. A typical situation might have a coil enter slot 1 and leave slot 7.This then covers six out of a possible nine slot pitches, and is a 6/9 or 66.7% pitch. The majority of AC machines are of fractional pitch type, for which there are a few important advantages:

The ends of the coils are shorter, which means less copper loss due to less total length.

The end coils can be formed more compactly. The end bells will need less winding space, resulting in a shorter unit.

There is a distinct reduction in machine harmonics due to cancellation of higher harmonics. Since all AC equipment is designed to operate on a pure sine wave, the generation of


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harmonics is to be avoided. This is especially so when the factor that achieves it is otherwise desirable.

TRANSPOSITION OF STATOR WINDINGS:-

Where the current by conductor necessities a large cross-section to be used, the liability to excessive eddy loss and heating makes it essential to subdivide the conductor into strips. This is due to fact that the conductors or parts of the conductors nearer the top of the slots have lesser self-inductance that those nearer the bottom of the slot. Hence, the current tends to flow in the top portions of each conductor. To prevent such unequal distribution of current the large conductors in alternator -

-armature are stranded, and each strand is insulated with enamel. Each conductor is made up so that all strands occupy top, intermediate and bottom positions for equal distances. This is done by twisting or transposition of coils. In a long-cored turbo-alternator, the twisting may be carried out three or four times in a single slot. The effects of transposition are the same as twisting the bundle of strands 180 degree or 360 degree. This is accomplished without substantially increasing the width of strands. For a multi turn coil 180-degree transposition usually suffices. For a single turn coil, because of its greater depth at 360 degree transposition may be necessary. The effect is to equalize the eddy e.m.f. in all the laminations and to allow the layers to be paralled at the ends without producing eddy circulating currents between the layers. The cross-over is obtained by special shaping of conductor. This kind of transposed conductor is called ROEBEL BAR.

Another type of transposition provides 180-degree twist of the strand bundle in the end turn position of the winding where the increase width dimensions can be tolerated.


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The group of strands can be insulated from adjacent groups through out the coils inclined in transposition.

END COVERS:

End covers of fabricated steel or aluminium alloy castings are employed with guide vanes on inner side for ensuring uniform distribution of cooling air or gas.

In case 1500 rpm generators,end windings are first enclosed in glass epoxy moulded end covers and an overall steel outer cover is provided over the stator.

Stator core is made up of following components:-

End Plates………………………(2 no’s/generator)

End Packets

Ventilation stampings

Insulating stampings……….(b/w the cores)

Insulating studs………………(b/w the sheets)

Core bars

Baskets…………………………..(3 no’s/ generator)

Compressing ring


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Hydraulic press

Heating units

Pressing fixtures.

Stator cores are never made up of a single iron piece instead of they are made up of laminated sheets in order to reduce the EDDY CURRENT LOSSES.

Components used for the manufacturing of stator:-

1.) Gas buffer ring :- it is a large circular shape ring made by aluminum . It is fixed inside the stator. It is used to protect the coolant in it like hydrogen and helium. When the stator works the coolant comes out so to prevent this we use the buffer ring. Its main use is to cover the stator's body. It another use is that it fixes the ends of rotor winding.

Diagram: -

2.) Insert cover :- it is used to cover the stator's parts


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so that the gas present outside the stator cannot come inside the stator and the gas present inside the stator cannot come out. It is made up of aluminum. It is manufactured in pieces as shown in the figure. When 4 pieces of insert cover plate are joined then it makes a ring shape which is known as the insert cover or the insert ring. Diagram:-

3.) Turbo-Generator Stator Body :- The working of the turbo-stator generator is same as the other stators.

Diagram:-


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4.) End shield :- It is fixed to both the sides of the stator. Two end shields are connected to both the sides of stator. The holes are joined to each other by the help of nuts and bolts. It supports the stator's parts.

Diagram:-

5.) Clamping ring :- it is fixed at the stator body . it works as a spring in the stator. And the vibrations are controlled by it. It works as a suspension in the stator to perform the desire vibration as shown in the figure.

Diagram:-

6.) Fli wheel housing :- it is used to cover the stator body after the winding is fixed. It is used vertically in the stator. Its shape is that of a wheel. It is made up of iron.

Diagram:-


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Stator winding


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Assembly of Stator-core & Stator frame


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ROTOR

Rotor of turbo-generators


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CONSTRUTIONAL FEATURE:-

In Turbo Genertator there are two types of rotor designs:

Forged solid rotor

Laminated rotor

The main function of the rotor is that the rotor acts like Electromagnet by taking currents from the excitation systems. It is coupled to Turbine rotor to take the driving torque and thus produce a flux, which leads to the generation of currents. The changes in the flux produced by the rotor windings

induce voltage in the stator winding. It also has top withstand high power torque produced by the by the turbine and the backward torque produced due to the generator current. For large capacity generator is forged from a single piece ingot of steel alloyed with nickel, chromium, manganese and vanadium, heated to obtain the required mechanical and magnetic properties. The forgings must be homogeneous and flawless. The forging undergoes a series of stringent quality control test like metallographic, ultrasonic and heat stability etc. before it is accepted for further processing.

The rotor forging is planed and milled to form the teeth. About 2/3 of the rotor pole-pitch is slotted, leaving 1/3 unslotted (or slotted to lesser depth) for the pole centre. Longitudinal slots are machined radially in the rotor body to accommodate field winding. The slot pitch is selected in such a way that two solid poles displaced by 180 degree are obtained.


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Rotor slots

Additional dummy slots and sub-slots (under the main slots) provide adequate passage for the cooling air for rotor body and winding.

Rotor shaft is subjected to assembly section in dust proof enclosure. In this section we mount insulation, winding damper, connecting lead and retaining ring on the shaft with great accuracy. They are described here:

ROTOR SHAFT:

Details of shaft are given here

Length :- 9 m (app)

Diameter :- 1 m (app)

Material :- Alloy steel


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No. of poles :- 2

ROTOR WINDING:

Rotor coils are of multi-turn type, manufactured from semi-hard, silver alloyed copper of rectangular cross-section, with ventilation holes punched in it. Two individual conductors are placed one over the other are bent to obtain half turns. Further these half turns are brazed in series to form coil on the rotor model.

The solid poles are provided with additional slots used to accommodate finger of damper segment acting as damper winding.

INSULATION:

The individual turns are insulated from each other by large layer of glass pregnated strips on turn of copper and backed under pressure and temperature to give a monolithic interturn insulation. Overall winding insulation with respect to rotor body is provided by epoxy glass laminated troughs located in the slots.

At bottom of slot D-shaped liners are put to provide a plane-seating surface for conductors and to facilitate easy flow gas from one side to another. These liners are made from moulding material. The overhang portion are separated by glass laminated blocks called liners. The overhang winding are insulated from retaining ring segment having L-shaped and made of glass cloth impregnated by epoxy resin.


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ROTOR WEDGE:

The rotor slot wedges are used to protect the windings against the effect of centrifugal force. This slot wedges are made of an alloy featuring high strength and good electrical conductivity. They extend below the shrink seals of the retaining rings. They

are short-circuited under retaining for short circuiting induced shaft current. The slot closing wedge laminate which also have drilled holes. Thus the cooling air entering sub-slots radially comes out through these holes, ensuring effective cooling of rotor.

RETURNING RING:

The overhang portion of field winding is held by non-magnetic steel forging of retaining ring against centrifugal force. They are shrink fitted to the end of the rotor body barrel at one end, while the other side of retaining ring does not make contact with the shaft.

The centering rings are shrink fitted at the free end of retaining ring that serves to reinforce the retaining ring, securing end winding in axial direction at the same time.

The returning rings are made of non magnetic alloy steel forging with very high mechanical properties. This material is stress and corrosion resistant. The material is worked to reduce stray losses.

FANS:

Two axial fans located at the two ends of rotor shaft circulate the cooling in the generator. The blades are aluminum


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alloy die forgings. Threading is made in the fan blades roots such that they can be fixed into the threaded pools provided on the rotor. The fans circulate required quantity of cooling air at required head to overcome the pressure drop inside the generator.

EXCITATION LEAD:

The excitation lead provides electrical connections between rotor windings and output from brushless exciter. A flexible copper connector electrically joins the rotor windings to the excitation leads through radial current carrying studs. The radial stud is screwed to field lead in the shaft bore through a hole drilled radially in the shaft. The field leads run in the axial direction from the radial stud to the end of the rotor. They consist of two semi circular conductors insulated from each other by an intermediate plate and from the shaft by tube. The ends are suitably drilled to accommodate multi contact pins to receive output from the exciter.

BEARINGS:

Bearings play an important role in the operation of the machines. The bearing should not develop any defect even continuous operation for years together and also should not show wear-outs. In the case of turbo-generators plain-bearings with rings for oil circulation are used. Large turbo generators have bearings lubricated by oil circulating under pressure. The oil flowing out of the bearings cooled by means of water coolers and after cooling the same oil is pumped in. The bearing must be oil-tight as any leakage of oil from the bearing has the


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possibility of entering the machine, spoiling its insulation and resulting in shut-down.

To prevent damage due to shaft currents, bearings and oil pipings on either side of the non-drive end bearings are insulated from the foundation frame. For facilitating and monitoring the healthiness of bearing insulation, split insulation is provided.

SLIP-RINGS:

Excitation current to the rotor winding is supplied through 2 shrunk fit slip rings located beyond the main pedestal bearing on the exciter side. These are made of steel, adequately insulated from rotor body using mica strips insulation. Actual excitation leads from slip rings to the winding are carried with in the shaft bore and are provided with adequate insulation of class'B' type. For better heat dissipation the surface of slip rings has been helical machined. Self-ventilation arrangement has been for slip rings.

BRUSH GEAR:

In order to effectively supply the excitation current to the rotor winding, the brush gears are robustly designed with radial type brush holders. Brushes of natural graphite composition with low co-efficient of friction and self lubricating properties are used, which ensure smooth and trouble free operation. The brush gear free operation. The brush gear is


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either fixed on to the end of the stator end covers or bearing or is mounted separately on a pedestal.

Depending on the requirements, generators are provided with on-load brush changing gears. The advantages of this arrangement are:

Constant spring tension over the entire brush wear.

Brush change-over without stopping the machine.

Safety of the personnel due to provision of insulated handle.

Different parts of rotor of TG

SPECIAL FEATURES OF ROTOR

Rotor slots are made tapped to increase mechanical strength of teeth part.


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Windings are connected in particular fashion to create opposite poles which is shown here.

In order to minimize windage losses, which tend to be high at turbine, the surface of the finished rotor are made as smooth as possible.

Slots Description

Main slots

38 degrees from centre line, then each slots are at 8 degrees apart.

Between two slots, distances are:

a) 50.9mm at front.

b) 36.7mm at rear.

c) 196.5mm depth.

Damper slots

22 deg. from centre line.

Cross pole slots

Breadth 10.5mm, Depth 110mm.

Rotor Winding Connections

2 pole, 3000rpm, 50Hz.

Total slots=(14+14=28).

11 conductors in each slot.

F type insulation is used in b/w two coils of 2mm thickness.

Diametrically opp. slots are connected in series.


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Holes are provided for passing hydrogen.

Liners are placed over the slot portion wdg. To keep them intact at one position.

Returning rings are provided in the overhead portion for keeping the wdg. intact at one position.

Assembly of Turbo-Generators


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Assembly of TG


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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. This AC is converted into DC and than fed to turbo generator via c.c. bolts. For rectification purpose we have got RC block and diode circuit.

The most beautiful feature of this type of exciter is that it automatically decides the magnitude of current to be circulated in rotor circuit. This happens with the help of A.V.R. system, which means automatic voltage regulator. A feedback path is given to this system which compares theoretical value to predetermined and then it sends the current to rotor as per requirement.


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Different parts of exciters:-

Exciters consist of the following parts:-

AVR (automatic voltage regulator) :-It controls the output voltage and converts the ac into dc.

Blowers: - This all acts as a cooler.

Sliprings: - This is the most important part of the exciter system.

It detects any kind of the fault and stops the panel from further working.

Armature

Resin bandage:- resin bandage are covered over the armature at 200kg/cm pressure( IMPORTED FROM ITALY ).

After that armature is kept at the oven for curing at 120 degree c for 24 hours.

Over the intermediate ring the DIODE WHEEL and the HEAT SHRINK are placed


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Installation of Pilot Exciter rotor


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Removal of Slip Ring Fan by heating it with Propane burners

Removal of Exciter Coupling for Slip Ring exchange


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CHAPTER 8: MICALASTIC IMPREGNATION

Definition

Impregnation is process by which the electrical conductivity of any electrical machinery can be increased at around 100 times.

High-quality mica, carefully selected epoxy resins and a well-matched vacuum/pressure impregnation process determine the characteristics of the MICALASTIC insulation for large turbine-generators. Logical development and process manufacturing quality control have led to an insulation system of high quality and operating reliability.

The first winding of turbine-generator being impregnated and cured under vacuum with solvent-free synthetic resin in 1958 was designed for 10.5 kV rated voltage. Ever since, Siemens AG and Kraftwerk Union AG have used this type of insulation for all direct-cooled windings and also for an increasing number of indirect-cooled windings.

At present, 240 turbine-generators with a total of more than 115,000 MVA output have been built. Since 1960, this insulation system has been registered for Siemens AG under the trade name MICALASTIC. The stator windings of the largest, single-shaft generators to date, rated 1560 MVA, 27 kV, has been built with MICALASTIC insulation.

Micalastic impregnation uses VPI (VAPOUR PRESSURE IMPREGNATION) technology. High-quality mica, carefully selected epoxy resins and a well-matched vacuum/pressure impregnation process determine the characteristics of the MICALASTIC insulation for large turbine-generators. Logical development and process manufacturing quality control have led to an insulation system of high quality and operating reliability.


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The first winding of a turbine-generator being

impregnated and cured under vacuum with solvent-free synthetic resin in 1958 was designed for 10.5 kV rated voltage. Ever since, Siemens AG and Kraftwerk Union AG have used this type of insulation for all direct-cooled windings and also for an increasing number of indirect-cooled windings. At present, 240 turbine-generators with a total of more than 115,000 MVA output have been built. Since 1960, this insulation system has been registered for Siemens AG under the trade name MICALASTIC. The stator windings of the largest, single-shaft generators to date, rated 1560 MVA, 27 kV, has been built with MICALASTIC insulation.

Impregnation tank of BHEL

Height = 4.5mtr Length = 9.0mtr


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Resin tank

There are 5 numbers of resin tank with a storage capacity of 12000 litres per tank.

Therefore a total storage capacity of resins are 5 * 12,000 = 60,000litres.

These tanks are explosion proof , software controlled with rotator facility.


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Advantages:-

Rotor withdrawal during initial inspection is not required.

Possibilities of loosening and fastening of core is eliminated.

Big savings in spare cost.

Additional revenue of apparatus are equal to 3750 lakhs.

Improved heat transfer during operation.

Manufacturing time reduces by 4.5 months.

Mechanically firm binding between core and winding components are better suited against thermal stress.

Thermal conductivity of VPI insulation is equal to 2.2 to 2.5 mw/cm oc, against that of air = 0.251mw/cm 0c.


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CHAPTER 09: TESTING OF TURBO -GENERATORS

There are many electrical as well as mechanical tests carried over the turbo generators:-

Mechanical Tests Vibration test

Temperature test

Electrical Tests Open circuit tests

Short circuit test

Milivolt test

High voltage test

Partial discharge test

tan δ test

TEST PROCEDURE FOR HIGH VOLTAGE TEST ON STATOR WINDINGS OF TURBO GENERATOR:

SCOPE:

This procedure covers the high voltage test on stator winding.

PURPOSE:


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This test is conducted to check whether the insulation is properly placed or not. The insulation placed over the windings should be in such a way that they make half overlaps with the next wrapping of the tape.

THIS TEST IS EXCLUSIVELY CONDUCTED TO TEST THE HEALTHINESS OF INSULATION OF WINDINGS.

TEST PROCEDURE FOR HIGH VOLTAGE ON ROTOR WINDING OF TURBO GENERATORS :

SCOPE:

This procedure covers the high voltage test on rotor winding.

PURPOSE:

This test is conducted to check whether the insulation is properly placed or not.

TEST PROCEDURE FOR MEASUREMENT OF DC RESISTANCE OF STATOR AND ROTOR WINDINGS OF TURBO GENERATORS:

SCOPE:

This procedure covers the measurement of dc resistance of stator windings.


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PURPOSE:

This test is conducted to measure the resistance content present in the conducting material of stator and rotor.

TEST PROCEDURE FOR MEASURMENT OF IMPEDANCE OF ROTOR WINDING WITH 5O AND 500 Hz SUPPLY:

SCOPE:

This procedure covers the measurement of impedance of Rotor winding 50 and 500 Hz source.

TEST EQUIPMENT:

50Hz (Power frequency)/500Hz AC source.

AC voltmeter (0-30,75,150V and 0-150,300,450V)

AC Ammeter (0-5 A)

Multimeter

Current transformer (50/5 A or 100/5 A)

Connecting leads

CALCULATIONS:


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Z = V/I OHM

Where Z = Impedance in ohms

V = Voltage in Volts

I = Current in Amperes

With 50 Hz, this test is done in following conditions:

Rotor outside the stator at standstill.

Rotor inside the stator at standstill.

Rotor inside the stator at speeds 1/3, 2/3, 3/3 of rated speed.

500 Hz source is used only during process testing.

ACCEPTANCE LIMITS:

IMPEDANCE WITH 50 Hz:

As the impedance of the rotor winding depends on physical geometry of the rotor, it is not possible to fix at particular value for acceptance. But a peculiar characteristic that impedance increase with increase of voltage can be assured. Value of increase is less in cylindrical rotors than in salient pole rotor.

IMPEDANCE WITH 500 Hz:


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This measurement is only to observe the voltage drop across each pole. Difference in voltage drops upto 2V is acceptable across two identical poles.

TEST PROCEDURE FOR MEASUREMENT OF LEAKAGE REACTANCE OF TURBO GENERATOR STATOR WINDING:

SCOPE:

This procedure covers the leakage reactance measurement of stator winding after completion of winding.

PURPOSE:

To determine total leakage reactance(xa)

To determine bore leakage reactance(xb)

To compute potier reactance(xd)


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TEST PROCEDURE FOR CAPACITANCE AND TAN$ MEASUREMENT OF STATOR WINDINGS:

SCOPE:

This procedure covers the measurement of capacitance per phase with respect to ground and tan δ of the stator winding.

PURPOSE:

To generate reference value for comparison in future at site.

PRINCIPLE:

The stator windings have two values of capacitances

Cg : Capacitance with respect to ground called ground

capacitance

Cm: Capacitance with respect to other windings called

mutual capacitance.

The measurement of capacitance is done using Schering Bridge and a Standard capacitor


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CHAPTER 10: CONCLUSION

The second phase of training has proved to be quite faithful. It proved an opportunity for encounter with such huge machines like turbo-generator hydro generator brushless exciters etc.

The architecture of B.H.E. L., the way various units are linked and the way working of whole plant is controlled make the students realize that Engineering is not just structural description but greater part is planning and management. It provides an opportunity to learn tech. Used at proper place and time can save a lot of labour. But there are few factors that require special mention. Training is not carried in true spirit. It is recommended that there should be projectors especially for trainees where presence of authorities is ensured. However, training has proved to be satisfactory. It has allowed us an opportunity to get an exposure of the practical implementation of theoretical fundamentals.


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Chapter 11:- Bibliography

1. Manual provided by Bharat Heavy Electricals Limited (BHEL), HARIDWAR.

2. Notes of BHEL.

3. http://www.power.alstom.com/home/new_plants/ steam/products/turbogenerators/_files/file_41105_83062.jpg

4. http://www.power.alstom.com/home/new_plants/gas/ products/turbogenerators/topair/_files/file_40430_236902.jpg

5. http://upload.wikimedia.org/wikipedia/commons/ 1/1a/Entrance_to_BHEL_Ranipur,_Haridwar_plant.JPG

6. http://www.bhelhwr.co.in/bhelweb/index.jsp

7. http://www.converteam.com/converteam/1/image/ Services/Service/Parts_Service_Minneapolis/Products/Brushless_Exciters.jpg


J.N.U, Jaipur

http://www.converteam.com/converteam/1/image/Services/Service/Parts_Service_Minneapolis/Products/Brushless_Exciters.jpg



http://www.bhelhwr.co.in/bhelweb/index.jsp

http://upload.wikimedia.org/wikipedia/commons/1/1a/Entrance_to_BHEL_Ranipur,_Haridwar_plant.JPG

http://upload.wikimedia.org/wikipedia/commons/1/1a/Entrance_to_BHEL_Ranipur,_Haridwar_plant.JPG

http://www.power.alstom.com/home/new_plants/gas/products/turbogenerators/topair/_files/file_40430_236902.jpg



http://www.power.alstom.com/home/new_plants/steam/products/turbogenerators/_files/file_41105_83062.jpg



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8. Dr. P S Bhimbra book.


J.N.U, Jaipur

anshul bhel

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