BHEL Internship Report BLOCK-1

April 2, 2018 | Author: Uzair Afridi | Category: Electric Generator, Rectifier, Insulator (Electricity), Mechanical Fan, Power (Physics)


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BHARAT HEAVY ELECTRICALS LIMITEDHARIDWAR VOCATIONAL TRAINING REPORT Submitted toMr.Satish Kumar Singh (Sr. Engineer, Electrical Machines, Planning) Submitted byMohd Uzair Khan 1312101085 B.Tech (EE) [1] ACKNOWLEDGEMENT I would like to express my gratitude for the people who were part of this Project Report, directly or indirectly people who gave unending support right from the stage the idea was conceived. In particular I would like to thanks to Mr.Satish Kumar Singh (Sr. Engineer, Electrical Machines, Planning) in BHEL, Haridwar for providing me with an opportunity to undergo training under his able guidance. I whole hearted appreciate the atmosphere provided to me by the staffs of Electrical Engineering. The data has been collected at primary source through discussions with officers of different sections. For this nice gesture on their part, I shall ever remain obliged to them. [2] CONTENT 1. Overview of BHEL 2. Different Blocks at HEEP 3. Block-1 Electrical Machines 4. Turbo Generator 5. Constructional features of Stator Body 6. Constructional features of Stator core 7. Constructional features of stator Winding 8. Constructional features of Rotor 9. Cooling System 10. Excitation System 11.Electrical generator Protection 12. CIM (Block-4) 13. ACM(Block-4) [3] [4] . BHEL business operations cater to core sectors of the Indian Economy like  Power  Industry  Transportation  Transmission etc. BHEL’s vision is to become world-class engineering enterprise. The high level of quality & reliability of its products is due to the emphasis on design. In 1976. making profits continuously since 1971-1972. BHEL is today the largest Engineering Enterprise of its kind in India with excellent track record of performance. generators.OVERVIEW OF BHEL The first plant of which is today known as BHEL was established nearly 50 years ago at Bhopal & was the genesis of the Heavy Equipment industry in India. turbines. systems and services efficiently and at competitive prices. Heavy Electrical Equipment Plant is equipped to produce Steam and Hydro Turbines with matching Generators. together with technologies developed in its own R&D centers. motors etc. The construction of the plant commenced in 1962 and the production of equipment was initiated in early 1967. The Heavy Electrical Equipment Plant was set up in technical collaboration with (Union of Soviet Socialist Republics) USSR. The company is striving to give shape to its aspirations and fulfill the expectations of the country to become a global player. engineering and manufacturing to international standards by acquiring and adapting some of the best technologies from leading companies in the world. manufacture. committed to enhancing stakeholder value. The BHEL plants in Haridwar have earned the ISO-9001 AND 9002 certificates for its high quality and maintenance. BHEL has 14 units spread all over India manufacturing boilers. BHEL entered into a collaboration agreement with West Germany for design. Industrial Manufacturing Thermal sets up to 1000 MW capacity. erection and Commissioning of large size steam turbines and turbo generators of unit rating up to 1000MW. These two units have also earned the ISO-14001 certificates. Besides 14 manufacturing divisions the company has 4 power sector regional centers. Two manufacturing plants of BHEL: Heavy Electrical Equipment Plant (HEEP) and Central Foundry Forge Plant (CFFP) employing about 10000 people. 8 service centers 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. transformers. systems and services – efficiently and at competitive prices.  Supplied over one million valves to power plants and other industries POWER SECTOR Power generation sector comprises thermal.175 MW in the country .  It possesses the technology and capability to procure thermal power generation up to 1000MW.  BHEL manufacturers 235MW nuclear sets and has also commenced production of 500MW nuclear turbine generator sets.for utilities captive and industrial users. gas.000 motors with drive control systems to power projects. hydro and nuclear power plant business . the company has commissioned a total of eleven Solar Power Plants in the Lakshadweep islands.BHEL supplied utility sets accounts to 87.38.646 MW 65% of the total installed capacity of 1. adding over 1 MW of Solar Power to the power generating capacity of the coral islands in the Arabian Sea.generation and combined cycle plants have also been introduced. fertilizers.  Supplied over 2.  BHEL has proven turnkey capabilities for executing power projects from concept to commissioning and manufactures boilers. eight service centers and 18 regional offices.000MW of power generation--.  Co. over 150 project sites. refineries. four power Sector regional centers.  Supplied Traction electrics and AC/DC locos to power over 12. [5] . steel. 25. With this. The wide network of BHEL's 14 manufacturing division. As part of India’s largest Solar Power-based Island Electrification Project in India. Bharat Heavy Electricals Limited (BHEL) has successfully commissioned two Grid-Interactive Solar Power Plants of 100 KW each in Lakshadweep.BHEL is the largest engineering and manufacturing enterprise in India in the energy related infrastructure sector today. cement plants etc. enables the Company to promptly serve its customers and provide them with suitable products. While the company contributes more than 75% of the national grid.000 kMs railway network. thermal turbine generator sets and auxiliaries up to 500MW. And this is none other than BHEL-HARIDWAR BHEL has: Installed equipment for over 90. petrochemicals.  Supplied over 25. as against nil in 1969 -70. interestingly a share of 45% comes from its single unit. aluminum.000 MVA transformer capacity and other equipment operating in transmission and distribution network up to 400 kV (AC & DC). all 700 utility sets of thermal. gas and nuclear have been placed on the company as on date. The Company has proven expertise in Plant Performance Improvement through renovation modernization and up rating of variety of power plant equipment besides specialized know how of residual life assessment. POWER TRANSMISSION AND DISTRIBUTION (T&D) BHEL offer wide-ranging products and systems for T & D applications Products. capacitor tanks. The power plant equipment manufactured by BHEL is based on contemporary technology comparable to the best in the world and is also internationally competitive. vacuum – and SF6 circuit breakers gas insulated switch gears and insulators. health diagnostics and life extension of plants. instrument transformers. shunt compensation systems (for power factor and voltage improvement) and HVDC systems (for economic transfer of bulk power). Presently a 400 kV Facts (Flexible AC Transmission System) project under execution. They manufactured include power transformers. BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines). A strong engineering base enables the Company to undertake turnkey delivery of electric substances up to 400 kV level series compensation systems (for increasing power transfer capacity of transmission lines and improving system stability and voltage regulation . hydro. series – and shunt reactor. INDUSTRY SECTOR – BHEL is a major contributor of equipment and system to important industries like –  Cement  Petrochemicals  Fertilizers  Steel papers  Refineries  Mining and telecommunication [6] . In.Custom made hydro sets of Francis. peloton and Kaplan types for different head discharge combination are also engineering and manufactured by BHEL. dry type transformers. TRANSPORTATION BHEL is involved in the development design. both for mainline and shunting duly applications.BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines). engineering. seamless steel tubes  Heat exchangers  Process control etc. Presently a 400 kV FACTS (Flexible AC Transmission System) projects is under execution. The company also undertakes retooling and overhauling of rolling stock in the area of urban transportation systems. installation. electrical multiple units and metro cars. and maintenance and after-sales service of Rolling Stock and traction propulsion systems. BHEL manufactures traction propulsion systems for other rolling stock producers of electric locomotives. In the area of rolling stock. marketing.. Rail-cum-road vehicle etc. [7] . diesel-electric locomotives. medium and large switching system. production. overhead equipment cars.. Special well wagons. light rail systems etc. BHEL is geared up to turnkey execution of electric trolley bus systems. Besides traction propulsion systems for in-house use. The electric and diesel traction equipment on India Railways are largely powered by electrical propulsion systems produced by BHEL. diesel-electric locomotives from 350 HP to 3100 HP. valves. The range of system and equipment supplied includes: Captive power plants  High speed industrial drive turbines  Industrial boilers and auxiliaries  Waste heat recovery boilers  Gas turbine pump. TELECOMMUNICATIONBHEL also caters to telecommunication sector by way of small. BHEL is also producing rolling stock for special applications viz. BHEL is also diversifying in the area of port handing equipment and pipelines transportation systems. BHEL manufactures electric locomotives up to 5000 HP. impregnation. pneumatic hammer for forgings. test bed test stand. contact relays master control etc. packing& preservation. assembly Products: Wooden packing. gas cutting press. fabrication of pipe coolers. machining. painting Products : Large size fabricated assemblies/ components for power equipments BLOCK-3: TURBINES & AUXILIARY BLOCK Facilities: Machining. hydraulic manipulators Products: Fabricated parts of steam turbine. gas fired furnaces. shot blasting. hydro generators insulation for AC & DC motors. straightening. assembly preservation & packing. CNC deep drilling. grinding. machining & preparation of insulating components plastic molding. welding . polishing etc. drilling. CNC flame cutting. test stands/ station. micalastic impregnation etc. special tooling BLOCK-4: FEEDER BLOCK Facilities: Bar winding. hydro turbines. painting grinding. over speed balancing. Generator exciters. sheet metal work. storage tank hydro turbine parts. water box. .Cutting. cleaning & Shot blasting. motors (AC& DC) BLOCK-2: FABRICATION BLOCK Facilities: Markings. hydro turbines assemblers & Components BLOCK-6: STAMPING & DIE MANUFACTURING Facilities: Welding. insulating components for TG. spacers etc. heat treatment. painting section.DIFERENT BLOCKS AT HEEP BLOCK-1: ELECTRICAL MACHINES Facilities: Machine Shop. Products: Turbo Generator. gas turbines. babbiting. mechanical assembly. sheet metal working marching. copper profile drawing electroplating. Windings bar preparation assembling. press molding Products: Windings for turbo generators. milling. facing wax melting. armature winding. Products: Stem turbines. Shot basting. BLOCK-5: CONDENSER FABRICATION & FORGE BLOCK Facilities: Fabrication. HG & Motors control panel. broaching. assembly. [8] . turbine bladders. Contractors & Customers ENGINEERING Facilities: Design and drawings of all products [9] . oil tanks. TELECOMMUNICATION Facilities: Telephone service HYDROTURBINE LAB Facilities: 3 test beds with electronic instrumentation. ACG collers. machines. spacers etc. It consists of cavitation’s test bed for reactions turbine & hydrodynamic test bed for Impulse turbines facilities for carrying out filed test at hydro power sets Products: Testing of turbine models HRDC Facilities: Training to Employees.5 MVA 132/6. jeeps trekkers. welding. cutting. Compressors of rating 100 m2 / min-Compressed air Oxygen Plat: 3 air separation unit 4 air compressors-Oxygen gas & Nitrogen gas 132 KV substation: 2 Nose 16. one no. BLOCK-8: HEAT EXCHANGE SHOP Facilities: Drilling . tig welding Products: LP Heater ejectors glad. saw. buses.Producer gas Acetylene Plat: A fully automated plant for acetylene generation & filling in cylinderAcetylene gas Compressor House: 4 No. 20 MVA & one no. fire tenders trucks etc. grinding . mini buses motorcycles.turning. steam cooler oil coolers. VTs Apprentices. packing Wooden packing.BLOCK-7: CARPENTRY SHOP Facilities: Wood Cutting. Products: Wooden packing. 12. bearing covers SERVICE PLAT Facilities: TPS: Power generation equipment & auxiliaries plat capacity 12 MWPower generation PGP Plat: Boiler Type gas generators.7 MVA/ 11 KV.6 KV transformer & other allied equipment-Power supply MOTOR TRANSPORT Facilities: A fleet of vehicles comprising of cars. spacers etc. Karnataka State Pollution Control Board. Department of Science and Technology. The laboratories of Pollution Control Research Institute have been recognized by Ministry of Environment and Forests. Most modern facilities for monitoring and analysis in the area of air. Govt. UP State Pollution control Board. PCRI provides consultancy services related to pragmatic approaches / methods to maintain pollution within permissible limits. ESPL SM – 32 minicomputer Nexus – 3500 CAE work station. It also has workshop and other support services. It has full-fledged computer facilities for prediction and forecasting pollution impact. water. noise and solid waste are available at the Institute. Govt. Madhya Pradesh Pradushan Nivaran Mandal. Haryana State Pollution Control Board. Punjab State Council for Technology. CPL (CENTRAL PLANT LAB) Facilities: Testing Lab for new materials & sample components POLLUTION CONTROL RESEARCH INSTITUTE To provide directional thrust to environmental control / protection activities. a Pollution Control Research Institute has been set up by BHEL at HEEP. of India.COMPUTER CENTRES Facilities: ICIM’s series 39 DX level 270-320 computer system HCL magnum mini compute system . PCs etc. of India. The Institute is concentrating on research and development activities related to environment protection against pollution emanating from industries. The main objective of the Institute is to develop technologies for pollution control in the areas of air. Bihar State Pollution Control Board. [10] . Haridwar with the assistance of United Nations Development Programme (UNDP). The other objectives include development of methods for recovery and recycling of industrial wastes. water noise and solid waste to obviate unintended side effects of economic growth. T.G. There is a special test bed area for testing of T. Testing facilities for Turbo generator are available in Bay-II. 4. TEST BED. 3.T.BLOCK-1: ELECTRICAL MACHINES 1. T/G STATOR WINDING. 2. L. There are also a number of self-propelled electrically driven transfer trolleys for the inter-bay movement of components/assemblies. Block-I is designed to manufacture Turbo Generators. L. The block consists of 4 bays.G ROTOR WINDING. TOTAL IMPREGNATION TECHNIQUE. BAY-1 ROTOR SHAFT MACHINING ROTOR SHAFT SLOTTING ROTOR WINDING OVER SPEED AND BALANCING TUNNEL LARGE SIZE T.S. EXCITER. T/G ROTOR WINDING. T/G IRON ASSEMBLY.G BAY-2 EXCITER SHAFT MACHINEING STATOR BODY MACINING STATOR WINDING TOTAL IMPREGNATION TEST BED BAY-3 ROTOR SUPPORT BEARING COOLING FANS MACHINING SHAFT SEAL BODY DC MOTOR WINDING BAY-4 ARRANGMENT & OTHER PARTS BASIC TURBO GENERATOR DEPARTMENTS:             MACHINE SHOP.G MAIN ASSEMBLY. T/G MAIN ASSEMBLY. 5. L. H/G IRON ASSEMBLY. Bay-II (36*360 meters) and Bay-III and Bay-IV (Of size 24*360 meters each).T.G STATOR WINDING.S. [11] .Bay-I (36*482 meters).S. of capacity of 500 MW Unit sizes. For handling and transporting the various components over-head crane facilities are available. depending upon the products manufactured in each Bay. whereas slot portion is pressed manually with the help of rotor wedges. [12] . block—VI and coils. The boring and facing of stators are done on CNC horizontal boring machine using a rotary table. these are connected at the ends. Stator winding is done by placing stator on rotating installation. insulating details and sheet metal components are received from coils and insulation manufacture and apparatus and control gear box (block — IV).III and Bay . with the help of ferrule and then soldered by resistance soldering. bars.I & Bay. The pressing of overhang portionis carried out on special ring type hydraulic press. After laying of lower and upper bars. The centering of core bar is done very precisely. are carried out to make generators ready for testing. Turbo Generators       Making of blanks is done for checking the availability of machining allowances.IV. VI. General assembly of Turbo Generators is done in the test bed. Prior to test run the complete generator is hydraulically tested for leakages. Punching are assembled manually and cores are heated and pressed in number of stages depending on the core length. bearings etc. The dynamic balancing of rotors is carried out on the over speed balancing installation. 500 MW Turbo Generators are balanced in vacuum balancing tunnel.II and other small components in Bay . Coils are wedged with special press after laying and curing. while castings and forgings are received from sister unit CFFP and other indigenous and foreign sources for Turbo Generators.MANUFACTURING PROCESS Fabricated components are received in respective machine sections from Fabrication blocks (Block — II. V. In case of large size Turbo Generators core bars are welded to stator frame with the help of telescopic centering device. Turbo Generators are tested as per standard practices and customer requirements. VIII). Rotor winding assembly is carried out on special installation where coils are assembled in rotor slots. Stampings are received from stampings manufacture block. Rotor is inserted in the stator and assembly of end shields. Machining of the major components is carried out in Bay . The shaft is turned on lathe having swift 2500 mm and the rotor slots are milled on a special rotor slot milling machines. diesel generators have a lower power density and hence.TURBO GENERATOR A turbo generator is the combination of a turbine directly connected to an electric generator for the generation of electric power.  As the above rotating system put into operation.  This supply is given to exciter field. The magnitude of emf is given by following formula: E = 4.  The voltage is rectified by Thyristor circuit to DC.  The main AC voltage of generator is finally available to turbo generator stator. the PMC produces AC voltage. For base loads diesel generators are usually preferred.  The non-drive side of rotor is equipped with a rotating side of armature which produces AC voltage. This induces an electromagnetic EMF in the stator winding. require more space. WORKING PRICIPLE OF TURBO GENERATOR  The generator rotor is driven by prime mover and on driver side gas/ diesel/ steam hydro depending on the equipment to which it is meant for. The rotor houses the field winding. The rectified DC supply out of exciter is supplied to turbo generator rotor winding either through brushes or central which will be directly connected to turbo generator. on the other hand. [13] . DC Commutator machines or brushes exciter. This depends on the type of exciter viz. Stator houses the armature winding.44* ø *ƒ*N volt. since they offer better fuel efficiency. Large steam turbo generators provide the majority of the world's electricity and are also used by steam-powered turboelectric ships .it consist generally of a stationery part called Stator and a rotating part called Rotor. but. This field is also controlled by taking feedback from main generator terminal voltage. When the rotor rotates.Smaller turbo-generators with gas turbines are often used as auxiliary power units. DC voltage is applied to field winding through the slip rings. Commutator / rotating diode wheel depending upon the type of exciter. to control exciter field variation by automatic voltage regulator.  The rear end of above exciter armature is mounted with a permanent magnet generator rotor. This is rectified to DC by using a DC. the lines of magnetic flux cut through the winding. Vertical hydrogen coolers Salient technical data      Rated output : 588 MVA .LARGE SIZE TURBO GENERATOR (LSTG) These types of generators are those which have taken steam turbine. Direct hydrogen cooling for rotor. 500 MW Turbo generators at a glance 2-Pole machine with the following features:      Direct cooling of stator winding with water. 500 MW Terminal voltage : 21 KV Rated stator current : 16 KA Rated frequency : 50 Hz Rated power factor : 0.55% [14] . Brushless Excitation system.85 Lag Efficiency : 98. Their prime mover and current is supplied by exciter system. Micalastic insulation system Spring mounted core housing for effective transmission of vibrations. Main types are:      THRI TARITHDI THDD THDF THFF Basic terms are:T = turbo generator A = air cooled H = hydrogen cooled R = radial cooling with gas D = direct axial cooling with gas F = direct axial cooling with water I = indirect cooling. testing at operational speed and for over speeding. Stator Frame Stator body is a totally enclosed gas tight fabricated structure made up of high quality mild steel and austenitic steel.83Mx4.  Other major facilities are as followsOver speed Balancing vacuum tunnel – For balancing and over speeding large flexible Turbo generators rotors in vacuum for ratings up to 1.The arrangement. The wagon has been used successfully for transporting one generator -from Calcutta Port to Singrauli STPP. an over speed and balancing tunnel has been constructed indigenously. This facility is suitable for all types of rigid and flexible rotors and also high speed rotors for low and high speed balancing. Generator transportation   Transport through300 Tons 24-Axle carrier beam railway wagon specially designed indigenously and manufactured at Haridwar.000 MW. CONSTRUCTIONAL FEATURES OF STATOR BODY 1. The natural frequency of the stator body is well away from any [15] .02M  Rotor dimensions : 1.15Mdia x 12. Haridwar is one of the best equipped and most modern plants of its kind in the world today. It caters to the most advanced requirement of testing by employing on-line computer for data analysis.11 M length  Total weight of turbo generator : 428 Tons Unique installationsHeavy Electrical Equipment Plant. location and shape of inner walls is determined by the cooling circuit for the flow of the gas and required mechanical strength and stiffness. Some of the unique manufacturing and testing facilities in the plant are: TG Test BedNew LSTG [Large Scale Turbo Generator] Test Bed has been put up with indigenous know-how in record time for testing Turbo generators of ratings 500MW and above up to 1000 MW.IMx4. It is suitably ribbed with annular rings in inner walls to ensure high rigidity and strength .Important dimensions & weights Heaviest lift of generator stator : 255 Tons  Rotor weight : 68 Tons  Overall stator dimensions [LxBxH] : 8. Steel [16] . inside the stator body. Core is stacked with lamination segments. which might arise on account of hydrogen air mixture explosion. Pipe Connection To attain a good aesthetic look. Stampings are hydraulically compressed during the stacking procedure at different stages. a perforated manifold is provided at the top inside the stator body. This material eliminates stray losses due to eddy currents. From sidewall these are connected to gas coolers by the means of eight U-tubes outside the stator body. Complete stator body is then subjected to gas tightness test by filling in compressed air. Segments are stamped out with accurately finished die from the sheets of cold rolled high quality silicon steel. Core It consists of thin laminations. The terminal box is a welded construction of (nonmagnetic) austenitic steel plates. Stampings are held in a position by 20 core bars having dovetail section. which emanates from bottom and emerges out of the sidewalls. Terminal Box The bearings and end of three phases of stator winding are brought out to the slip-ring end of the stator body through 9 terminals brushing in the terminal box. Before insulation on with varnish each segment is carefully debarred. CONSTRUCTIONAL FEATURES STATOR CORE 1. Insulating paper pressboards are also put between the layer of stamping to provide additional insulation and to localize short circuit. the water connection to gas cooler is done by routing stainless steel pipes. it is subjected to a hydraulic pressure of 8 kg/cm for 30 minutes for ensuring that it will be capable of withstanding all expansion pressure. Each lamination made of number of individual segments. Inner and sidewalls are suitably blanked to house for longitudinal hydrogen gas coolers inside the stator body. Between two packets one layer of ventilating segments is provided. which may results in excessive heating.of exiting frequencies. These stainless steel pipes serve as inlet and outlet for gas coolers. 4. 2. 3. Testing Of Stator Body On completion of manufacture of stator body. Segments are assembled in an interleaved manner from layer to layer for uniform permeability. For filling the generator with hydrogen. General The stator has a three phase. The ring screens the flux by short-circuiting. The slot lower bars and slot upper are displaced from each other by one winding pitch and connected together by bus bars inside the stator frame in conformity with the connection diagram. Core SuspensionThe elastic suspension of core consist of longitudinal bar type spring called core bars. CONSTRUCTIONAL FEATURES OF STATOR WINDING 1. These are made up of spring steel having a rectangular cross section and dove-tail cut at tap. To ensure that core losses are within limits and there are no hot spots present in the core. Alternate arrangement hollow and solid conductors ensure an optimum solution for increasing current and to reduce losses. To avoid-heating of press ring due to end leakage flow two rings made of copper sheet are used on flux shield. 2. 2. A separator insulates the individual layers from each other. double layer. Thus offering a hold point for stamping core bars have longitudinal slits which acts as inertial slots and help in damping the vibrations. The pressure of the pressure ring is transmitted to stator core stamping through press fringes of non-magnetic steel and duralumin placed adjacent to press ring. Conductor ConstructionEach bar consists of solid as well as hollow conductor with cooling water passing through the latter. The conductors of small rectangular cross section are provided with glass lapped strand insulation. The core bars are designed to maintain the movement of stator core with in satisfactory limits. similar type of dovetail is also stamped on to stamping and fit into that of core bar dovetail. The pressed core is held in pressed condition by means of two massive non-magnetic steel castings of press ring. Each slots accommodated two bars. short pitched and bar type of windings having two parallel paths. The core loss test is done after completion of core assembly. Twenty core bars are welded to inner walls of stator body with help of brackets.spacers are spot welded on stamping. The press ring is bolted to the ends of core bars. The transposition provides for mutual neutralization of voltage induced in the individual strands due to the slots [17] . These 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. To monitor the formation of hot spots resistance transducer are placed along the bottom of slots. The bar insulation is cured in an electrically heated process and thus epoxy resin fill all voids and eliminate air inclusions. The various test for manufacture the bar is performed which are as follows—  Inter turn insulation test on stuck after consolidation to ensure absence of inter short.cross field and end winding field. Bar insulation is done with epoxy mica thermosetting insulation. 4.  Leakage test by means of air pressure is performed to ensure gas tightness of all joints. This type of insulation is more reliable for high voltage. 3. This insulation is void free and possess better mechanical properties. Corona PreventionTo prevent corona discharges between insulation and wall of slots. Driving in semi conducting filler strips compensates any manufacturing tolerances. a layer of glass tape is wrapped over the complete stack. Laying Of Stator Winding The stator winding is placed in open rectangular slots of the stator core.  Dielectric loss factor measurement to establish void free insulation. the insulation in slot portion is coated with semiconductor varnish. This is applied continuously and half overlapped to the slot portion. Method of Insulation Bar is tapped with several layers of thermosetting epoxy tape. A semi conducting spacer is placed in bottom of slots to avoid any damage to bar due to any projection. This insulation shows only a small increase in dielectric dissipation factor with increasing test voltage. The tapped bar is then pressed and cured in electrical heated press mould for certain fixed temperature and time. The voltage of machine determines the thickness of insulation. After laying top [18] . 5. The current flowing through the conductor is uniformly distributed over the entire bar cross section reduced.  High voltage to prove soundness of insulation. which are uniformly distributed on the circumference.  Each bar is subjected to hydraulic test to ensure the strength of all joints  Flow test is performed on each bar to ensure that there is no reduction in cross section area of the ducts of the hollow conductor. To ensure that strands are firmly bonded together and give dimensionally stability in slot portion. Approximately 60 % of the rotor body circumference is with longitudinal slots. Brazing the two lugs properly makes connection. Bus bars are connected to bring out the three phases and six neutrals. 6. slot wedges are inserted. the bars are arranged close to each other.bar. Rotor Shaft — The rotor shaft is a single piece solid forging manufactured from a vacuum casting. Ending Winding In the end winding. Following tests are done: (A) Mechanical test      Chemical analysis Magnetic permeability test Micro structure analysis Ultrasonic examination Boroscope examination [19] . The prepag material is also placed between the brackets and binding rings. The shaft and body are forged integral to each other by drop forging process. high strength glass texolite spacers are put to have proper tightness. The rotor shaft is a long forging measuring more than 9m inlength and slightly more than one meter in diameter. 4. Bus bars are also hollow from inside. CONSTRUCTIONAL FEATURES OF ROTOR The rotor comprises of following component: 1. Rotor shaft Rotor winding Rotor wedges and other locating parts for winding Retaining ring Fans Field lead connections 1. molybdenum. Any gaps due to design or manufacturing considerations are fitted with curable prepag with spacer in between. In between top and bottom bars. spacers are also put. nickel and vanadium. 5. 3. Both are water-cooled. Lower and upper layers are fixed with epoxy glass ring made in segment and flexible spacer put in between two layers. Below slots wedges. The main constituents of the steel are chromium. 2. 6. which hold the field winding. These bus bars are connected with terminal bushing. The solid poles are provided with additional slots in short lengths of two different configurations. Two individual conductors placed-one over the other are bent to obtain half turns. At the bottom of slot D-shaped liners are put to provide a plane seating surfaces for conductors and to facilitate easy flow of gas from one side to another. The overhang winding is separated by glass laminated [20] . longitudinal slots are milled on sophisticated horizontal slot milling machine. One type of slots served as an outlet for hydrogen which has cooled the overhang winding and other type used to accommodate finger of damper segments acting as damper winding. The coils are insulated from rotor body by U-shaped glass laminate module slot through made from glass cloth impregnated with epoxy varnish. These liners are made from molding material. Further these half turns are brazed in series to form coil on the rotor model. 2. The rectangular cross section copper conductors have ventilating ducts on the two sides thus providing a channel for hydrogen flow. Rotor Winding After preliminary turning. 2.2 Insulation The individual turns are insulated from each other by layer of glass prepag strips on turn of copper and baked under pressure and temperature to give a monolithic inter turn insulation.1 Copper ConductorThe conductors are made of hard drawn silver bearing copper. The slot pitch is selected in such a way that two solid poles displaced by 180o C are obtained.On 2/3 of its circumference approximately the rotor body is provided with longitudinal slot to accommodate field winding. For high accuracy the rotor is subjected to 20% over speeding for two minutes. The slot house the field winding consists of several coils inserted into the longitudinal slots of rotor body2. The centering rings are shrinking fitted at the free end of retaining ring that serves to reinforce the retaining ring. The wedges at the ends of slot are made from an alloy of chromium and copper. They are shrinking fitted to end of the rotor body barrel at one end. The gas then passes into the corresponding ducts on the other side and flows outwards and thrown into the gap in outlet zones. Retaining Ring The overhang portion of field winding is held by non-magnetic steel forging of retaining ring against centrifugal forces. In this cooling method the temperature rise becomes independent of length of rotor. end winding in axial direction at the same time. 3.blocks called liners. Ventilation slot wedges are used to cover the ventilation canals in the rotor so that hydrogen for overhang portion flows in a closed channel. austenitic steel and cold worked. The wedges are made from duralumin. Cold gas enters the overhang from under the retaining rings through special chamber in the end shields and ducts under the fan hub and gets released into the air gap at rotor barrel ends. while at the other side of the retaining ring does not make contact with the shaft. resulting in high mechanical strength. 4. These are connected with damper segments under the retaining ring for short circuit induced shaft current. The overhang winding are insulated from retaining rings segments having L-shape and made of glass cloth impregnated by epoxy resin.2 Cooling Of WindingThe rotor winding are cooled by means of direct cooling method of gap pick-up method. magnesium and aluminum having high good electrical conductivity and high mechanical strength. the retaining rings are made of nonmagnetic. In this type of cooling the hydrogen in the gap is sucked through the elliptical holes serving as scoop on the rotor wedges and is directed to flow along lateral vent ducts on rotor cooper coils to bottom of the coils. Rotor Wedges For protection against the effect of centrifugal force the winding is secured in the slots by slot wedge. 2. The overhang portion of the winding is cooled by axial twosystems and sectionalized into small parallel paths to minimize temperature rise. an alloy of copper. To reduce stray losses. securing. [21] . Direct cooling essentially eliminates hot spots and differential temperature between adjacent components. Fan blades. insulation. which has similar construction as. which are precision casting with special alloy.5.) through hydrogen and Primary water. 6. The helical grooves cut on the outer surfaces of the slip rings improve brush performance by breaking the pressurized air pockets that would otherwise get formed between the brush and slip rings. The radial holes with current carrying bolts in the rotor shafts are effectively sealed to prevent the escape of hydrogen. Hot gases is drawn [22] . are machined in the tail portion so that they fit into the groove of the fan hub. Hydrogen Cooling Circuit: The hydrogen is circulated in the generator interior in a closed circuit by one multistage axial flow fan arranged on the rotor at the turbine end. which could result in mechanical stresses. particularly to the copper conductors. Fans – Two single stage axial flow propeller type fans circulate the generator cooling gas. A field lead bar. Fans hubs are made of alloy steel forging with three peripheral grooves milled on it. does the connection between current carrying bolt and field winding that of semi flexible copper leads (they are insulated by glass cloth impregnated with epoxy resin for low resistance and ease of assembly). condensate etc. and rotor body and stator core. The fans are shrinking fitted on either sides of rotor body. Field Lead The slip rings are connected to the field winding through semi flexible copper leads and current-carrying bolts placed in the shaft. The slip rings are provided with inclined holes for self-ventilation. Field Lead Connections — Slip Rings The slip ring consists of helical grooved alloy steel rings shrunk on the body shaft and insulated from it. COOLING SYSTEM Heat losses arising in generator interior are dissipated to secondary coolant (raw water. The cooling water flow through the hydrogen coolers should automatically control to maintain a uniform generator temperature level for various loads and cold-water temperature. The heat removing capacity is selected such that approximately identical temperature is obtained for all conductors. The hot gas of the second cooling zone is discharged into the air gap at the mid length of the rotor body through radial openings in the hollow conductors and wedges. cold gas is passes to the individual frame compartment via separate cooling gas ducts.by the Ian from the air gap and delivered to the coolers where it is re-cooled and then divided into three flow paths after each cooler: Flow path I: Flow path I is directed into the rotor at the turbine end below the fan hub for cooling of the turbine end half of the rotor. The gas of the first cooling zone is discharged from the coils at the pole center into a collecting compartment within the pole area below the end winding from the hot gases passes into air gap through the pole face slots at the end of the rotor body. Flow path II: Flow path H is directed from the cooler to the individual frame compartments for cooling of the stator core. Flow path III: Flow path III is directed to the stator end winding space at the exciter end through guide ducts in the frame of cooling of the exciter end half of the rotor and of the core end portion. Cooling Of Rotors: For direct cooling of rotor winding cold gas is directed to the rotor end wedges at the turbine and exciter ends. Each coil quarter is divided into two cooling zones consists of the rotor end winding and the second one of the winding portion between the rotor body end and the midpoint of the rotor. The rotor winding is symmetrical relative to generator centerline and pole axis. From these frames compartment the gas then flow into [23] . Cold gas is directed to each cooling zone through separate openings directly before the rotor body end. Cooling of stator core: For cooling of the stator core. The three flow paths miss the air gaps. The hydrogen flows through each individual conductor is closed cooling ducts. The gas is then returned to the coolers via the axial flow fan. Relatively movements due to the different thermal expansions between the top and the bottom bars are thus minimized. The primary water is circulated in a closed circuit and dissipates the absorbed heat to the secondary cooling in the primary water cooler. The secondary water flow through the primary water cooler should be controlled automatically to maintain a uniform generator temperature level for various loads and cold-water temperatures. To ensure that the cold gas directed to the exciter end cannot be directly discharged into the air gap. The six bushings and phase connectors arranged in a circle around the stator winding are hydraulically interconnected so that three parallel flow paths are obtained. Inside the bars the cooling water flows through hollow strands. To ensure effective cooling these ventilating ducts are supplied from end winding space.). Flow Path II: Flow path II cools the phase connectors and the bushings. compensator etc. The primary water enters three bushings and exits from the three remaining bushings. the water is passed through the similar hoses to another water manifold and then return to the primary water tank. The pump is supplied with in the primary water tank and delivers the water to the generator via the following flow paths: Flow path I: Flow path I cools the stator winding. [24] .the air gap through slots and the core where it absorbs the heat from the core. To dissipate the higher losses in core ends the cooling gas section. An air gap choke is arranged with in the stator end winding cover and the rotor retaining rings at the exciter end. Primary Cooling Water Circuit in the Generators: The treated water used for cooling of the stator winding. phase connectors and bushings is designated as primary water in order to distinguish it from the secondary coolant (raw water. only a minimum temperature rise is obtained for both the coolant and the bars. The air gap is then returned to the coolers via the axial flow fan. Since a single pass water flow through the stator is used. This flow path passes through water manifold on the exciter end of the generator and from there to the stator bars via insulated bar is connected to the manifold by a separate hose. All the flows mix in the air gap and cool the rotor body and stator bore surfaces. Another flow path is directed from the stator end winding space paste the clamping fingers between the pressure plate and core section into the air gap along either side of flux shield. The pump is supplied with in primary water cooler. The bushing and the phase connectors consist of the thick walled copper tubes through which the cooling water is circulated. At the turbine end. Low power field winding on the rotor gives a lighter rotor and therefore low centrifugal forces. Stationary armature winding can be cooled more efficiently. In view of this. Stationary armature windings can be insulated satisfactorily for higher voltages. allowing the construction of high voltage synchronous machines. higher rotor speeds are permissible. because it has certain advantages they are:     It is economical to have armature winding on the stator and field winding on the rotor. the field winding is always provided on the rotor.EXCITATION SYSTEM In large synchronous machines. thus increasing the synchronous machine output for given dimensions. [25] . The generator & exciter rotors are supported on total three bearings. The three phase connections between armature & diodes are obtained via copper conductors arranged on the shaft circumference between the rectifier wheels &the main exciter armature. At the pole shoe. Rectifier wheel The silicon diode is the main component of the rectifier wheels. bars are provided which are connected to form a damper winding. The frame accommodates the laminated core with the three-phase winding. the complete rotor is shrunk on the shaft. The threephase ac output of this exciter is fed to the field of the main exciter via a stationary regulator & rectifier unit. Between the two poles. which are arranged in a three-phase bridge circuit.. Three Phase main exciter The three phase main exciter is a six-pole armature-revolving unit. which form the positive & negative side of the bridge. R-C blocks are provided in each bridge in parallel with each set of diodes. After completing the winding & insulation etc. A common shaft carries the rectifier wheels. a quadrature-axis coil is provided for inductive measurement of the field current. the rotor of the main exciter & PMG rotor. [26] . Each pole consists of separate permanent magnets that are housed in a non-magnetic metallic enclosure. The rings. Three Phase Pilot Exciter It is a six-pole revolving field unit. are insulated from the rectifier wheel which in turn is shrunk on the shaft.Design features The excitation system has a revolving field with permanent magnet poles. a fuse is provided which serves to cut off the diode from the circuit if it fails. Three-phase ac induced in the rotor of the main exciter is rectified by the rotating Rectifier Bridge & supplied to the field winding of the generator rotor through the dc lead in the rotor shaft. For suppression of the momentary voltage peaks arising from commutation. The shaft is rigidly coupled to the generator rotor. The field winding is arranged on the laminated magnetic poles. With each diode. the controlled voltage level then rising together with the reactive current (overexcited) thereby increasing the generator degree of activity in compensating system voltage functions.e. which can be adjusted from the control room. which is a small D. For this purpose the gate control set changes the firing angle of the Thyristor as a function of the output voltage of the voltage regulator. Further.g. signals can be added if necessary via free inputs. exciter and stationary solid-state rectifier. feeds the field winding of main exciter is given to the field winding of the main alternator. the control amplifiers for the generator voltage controls via the gate control set the Thyristor so as they provide quick correction of the generator voltage on changing generator load. has rotating [27] .C. 0 to 20%). In this case the setting range is 90 to 110%. The main quantities acting on the input of the voltage regulator are the set point and the actual value of the generator voltage. The A. With operation at the respective limits of the capability curve. i. for supplying D. influencing variable are supplied by the under and over excitation limiters. which is coupled to shaft of generator.C. In this second scheme it consists of main A.g. BRUSHLESS EXCITOR STATOR The various schemes. and the power supply circuits.C. through slip-rings and brushes. further. shunt generator. The set point is divided into a basic set point (e.Voltage regulator The voltage regulator is intended for the excitation and control of generators equipped with alternator exciters employing rotating uncontrolled rectifiers. main exciter. Voltage regulation The active and reactive power ranges of the generator have required a wide excitation setting range. excitation to the field winding to large turbo generators are given below:   The Pilot Exciter and the main exciter are driven by the turbo generators main shaft. To partly compensate the voltage drop at the unit transformer. 90% rated voltage) and an additional value (e.C. a signal proportional to the reactive current can be added to the input. an open loop control system for exchanging signal between the regulator equipment and the control room. The voltage regulator in the restricted sense. field discharge circuit. The function of the regulator is to keep the alternator terminal voltage constant at a particular value. The main parts of the regulator equipment are two closed-loop control systems including a separate gate control set and Thyristor set each. The pilot Exciter. Self-generating excitation unaffected by system faults or disturbances of shaft mounted pilot exciter.C.0 exciter is fed. Here are some merits of Brush less Exciters. without any slip rings and brushes. In third scheme the A. field breaker and excitation bus/cables. In the other words.0 exciter. In view of its many advantages. brush gear. through slip rings and brushes. the power flows along the wires mounted on the main shaft. over voltage. The only promising solution of feeding the field winding of large turbo generator is the brush less excitation system. along the main shaft. The output from these rectifiers is also given. along the main shaft. field and stationary armature.      Eliminates slip rings. Eliminates all the problems associated with transfer of current via sliding contacts. the direct cooling required by the rotating field winding increases considerably (up to 10 kA or so). For large turbo generators of 500 MW excitation systems. coupled to the shaft that drives the main generator. exciter has a frequency of about 400 Hz. The armature output from the A. This output is given to the stationary solid-state controlled rectifier. the brush less excitation system is employed in almost all large turbo generators being designed and manufactured now days. to the rotating silicon-diode rectifiers mounted on the same shaft. exciter to the silicon diode rectifiers and then to the main generator field. the brush gear design becomes more complicated and reliability of turbo generator operation decreases. this arrangement of exciting the turbo generators has come to be called as Brush less Excitation system. under excitation and excessive thermal stresses. ground fault. from the A. Since the scheme does not require any sliding contacts and brushes. The following protective equipment is recommended 1) Differential protection 2) Stator ground fault protection 3) Rotor ground fault protection 4) Under excitation protection 5) Over current protection [28] .C. to the man generator field. reliable and ideally suited for large sets. In such cases. the power is fed to the main generator field. has stationary field and rotating 3-phase armature. ELECTRICAL GENERATOR PROTECTIONGenerator may be endangered by short circuit. The 3-phase power from the A. Minimum operation and maintenance cost. After rectification. Simple. .6) Load unbalance protection 7) Rise in voltage protection 8) Under-frequency protection 9) Reverse power protection 10)Over voltage protection SALIENT DESIGN FEATURES 1) Air Cooled Turbo Generators Up To 200 MW Range (Type.TARI)  Stator core and rotor winding direct air cooled  Indirect cooling of stator winding  Horizontally split casing design of stator  Vertically side mounted coolers in a separate housing  Moralistic bar type insulation system Separately assembled stator core and winding for reducing the manufacturing cycle   Brush less/static excitation system 2) Hydrogen & Water-Cooled Turbo Generators Of 200-235 MW range (Type: THW)  Stator winding directly water cooled  Rotor winding directly hydrogen cooled by gap pick up method  Resiliently mounted stator core on flexible core bars  Thermo reactive resin rich insulation for stator winding  Top ripple springs in stator slots  Enclosed type slip rings with forced ventilation  Ring/thrust type shaft seal  Two axial fans for systematic ventilation and four hydrogen coolers  Static excitation [29] . 3) Hydrogen Cooled Turbo Generators Of 140-260 MW range (Type: THRI)  Stator core and winding directly hydrogen cooled  Indirect cooling of stator winding  Rigid core bar mounting  Micalastic insulation system  End shield mounted bearings  Top ripple springs in stator slots  Ring type shaft seals  Symmetrical ventilation  Brush less/ static excitation  Integral coupling of rotor 4) Hydrogen & Water-Cooled Turbo Generators of 500 MW range (Type: THW)  Stator winding directly water-cooled  Rotor winding direct hydrogen cooled (axial)  Leaf spring suspension of stator core  Micalastic insulation system  End shield mounted bearings  Support ring for stator over hang  Magnetic shunt to trap end leakage flux  Ring type shaft seals with double flow  Multistage compressor and vertical coolers on turbine end  Brush less/static excitation  Integral coupling of rotor [30] . . .STATOR BAR MANUFACTURING AT CIM (BLOCK-4) This Block manufactures stator bars for all types of TGs [i.e. 210MW. 800MW] the steps involving in the process of stator bar manufacturing are as follows: . . .OCP on stator Bar.Pickling of bar ends (1) . . .Assembly of all conductors to be used in stator Bars.Thermal Shock Application. ..Reforming of Bar.Preparation of bar for HV and Tan  Test.Consolidation if slot portion of Bar.Cross over insulation.Conductor cutting and end cleaning.Brazing of Contact sleeve & bottom part of water box. 500MW. . . .Forming or Bar (to shape overhang portion). 600MW. .S.Pickling of bar ends (2) . . In this process the pre-insulated copper conductor is cut into number of pieces of required length (length given in drawing as per design) insulation is removed from both ends of the copper conductor out.Conductor Draw from Store.Transposition of conductor.Surface finishing of stator bar. .Insulation of bar on CNC machine.Mounting of Contact sleeve & bottom part of water box. . Test (i. 1. . inter strand test).Helium Leak Test. . . . .Re-pickling.I.e. . Conductor cutting: This process is done by automatic CNC machine.Impregnation a curing of bar insulation.Mounting of water box leak test. [31] .Water flow and N2 test. Transposition: Transposition means changing/shifting of position of each conductor in active core (slot) part. This process is repeated for making another half of the bar which would be mirror image of the first half. the conductors are arranged on the comb in staggered manner and then bends are given to the conductors with the help of bending die at required distance. 6.2. Forming The straight bar stack is formed as per overhang profile (as per design). 3. Brazing of coil lugs: For water cooled generator bars. Nitrogen leak test: The bar is tested for water flow test. The overhang portion is consolidated after forming. Crossover insulation: The pre insulation of the copper conductor may get damaged due to mechanical bending in die during transposition. [32] . The consolidated stack is withdrawn from the press and the dimensions are checked. Inter Strand Short test: The consolidation bar stack is tested for the short between any two conductors in the bar. 5. Stack Consolidation: The core part of the bar stack is pressed in press (closed box) under pressure (varies from product to product) and temperature of 1600 C for a given period. The two halves of the bar are overlapped over each other and a spacer is placed between the two halves. 7. 8. if found then it has to be rectified. nitrogen leak test and pressure test for given duration. After cutting the required number of conductors. Then the conductors are taken out from the comb and die and placed with their ends in a line and transposition is carried out. hence the insulating spacers are provided at the crossover portion of the conductors. the electrical connection contact and water box for inlet and outlet of water are brazed. A filler material (insulating putty of molding micanite) is provided along the height of the bar to maintain the rectangular shape and to cover the difference of level of conductors. 4. Then extra resin is drained out and bars are heated and baked under pressed condition in closed box fixture. 10. layer by layer. 12. 11. Thermal shock Test: The cycles of hot (800C) and cold (300C) water are flew through the bar to ensure the thermal expansion and contraction of the joints . Insulation [33] .9. Then bar is taken out and pressed in closed box fixture and then baked at given temperature for given duration. d) VIP Micalastic System: The individual (Separate) bar is heated in vacuum and impregnated in resin. Impregnation and baking: a) Thermo reactive System: In case of rich resin insulation the bar is pressed in closed box in heated condition and baked under pressure and temperature as per requirement for a given period. Helium leakage test: After thermal shock test bar is tested for any leakage with the help of helium gas. with resin. c) VPI Micalastic System: The bars already laid in closed fixture and full fixture is impregnated (dipped) in resin and then fixture with box is baked under given temperature for given duration. b) Micalastic System : In case of poor resin system the insulated bars are heated under vacuum and the impregnated (dipped) in heated resin so that all the air gaps are filled. 14.E up to 120C Class.The bar is insulated with the given number of layers to build the wall thickness of insulation subjected to the generating voltage of the machine. Test: The each bar is tested momentarily at high voltage increased gradually to three times higher than rated voltage. if required. Insulation Classification: Thermal classification of insulation depends upon the temperature withstand capacity of the insulation. for the dimension. Conducting varnish coating (i) OCP (Outer Corona Protection) Coating:-The black semiconducting varnish coating is applied on the bar surface on the core length.Y up to 90C Class. Finishing The baked and dimensionally correct bars are sanded . 15. Class. (ii) ECP (End Corona Protection) Coating: The grey semiconducting varnish is applied at the bend outside core end of bars in gradient to prevent from discharge and minimize the end corona.off to smoothen the edges and the surface is calibrated. Set type 210 MW 250 MW 500 MW 600 MW Exciter Conductor Length(mm) [Upper/lower] 7000/7300 8200 10050/10200 10887/11053 1680/1620 No. of conductors [solid/hollow] 28/14 80 20/10 & 10/10 28/14 144 [34] .A up to 105C Class. (b) H. Testing: (a)Tan Δ Test: This test is carried out to ensure the healthiness of dielectric Insulation) i.e. dense or rare and measured the capacitance loss.C > 180C and up to 220C 13.V.B up to 130C Class.H up to 180C Class.F upto150C Class. Degreasing and Pickling Process .Cleaning by Spirit . This process is repeated for making another half of the bar which would be mirror image of the first half.M. water. the conductors are arranged on the comb in staggered manner and then bends are given to the conductors with the help of bending die at required distance.Cleaning by Water : Take out Cu bars 3 Times in 1 minute . 3.Cleaning by Water : Flowing Water . The two halves of the bar are overlapped over each other and a spacer is placed between the two -halves.Pickling : Pickling Solution at 45⁰C . Then the conductors are taken out from the comb and die and placed with their ends in a line and transposition is carried out.Transposition Transposition means changing/shifting of position of each conductor in active core (slot) part. Dip 3 minutes . Equalize the voltage generator. [35] . 2.Cleaning of Insulation (at ends due to formation of oxides): Sulphuric Acid . After cutting the required number of conductors.Neutralizing: Neutralizing Solution.Cleaning by Water: Flowing water .Degreasing : Trichloroethylene . Why Transposition is required? 1. To reduce the eddy current loses. To minimize skin effect of ac current so small cross section of conductor is used and also hollow conductors are used for effective cooling by D. Also.2nd Annealing .Finishing Bars for 600MW Rotor Same as 500MW but here.1st Annealing . the cooling of Rotor is Radial type where the blades on the rotor force H2 to pass through the slots and cool the rotor. . so no brazing.ROTOR BAR MANUFACTURING AT ACM (BLOCK-4) Following Steps are involved in manufacturing of Rotor Bars depending upon the capacity of the generator. Bars for 250MW Rotor . slots are inevitable as they increase the surface area of cooling of rotor bars.Edge wise Bending .Moulding .No filler. For this reason.2nd Annealing .Pressing .1st Annealing .Drilling .Moulding .Pressing . this category of bars has a full arc on ½ side of the coil unlike 500MW where both coil sides have ½ of the arc. [36] . but. so no annealing .Radius Bending .Radius Bending .Slot Punching . Significance of Important Processes: 1.Scraping .Centre Champhering + Internal Debarring .Edge Bending . Slot Punching: In THRI.Cocking (Small and Large Filling) .Finishing Bars for 500MW Rotor . The raw materials are ready to use and require preservation and working on temperature 20-25C. For THRI (Generators with generating capacity of <250 MW) have solid rotor bars with slots punched through them. They are arranged in concentric manner to generate a concentrated field through rotor’s physical poles. The temperature control need not required. Hollow Rotor Bars For THDF (LST Generators with generating capacity of >250 MW like 500MW and 600MW) have hollow rotors through which H2 enters through one end and leaves at the middle of the bars through holes provided for the same. The insulating material is applied on job and then the same is impregnated in the resin. A has the least arc while G has the largest arc. Annealing: Every metal responds to thermal shocks in different way.2. Copper when molded by hammering. The arc required to make a full concentric coil is done through this process on a mold by hammering manually. 3. Solid Rotor Bars. annealing cures this. [37] . They are numbered here from A through G. develops cracks due to brittleness. Types of Rotor Bar as per Cooling Method Employed: 1. The arc is full in case of 600 MW and half in case of 500MW. Resin system: (a) Rich resin or Thermo reactive insulation system: In this type of insulation system the bond content in resin is 35-37%. So. 2. There are 7 types of Rotor bars depending upon the arc. its shelf life is one year when kept at temperature 20C which could be increased when kept at temperature of 5C (b) Poor resin or Micalastic insulation system: In this type of insulation the bond content in the resin is 5-7% and insulation material is prepared with accelerator treatment. Radius Bending: This is the most important part of the process. CONCLUSION The training at BHEL-Haridwar provided me the knowledge on manufacturing of Turbo Generator sets. The staff and the engineers here were very cooperative and I thank them for sharing their knowledge and experience with us. [38] .
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