National Hydroelectric Power Corporation Limited

SUMMER TRAINING NHPC – FARIDABAD A Project Report On Study of Hydro Power Plants and Detailed Design of Large Hydro Generators July 19, 2006

Aditya Lad Ankur Singhal Hanish Kukreja III Year, Electrical Engineering, IIT Roorkee.

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TABLE OF CONTENTS National Hydroelectric Power Corporation Limited (NHPC)................................................... 6 CORPORATE MISSIONS........................................................................................................ 7 CORPORATE OBJECTIVES................................................................................................... 7 PROFILE OF NHPC:................................................................................................................ 7 PERFORMANCE HIGHLIGHTS(2005-06).............................................................................8 PROJECT DETAILS............................................................................................................... 10 PROJECTS (Completed and in operation):......................................................................... 10 PROJECTS UNDER CONSTRUCTION............................................................................11 PROJECTS UNDER DEVELOPMENT............................................................................. 11 PROJECTS AWAITING CLEARANCE/GOVT. APPROVAL (Stage-II)........................ 11 PROJECTS FOR DPR & INFRASTRUCTURE DEVELOPMENT (Stage-II)................. 12 PROJECTS UNDER SURVEY AND INVESTIGATION (Stage-I)..................................12 PROJECTS IN PIPELINE ..............................................................................................................................................12 SMALL HYDRO/GEOTHERMAL PROJECTS................................................................ 13 PROJECTS ON DEPOSIT / TURNKEY CONTRACT BASIS......................................... 13 PROJECTS IN JOINT VENTURE..................................................................................... 13 LOCATION MAP OF NHPC PROJECTS............................................................................. 14 EXPERTISE OF NHPC IN HYDROELECTRIC PROJECTS............................................... 15 REHABILIATION & RESETTLEMENT.............................................................................. 15 METHODOLOGY OF FORMULATION OF R & R PLAN............................................. 15 DESIGN E & M (ELECTRICAL AND MECHANICAL) DIVISION...................................17 DATA GROUP .....................................................................................................................17 GENERAL INTRODUCTION................................................................................................18 HYDROPOWER GENERATION AND ITS PRINCIPLES.............................................. 18 HYDROPOWER PLANT....................................................................................................... 19 MAIN PARTS OF HYDROPOWER PLANT.................................................................... 19 TYPES OF HYDROPOWER PLANTS..............................................................................20 PLANT DESIGN ................................................................................................................ 21 HYDRO TURBINES...............................................................................................................22 TYPES OF HYDRO-TURBINES :..................................................................................... 22 MAJOR COMPONENTS OF TURBINE:.......................................................................... 22 VALVES:.................................................................................................................................23 POWER HOUSE..................................................................................................................... 24 PROCEDURE FOR DIMENSIONING OF POWER HOUSE .......................................... 24 HEAD CALCULATION......................................................................................................... 24 SELECTION OF MACHINE SPEED.....................................................................................25 CALCULATION OF SPEED:.................................................................................................25 HYDRO GENERATORS........................................................................................................25 CLASSIFICATIONS...........................................................................................................26 DESIGNATION.................................................................................................................. 26 Page 2 of 67

GENERATOR BARREL.....................................................................................................27 COMPONENTS OF GENERATOR................................................................................... 29 PARTS OF STATOR ........................................................... 29 ROTOR COMPONENTS ..................................................................30 BRACKETS.....................................................................................................................33 GENERATOR AUXILIARIES....................................................................................... 34 TURBINE – GENERATOR SET............................................................................................36 DESIGN STUDY.....................................................................................................................37 OUTPUT COEFFICIENT................................................................................................... 37 MACHINE PARAMETERS............................................................................................... 38 STATOR DESIGNING....................................................................................................... 40 MODIFIED CALCULATION.............................................................................................42 RADIAL LENGTH OF AIR GAP...................................................................................... 42 SHORT CIRCUIT RATIO.................................................................................................. 43 EFFECT OF SCR ON MACHINE PERFORMANCE.................................................... 43 CALCULATION OF MEAN LENGTH OF A TURN. ..................................................... 44 NUMBER OF RADIAL VENTILATING DUCTS.......................................................... 44 ARMATURE WINDINGS, COILS AND THEIR INSULATIONS.................................. 45 WINDINGS........................................................................................................................ 47 ARMATURE WINDINGS: ..............................................................................................48 CHOICE OF TYPE OF STATOR WINDING....................................................................50 Annexure I............................................................................................................................... 52 Annexure II.............................................................................................................................. 55

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ACKNOWLEDGEMENT We are thankful to Mr. V.K Abbey -Executive Director, Mr. M.A. Padmanabhacharya – Chief Engineer (E) ,Mr. Anish Gouraha – Deputy Manager (E) , Mr. Abhishek Ranjan – Engineer (E) , Mr. Sunil Kumar –Engineer (E), Mr. Kapil Shrivastava, Engineer (IT) of Design (E&M) Division for their regular guidance and kind co-operation in the project. We are also thankful to the Design (E&M) staff for their cooperation and help in solving our problems.

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ABSTRACT This project report includes the overview of a typical hydropower plant and describes the technical aspects of designing a hydropower plant. It also includes detailed study of turbines, large hydro generators. The report discusses the various design parameters of a hydro generator and the ways to calculate them. To automate this task, we have also developed an application in Visual Basic 6.0 which accepts rating of a generator as input from the user, computes the design parameters and the user has option to save the result in excel format. Annexure I, at the end of the project report, includes the screenshots of the application.

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National Hydroelectric Power Corporation Limited (NHPC)

NHPC, a Govt. of India Enterprise, was incorporated in the year 1975 with an authorised capital of Rs. 2000 million and with an objective to plan, promote and organise an integrated and efficient development of hydroelectric power in all aspects. Later on NHPC expanded its objects to include other sources of energy like Geothermal, Tidal, Wind etc. At present, NHPC is a schedule 'A' Enterprise of the Govt. of India with an authorised share capital of Rs. 1,50,000 million. With an investment base of over Rs. 2,22,000 million, NHPC is among the TOP TEN companies in the country in terms of investment. National Hydroelectric Power Corporation is one of the largest organisation for hydro-power development in India having constructed 13 hydro-power projects in India and abroad with a total installed capacity of 3694.35 MW (Including the projects under joint venture). With an asset value of Rs. 2,00,000 million NHPC has planned to add 2480 MW of power during Xth plan and 6297 MW of power during Page 6 of 67

XIth plan. NHPC's capabilities include the complete spectrum of hydropower development from concept to commissioning.

CORPORATE MISSIONS •

To achieve international standards of excellence in all aspects of hydro power and diversified business.

•

To execute and operate projects in a cost effective, environment friendly and socio-economically responsive manner.

•

To foster competent trained and multi-disciplinary human capital.

•

To continually develop state-of-the-art technologies thru innovative R&D and adopt best practices.

•

To adopt the best practices of corporate governance and institutionalize value based management for a strong corporate identity.

•

To maximize creation of wealth through generation of internal funds and effective management of resources.

CORPORATE OBJECTIVES 1. Development of vast hydro potential at faster pace and optimum cost eliminating time and cost over-run. 2. Completion of all on-going projects within stipulated time frame. 3. Ensure maximum utilization of installed capacity and help in better system stability. 4. Generation of sufficient internal resources for expansion and setting up new projects. 5. Corporate development along with simultaneous Human Resource Development.

PROFILE OF NHPC: Authorised Capital

Rs. 1,50,000 Million

Paid up Capital

Rs. 1,02,150 Million (31.03.2006)

Value of Assets

Rs. 2,20,000 Million (Approx.)

Projects Completed

10 Nos. (3755 MW) *

Projects Under Construction

11 Nos. (5623 MW)

Projects for DPR & Infrastructure Development [Stage - II]

19 Nos. (14190 MW)

Projects Under Investigation [Stage - I]

1 No. (11000 MW) Page 7 of 67

Joint Venture Projects

2 Nos. (1520 MW)

Projects on Turnkey Basis

5 Nos. (89.35 MW)

Other Projects

13 Nos. (9610 MW)

In 2005 - 2006 Energy Generated (Including Deemed Generation)

12567 MU

Capacity Index

98.16%

Sales Turnover

18340 Million

Net Profit

7010 Million

Performance Rating

"Excellent"

NHPC presently own and operates total 9 Hydro Power Stations situated in Northern, Eastern and North-Eastern regions of India.

PERFORMANCE HIGHLIGHTS(2005-06) 1. Registered a net profit of Rs. 701 crore against Rs. 685 crore during the previous financial year. 2. Achieved an all time high sales turnover of Rs. 1834 crore as against Rs. 1668 crore during the year 2004-05. 3. Rs. 140 crore given to Government of India as Dividend for 2005-06. 4. The Corporation is in the process of raising 100 Million USD loan through ECA route for part financing of prestigious Subansiri lower Project. 5. Obtained new consultancy assignments amounting to Rs. 65 crore against the target of Rs. 20 crore. 6. Total bills for Rs. 1858 crore raised to SEBs. 7. Achieved total realization of Rs. 1911 crore. 8. Standard & Poors (S & P) & Fitch Ratings reaffirms NHPC’s Long Term Foreign Currency Rating to BB+(Stable). Fitch Rating also reaffirmed rating for Domestic borrowings as AAA. 9. Paid up capital of the Corporation raised to Rs. 10215 crore. 10. The Power Stations achieved a capacity index of 98.16% this year against the last year index of 95.28 %.

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11. Achieved highest ever generation of 12567 million units against last year generation of 11286 million units. 12. Commissioned the 280 MW Dhauliganga Power Station in Uttaranchal. 13. Power Purchase agreements signed for Kishanganga, Nimmo Bazgo, Chutak, Uri-II, Dul Hasti, Chamera-III and Teesta Low Dam Project Stage-IV with the concerned beneficiaries. 14. Finalized major contract agreements for civil works of Uri-II, Chamera-III, Parbati-III & Teesta Low Dam Stage-IV Projects. 15. Baira Siul Power Station in Himachal Pradesh completed 25 years of operation. 16. Achieved the feat of excavating one of the longest Inclined Pressure Shafts in the World at Parbati Stage-II Project. 17. Signed agreements with Government of Sikkim for execution of the 495 MW Teesta Stasge-IV and 210 MW Lachen Hydroelectric Projects in Sikkim on BOOM basis. 18. MOU signed with Uttaranchal Government for implementation of 240 MW Chungar Chal, 630 MW Garba Tawaghat and 55 MW Karmoli Lumti Tulli Projects in Uttaranchal. Environment clearance accorded by Ministry of Environment & Forest for 520 MW Parbati-III Project in Himachal Pradesh, 45 MW Nimoo Bazgo and 44 MW Chutak Projects in Jammu & Kashmir.

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Fig 1. Analysis of Revenue 2004-05

PROJECT DETAILS PROJECTS (Completed and in operation): POWER STATIONS

S. No.

Project

State

Installed Year of Capcaity Commissioning (MW)

1

Baira Siul

Himachal Pradesh

3 x 60

1981

2

Loktak

Manipur

3 x 30

1983

3

Salal - I

Jammu & Kashmir

3 x 115

1987

4

Tanakpur

Uttaranchal

3 x 40

1992

5

Chamera - I

Himachal Pradesh

3 x 180

1994

6

Salal - II

Jammu & Kashmir

3 x 115

1996

7

Uri

Jammu & Kashmir

4 x 120

1997

8

Rangit

Sikkim

3 x 20

1999

9

Chamera - II

Himachal Pradesh

3 x 100

2003

10

Dhauliganga Stage - I

Uttaranchal

4 x 70

2005-06

Madhya Pradesh

8 x 125

2004-05

11 Indira Sagar *

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Total

3755

No. of Beneficiary States / UTs / Corporations : 24

PROJECTS UNDER CONSTRUCTION S. No. 1 2 3 4 5 6 7 8 9 10 11 #

Project Dulhasti Teesta Stage - V Parbati - II Sewa - II Subansiri (Lower) Uri-II Chamera-III Teesta Low Dam - III Teesta Low Dam - IV Parbati - III Omkareshwar #

State Jammu & Kashmir Sikkim Himachal Pradesh Jammu & Kashmir Arunachal Pradesh Jammu & Kashmir Himachal Pradesh West Bengal West Bengal Himachal Pradesh Madhya Pradesh Total

Capacity (MW) 390 510 800 120 2000 240 231 132 160 520 520 5623

Under joint venture

PROJECTS UNDER DEVELOPMENT The upcoming projects of NHPC are categorised broadly into three groups depending upon the clearance obtained from the government. This broad classification of new projects also indicate the stage / present status of the projects.

PROJECTS AWAITING CLEARANCE/GOVT. APPROVAL (Stage-II) S. No. Project State Capacity (MW) Kishenganga 1 Jammu & Kashmir 330 Nimmo-Bazgo 2 Jammu & Kashmir 45 Chutak 3 Jammu & Kashmir 44 4 Siyom * Arunachal Pradesh 1000 Total 1419

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PROJECTS FOR DPR & INFRASTRUCTURE DEVELOPMENT (Stage-II) S. No. Project 1 Lakhwar Vyasi 2 Dibang 3 Pakal Dul 4 Bursar 5 Siang Lower 6 Subansiri Upper 7 Subansiri Middle 8 Bav - II 9 Kotli Bhel Stage - I A 10 Kotli Bhel Stage - I B 11 Kotli Bhel Stage - II 12 Teesta - IV

State Capacity (MW) Uttaranchal 420 Arunachal Pradesh 3000 Jammu & Kashmir 1000 Jammu & Kashmir 1020 Arunachal Pradesh 1600 Arunachal Pradesh 2000 Arunachal Pradesh 1600 Maharashtra 20 Uttranchal 240 Uttranchal 280 Uttranchal 440 Sikkim 495 Total 12115

PROJECTS UNDER SURVEY AND INVESTIGATION (Stage-I) S. No.

Project

State

1

Siang (Upper/Inter.)

Arunachal Pradesh Total

Capacity (MW) 11000 11000

PROJECTS IN PIPELINE Projects Taken up for DPR under Prime Minister's 50,000 MW Hydroelectric Initiative S. No. Project State Capacity (MW) 1 Etalin Arunachal Pradesh 4000 2 Naba Arunachal Pradesh 1000 3 Niare Arunachal Pradesh 800 4 Attunli Arunachal Pradesh 500 5 Shamnot Jammu & Kashmir 370 6 Ratle Jammu & Kashmir 560 7 Kiru Jammu & Kashmir 430 Page 12 of 67

8

Kawar

Projects in Pipeline Project State

S. No. 1 2 3 4

Jammu & Kashmir Total

Karmoli Lumti Tulli Garba Tawaghat Chungar Chal Lachen

Uttranchal Uttranchal Uttranchal Sikkim Total

320 7980

Capacity (MW) 55 630 240 210 1135

SMALL HYDRO/GEOTHERMAL PROJECTS Kambang Project (6MW), Ar. Pradesh: In Kambang project about 90 % of earth work and 84% concreting work has been completed. Erections of E&M equipments are in full swing. Works are in advance stage of commissioning. Sippi Project (4MW), Ar. Pradesh: In Sippi project about 80 % of earth work and 41% concreting work has been completed.

PROJECTS ON DEPOSIT / TURNKEY CONTRACT BASIS Project Devighat Kurichu Kalpong Sippi Kambang

Country / State Nepal Bhutan Andaman & Nicobar Arunachal Pradesh Arunachal Pradesh Total

Capacity (MW) 14.10 60.00

Completed Completed

5.25

Completed

4.00 6.00

Status

Under Construction Under Construction

89.35

PROJECTS IN JOINT VENTURE Narmada Hydroelectric Development Corporation Ltd. (NHDC) Project State Capacity (MW) Status Indira Sagar M.P 1000 ( 8 x 125 Commissioned MW ) Page 13 of 67

Omkareshwar

M.P Total

520 ( 8 x 65 MW ) 1520 MW

Under Construction

LOCATION MAP OF NHPC PROJECTS

Fig 2. Location of NHPC Projects

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EXPERTISE OF NHPC IN HYDROELECTRIC PROJECTS A. World Class expertise in Design & Hydroelectric Projects B. Construction of underground works of medium to large dimensions in all types of rock conditions. C. Construction of medium to large diversion structures. D. Handling sophisticated indigenous as well as imported construction equipment. E. Tackling operation and maintenance problems of hydroelectric projects particularly in Himalayan region. F. Equipped with state of art equipment and techniques for investigation of projects and preparation of detailed project reports. G. Information technology and communication: •Very large network of personal computers. •VSAT based satellite communication network •Software development in house on oracle/developer 2000 platforms. H. Consultancy Services : •Detailed Investigation • River basin studies •Preparation of DPRs •Design and Engineering •Tender documents and evaluation of Bids •Construction planning and management •Environment management •Operation and management •Quality control and assurance •Renovation and modernization of power plants

REHABILIATION & RESETTLEMENT The basic law which has guided the R & R of the displaced people has been the Land Acquisition Act of 1894 where the Government is empowered to acquire any land for “public purpose” and to pay cash compensation determined by it according to a prescribed procedure. As a part of EIA process, Resettlement and Rehabilitation packages for people being displaced are also assessed by MOEF.

METHODOLOGY OF FORMULATION OF R & R PLAN Page 15 of 67

a. Socio-economic and Ethnographic Survey: A detailed socio-economic survey is conducted before formulation of Resettlement and Rehabilitation (R&R) Plan for the Project Affected Persons (PAPs). In places where ethnic minorities dominate, as in Sikkim, a separate Ethnographic Survey has also been conducted to understand the local culture and behaviour of the people. b. Formulation of R & R Plan: The R & R plan is formulated in association with State Revenue Department, District Administration and representatives of the local people. After the Plan is formulated, it is forwarded to the concerned State Government for its approval and modification, if any. The revised Plan is then in some case is sent to the Ministry of Environment and Forests for final approval. NHPC makes every effort towards socio-economic upliftment of the affected people thereby improving their quality of life. c. Implementation: After getting approval from MOEF or from the concerned Department of the State Government, the Plan is set for implementation by NHPC in close coordination with the District Administration. d. Monitoring: To ensure effective implementation of the R & R Plan a Monitoring Committee is constituted (project level) at each project comprising of State Government Officials, representatives from the affected families, officials from NHPC, a representative from State Forest Department, and a Senior Citizen of the area/Member Legislative Assembly (generally an elected representative of the local residents of the area). Apart from this a Grievance Redressal System is also set up where the affected people can send in their grievance, if any. This aspect is also monitored by a Central Level Monitoring Committee with representatives from MOEF, constituted for overall environmental safeguards.

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DESIGN E & M (ELECTRICAL AND MECHANICAL) DIVISION Objectives 1. Planning and preparation of Electrical and Mechanical design for DPR of new projects and assistance in clearance by CWC & CEA. 2. Power Potential Studies, Power System Studies and Detailed Engineering. 3. Preparation of Technical specification of Electrical and Mechanical equipments and various units of Power House and Switchyard. 4. Standardization of Technical specification for Electrical and Mechanical equipments. 5. Assistance in evaluation of all tenders pertaining to Electrical and Mechanical equipments and systems of Power House and Switchyard. 6. Detailed Engineering of E & M equipments, approval of civil, E & M drawings etc. 7. Technical / Design support to projects. 8. Professional up gradation including recommending training programs for employees in the division. 9. Preparation of operation manuals for electro-mechanical installations/equipments. 10. Assistance in preparation of project completion reports.

DATA GROUP Objectives 1. Engineering Data 2. Collection group 3. EDP Related Works of DEM Division. 4. ERP Coordination. 5. Standardization of all existing processes of designing. 6. To device a methodology with or without the help of software for managing data. Page 17 of 67

GENERAL INTRODUCTION Oceans cover more than 70% of the earth's surface, making them the world's largest source of hydro energy. There are many different ways to extract energy from water. Seawater is the source of deuterium, the ideal fuel for nuclear fusion. Surface water also stores a massive amount of solar energy that can be exploited to design thermal power plants. In addition, water contains mechanical energy that can be converted to useful work in the form of the potential energy of waterfalls, tides, and ocean waves. According to some estimates, these resources have the potential to produce 1-2 terawatts of electricity, enough to cover the energy demands of the entire globe, but tapping into most of that potential is not yet economically feasible.

HYDROPOWER GENERATION AND ITS PRINCIPLES Egyptians harnessed energy from flowing water about 2,000 years ago by turning waterwheels to grind their grain. These primitive devices allowed the force of falling water to act on a waterwheel and provide rotational energy or shaft power. Through the centuries, mechanisms were designed to facilitate many other applications beyond the simple grain mills of the Egyptians. By the time of the industrial revolution, waterpower was used to drive tens of thousands of waterwheels. Today, hydropower is the most widely available renewable energy, and is used almost exclusively for electric power generation. Hydropower provides 19% of all electricity used around the world. Two medieval varieties of waterwheels were undershot and overshot wheels. Undershot refers to a paddle wheel fixed to the bank of a river or hung from an overhead bridge. It is turned by the impulse of the water current. Overshot water mills work by bringing a stream of water through a pipe or canal and pouring it onto the wheel from above.

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Undershot Wheel

Overshot Wheel

HYDROPOWER PLANT The most common type of hydropower plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which, in turn, activates a generator to produce electricity. But hydropower doesn't necessarily require a large dam. Some hydropower plants just use a small canal to channel the river water through a turbine. MAIN PARTS OF HYDROPOWER PLANT

Fig 3. Inside a Hydropower project

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Fig 4. Side view of HE project

Fig 5. Section view of HE project

Fig 6. Penstock

1. Dam - Most hydropower plants rely on a dam that holds back water, creating a large reservoir. Often, this reservoir is used as a recreational lake, such as Lake Roosevelt at the Grand Coulee Dam in Washington State. 2. Intake - Gates on the dam open and gravity pulls the water through the penstock, a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe. 3. Turbine - The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE). 4. Generators - As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons. 5. Transformer - The transformer inside the powerhouse takes the AC and converts it to higher-voltage current. 6. Power lines - Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three. 7. Outflow - Used water is carried through pipelines, called tailraces, and re-enters the river downstream. TYPES OF HYDROPOWER PLANTS There are three kinds of hydropower plants: storage plants, pumped storage plants, and run-of-the-river plants.

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Storage plants impound and store water in a reservoir formed behind a dam. During peak demands, where sufficient electricity cannot be generated by conventional means, enough water is released from the reservoir to meet additional power requirements. The water storage and release cycles can be relatively short (storing water at night for daytime power generation), or long (storing spring runoff for power generation in the summer). In these plants, water always flows downward from a storage reservoir behind a dam to the turbine. The major objection to these plants is that the water flow rate downstream from the dam can change greatly, causing a sudden power surge. This often involves dramatic environmental consequences including soil erosion, degrading shorelines, crop damage, disrupting fisheries and other wildlife, and even flooding and droughts. Pumped storage plants (PSP) reuse water after it is initially used to generate electricity. This is accomplished by pumping water back into a storage tank at a higher elevation during off-peak hours when the need for electric power is low. During peak demands and when there is an unexpected spike in the electrical load, water is allowed to flow back into the lower reservoir to produce more electricity. An important advantage of PSPs is the quick delivery of power during emergencies and power surges. In comparison, a typical coal- or natural gas-fired power plant takes many hours to start. In the United States, about one quarter of all hydropower generated is from pumped storage plants. In modern pumped storage plants, the same turbine-generator that generates electricity from falling water can also be used to pump the water back into the storage tank. In this case, the generator changes the direction of the electric field, forcing the turbine to rotate in the reverse direction and act as a motor, which runs the pump. Run-of-River Plants are typically low dams where the amount of water running through the turbine varies with the flow rate of water in the river. The flow rate of water in the run-of-river plants is usually smaller than in pumped storage plants, and the amount of electricity that is generated changes continuously with seasons and weather conditions. Since these plants do not block water in a reservoir, their environmental impact is minimal. A peaking plant can be turned into a run-of-river plant if a healthy stream of water is allowed to flow downstream of the dam from the reservoir. PLANT DESIGN Water used by a hydroelectric plant is usually stored behind a dam at a certain elevation above the turbine. Turbines are devices that are used to convert the energy of a moving fluid (usually water, steam, or air) into the rotational energy of a shaft. The water flows through a penstock and through the blades of the turbine, causing the turbine to rotate. The turbine shaft then turns a generator shaft and electricity is produced. Gates and valves depending on the amount of electric energy required can control the flow through the turbine. In a typical small hydro scheme, a portion of the water is diverted from a river or Page 21 of 67

stream through an intake valve to a man-made weir, and passed through a heavy metal screen into a settling chamber in which stones, timbers and other debris are removed and suspended particles of dirt settled before entering the turbine. Since no reservoir is blocking the flow of water, the impact on the river and habitat is minimized. Depending on application, either an impulse or a reaction turbine is used. In an impulse turbine, the available head is converted into kinetic energy by a contracting nozzle. The high velocity jet then impinges on the blades and turns the turbine. The most common impulse turbines are of the Pelton type, where a series of cupped buckets are set around its rim. A high-speed jet of water enters the wheel tangentially, and since water is deflected 180 degrees by the cups, nearly the entire momentum of the water is used to impart an impulse that forces the wheel to turn. The operator of an impulse turbine lets in air in order to maintain atmospheric pressure on the water before and after impinging the blades. Impulse turbines are used most often with heads exceeding 300 meters.

HYDRO TURBINES TYPES OF HYDRO-TURBINES : A) Reaction Turbines 1. 2. 3. 4.

Francis Kaplan Propeller Bulb

B) Impulse Turbines 1. Pelton Head Range 2m

to

70 m

Kaplan

30m

to

450 m

Francis

300m to

1700 m

Pelton

MAJOR COMPONENTS OF TURBINE: 1. Draft Tube/Draft Tube Cone Page 22 of 67

2. Spiral Case 3. Stay Ring/Vanes 4. Distributor • Guide Vanes/Nozzles(Deflectors) • Top Cover/Head Cover • Lower Ring/Pivot/Bottom Ring 5. Runner and Labyrinths 6. Turbine shaft 7. Turbine pit liner (Upper & Lower) 8. Turbine guide bearing • Housing • TGB Pads 9. Servomotors 10. Regulating ring/Regulating Mechanism 11. Shaft seal 12. Governor & OPU system Specific speed of a turbine: The specific speed (m-KW system) of a turbine is the speed of a geometrically similar turbine that would develop one kW power under a head of one meter. Specific Speed in M-KW System Francis

60

Kaplan

300

Pelton

4

to 400 to 1100 to

60

VALVES: There are two types of valves: 1. Spherical valve: It is used where the head is high, i.e. to sustain high pressure. (For Heads above 200m) 1. 2. Butterfly valve: It is used where the inlet pressure of water is comparatively lower. (For Heads above 200m) They are used in Page 23 of 67

1. Penstocks 2. Turbine Inlet Valve

POWER HOUSE POWER HOUSE BUILDING CONSISTS OF THREE MAIN AREAS NAMELY 1. Machine Hall/Unit Bay 2. Erection/Service Bay 3. Control Room/Auxiliary Bay

PROCEDURE FOR DIMENSIONING OF POWER HOUSE • Head Calculation. • Selection of specific speed and synchronous speed of turbine. • Fixing the turbine setting • Calculation of discharge diameter. • Calculation of spiral case dimensions • Calculation of draft tube dimensions • Calculation of Generator dimensions. • Finalization of overall dimensions of the power house.

HEAD CALCULATION • Avg. Gross Head

= MDDL + 2/3(FRL - MDDL) -TWL(4 Units Running) = 203 + 2/3(208 - 203) -184.24 = 22.09 m. • Rated/Net Head = Avg. Gross Head - Head Loss = 22.09 - 0.75 = 21.34 m. • Max. Gross Head = FRL - min TWL = 208.00 - 181.78 = 26.22 m • Max. Net Head

= Max. Gross Head-Head Loss = 26.22-0.75 = 25.47 m • Min. Gross Head = MDDL - TWL(4 Units Running) = 203.00 - 184.24 Page 24 of 67

• Min. Net Head

= 18.76m = Min. Gross Head - Head Loss =18.76 - 0.75 =18.01 m.

SELECTION OF MACHINE SPEED • From economical point of view, the turbine and generator should have the highest practicable speed to develop given hydropower for given design head. However, final speed may be selected considering the following parameters: • Variation of head, • Silt content, • Cavitation, • Vibrations, • Drop in peak efficiency etc. • From the available formulae, the specific speed for a specific head is calculated. Then for even number of poles of generator, rated speed is obtained. On the basis of this rated speed, corrected specific speed is calculated.

CALCULATION OF SPEED: • Specific speed w.r.t. Head – Kaplan Turbine, Ns = 2570 * H-0.5 = 2334 * H-0.5

….HARZA ….USBR

– Francis Turbine, Ns = 3470 * H-0.625 ….HARZA • Rated Speed –N = Ns * H5/4 * P-1/2 • Synchronous speed (N=120f/p) nearest to Rated speed obtained from above formulae is selected. • Corrected Specific speed, Ns = N * P1/2/H5/4

HYDRO GENERATORS Hydro Generators are low speed salient pole type machines. Rotor is characterized by large diameter and short axial length. Page 25 of 67

Capacity of such generator varies from 500 KW to 500 MW. Power factor are usually 0.90 to 0.95 lagging. Available head is a limitation in the choice of speed of hydro generator. Standard generation voltage in our country is 3.3KV, 6.6KV, 11 KV ,13.8 KV, & 16KV at 50 Hz. Short Circuit Ratio varies from 1 to 1.4.

Fig 7. Hydro Generator

CLASSIFICATIONS Classification of Hydro Generators can be done with respect to the position of rotor ( i) Horizontal (ii) Vertical (two types) a) Suspension Type b) Umbrella Type DESIGNATION Type of Hydro generator is designated as follows: SV 505 - 16 190 Where, SV 505 190 16

Þ Þ Þ Þ

SYNCHRONOUS VERTICAL OUTER DIAMETER OF STATOR CORE ACTIVE LENGTH AT STATOR CORE IN NO. OF POLES Page 26 of 67

in cm in cm

GENERATOR BARREL Di (Air gap diameter, select from fig. 8 on page no. 25 of BHEL curve) Da (outer core diameter) Df (Stator frame diameter) Db ( Inner diameter of generator barrel)

Fig 8. Generator Barrel

UMBRELLA TYPE GENERATOR COMBINED LOWER THRUST & GUIDE BEARING

Fig 9. Umbrella type generator

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Fig 10. Semi-Umbrella Type Fig 11. Umbrella Type

SUSPENDED TYPE GENERATOR

• UPPER THRUST BEARING • UPPER GUIDE BEARING • LOWER GUIDE BEARING

-1 -1 -1

Fig 12. Suspended Type (Section view)

Fig 13. Suspended Type

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SELECTION OF NO. OF POLES  Nsyn (Sync. Speed) = 120 F P  Synchronous Speed Of The Generator Depends Upon The Specific Speed Of The Turbine  Nsyn = Ns X Hn 1.25 / Pt 0.5

COMPONENTS OF GENERATOR  STATOR  ROTOR  BRACKETS  GENERATOR AUXILIARIES

PARTS OF STATOR  STATOR SOLE PLATES  STATOR FRAME  STATOR MAGNETIC CORE  STATOR WINDINGS STATOR SOLE PLATES

Fig 14. Stator segment

 Sole plates are embedded in the secondary concrete and are designed to support generator frame.  The sole plates are designed to transmit the tangential stresses of the generator to the concrete under most severe conditions.  The design should accommodate for free radial movement of frame on account of radial expansion caused by temperature rise. STATOR FRAME The stator frame has to ensure following functions:  Support weight of magnetic core, winding and upper bracket.  Transmit vertical loads, normal and accidental torques to the foundations.  Withstand centripetal and unidirectional magnetic forces which may result on account of eccentricity of rotor  Guide the cooling air towards heat exchangers  Allow a good positioning of magnetic core punchings.  Allow stator handling.  Support the connections and terminals. Page 29 of 67

 The frame is made up of rolled steel sheets supported by vertical beams of high inertia.  The frame is shipped to site in single or several parts depending upon the handling and transportation limitations of the site. STATOR MAGNETIC CORE  Provides House for stator windings  The core is made by stacking of Grain Oriented magnetic steel punchings.  The punchings are insulated with varnish on both sides in order to give smooth coating and high insulation quality.  The punchings are stacked into elementary layers which are separated by spacers to cater for radial ventillation which enables air circulation for cooling active parts.  The punchings are axially clamped to reach a strong cohesion to form rigid system and the stacking process is done at different stages. STATOR WINDINGS  Stator Windings can be of Double Layer Bar Type Wave connected or Coil type Lap connected.  For Hydro generators normally bar type wave connected windings are used.  Each bar is composed of an assembly of strands of small radial section in order to reduce copper losses.  Each strand is in turn insulated by glass lapped tape with epoxy resin.  Each bar is insulated over its whole length by continuous taping according to class ‘F’ insulation.  The connection between bars is achieved by means of copper plates brazed to the individual strands and are insulated by having gaps filled with post polymerized resin.  The whole winding is totally insulated without any bare point to avoid fault on account of moisture/polluting agent.  The windings are fastened to the supporting rings to form a homogeneous and solid assembly. Fig 15. Cross Section of the stator bar

ROTOR COMPONENTS  ROTOR SHAFT  ROTOR SPIDER  ROTOR RIM  ROTOR POLES  RING COLLECTORS

Page 30 of 67

Fig 16. Rotor

Fig 17. Rotor

Fig 18. Rotor

ROTOR SHAFT Rotor shaft has to achieve the following functions:  Provide coupling face for turbine shaft  To transmit the motor or braking torques between the turbine shaft and the rim through rotor spider.  Provide surface for thrust, upper and lower bearings To provide for lifting of rotor. The shaft is made either as a single part or in case of shaft less rotor, then two stub shafts are connected to the rim at the upper and lower parts for accommodating thrust bearing surface and coupling flanges . ROTOR SPIDER Rotor spider has to ensure following functions:  To transmit the motor or braking torques between the turbine shaft and the rim.  To ensure the centering of the rim and the poles.  To support the braking track and withstand its centrifugal forces.  To ensure the passage of the cooling air flow to the rim.  The spider is composed of discs and ribs welded longitudinally to the shaft.  The ribs are designed to accommodate machined bars for guiding the rim plates

Page 31 of 67

Fig 19. Rotor Spider

ROTOR RIM The rotor rim ensures the following functions:  To accommodate the field poles.  To ensure the magnetic flux path from one pole to the other.  To take part in the fan effect of the radial cooling of the synchronous machine.  To contribute in providing the required inertia.  The rim constituted by stacking of 3 to 5 mm thick segments made of rolled sheet  Segments are clamped axially by means of high resistance steel bolts  The stacking is so designed in to numerous overlapped layers so as to permit provision of radial ducts in the inter-pole axis without reckoning mechanical resistance. Thus, rim acts as centrifugal fan uniformly distributing air flow over the whole generator length.

Fig 20. Rotor Rim

ROTOR POLES The rotor poles ensures the following functions:  Create the induction flux and distribute it properly in the air gap  Suppress the asynchronous flux waves and damp the oscillations (damper winding)  Transmit the torque from rim to the air gap  The pole cores are constituted of a stack of punched laminations which are clamped between two end plates traversing the entire length of the pole  The field coils are made of flat copper strips brazed at each coil edge.  The inter-turn insulation is achieved by strips of epoxy insulation.  The coil assembly is hot polymerized under pressure to achieve required electrical and mechanical properties.  Coil insulation w.r.t. ground is made by wrapping the pole core with an insulating complex  The poles are weighed and distributed around the rim during the assembly so as to have same weight diametrically opposite to each other.

Page 32 of 67

RING COLLECTORS  The field current is supplied to the field winding from the excitation system, through a system composed of slip rings and brushes.  The slip rings, which are made of forged steel, are installed in the upper part of the rotor.  The connection between the slip rings and field windings is achieved through copper bars fitted inside or along the shaft on the upper part of the rotor.  The slip rings are designed to fit properly with the brushes and are grooved spirally to reduce brush wear.  The brushes are carefully designed so as to carry required field current  Brushes are held by insulated brush holders

BRACKETS  Provided for housing of Thrust and Guide bearings Two types of brackets are provided for a generator: 1. Upper bracket 2. Lower bracket

UPPER BRACKET The upper bracket has to ensure the following functions:  Support vertical loads of generator upper floor and the superstructure  To take upper guiding radial forces tangentially to the concrete walls of the generator pit  To accommodate and transfer the vertical load of the rotor and turbine assembly in case of suspended type of machine.  To provide path for circulation of air.  The upper bracket is composed of central hub supporting the guide and/or thrust bearing  The structure is formed by lattice of laminated steel beams resting on upper part of the stator frame which are anchored to the generator pit either directly or through radial jacks.  Air baffles fitted on the bottom side of the upper bracket allow proper circulation of air flow  The upper bracket is shipped in single or several parts and are assembled at site as per the requirements. LOWER BRACKET The lower bracket has to ensure the following functions: Page 33 of 67

 Supports the lower guide bearing and it combines braking and lifting jacks  In case of umbrella / semi-umbrella it may also house the thrust bearing and therefore need to transfer load of rotor and turbine to the foundations .  It is composed of central hub with steel arms welded to it.  The bottom side of the arms are provided with fixing arrangement for fixing them upon anchoring plates which are embedded in the concrete  The upper side of the arms accommodate for braking and lifting jacks along with necessary pipeline i.e., oil and air pipelines . The hub will accommodate for guide bearing and / or thrust bearing as per the requirement .

GENERATOR AUXILIARIES  EXCITATION SYSTEM  AIR COOLING SYSTEM  BRAKING AND JACKING SYSTEM  BEARINGS  FIRE PROTECTION  HEATERS

EXCITATION SYSTEM Excitation systems supply and regulate the amount of dc current sent to the generator field winding.

EXCITATION SYSTEM –OBJECTIVES Good

response in voltage and reactive power control.  Satisfactory steady state stability i.e. sufficient clamping of electro – magnetic & electro – mechanical transient.  Transient stability for all stated conditions.  Quick voltage recovery after fault clearance. TYPES OF EXCITATION SYSTEM Modern excitation system consists of following two major types of systems:  Static excitation system  Brushless excitation system They utilise microprocessor based digital controllers as AVR’s. Page 34 of 67

EXCITATION SYSTEM – COMPONENTS 1. 2. 3. 4. 5. 6.

EXCITATION TRANSFORMER (DRY TYPE ) RECTIFIER SYSTEM AUTOMATIC VOLTAGE REGULATOR FIELD FLASHING UNITS FIELD CIRCUIT BREAKER DISCHARGE RESISTOR

AIR COOLING SYSTEM  Generator is provided with a closed, recirculating air cooling system  The cooling pressure is created by fanning action of rotor spider  The air circulates through radial ducts provided in the rotor rim which allows a cooling air flow to be distributed radially and uniformly all along the machine axis  The air circulation path is spider-> rim -> inter-pole areas-> stator winding-> stator core radial duct-> air coolers-> lower and upper floors-> lower and upper air baffles-> spider

BRAKING AND JACKING SYSTEM  The hydro generators are provided with mechanical friction braking system which helps to stop the generator’s rotation after unit is stopped / tripped off-line  The brakes are normally applied when the unit speed is slowed down to less than 25% of the rated speed to avoid wearing of thrust bearing pads  Brake shoes situated on the lower bracket are pressed against the brake tracks on the rotor to bring the machine to the rest  Brake shoes are also used as jacks for lifting of the rotor for which the oil under pressure (about 100 kg/cm2) is fed from high pressure pump unit. After jacking the rotor can be maintained in lifted position by turning the locking nut and releasing oil pressure.  In modern hydro electric generators specially Pelton wheels, electrical dynamic braking is used in addition to mechanical braking system which will reduce wear on the mechanical brakes  The dynamic braking is initiated at around 50% of rated speed and maintained until mechanical friction brakes are applied which are normally applied at 10 -15% in conjunction with dynamic braking BEARINGS  Vertical hydro generators are normally provided with thrust bearings and guide bearings. Page 35 of 67

 The number of guide bearings depends on the size of the machine. THRUST BEARINGS The hydro generators have thrust bearings located either at the top (Suspended) or at bottom (Umbrella / Semi-umbrella) of the generator to support the rotating weight of the machine.

GUIDE BEARINGS Hydro generators are provided with lower and / or upper Guide bearings for maintaining the shaft in alignment

TURBINE – GENERATOR SET T.G. SET ASSEMBLY

Fig 21. T.G. Set Assembly

T.G. SET SECTION

Page 36 of 67

Fig 22. T.G. Set Section

DESIGN STUDY OUTPUT COEFFICIENT (derived from output equation of AC machines) (Pg-456,AK Sawhney) Output Equation: Q = C0 * D2 * L * Ns Where, output coefficient, C0 = 11 * Bav * ac * Kw * 10^(-3) Q = kVA rating of machine Bav = specific magnetic loading ac = specific electrical loading Kw = winding factor From these equations we can infer that the volume of active parts is inversely proportional to the value of output coefficient C0. Thus an increase in value of Results in reduction in size and cost of machine and so looking from the economics point of view the value of output coefficient should be as high as possible. Now we see that output coefficient is proportional to specific magnetic and electric loading .Therefore the size and cost of the machine decreases if we use increased values of specific magnetic and electric loading. Hence economically these values should be as high as possible. their limit is decided by analyzing the effect of increased loadings on performance characteristics of machine. Too high values may have adverse effects on temperature rise,efficiency,power factor(in case of induction motors) and commutation conditions (in case of dc machines).Therefore optimum values are selected.

Page 37 of 67

We can calculate the output coefficient from a graph (Large AC Machines, JH Walker, Figure 1-1 page 4.) if we know the number of poles of the machine. The graph is obtained by analyzing the published data of 40 generators in manufacture in USA, Canada, UK, Japan a Europe. MACHINE PARAMETERS Bore Diameter : It is the inner diameter of the stator core. Flywheel Effect: (or Mechanical Inertia is defined in terms of the start up time of the unit) (Standard Handbook of Powerplant Engineering by Thomas C. Elliott, Kao Chen, Robert Swanekamp)

Tm = (WR2 * n2) / [(1.6 * 10^6)P] Where n = rotational speed of unit in rounds/min P = full gate turbine capacity in H.P. WR2 = Product of revolving parts of unit and square of radius of gyration (turbine runner, shaft and generator rotor), lb-ft2 For preliminary design studies in which the unit WR2 is not known, its value may be estimated from the following U.S. Bureau of Reclamation formulas: Turbine WR2 = 23,800 [P / n^(3/2)]^(5/4) Generator WR2 = 356,000 [kVA / n^(3/2)]^(5/4) The heavy pole pieces produce a flywheel effect on a slow speed rotor. This helps to keep the angular speed constant and reduce variations in voltage and frequency of the generator output. In our design we have used the formula: Flywheel effect (GD2) is computed as follows: Generator WR2= 15000 x (KVA/ N3/2)5/4 Where KVA = Unit rating in KVA N = Unit speed in RPM Page no. 1.51. Power Engineer’s Handbook by TNEB Engineer’s Association, Chennai GD2 = 4 x WR2 (Page 810, Water Power Development Vol. TWO/B, E. Mosonyi) Number of poles : Can be calculated as P=120f/N Page 38 of 67

Where f =frequency of output N=speed of the rotor Air gap Diameter calculation (same as bore diameter) a. Di Obtained from BHEL graph (Air Gap diameter) b. Di = (60 * Vr) / (pi * N) pi=22/7 Where Vr = Max. Peripheral velocity. It can be obtained from Fig. 1-2 Page 5, Large AC Machines by J.H. Walker The bigger of the above two diameters is selected.

Stator Core and frame length calculation: Stator core length is the gross length of the stator. It can be calculated using the formula for output coefficient.The output coefficient can be obtained from graph and air gap diameter calculated above. Once these two are known stator length can be calculated using the formula: Stator core length,

Lt = W/ (Ko* Di2 * N)

Where W = Rated KVA of machine Ko = Output coefficient obtained from curve (Fig 1-1, Page 4, Large AC Machines by J.H. Walker.) N = Rated RPM of the machine

Radial and Axial Ventilation The ventilating systems can be classified into three types depending upon how the air passes over the heated machine parts ,as :(a)Radial, (b)Axial. Radial Ventilating System :This system is most commonly employed because the movement of rotor induces a natural centrifugal movement of air, which may be augmented by provisions of fans if required . The advantages of radial system are : (1)minimum energy losses for ventilation (2)sufficiently uniform temperature rise of machine in the axial direction The disadvantages are :_ Page 39 of 67

(1) It makes the machine lengths larger as space for ducts has to be provided along the core length . (2) The ventilating system sometimes becomes unstable in respect to quantity of cooling air flowing. Axial Ventilating System: In this case the ventilating ducts are parallel to the axis .This system is suitable for machines with medium output and high speeds. This is because in high-speed machines, a solid rotor construction with restricted spider is used in order to avoid centrifugal stresses and this restricts the provision of using radial ducts. This disadvantages of axial ventilation are: (1) non uniform heat transfer (2) increased iron loss – the provision of axial ventilating ducts behind the slots of the stator reduces the amount of iron giving rise to increased flux density in the stator core, this increases the iron loss. However in large number of cases this loss is compensated by improved cooling.

STATOR DESIGNING Pole pitch is defined as the peripheral distance between two consecutive poles. It may be expressed as number of slots, degrees .(electrical or mechanical) Calculated as :

ψ= pi x Di/P

Where Pi (constant) =22/7 Di = Air gap diameter in meters P = No. of poles Pole Arc = Pole pitch * 0.7 Gross area of air gap/pole = Stator core length x pole pitch (See page 318, Electrical Machinery ,Dr. P.S. Bimbhra)

In a typical hydro generator wound for 11-16kV experience shows that to obtain flux densities in the stator and rotor which are satisfactory both as to magnetizing ampere-turns and core loss and to obtain acceptable values of the transient reactances , a mean flux density (Bm) of 0.6-0.7 Wb/m^2 should be assumed. Flux per pole (φ) =Mean flux density * Pole pitch (ψ)* Length of core * 0.01 Assuming a suitable value of Bm, the flux per pole can be calculated. Page 40 of 67

In the preliminary stage, tentative value of number of turns per phase can be calculated as T ph

= (k1k2 V ph)/4.44fφ

We can assume the value of k1k2 as 1.1 (source : page 14,Large AC Machines J.H. Walker) Where Vph is the rated generator voltage. Calculation of number of parallel paths . Total current in a slot should not exceed 5000 A. (Current in Slot should lie between 3000 to 5000A as per CEA) If I be the rated current per phase and there be p parallel paths then current per conductor is I/p , and current per slot is 2*I/p This should not exceed the limit of 5000 A. 5000 > 2 * I / p this gives a minimum value of p , the value of p greater than or equal to this value which satisfies other designing constraints are chosen as the appropriate number of parallel paths. After the calculation of turns per phase we can calculate the approximate no. of stator slots. No. of slots is given by, Ns = (no. of phases) * T ph * (no. of parallel paths) / (turns per coil) Note: Turns per coil = 1 for bar winding Number of conductor per slots = 2 ( for bar winding) Number of conductors in series per phase = Nc= Z x S/ (Parallel path x 3) Where Z = No. of conductors per slot and S = Total no of slots Stator slot pitch = Pi x Di / total no of slots Slot angle (Mechanical) = 2*Pi / S (P = no of poles S = Total no of slots) in radians Slot angle (Electrical) = P * (Mechanical Slot Angle) /2 Page 41 of 67

MODIFIED CALCULATION Turns per phase as calculated from slot selection = No of slots / (3 x No of parallel paths)

New Flux per pole=k1 x k2 x rated generator voltage/(4.44 x Turns per phase x f) f = 50 Hz k1 x k2 = 1.1 (source : page 14,Large AC Machines J.H. Walker)

Modified Flux density = Flux per pole / (Stator core length x pole pitch) Where, Stator core length and pole pitch are expressed in meters

Maximum Flux density (Bg) = Modified flux density / Form Factor

RADIAL LENGTH OF AIR GAP In the absence of specified values of Xd (direct axis synchronous reactance in p.u.) and Xl( leakage reactance in p.u.) on a 0.9 pf machine a value of unity may be assumed for the former and 0.15 p.u. for the latter. The value of armature reaction (Ma) may be calculated as Ma = (2.12* Iph *Tph* ka)/(Np *k1*k2) (ampere-turn /pole) Where I ph =current per phase Tph = turns per phase Ka =Amplitude factor obtained from the graph (given on page 79 ,fig 5-1,Large AC machines by J.H.Walker) k1*k2=1.1 Page 42 of 67

Then , Air gap Ampere Turn (open circuit) Mg =Ma/(Xd-Xl) (source :Page 79 equation 5-2 ,Large AC machines J.H.Walker) where, Xl = leakage reactance in p.u. Xd = direct axis synchronous reactance p.u. The value of φ we used earlier was based on an assumed value of Bm=0.675 Wb/m^2 and this corresponds approximately to Bg =0.85 Wb/m^2.Then Ma=0.796*ge*Bg * 10^4 gap = 1.26 x Air gap Ampere –turn / (Max flux density) (source page 79,81 Large AC Machines by J.H.Walker) SHORT CIRCUIT RATIO The short ratio (SCR) of a synchronous machine is defined as the ratio of field current required to produce rated voltage under open circuit conditions to the field current required to circulate rated current at short circuit. Short circuit ratio is the reciprocal of synchronous reactance Xd ,if Xd is defined in per unit value for rated voltage and rated current. The value of Xd for a given load is affected by saturation conditions then exist, while SCR is specific and univalued for a given machine as it is defined at the rated voltage. For salient pole hydro electric generators SCR varies from 1.0 to 1.1. EFFECT OF SCR ON MACHINE PERFORMANCE (a) Voltage Regulation A low value of SCR means large synchronous reactance .Thus the machine has greater changes in fluctuations of load. The inherent voltage regulation of the machine is poor. (b) Stability. A low value of SCR has a lower stability limit as the maximum power output of the machine is inversely proportional to Xd. (c) Parallel Operation Machines with a low value of SCR are also difficult operate in parallel because a high value of Xd gives a small value of synchronizing power. This power is responsible for keeping the machines in synchronism. Also the transmission line impedance adds up to the machine impedances thus it further reduces the synchronizing power as the machines are weakly held in synchronism. They become more sensitive to torque and voltage disturbances. Page 43 of 67

(d) Short circuit current A small SCR indicates a small value of short circuit current as Xd is high. But this is not a problem as short circuit currents can be limited and the machines need not be designs with low values of SCR. (e) Self Excitation Machines feeding long transmission lines should not be designed with a small SCR (high Xd) as this would lead to large voltages on open circuit produced by self excitation owing to large capacitive currents drawn by the transmission lines. We have seen that a machine with low value of SCR has a lower stability limit and a low value of inherent voltage regulation. On the other hand a higher value of SCR means a high value of short circuit current. Also the machine designed with a higher value of SCR has a long air gap which means that the mmf required by the field is large. Hence a machine with higher SCR is costlier to build. Present trend is to design the machine with a low value of SCR . This is due to the recent advancement in the fast acting control and excitation systems. CALCULATION OF MEAN LENGTH OF A TURN. The MLT is assumed to be made up of the following portions: The length of coil in the slot (Lc) ,the length of the straight portion extending from the core to the angled portion of the end winding (Ac), the angled portion (Y) and the portion at the end consisting either of the evolutes (multi-turn-coil) or clips (single turn bar) . The MLT is then given by MLT =2*Lc +4(Ac+Bd)+4Y ,(Lc is in cms) Where Ac + Bd is obtained from fig 3-9 ,Large AC Machines J.H.Walker. And Y =Pdsecθ3/2 Pd = [pi *(100Dg + 2ds)/Np]*[percentage coil pitch/100] Ds=depth of slot And sin θ3 =Xc/λs1 λs1 = pi*(Dg100 +2ds)/Ns Xc = coil pitch at end winding = width of insulated coil + clearance (w) (see page 39,49 Large AC Machines by J.H.Walker) NUMBER OF RADIAL VENTILATING DUCTS. nd = 0.26(Lc100 -12.5)

for duct width = 6.6mm Page 44 of 67

(page 68, 69 Large AC Machines J.H.Walker) Le (effective length of core) = (Lc – nd*wr*.01) Where nd=number of radial ventilating ducts wr=width of duct beam in cm (Page 70, Large AC Machines by J.H. Walker.) Active length of stator core = Stacking factor x Length of core duct Where, stacking factor = 0.93 (Page 89, Large AC Machines by J.H. Walker.)

ARMATURE WINDINGS, COILS AND THEIR INSULATIONS

There are two types of coils : 1. Single turn bar 2. Multi turn bar Single turn coil : A single turn bar winding is used in machines when the armature current per circuit exceeds 1500 A. As the current is quite large so the cross-section of the conductors used is very large and so bars used are subdivided into many parts to reduce the eddy current losses in them.

Basic structure of the conductors used: There are two conductors in a slot if the bar winding is used. Each conductor consists of two vertical stacks of copper laminations insulated by either asbestos or glass rovings. The advantage of using glass is that it gives a high space factor. The two vertical stacks used are also insulated from each other. The dimensions of individual strand is determined partly by electrical considerations so as to reduce the eddy current losses to less than 1/5 the of I^2R losses and partly by the manufacturer considerations. Page 45 of 67

Further the eddy current loss in the top coil side is more than that in the lower one so there is a difference in the rise of temp of the two. This temp rise difference is reduced by increasing the no of strands in the top coil side there by reducing the thickness of the strands in the top coil side. To reduce the circulating current losses it is essential to use some form of transposition of conductor laminations in the slots. In the transposition each conductor lamination is arranged to move continuously through all positions in depth of coil side so that the leakage reactance of all the conductor laminations is equalized so that no circulating current flows. Roebel transposition is widely used for this purpose.

Particulars used (Terminology and dimensions and material used ) : 1. Strand insulator: Insulator used between adjacent strands of a stack. Usually asbestos or glass is used. Asbestos has a diametric thickness of about 0.38 mm while the thickness of the glass varies from 0.29 to 0.38 mm. Width of the strands varies between 4 mm to 7 mm. Thickness of the strands rarely exceeds 3mm. The maximum thickness used depends on the eddy current losses. 2.

Slot insulation: Insulation used for insulating the conductor from the slot. The width of the slot is usually less than 25 mm with a value of 5 mm for the thickness of main slot insulation.

3. Separator: Even the two conductors in a slot have to be separated electrically from each other so a separator in used for the purpose.

Type of insulation systems generally used : 1. Bitumen Mica flake insulation system: The application of the bitumen main insulation leaves voids at each cross over so as to give rise to corona losses. This can be avoided by using asbestos boards as packers or by applying asbestos or mica putty. Page 46 of 67

Bitumen mica folium applied to the slot portion of the bar while mica tape on the overhang portion was most commonly used insulating materials earlier. The mica tape 0.13 mm thick and 20 mm wide is wrapped by hand up to 20 half layers. So this process is both time consuming and expensive. 2. Epoxy Novalak mica paper insulation system: The rows of conductor stacks are bound with epoxy based resins. This is done by using two highly loaded epoxy glass separators. The stack is then pressed at 160 degree Celsius to form a rigid mass. This type of construction does not require the filling of external voids. The over hang insulation is in the form of a no of layers of flexible isopthalate varnished polyester backed mica flake tapes. The insulation of the slot portion consists of a no of half lap layers of epoxy novalak bonded glass backed mica paper tape. This system permits the machine to be operated at a higher temp rise due to its greater thermal conductivity.

Multi turn coil: In this type of coils an additional insulation between between individual turns has to be provided. The interturn insulation must be designed to withstand surges of magnitude 1.5 times of the line voltages. The inter turn insulation used is mica tape half overlap and asbestos. The thickness of the mica tape is 0.13 mm and that of asbestos 0.38 mm. Multi turn coils epoxy novalak mica paper system : The epoxy novalak mica paper insulation used is different for the slot portion of the conductor and the over hang. Novalak mica paper tapes are used for the slot portion while isopthalate varnished mica flake tapes are used for the over hang. (source: Pg-744, A.K. Sawhney)

WINDINGS

TWO TYPES: 1. Concentrated windings: these the mainly used in design of field windings for salient pole machine 2. Distributed windings : are used in stator and rotor of all the ac machines. Page 47 of 67

ARMATURE WINDINGS: 1. Closed windings: are used for dc machines and ac commutator machines . 2. Open windings : are used only for ac machines like synchronous machines and induction machines.

Related Terms: 1. Pole pitch poles. 2. Coil span 3. Full pitch coil 4. Chorded coil

: : : :

peripheral distance between adjacent

peripheral distance between two coil sides. coil span = pole pitch coil span < pole pitch

CLOSED WINDINGS : Two types: 1. Lap windings : a=P 2. Wave windings : a = 2 Where, a = no of parallel paths P = no of poles Lap Windings :

yb = 2C / P +/- K yw = yb – yf = 2 yc = 1 Where, C = no of coils P = no of poles yc = commutator pitch yb = back pitch yw = winding pitch K = Fraction or integer such that yb is an odd integer.

Page 48 of 67

Wave windings :

yc = (C + 1) / (P/2) yw = 2 yc yw = yb + yf Where, C = no of coils P = no of poles yc = commutator pitch yb = back pitch yw = winding pitch Note : Above relations are given only for progressive windings retrogressive windings are rarely being used.

as

OPEN WINDINGS : Closed or commutator windings are always double layer windings whereas A.C. armature windings may be a single layer or double layer windings. Single layer windings are used for small rating ac machines whereas double layer windings are used for machines above about 5 kW.

Advantages of double layer windings over single layer windings : 1. 2. 3. 4.

Easier to manufacture and low cost. Chorded winding is possible. Lower leakage reactance so better performance Better e.m.f. in case of generators.

In poly phase windings it is essential that 1. Generated e.m.f.s of all the phases are equal in magnitudes. 2. The wave forms of phase e.m.f.s are identical. 3. The frequency of phase e.m.f.s is equal. Double layer windings: Page 49 of 67

Related terms: 1. Phase spread: May be defined as the angle subtended by one phase belt where phase belt is the group of adjacent slots belonging to one phase. 2. Integral slot windings: In this type of windings the slots per pole per phase is an integer. These may be full pitched or chorded windings. 3. Fractional slot windings: In this type of windings the slots per pole per phase is not an integer. These may again be full pitched or chorded windings.

Single layer windings: Two types: 1. Concentric Windings: These again can be of two types: A) Half coil windings : In this type of windings the adjacent coil groups have the current in the same direction. No of coil groups = P/2 B) Whole coil windings: In this type of windings the adjacent coil groups have the current in opposite directions. No of coil groups = P 2. Mush windings These type of windings have the following limitations: 1. Concentric SLW cannot have chorded windings. 2. In concentric SLW effective coil span is equal to pole pitch even though the coil span of individual coils in a coil group differs from pole pitch. 3. In mush windings coil span is constant. (source: P.S. Bhimbra) CHOICE OF TYPE OF STATOR WINDING For making a choice between the two types of windings we need to compare the two windings (multi turn and single bar) : Page 50 of 67

1.The multi turn coil winding allows greater flexibility in selecting the value of number of slots to give required number of turns per phase than the bar winding. 2.The process of winding multiturn coils involves bending the top coil-side after the bottom coil side has been placed in the slot. To ensure that this bending does not damage the insulation at the point where the coil side emerges from the slot, the insulation has to have sufficient flexibility . This is also helpful when faulty coils have to be replaced in service. With the bar winding , bottom and top bars are laid in the slots separately and no bending is involved. 3.The choice between a multi turn coil lap and a bar winding may in the first place be determined solely on a cost basis since a multi turn coil being machine made is cheaper than the hand made bar. For heavy current generators having current > 1500 amps (source:page 23,Large AC Machines by J.H.Walker) the choice is a bar winding and this may use the lap or wave connection. The extension of the end windings from the core are greater with the wave than with the lap but this is largely counterbalanced by the reduced end connections of a wave winding. 4.The bar windings require clips to be soldered at each pair of bars at the back and front of each pair of bars in order to produce series connection of the coils. These are obviously not required with the multi-turn coils so that in this respect the latter is cheaper to wind than the former. 5.In deep coil sides, it is necessary to consider the transposition of individual strands in each effective turn to avoid excessive eddy current effects. In multi turn coils with the turns per coil greater than three the transposition is inherent in the 180 degree turn in the evolute if the coil, is effective in restricting the circulating eddy current loss to an acceptable value. With 2 or 3 turns a semi Roebal transposition in one turn of the coil will again satisfactorily reduce the circulating eddy current loss. With the single turn bar winding with the solid connection of the strands and thus no transposition in the evolute, full Roebel transposition which eliminates the circulating eddy current loss, is essential. 6.In addition to the main insulation to earth the multi turn coil requires each turn to be insulated with several layers of mica tape, to provide sufficient dielectric strength to withstand steep fronted impulses set up by switching or lightning strokes on the line . This turn insulation lowers the space factor in the depth of the slot. In the single turn bar winding with 2 effective bars per slot the inter turn insulation is of course twice the thickness of the insulation to earth so that no special precautions against impulses are necessary. 7. With say, 2 circuits in parallel in each phase, in the multi-turn coil an inter turn insulation failure will lead to a circulating current in the 2 parallel circuits and a reduction in the line current. However, with only one ineffective turn the out of balance in the line current may be insufficient to operate the Merz-Price relay. This situation is covered by bringing out the ends of the two circuits and installing a circuit balance relay, which operates as soon as the voltages in the two circuits are Page 51 of 67

unequal. Such a relay is of course connected in each phase .As discussed above with a single bar winding no inter turn insulation failure may be anticipated and such relays are unnecessary. Many firms in Europe and the USA, particularly the latter where labor charges are high, prefer the multi turn coil with its relatively low labor content and thus overall cost. In the USSR the single turn bar winding with wave connection is used on all hydro electric generators, its technical advantages, in the opinion of Russian designers, outweighing the slight additional cost.

Annexure I a) Input Screen

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b) Output Page 53 of 67

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Annexure II Software Code

a) Form1 'Dim curr_rated, volt_rated, speed_rated, pow_rated, pow_fac, scr, stack_fac As Double Dim stack_fac As Double Dim scheme As Integer

Private Sub cmd_clear_Click() Dim i As Integer For i = 0 To 5 Text1(i).Text = "" Next i Form1.cmd_Excel.Enabled = False End Sub Private Sub cmd_close_Click() End End Sub Private Sub cmd_Excel_Click() Dim pet As Integer pet = Module1.display_excel(volt_rated, pow_rated, speed_rated, scr, pow_fac, stack_fac) MsgBox ("Data Written in" & App.Path & " \specification.xls") End Sub Private Sub cmd_submit_Click() Dim k, m As Integer For k = 0 To 5 If Text1(k).Text = "" Then MsgBox ("Please enter some value in the empty box!") Exit Sub End If Next k For m = 0 To 5 If Text1(m).Text = "0" Then Page 55 of 67

MsgBox ("Please enter a non zero value in the input box!") Exit Sub End If Next m pow_rated = Val(Text1(0).Text) ' in MW speed_rated = Val(Text1(1).Text) ' IN RPM volt_rated = Val(Text1(2).Text) 'in KV scr = Val(Text1(3).Text) stack_fac = Val(Text1(4).Text) pow_fac = Val(Text1(5).Text) If Option1.Value = True Then scheme = 1 Else scheme = 0 End If Dim ret As Integer ret = Module1.calculate(volt_rated, pow_rated, speed_rated, scr, pow_fac, stack_fac, scheme) 'ret = Module1.display_excel(volt_rated, pow_rated, speed_rated, scr, pow_fac, stack_fac) MsgBox ("Calculation Done!!!") Form1.cmd_Excel.Enabled = True '---------------------------------------------------------------Dim spec(1 To 10) As Double Dim cur_row As Integer Dim count1, count2 As Integer spec(1) = curr_rated spec(2) = num_pole spec(3) = out_coeff spec(4) = air_gap_dia spec(5) = parall_path spec(6) = num_slots spec(7) = num_radial_duct spec(8) = len_core_eff spec(9) = num_strand spec(10) = slot_depth Form1.MSFlexGrid1.Cols = 2 Form1.MSFlexGrid1.Rows = 11 For count1 = 0 To 1 'Form1.MSFlexGrid1.Col = count1 Form1.MSFlexGrid1.ColWidth(count1) = 2000 Next count1 For count2 = 0 To 10 'Form1.MSFlexGrid1.Row = count2 Form1.MSFlexGrid1.RowHeight(count2) = 600 Page 56 of 67

Next count2 'Next count1 Form1.MSFlexGrid1.Col = 0 Form1.MSFlexGrid1.Row = 0 Form1.MSFlexGrid1.Text = "PARAMETER" Form1.MSFlexGrid1.Row = 1 Form1.MSFlexGrid1.Text = "Rated Current" Form1.MSFlexGrid1.Row = 2 Form1.MSFlexGrid1.Text = "Number of Poles" Form1.MSFlexGrid1.Row = 3 Form1.MSFlexGrid1.Text = "Output Coefficient" Form1.MSFlexGrid1.Row = 4 Form1.MSFlexGrid1.Text = "Air Gap Diameter" Form1.MSFlexGrid1.Row = 5 Form1.MSFlexGrid1.Text = "Number of Parallel Paths" Form1.MSFlexGrid1.Row = 6 Form1.MSFlexGrid1.Text = "Number of Slots" Form1.MSFlexGrid1.Row = 7 Form1.MSFlexGrid1.Text = "Number of Radial Ducts" Form1.MSFlexGrid1.Row = 8 Form1.MSFlexGrid1.Text = "Effective Core Length" Form1.MSFlexGrid1.Row = 9 Form1.MSFlexGrid1.Text = "Number of Strands" Form1.MSFlexGrid1.Row = 10 Form1.MSFlexGrid1.Text = "Depth of Slot" Form1.MSFlexGrid1.Col = 1 Form1.MSFlexGrid1.Row = 0 Form1.MSFlexGrid1.Text = "VALUE" Form1.MSFlexGrid1.Col = 1 For cur_row = 1 To 10 Form1.MSFlexGrid1.Row = cur_row Form1.MSFlexGrid1.Text = spec(cur_row) Next '--------------------------------------------------------------------

End Sub Private Sub Form_Load() Option1.Value = True Form1.cmd_Excel.Enabled = False End Sub Page 57 of 67

Private Sub Text1_KeyPress(Index As Integer, KeyAscii As Integer) Dim acceptable_text_symbols As String Dim ch As String * 1 Dim decimal_flag As Integer decimal_flag = InStr(Text1(Index).Text, ".") acceptable_text_symbols = "1234567890" ch = Chr(KeyAscii) If Chr(KeyAscii) = "." And decimal_flag = 0 Then KeyAscii = KeyAscii ElseIf InStr(acceptable_text_symbols, ch) Or KeyAscii = 8 Then KeyAscii = KeyAscii Else KeyAscii = 0 End If End Sub

b) Form2 Private Sub cmd_clear_Click() Dim i As Integer For i = 0 To 2 Text1(i).Text = "" Next i End Sub Private Sub cmd_save_Click() Form2.Visible = False End Sub Private Sub cmd_save_airgap_Click() flag_save_airgap = 1 End Sub Private Sub cmd_save_num_slt_Click() flag_save_num_slots = 1 End Sub Private Sub cmd_save_outcoeff_Click() flag_save_outcoeff = 1 End Sub Private Sub Command1_Click()

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Form2.Visible = False End Sub Private Sub Form_Load() Text1(0).Text = Str$(out_coeff) Text1(1).Text = Str$(num_slots) Text1(2).Text = Str$(air_gap_dia) End Sub Private Sub Text1_KeyPress(Index As Integer, KeyAscii As Integer) Dim acceptable_text_symbols As String Dim ch As String * 1 Dim decimal_flag As Integer decimal_flag = InStr(Text1(Index).Text, ".") acceptable_text_symbols = "1234567890" ch = Chr(KeyAscii) If Chr(KeyAscii) = "." And decimal_flag = 0 Then KeyAscii = KeyAscii ElseIf InStr(acceptable_text_symbols, ch) Or KeyAscii = 8 Then KeyAscii = KeyAscii Else KeyAscii = 0 End If End Sub

c) Module1 Public pow_fac, volt_rated, scr, pow_rated, curr_rated@, speed_rated@, fly_eff@, out_coeff@, air_gap_dia@, len_core@, pole_pitch@, pole_arc@, flux_den_old@, turns_ph_old@, parall_path, num_slots, num_cond_slot As Double Public num_cond_series_ph, slot_pitch, slot_ang_mech, slot_ang_elec, turns_ph_new, flux_pole_new, flux_den_new, flux_den_max, d_axis_react, leak_react, arm_rxn As Double Public amplitude_fac, peri_velocity, air_gap_ampturn, radial_airgap, num_radial_duct, len_core_eff, len_core_active, cross_sec_cond, num_strand, total_depth_strand, main_insu, asbest_insu, tape_anti_corona, slot_depth@, slot_wedge As Double Public num_pole As Double Public len_copper_strand, Main_Insulation, Asbestos_insulation, Strand_insulation, asbestos_tape_anti_corona, Width_Stator_Bar As Double Public mean_len_turn, Pd, coil_pitch_endw, dinominator, X1, X2 As Double Private Const Pi = 22 / 7 Dim My_path As String Public xlapp As Excel.Application Public wbook As Excel.Workbook Public wsheets As Excel.Worksheet Page 59 of 67

Public Function output_coeff(x As Double) As Double Dim out_coeff As Double Select Case x Case 6 To 9 out_coeff = 0.5 * (x - 8) + 6 Case 9 To 10 out_coeff = 0.2 * (x - 9) + 6.5 Case 11 To 12 out_coeff = 0.15 * (x - 12) + 7 Case 13 To 15 out_coeff = 0.1 * (x - 12) + 7 Case 16 To 20 out_coeff = 0.06 * (x - 20) + 7.6 Case 21 To 27 out_coeff = 0.04 * (x - 20) + 7.6 Case 27 To 39 out_coeff = 0.017 * (x - 27) + 7.9 Case 39 To 70 out_coeff = 0.013 * (x - 70) + 8.5 End Select output_coeff = out_coeff 'returning the value End Function Public Function calculate_airgap_dia(x As Double) As Double Dim peri_velocity As Double Select Case x Case 5 To 17 peri_velocity = -2 * (x - 5) + 110 Case 18 To 20 peri_velocity = -1 * (x - 17) + 86 Case 21 To 26 peri_velocity = -0.67 * (x - 20) + 83 Case 27 To 35 peri_velocity = -0.55 * (x - 26) + 79 Case 36 To 50 peri_velocity = -0.33 * (x - 35) + 74 Case 50 To 70 peri_velocity = -0.2 * (x - 50) + 69 End Select calculate_airgap_dia = peri_velocity

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End Function Public Function calculate(volt_rated, pow_rated, speed_rated, scr, pow_fac, stack_fac As Double, scheme As Integer) As Variant '------------------------------------------------------curr_rated = (pow_rated * 1000 / pow_fac) / (1.732 * volt_rated) 'in AMP num_pole = (120 * 50) / speed_rated num_pole = Round(num_pole, 0) If num_pole Mod 2 = 1 Then If scheme = 0 Then 'run of the river type num_pole = num_pole + 1 Else 'reservoir type num_pole = num_pole - 1 End If End If

fly_eff = 60000 * (((pow_rated * 1000 / pow_fac) / (speed_rated ^ (1.5))) ^ 1.25) 'see units out_coeff = 8.166 'out_coeff = output_coeff(num_pole) peri_velocity = calculate_airgap_dia(num_pole)

'm/s

air_gap_dia = (peri_velocity * 60) / (Pi * speed_rated) 'in m len_core = (pow_rated * 1000 / pow_fac) / (out_coeff * speed_rated * (air_gap_dia ^ 2)) 'in m pole_pitch = Pi * (air_gap_dia / num_pole) pole_arc = 0.7 * pole_pitch 'flux_den_old = 0.675 wb/m2 flux_pole_old = 0.675 * pole_pitch * len_core

'in wb

turns_ph_old = 1.1 * (volt_rated * 1000 / 1.732) / (4.44 * 50 * flux_pole_old) 'parall_path loop '-----------------------------------------------Dim limit As Double limit = (2 * curr_rated) / 5000 parall_path = 0 Do While parall_path < limit Page 61 of 67

parall_path = parall_path + 1 Loop '-----------------------------------------------num_slots = 3 * turns_ph_old * parall_path num_slots = Round(num_slots, 0) 'num_cond_slot=2 for stator bar type num_cond_series_ph = (2 * num_slots) / (3 * parall_path) slot_pitch = Pi * air_gap_dia / num_slots 'in metre slot_ang_mech = 2 * Pi / num_slots ' in radians slot_ang_elec = (num_pole / 2) * slot_ang_mech 'in radians

'----------------MODIFIED CALCULATION----------------turns_ph_new = num_slots / (3 * parall_path) flux_pole_new = (1.1 * (volt_rated * 1000 / 1.732)) / (4.44 * turns_ph_new * 50) flux_den_new = flux_pole_new / (len_core * pole_pitch) flux_den_max = flux_den_new / 1.1 amplitude_fac = 1.054 'for pole arc/pole pitch =0.7 arm_rxn = (2.12 * curr_rated * turns_ph_new * amplitude_fac) / (num_pole * 1.1) 'amp-turns per pole air_gap_ampturn = arm_rxn / ((1 / scr) - 0.15) 'for power fac =0.9 ,Xd=1pu,Xl=.15pu radial_airgap = (1.26 * air_gap_ampturn) / 8500 ' doubt abt units 'Bg=0.85 Wb/m^2 num_radial_duct = 0.26 * (len_core * 100 - 12.5) 'len_core is in metre width_radial_duct = 0.66 'in cm len_core_eff = len_core - num_radial_duct * width_radial_duct * 0.01 'width_radial_duct not known at this point,len_core_eff is in metres 'take stack_fac=0.93 len_core_active = len_core_eff * stack_fac

'in metre

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'----------------SLOT DESIGNING-----------------------cross_sec_cond = curr_rated / (parall_path * 3.5 * 100) 'in cm^2 num_strand = cross_sec_cond / (2 * 0.65 * 0.25) num_strand = Round(num_strand, 0) total_depth_strand = 2 * (num_strand + 1) * 0.25 main_insu = 4 * 0.38

'cm

'cm

asbest_insu = 2 * (num_strand + 1) * 0.038

'cm

tape_anti_corona = 4 * 0.015 'cm slot_wedge = 0.63 'cm slot_depth = total_depth_strand + main_insu + asbest_insu + tape_anti_corona + slot_wedge 'in cm 'height '-----------------SLOT WIDTH-------------------------len_copper_strand = 2 * 0.65 'cm Main_Insulation = 2 * 0.38

'cm

Asbestos_insulation = 2 * 0.038 Strand_insulation = 4 * 0.01

'cm

'cm

asbestos_tape_anti_corona = 2 * 0.015

'cm

Width_Stator_Bar = len_copper_strand + Main_Insulation + Asbestos_insulation + Strand_insulation + asbestos_tape_anti_corona 'Tooth width at 1/3rd of its height = (Length of air gap + 2 x Depth of stator slots / 3) x (Pi / No. of slots) - Width of stator bar Source?? 'Flux density at tooth = Flux per pole / (Slots per pole per phase x Tooth width at 1/3rd of its length x Effective pole arc) in Wb/sq m Source not given '--------------------MEAN LENGTH OF TURN---------------'percent_coil_pitch Pd = (Pi * (air_gap_dia * 100 + 2 * slot_depth) / num_pole) * 0.01 * percent_coil_pitch coil_pitch_endw = Width_Stator_Bar + 2.3 'cm dinominator = (Pi * (air_gap_dia * 100 + 2 * slot_depth)) / num_slots X2 = coil_pitch_endw / dinominator Page 63 of 67

X1 = 5.5 * (x - 18) + 119 mean_len_turn = 200 * len_core + 4 * X1 + 4 * X2

'cm

End Function '====================================================== Public Function display_excel(volt_rated, pow_rated, speed_rated, scr, pow_fac, stack_fac As Double) As Integer '*************************************************** On Error Resume Next wbook.Close xlapp.Quit Set xlapp = Nothing '***************************************************

On Error Resume Next Set xlapp = GetObject("excel.application") If xlapp Is Nothing Then Set xlapp = CreateObject("excel.application") If xlapp Is Nothing Then m = MsgBox("Could not open Excel.End the running program", vbOKOnly) End End If End If xlapp.Visible = False Err.Clear 'opening the excel file My_path = App.Path & "\specification.xls" Set wbook = xlapp.Workbooks.Open(My_path) If Err Then MsgBox Err.Description End If xlapp.Workbooks("wbook").Activate Set wsheets = xlapp.Sheets("sheet1") 'wsheets.Cells(2, 1) = Str$(curr_rated) 'data read from the excel sheet. '----------------------------------------wsheets.Cells(3, 4) = Str$(pow_rated) wsheets.Cells(4, 4) = Str$(volt_rated) wsheets.Cells(5, 4) = Str$(speed_rated) wsheets.Cells(6, 4) = Str$(scr) wsheets.Cells(7, 4) = Str$(pow_fac) Page 64 of 67

wsheets.Cells(8, 4) = Str$(stack_fac) wsheets.Cells(9, 4) = Str$(50) wsheets.Cells(10, 4) = Str$(1 / scr) wsheets.Cells(11, 4) = Str$(0.15) wsheets.Cells(12, 4) = Str$(amplitude_fac) wsheets.Cells(13, 4) = Str$(curr_rated) wsheets.Cells(14, 4) = Str$(num_pole) wsheets.Cells(15, 4) = Str$(fly_eff) wsheets.Cells(16, 4) = Str$(out_coeff) wsheets.Cells(17, 4) = Str$(air_gap_dia) wsheets.Cells(18, 4) = Str$(pole_pitch) wsheets.Cells(19, 4) = Str$(pole_arc) wsheets.Cells(20, 4) = Str$(parall_path) wsheets.Cells(21, 4) = Str$(num_slots) wsheets.Cells(22, 4) = Str$(2) wsheets.Cells(23, 4) = Str$(num_cond_series_ph) wsheets.Cells(24, 4) = Str$(slot_pitch) wsheets.Cells(25, 4) = Str$(slot_ang_mech) wsheets.Cells(26, 4) = Str$(slot_ang_elec) wsheets.Cells(27, 4) = Str$(turns_ph_new) wsheets.Cells(28, 4) = Str$(flux_pole_new) wsheets.Cells(29, 4) = Str$(flux_den_new) wsheets.Cells(30, 4) = Str$(flux_den_max) wsheets.Cells(31, 4) = Str$(arm_rxn) wsheets.Cells(32, 4) = Str$(air_gap_ampturn) wsheets.Cells(33, 4) = Str$(radial_airgap) wsheets.Cells(34, 4) = Str$(num_radial_duct) wsheets.Cells(35, 4) = Str$(len_core) wsheets.Cells(36, 4) = Str$(len_core_eff) wsheets.Cells(37, 4) = Str$(len_core_active) wsheets.Cells(38, 4) = Str$(cross_sec_cond) wsheets.Cells(39, 4) = Str$(num_strand) wsheets.Cells(40, 4) = Str$(total_depth_strand) wsheets.Cells(41, 4) = Str$(slot_depth) wsheets.Cells(42, 4) = Str$(Width_Stator_Bar) wsheets.Cells(43, 4) = Str$(mean_len_turn) xlapp.Visible = True 'wbook.Close 'xlapp.Quit 'Set xlapp = Nothing End Function

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REFERNECES

1. Large A C machines By J. H. Walker 2. Electrical machinery By P. S. Bimbhra 3. Power Engineer’s Handbook by TNEB Engineer’s Association, Chennai Page 66 of 67

4. Water Power Development Vol TWO/B, E. Mosonyi 5. A K Sawhney

Web Links 1. http://www.nhpc.co.in 2. http://www.abb.com 3. http://www.hydropower.alstom.com 4. http://www.power-technology.com 5. http://www.iri.columbia.edu

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