heavy engineering coorporation ltd

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ACKNOWLEDGEMENT

I would like to express my gratitude to Mr. Anugra Jha (Senior DGM HRD) HEC-

Ranchi who provided me opportunity to undergo In-plant Training in HEC.Not onlyhe has been source of inspiration throughout the training but also helped me tolearn about various machines and equipments used in the field of Electrical &Mechanical Engineering.

I am extremely thankful to all the following engineers of HEC for their cooperationand guidance during my training period

Mr. D.K. Singh-Sr. Manager ERS

Mr. Chotu Mahli-Sr.Manager GSS

Mr. A Singh-Assistant Eng. PSD Mr. RK Jha-DGM EDD

I have also learned a lot from the workers of HEC and I express my gratitudetowards them.

I will also like to thank my mentor Mrs. Nidhi Gupta for providing me her valuableexperience and knowledge prior to training.

About HEC Plant

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Heavy Engineering Corporation Limited or "HECLtd." is a Public Sector Undertaking ("PSU")

in India. HEC was established in the year 1958 as one of the largest Integrated Engineering

Complex in India. It manufactures and supplies capital equipments & machineries and renders

project execution required for core sector industries. It has complete manufacturing set up starting

from casting & forging, fabrication, machining, assembly and testing - all at one location, Ranchi,

backed by a strong design - engineering and technology team.It has THREE UNITS as follows

Heavy.Machine.Building.Plant.(HMBP) .

The Plant has a fenced area of 5,70,000 sq.m and a floor area of nearly 2,00,000 sq.m. It is well

equipped with sophisticated machine tools and handling equipment to undertake manufacture of

heavy machinery and equipment of top quality. It is engaged in design and manufacture of

equipment and components for Steel Plant, Mining, Mineral Processing, Crushers, Material

Handling, Cranes, Power, Cement, Aluminium, Space Research, Nuclear Power etc.

Heavy.Machine.Tools.Plant(HMTP)

Set up in collaboration with M/s Skodaexport Czechoslovakia, HMTP is the most modern and

sophisticated of its kind in the country which produces machine tools in heavier ranges. The Plant

covers an area of over 2,13,500 sq.m. It designs and manufactures medium & heavy duty CNC and

conventional Machine Tools for Railways, Defense, Ordnance factories, HAL, Space and other

strategic sectors.

Foundry.Forge.Plant(FFP)

It is the largest foundry and forging complex in India and one of the largest of its kind in the world.

The area of the Plant is 13,16,930 sq.m accommodating 76,000 tonnes of installed machinery to

cope up with the various operations effectively. This Plant is the manufacturer of heavy castings

and forgings for various HEC make equipments and related to Steel plant, Defence, Power, Nuclear

energy etc.. Manufacturer of Forged Rolls for Steel Plants, Crank Shafts for Railway Loco etc.

Project.Division

Design, Engineering and execution of Turnkey Projects related to Bulk Material handling, Steel

Plant projects, Cement Plant and other sectors.

HEC Ltd. Products:

Steel Plant & it's Equipment

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Blast Furnace

Coke Oven Batteries

Continuous Casting Machine

Steel Melting Converters

Forged Rolls

Mining Equipment

Electric Rope Shovel (5 CuM)

Electric Rope Shovel (10 CuM)

Draglines

Crushing Equipment and mineral processing products

Primary Gyratory Crusher

Cone Crusher

Four Roll Crusher

Reversible Hammer Crusher

Rod Mill

Machine Tools

Vertical Turning & Milling Machine

Lathe

Roll Grinding Machine

Deep Hole Boring Machine

Horizontal Boring Machine

Radial Drilling Machine

Planning Machine

Plano Milling Machine

Castings & Forgings

Steel Castings

Steel Forgings

Grey Iron Casting

Cranes

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EOT crane

Laddle crane

Rotating Trolley Crane

Magnet Grab Crane

Turn Key Projects:

Sl . Project & features Capacity

1 Coal Handling Plant at PARICHHA Thermal PowerStation (UPSEB), UPSEBTurnkey: Design to commissioningWagon Tippler, Ring Granulator, Plough Feeder, Conveyor(1.6 Km)Civil, Structure, Electrics

675 TPH

2 Jayant CHP, Northern Coal Fields Ltd.Turnkey: Design to commissioningGyratory Crusher, Apron Feeder, EOT Crane, Conveyor (1Km)Civil, Structure, Electrics

1200 TPH

3 Dankuni Coal Complex, Coal India Ltd.Turnkey: Design to commissioningLow Temperature Carbunisation Complex including : WagonTripler, Crusher, Screens, Conveyor (2.5 Km)Civil, Structure, Electrics Upto

1000 TPH

4 Lime Storage & Screening Plant, Bokaro Steel PlantTurnkey: Design to commissioningScreens, ConveyorsCivil, Structure, Electrics

1500 TPH

5 Coal Preparation Plant, Kedla, Central Coalfiels Ltd.Consultancy servives for project & detailed engineering,construction, erection & commissioning of washery includingCHPConveyors (4 Km)

650 TPH

6 Raw Material Handling System (Phase-II), Rourkela Steel

PlantTurnkey: Design to commissioningWagon Tripler, Wagon Pusher, Apron Feeder, Cone & RollCrushers, Inspectors, Rod Mills, Weigh feeders, VibroFeeders & Screen, Conveyor (7 Km)Civil, Structure, Electrics & PLC system Up to

1200 TPH

7 Raw Material Handling System, NINLTurnkey: Design to commissioningHammer Crusher, Feeders & screen, Conveyor (10.5 Km)

1000 TPH

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Up to

8 Second Launching Pad, ISRO400 / 60 EOT Crane,200 / 30 T EOT Crane10T Tower Crane,

FCVRP, SDClean RoomMobile Launching Pad

9 Coal Handling Plant (Ph-II), Nigahi, Northern Coal FieldsLtd.Planning, Design, Engineering, Construction, Fabrication,Supply, Erection, Trial run and Commissioning on Turnkeybasis.Major Items : Gyratory Crusher, Apron Feeder, EOT Crane,complete utilities etc.Conveyor system of length approx. 4.0 km3000T Silo with rapid wagon loading system of 5500 TPH.

1600 TPH

10 Cyclotron Magnet Poles

Magnet pole and associated component for VECC

(Atomic Energy)

Unique Facilities at HEC:

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acilities

Melting Furnaces:

30T Electric arc Furnace 2 Nos.

10T Electric arc Furnace 1 No.

5T Induction Furnace 1 No.

2T Induction Furnace 1 No.

VD UNIT

Secondary Refinement Furnaces:

60T Vacuum Arc Degassing unit 1 No

90T Vacuum Degassing unit 2 Nos.

60T Ladle Furnace 1 No

VAD Furnace

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Forging Facilities

6000T Hydraulic Press 1 no.




3T/1.6T Hammer 2 nos.

Die Forging Units (15T & 1600 Kg) 1 each

6000 T Press

Heat Treatment Facilities

Low Frequency Induction Hardening M/c (50 Cycles) 1

Medium Frequency Induction M/c (1000 Cycles) 1

Nitriding Furnace 1

Thermal Stability Testing Equipment 1

Vertical & Horizontal Mist Quenching M/c(Up to 50T & 18M long jobs)

2

Electric H/T Pit Furnace up to 18 M Depth 1

Bogies Type H/T Furnace up to 12M x 6m x 3.5m 2

Bogies Type H/T Furnace up to 19M x 4m x 3m 2Electric Pit Furnace dia 2.5M 1

Electric Pit Furnace dia 4.0 M 1

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Machining Facilities

CNC Heavy Duty Gear ShaperPitch Dia Internal/External Gear 500 mm, Module Max 8mm

Maag Gear Shaper (Speciality - Narrow Gap Herringbone grs)MaxDia 1800mm, Max. Module 18mm

Vertical Gear Hobbing M/CMax Job Dia 5M, Module 50 mm, Max. Width of Job 2M

> Horizontal Gear Hobbing M/CJob Dia 5M, Module 40 mm, Max. Job Length 5.6M

Maag Gear Grinding MachinesDia 1800mm, Max. Module 0.5mm to 16mm

CNC Gear Shaper

CNC Vertical Turning and Boring M/c (O&M Make) Max Job Dia 14MMax Job weight 250T

CNC Planomilling M/c (Waldrich Coburg) Max. Job size 3.5M x 7M x 2.5M

Max Job weight 120T

CNC Hor. Boring M/c (Skoda Make) Max. Spindle Dia 200mmMax Column Travel 20M

Gear Cutting M/c Max. Job dia 5MMax. module 40mm (Hobbing

Machining of HYDRO TURBINE SHAFT Machining of Bull Gear for Steel Plant

CNC Slant Bed Turning Centre Distance Between Centres 1500mmSwing Over carriage 250mm

CNC Horizontal Machining Centre Table size 1000 x 1000mmTravel 1800/1300/1000mm

CNC Vertical Machining Centre Table Size 500 x 500mmTravel x axis 1200mm, Y axis-510mm& z axis 510mm

CNC Horizontal Boring Machine Spindle Dia 200mmTable size 3500 x 4000mm

CNC Heavy duty Gear Shaper (Liebherr Make) Pitch Dia - Internal Gear 500mmExternal Gear 500mmModule Max 8 m

Fabrication facilities: CNC flame cutting

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Submerged Arc Welding

Electro Slag Welding

Job under CNC flame cutting

Number of Equipments Supplied till Date:

STEEL SECTOR

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Equipment Nos. Supplied to

1. Blast Furnace (1033 to 3200 Cu. M) 9 Bhilai, Bokaro, Vizag Steel Plant,Turkey, Egypt.

2. Coke Oven (4.3 to 7 M high) 21 Bhilai, Bokaro, Vizag, Durgapur Steel Plant, Turkey, USSR, Sri Lanka

3. Continuous Casting Machine forBlooms/slabs of various sizes Turkey

13 Bhilai, Bokaro, Vizag Rourkela Steel Plant,

4. Rolling Mills of various types & sizesincluding 3600MM wide Plate Mill

19 Bhilai, Bokaro, Vizag Steel Plant, Salem Steel Plant,Misra Dhatu NigamAhmadabad Advance Mill,Bombay Mint

5. Steel Melting Converters (55 to 300T) 10 Bhilai, Bokaro, Vizag, Durgapur,Rourkela Steel Plant, Malvika Steel Ltd

6. Mixer (600 to 1300T) 10 Malvika Steel Ltd., Indomag, Bhilai,Vizag Steel Plant

7. Sinter Plant Equipment (75 to 312 Sq.M.) 24 Bhilai, Bokaro, Vizag Steel Plant,Turkey, USSR

8. General Purpose & Steel Plant Cranesupto 450T

300 Bokaro, Durgapur, Bhilai, Rourkela, Vizag Steel Plant, BHEL, MalvikaSteel,TISCO, CIL, TYAZPROMEXPORT (USSR) ISRO

9. Forged Rolls (HRM & CRM) 3800 Bokaro, Bhilai, Rourkela, Durgapur, Vizag Steel Plant,Jindal, NipponDendro, Steelco, Tinplate, Jindal, Uttam Galva

10. 22 M3 Slag Cups 10 ESSAR STEEL, RSP

11. 20 M3 Slag Cups 1 Tata International

12. 16 Cu. M. Slag Cups 2900 Bokaro, Bhilai, Rourkela, Vizag,Durgapur Steel Plant, TISCO

13. 18 M3 Slag Cups 20 RSP, TISCO, VSP, JindalNINL

14. Machine Tools 149 Bokaro, Bhilai, Rourkela, Vizag,Durgapur Steel Plant, TISCO, NINL.

COAL / MINING


1. 4.6/5 CuM Elect. Rope Shovel 540 All Subsidiaries of CIL, NMDC,TISCO, HCL, BSL, BSP, RSP

2. 10 CuM Elect. Rope Shovel 30 CIL, SECL

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3. 12.5 CuM Elect. Rope Shovel 2 CIL

4. Draglines (20/90) 1 CIL

5. Draglines (24/96) 12 CIL

6. Hyd. Shovel (RH-30C, 3.5CuM) 8 CIL

7. Hyd. Shovel (RH-40C, 5CuM) 12 TISCO & CIL

8. Hyd. Shovel (RH-75C, 8.1 CuM) 3 CIL

9. Over Burden Drill 89 All Subsidiaries of CIL, NMDC

10. Mine Winder / Friction Winder 16 BCCL, ECL, SECL, HZL

11. Crushers (Gyratory, Jaw, Cone Crushers, Single,Two, Four Roll Crushers)

144 Bokaro, Bhilai, Vizag Steel Plant, NMDC, HCL, CIL, USSR,MESCO, NINL, HZL.Yugoslavia, Bulgaria

12. Ball Mills 10 Bokaro Steel Plant

13. Rod Mills 3 Rourkela Steel Plant

14. Stacker/Reclaimer/Wagon Loader 5 NMDC (Kiriburu, Bailadilla),Bongaigaon Thermal Plant

15. Wagon Pusher & Wagon Tippler 41 BSL, BSP, RSP, VSP, IISCO,DANKUNI, PARICHA, Patratu,Bongaingaon

OTHERS


1. Cyclotron Magnet 1 VECC

2. K-500 Super conducting Cyclotron Magnet 1 VECC

3. Horton Sphere 2 FCI Barauni

4. Heavy Tyre Casting (Dia. 5.5M wt. 30T) 2 TISCO

5. Heavy Tyre Casting (Dia. 5.9M) wt. 55MT 3 Jindal, AARTI, Madras Cement

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6. Hydro Turbine Shaft 12 BHEL

7. T.G. Rotor Shaft (For 200MW) 1 BHEL

8. Industrial Turbine Shaft 2 BHEL

9. Francis Runner Turbine Casting of Stainless Steel (Wt. 15T) 1 BHEL

10. Stainless Steel Die Forgings 6000 Rourkela Steel Plant

11. Oil Drilling Rigs 2 ONGC

12. Crank Shaft for Meter & Broad Gauge Locomotives 1500 Indian Railways

13. Vertical Stand with Drive Roller Table 1 BALCO

14. Slitting & Trimming Line 1 INDALCO

15. Electrolyser Pots with Anode Mechanism 801 BALCO, NALCO, Yugoslavia & Egypt

16. Folding-cum-Vertically Repositionable Platform 6 Sets ISRO, Sriharikota

17. 10T Tower Crane for SLP 1 ISRO, Sriharikota

18. 400T EOT Crane for GSLV MK-III 1 ISRO, Sriharikota

19. Folding-cum-Vertically Repositionable Platform for GSLV MK-III 3 ISRO, Sriharikota

20. Horizontal Sliding Doors for GSLV MK-III 3 ISRO, Sriharikota

21. Mobile Launch Pedestal for GSLV MK-III 1 ISRO, Sriharikota

MACHINE TOOLS

CONVENTIONAL MACHINES


1. Radial Dril l 166 BHEL, BHPV, L&T, Indian Railway, TISCO,Mukund, Telco, Bhilai, Bokaro Steel, NINL, etc.

2. Horizontal Borer 197 BHEL, Indian Railway, Hindustan Motor,Telco, Bhilai, Bokaro Steel, IISCO, Defence,NINL, etc.

3. Planer 56 TISCO, BHPV, HMT, BARC, IISCO, HCL,Indian Railway, Braithwaite etc.

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8. Plano Miller 2 Durgapur, Vizag Steel Plant

4. Heavy Duty CentreLathe

120 BHEL, ASP, HMT, GRW, Jessop, BSL, RSP,BSP, VSP, NINL, NTPC, CIL, SCCL, MSR etc

5. Vertical Turning &Boring

50 BHEL, Vizag, Bokaro, Indian Railways,L&T, NTPC, Air Force Base Workshop etc.

6. Roll Grinder 20 Tayo, BALCO, Durgapur, L&T, Tinplate,INDALCO, Defence, IG MINT.

7. Deep Hole Boring 1 Foundry Forge Plant

9. Edge Planing 9 BHPV, Bokaro, TISCO, BHEL, ATV etc.

RAILWAY MACHINES


10. Surface Wheel Lathe 74 Indian Railways, Vizag Steel Plant, NALCO

11. Under Floor Wheel Lathe 49 Indian Railways, Metro Railway, Bokaro Steel

12. Axle Journal Turning & Burnishing Lathe 31 Indian Railways

13. Multi Purpose Wheel Lathe 4 Indian Railways

CNC MACHINES


14. Roll Turning Lathe 10 Tata Yodogawa, Vizag Steel Plant, L&T, BSL

15. Vertical Turning & Boring 20 Durgapur Steel Plant, TELCO, HAL, SDSC/SHAR

VSSC


16. Horizontal Borer 1 HMTP

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17. Deep Hole Boring 3 Field Gun Factory, Kanpur, MSF Ishapore

18. Planer 1 Rourkela Steel Plant

19. Lathe 5 WCL, BHEL, HMBP, FFP

20. Surface Wheel Lalthe 2 Indian Railways, NTPC

Total = 821

PROJECTS COMMISSIONED

Project Supplied to

1. Coal Handling Plant Jayant (NCL), Bina (NCL),Kedla (CCL), Paricha (UPSEB),Bongaigaon (ASEB)

2. Raw Material Handling Plant Rourkela Steel Plant, Neelachal Ispat Nigam Ltd.

3. Low Temperature Coal Carbonisation Plant Dankuni Coal Complex, West Bengal

4. Coal Washery Kedla (CCL)

5. Continuous Casting Plant (SMS-I) for Slab Rourkela Steel Plant

6. Rotaside Wagon Tippler Complex Patratu (BSEB)

7. Rotary Wagon Tippler Complex IISCO Burnpur

8. Pilot Sponge Iron Plant (3600 TPA) RDCIS/SAIL

9. New Hammer Mill Complex Durgapur Steel Plant

10. Super Alloy Plant Misra Dhatu Nigam Limited, Hyderabad

11. Lime Stone Screening Plant Bokaro Steel Plant

12. Flux Storage, Crushing and Screening Complex inSinter Plant

Bokaro Steel Plant

13. Modernisation of Cement Plant Chhatak Cement Plant, Bangladesh

14. Wheel & Axle Plant Durgapur Steel Plant

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CNC Machines

IntroductionToday, computer numerical control (CNC) machines are found almost everywhere, fromsmall job shops in rural communities to Fortune 500 companies in large urban areas.Truly, there is hardly a facet of manufacturing that is not in some way touched by whatthese innovative machine tools can do.

Everyone involved in the manufacturing environment should be well aware of what ispossible with these sophisticated machine tools. The design engineer, for example,must possess enough knowledge of CNC to perfect dimensioning and tolerancingtechniques for workpieces to be machined on CNC machines. The tool engineer must

understand CNC in order to design fixtures and cutting tools for use with CNCmachines. Quality control people should understand the CNC machine tools used withintheir company in order to plan quality control and statistical process control accordingly.Production control personnel should be abreast of their company's CNC technology inorder to make realistic production schedules. Managers, foremen, and team leadersshould understand CNC well enough to communicate intelligently with fellow workers.

And, it goes without saying that CNC programmers, setup people, operators, and othersworking directly with the CNC equipment must have an extremely good understandingof CNC.

In this presentation, we will explore the basics of CNC, showing you much of what isinvolved with using these sophisticated machine tools. Our primary goal will be to teachyou how to learn about CNC. For readers who will eventually be working directly withCNC machine tools, we will show you the basics of each major CNC function.

Additionally, we will make suggestions as to how you can learn more about each CNCfunction as it applies to your particular CNC machine/s. At the completion of thispresentation, you should have a good understanding of how and why CNC functions asit does and know those things you must learn more about in order to work with any styleof CNC machine tool.

For readers who are not going to be working directly with CNC equipment in the nearfuture, our secondary goal will be to give you a good working knowledge of CNCtechnology. At the completion of this presentation, you should be quite comfortable withthe fundamentals of CNC and be able to communicate intelligently with others in yourcompany about your CNC machine tools.

To proceed in an organized manner, we will be using a key concepts approach to allpresentations. All important functions of CNC are organized into ten key concepts (We'llshow five of the ten key concepts in this presentation. All five are related toprogramming). Think of it this way. If you can understand ten basic principles, you arewell on your way to becoming proficient with CNC. While our main focus will be for thetwo most popular forms of CNC machine tools (machining centers and turning centers),these ten key concepts can be applied to virtually any kind of CNC machine, making iteasy to adapt to any form of CNC equipment. With so many types of CNC machine

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tools in existence, it is next to impossible for this presentation to be extremely specificabout any one particular type. The key concepts allow us to view the main features ofCNC in more general terms, stressing why things are handled the way they are evenmore than the specific techniques used with any one particular CNC machine tool.

With the broad background we give, you should be able to easily zero in on any kind of

CNC machine tool you will be working with. As yet a third goal, this presentation shouldhelp instructors of CNC. The key concepts approach we show has been proven timeand time again during live presentations in CNC courses. This method of presentationwill help instructors organize CNC into extremely logical and easy to understandlessons.

Why CNC?

Laborious, tedious, poor use of skilled boat builders who can be working on otherjobs

Predictability of turn-around timeQuality, repeatability, symmetry and tolerance are controlled.

Arbitrary plan forms and arbitrary sections can be easily accomodated usingCAD/CAM systems.

Mathematically correct surfaces as the designer specified. eg As the chordreduces, the thickness should also reduce in proportion. This is difficult to domanually without good templates and lots of time.

The fairness of the machined surface reduces the time and materials spent in thefinishing process. Machined foils generally only need sanding (to remove

machining marks) before glass, primer and paint.Machined shape is not affected by material combinations (changes in density,hardness do not change the resulting shape).

Accurately shaped foils not only improve performance, but also handling.

Concave shapes (such as moulds) are just as easy to manufacture.

Fundamentals of CNC

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While the specific intention and application for CNC machines vary from one machinetype to another, all forms of CNC have common benefits. Though the thrust of thispresentation is to teach you CNC usage, it helps to understand why these sophisticatedmachines have become so popular. Here are but a few of the more important benefitsoffered by CNC equipment.

The first benefit offered by all forms of CNC machine tools is improved automation. Theoperator intervention related to producing workpieces can be reduced or eliminated.Many CNC machines can run unattended during their entire machining cycle, freeingthe operator to do other tasks. This gives the CNC user several side benefits includingreduced operator fatigue, fewer mistakes caused by human error, and consistent andpredictable machining time for each workpiece. Since the machine will be running underprogram control, the skill level required of the CNC operator (related to basic machiningpractice) is also reduced as compared to a machinist producing workpieces withconventional machine tools.

The second major benefit of CNC technology is consistent and accurate workpieces.Today's CNC machines boast almost unbelievable accuracy and repeatabilityspecifications. This means that once a program is verified, two, ten, or one thousand

identical workpieces can be easily produced with precision and consistency.

A third benefit offered by most forms of CNC machine tools is flexibility. Since thesemachines are run from programs, running a different workpiece is almost as easy asloading a different program. Once a program has been verified and executed for oneproduction run, it can be easily recalled the next time the workpiece is to be run. Thisleads to yet another benefit, fast change-overs. Since these machines are very easy tosetup and run, and since programs can be easily loaded, they allow very short setuptime. This is imperative with today's Just-In-Time product requirements.

Motion control - the heart of CNCThe most basic function of any CNC machine is automatic, precise, and consistentmotion control. Rather than applying completely mechanical devices to cause motion asis required on most conventional machine tools, CNC machines allow motion control ina revolutionary manner. All forms of CNC equipment have two or more directions ofmotion, called axes. These axes can be precisely and automatically positioned alongtheir lengths of travel. The two most common axis types are linear (driven along astraight path) and rotary (driven along a circular path).

Instead of causing motion by turning cranks and handwheels as is required onconventional machine tools, CNC machines allow motions to be commanded throughprogrammed commands. Generally speaking, the motion type (rapid, linear, andcircular), the axes to move, the amount of motion and the motion rate (feedrate) areprogrammable with almost all CNC machine tools.

Accurate positioning is accomplished by the operator counting the number of revolutionsmade on the handwheel plus the graduations on the dial. The drive motor is rotated acorresponding amount, which in turn drives the ball screw, causing linear motion of theaxis. A feedback device confirms that the proper amount of ball screw revolutions haveoccurred.

A CNC command executed within the control (commonly through a program) tells thedrive motor to rotate a precise number of times. The rotation of the drive motor in turnrotates the ball screw. And the ball screw causes drives the linear axis. A feedback

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device at the opposite end of the ball screw allows the control to confirm that thecommanded number of rotations has taken place.

Though a rather crude analogy, the same basic linear motion can be found on acommon table vise. As you rotate the vise crank, you rotate a lead screw that, in turn,drives the movable jaw on the vise. By comparison, a linear axis on a CNC machine tool

is extremely precise. The number of revolutions of the axis drive motor preciselycontrols the amount of linear motion along the axis.

How axis motion is commanded - understanding coordinate systems It would beinfeasible for the CNC user to cause axis motion by trying to tell each axis drive motorhow many times to rotate in order to command a given linear motion amount. (Thiswould be like having to figure out how many turns of the handle on a table vise willcause the movable jaw to move exactly one inch!) Instead, all CNC controls allow axismotion to be commanded in a much simpler and more logical way by utilizing some formof coordinate system. The two most popular coordinate systems used with CNCmachines are the rectangular coordinate system and the polar coordinate system. Byfar, the most popular of these two is the rectangular coordinate system, and we'll use itfor all discussions made during this presentation.

One very common application for the rectangular coordinate system is graphing. Almosteveryone has had to make or interpret a graph. Since the need to utilize graphs is socommonplace, and since it closely resembles what is required to cause axis motion on aCNC machine, let's review the basics of graphing.

As with any two dimensional graph, this graph has two base lines. Each base line isused to represent something. What the base line represents is broken into increments.

Also, each base line has limits. In our productivity example, the horizontal base line isbeing used to represent time. For this base line, the time increment is in months.Remember this base line has limits - it starts at January and end with December. Thevertical base line is representing productivity. Productivity is broken into ten percentincrements and starts at zero percent productivity and ends with one hundred percentproductivity.

The person making the graph would look up the company's productivity for January oflast year and at the productivity position on the graph for January, a point is plotted. Thiswould then be repeated for February, March, and each month of the year. Once allpoints are plotted, a line or curve can be drawn through each of the points to make itmore clear as to how the company did last year.

Let's take what we now know about graphs and relate it to CNC axis motion. Instead ofplotting theoretical points to represent conceptual ideas, the CNC programmer is goingto be plotting physical end points for axis motions. Each linear axis of the machine toolcan be thought of as like a base line of the graph. Like graph base lines, axes arebroken into increments. But instead of being broken into increments of conceptual ideaslike time and productivity, each linear axis of a CNC machine's rectangular coordinatesystem is broken into increments of measurement. In the inch mode, the smallestincrement is usually 0.0001 inch. In the metric mode, the smallest increment is 0.001millimeter. (By the way, for rotary axes the increment is 0.001 degrees.)

Just like the graph, each axis within the CNC machine's coordinate system must startsomewhere. With the graph, the horizontal baseline started at January and the verticalbase line started at zero percent productivity. This place where the vertical andhorizontal base lines come together is called the origin point of the graph. For CNC

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purposes, this origin point is commonly called the program zero point (also called workzero, part zero, and program origin).

For this example, the two axes we happen to be showing are labeled as X and Y butkeep in mine that program zero can be applied to any axis. Though the names of eachaxes will change from one CNC machine type to another (other common names include

Z, A, B, C, U, V, and W), this example should work nicely to show you how axis motioncan be commanded.

The program zero point establishes the point of reference for motion commands in aCNC program. This allows the programmer to specify movements from a commonlocation. If program zero is chosen wisely, usually coordinates needed for the programcan be taken directly from the print.

With this technique, if the programmer wishes the tool to be sent to a position one inchto the right of the program zero point, X1.0 is commanded. If the programmer wishesthe tool to move to a position one inch above the program zero point, Y1.0 iscommanded. The control will automatically determine how many times to rotate eachaxis drive motor and ball screw to make the axis reach the commanded destination

point. This lets the programmer command axis motion in a very logical manner.

With the examples given so far, all points happened to be up and to the right of theprogram zero point. This area up and to the right of the program zero point is called aquadrant (in this case, quadrant number one). It is not uncommon on CNC machinesthat end points needed within the program fall in other quadrants. When this happens,at least one of the coordinates must be specified as minus.

Knowing your machineA CNC user MUST understand the makeup of the CNC machine tool being utilized.While this may sound like a basic statement, a CNC user must be able to view themachine from two distinctly different perspectives. Here in key concept number two, wewill be viewing the machine from a programmer's perspective. Much later, in key

concept number seven, we will look at the machine from an operator's viewpoint.

The key to success with any CNC machineMany forms of CNC machines are designed to enhance or replace what is currentlybeing done with more conventional machines. The first goal of any CNC beginnershould be to understand the basic machining practice that goes into using the CNCmachine tool. The more the beginning CNC user knows about basic machining practice,the easier it will be to adapt to CNC.

Think of it this way. If you already know basic machining practice as it relates to theCNC machine you will be working with, you already know what it is you want themachine to do. It will be a relatively simple matter of learning how to tell the CNCmachine what it is you want it to do (learning to program). This is why machinists makethe best CNC programmers, operators, and setup personnel. Machinists already knowwhat it is the machine will be doing. It will be a relatively simple matter of adapting whatthey already know to the CNC machine.

For example, a beginner to CNC turning centers should understand the basic machiningpractice related to turning operations like rough and finish turning, rough and finishboring, grooving, threading, and necking. Since this form of CNC machine can performmultiple operations in a single program (as many CNC machines can), the beginner

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should also know the basics of how to process workpieces machined by turning so asequence of machining operations can be developed for workpieces to be machined.

This point cannot be overstressed. Trying to learn about a particular CNC machinewithout understanding the basic machining practice related to the machine would be liketrying to learn how to fly an airplane without understanding the basics of aerodynamics

and flight. Just as a beginning pilot will be in for a great number of problems withoutunderstanding aerodynamics, so is the beginning CNC user have difficulty learning howto utilize CNC equipment without an understanding of basic machining practice.

.

Understanding interpolation or motion of CNCSay for example, you wish to move only one linear axis in a command. Say you wish tomove the X axis to a position one inch to the right of program zero. In this case, thecommand X1. would be given (assuming the absolute mode is instated). The machinewould move along a perfectly straight line during this movement (since only one axis is

moving). Now let's say you wish to include a Y axis movement to a position one inchabove program zero in Y (with the X movement). We'll say you are trying to machine atapered or chamfered surface of your workpiece in this command. For the control tomove along a perfectly straight line to get to the programmed end point, it must perfectlysynchronize the X and Y axis movements. Also, if machining is to occur during themotion, a motion rate (feedrate) must also be specified. This requires linearinterpolation.

During linear interpolation commands, the control will precisely and automaticallycalculate a series of very tiny single axis departures, keeping the tool as close to theprogrammed linear path as possible. With today's CNC machine tools, it will appear thatthe machine is forming a perfectly straight line motion. However, Figure 3.1 shows whatthe CNC control is actually doing during linear interpolation. Figure 3.1 - Actual motiongenerated with linear interpolation. Notice the series of very tiny single axis movements.The step size is equal to the machine's resolution, usually 0.0001 in or 0.001 mm.

In similar fashion, many applications for CNC machine tools require that the machine beable to form circular motions. Applications for circular motions include forming radii onturned workpieces between faces and turns and milling radii on contours of machiningcenter workpieces. This kind of motion requires circular interpolation. As with linearinterpolation, the control will do its best to generate as close to a circular path aspossible.

The three most basic motion typesWhile your particular CNC machine may have more motion types (depending on your

application), let's concentrate on becoming familiar with the three most common typesof motion. These three motion types are available on almost all forms of CNCequipment. After briefly introducing each type of motion, we'll show an example programthat stresses the use of all three.

These motion types share two things in common. First, they are all modal. This meansthey remain in effect until changed. If for example, several motions of the same kind areto be given consecutively, the corresponding G code need only be specified in the first

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command. Second, the END POINT of the motion is specified in each motion command.The current position of the machine will be taken as the starting point.

Rapid motion (also called positioning)This motion type (as the name implies) is used to command motion at the machine'sfastest possible rate. It is used to minimize non-productive time during the machining

cycle. Common uses for rapid motion include positioning the tool to and from cuttingpositions, moving to clear clamps and other obstructions, and in general, any non-cutting motion during the program.

You must check in the machine tool builder's manual to determine a machine's rapidrate. Usually this rate is extremely fast (some machines boast rapid rates of well over1000 IPM!), meaning the operator must be cautious when verifying programs duringrapid motion commands. Fortunately, there is a way for the operator to override therapid rate during program verification.

The command almost all CNC machines use to command rapid motion is G00. Withinthe G00 Command, the end point for the motion is given. Control manufacturers varywith regard to what actually happens if more than one axis is included in the rapid

motion command. With most controls, the machine will move as fast as possible in allaxes commanded. In this case, one axis will probably reach its destination point beforethe other/s. With this kind of rapid command, straight line movement will NOT occurduring rapid and the programmer must be very careful if there are obstructions to avoid.With other controls, straight line motion will occur, even during rapid motion commands.

Straight line motion (also called linear interpolation)This motion type allows the programmer to command perfectly straight line movementsas discussed earlier during our discussion of linear interpolation. This motion type alsoallows the programmer to specify the motion rate (feedrate) to be used during themovement. Straight line motion can be used any time a straight cutting movement isrequired, including when drilling, turning a straight diameter, face or taper, and whenmilling straight surfaces. The method by which feedrate is programmed varies from onemachine type to the next. Generally speaking, machining centers only allow the feedrateto be specific in per minute format (inches or millimeters per minute). Turning centersalso allow feedrate to be specified in per revolution format (inches or millimeters perrevolution).

A G01 word is commonly used to specify straight line motion. Within the G01, theprogrammer will include the desired end point in each axis.

Circular motion (also called circular interpolation)This motion type causes the machine to make movements in the form of a circular path.

As discussed earlier during our presentation of circular interpolation, this motion type isused to generate radii during machining. All feedrate related points made during ourdiscussion of straight line motion still apply.

Two G codes are used with circular motion. G02 is commonly used to specify clockwisemotion while G03 is used to specify counter clockwise motion. To evaluate which to use,you simply view the movement from the same perspective the machine will view themotion. For example, if making a circular motion in XY on a machining center, simplyview the motion from the spindle's vantage point. If making a circular motion in XZ on aturning center, simply view the motion from above the spindle. In most cases, this is assimple as viewing the print from above.

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Additionally, circular motion requires that, by one means or another, the programmerspecifies the radius of the arc to be generated. With newer CNC controls this is handledby a simple "R" word. The R word within the circular command simply tells the controlthe radius of the arc being commanded. With older controls, directional vectors(specified by I, J, and K) tell the control the location of the arc's center point. Sincecontrols vary with regard to how directional vectors are programmed, and since the R

word is becoming more and more popular for radius designation, our examples willshow the use of the R word. If you wish to learn more about directional vectors, youmust reference your control manufacturer's manual.

A typical Horizontal Drilling Machine

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Closed Loop Single Axis CNC block Diagram

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Motor Used in CNC System

Stepping Motors

Hybrid stepping motors have a variable-reluctance rotor with a permanent magnet in its magneticpath, usually in the rotor.

The term hybrid refers to the use of two sources of magnetic field, the stator windings and the

permanent magnet.

Hybrid stepping motors are used when small step angles are required.

The 1.8 degree stepping motor is the predominant standard for industrial automation.

A 200 step hybrid motor

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Servo MotorsThere are basically three type of servo motor, the DC brushed (2 wire) and BLDC,(brushless DC) and AC sinusoidal, both of these have three stator leads and have the

identical appearance the difference is in the BLDC has two windings energised at anygiven time, hence brushless DC, the AC sinusoidal has all three winding energised by

three phases 120 apart.All servo motors should also have one other conductor connected to the frame for

Earth Ground.

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Comparison of servo and stepper motors

Stepper Vs. Servo Motors

Characteristics Servo Motor (DC Brushed Stepper (Hybrid)

Cost

The cost for a servo motor and servo

motor system is higher than that of a

stepper motor system with equal

power rating.

This feature would have to go to

stepper motors. Steppers are generally

cheaper than servo motors that have

the same power rating.

Versatility

Servo motors are very versatile in

their use for automation and CNC

applications.

Stepper motors are also very versatile

in their use for automation and CNC

applications. Because of their

simplicity stepper motors may be

found on anything from printers to

clocks.

Reliability

This is a toss up because it depends

on the environment and how well the

motor is protected.

The stepper takes this category only

because it does not require an encoder

which may fail.

Frame Sizes

Servo motors are availible in a wide

variety of frame sizes, from small to

large motors capable of running huge

machines. Many of the motors come

in NEMA standard sized.

Stepper motors do not have as many

size selections as servo motors in the

large sizes. However stepper motors

may still be found in a variety of

NEMA frame sizes.

Setup Complexity

Servo motors require tuning of the

(PID) closed loop variable circuit to

obtain correct motor function.

Stepper motors are almost plug-and-

play. They require only the motor

wires to be wired to the stepper motor

driver.

Motor Life

The brushes on servo motors must be

replaced every 2000 hours of

operation. Also encoders may need

replacing.

The bearing on stepper motors are the

only wearing parts. That gives stepper

motors a slight edge on life.

Low Speed High

Torque

Servo motors will do fine with low

speed applications given low friction

and the correct gear ratio

Stepper motors provide most torque at

low speed (RPM).

High speed High

Torque

Servo motors maintain their rated

torque to about 90% of their no load

RPM.

Stepper motors lose up to 80% of their

maximum torque at 90% of their

maximum RPM.

Repeatability

Servo motors can have very good

repeatability if setup correctly. The

encoder quality can also play into

repeatability.

Because of the way stepper motors are

constructed and operate they have

very good repeatability with little or

no tuning required.

Overload SafetyServo motors may malfunction if

overloaded mechanically.

Stepper motors are unlikely to be

damages by mechanical overload.

Power to Servo motors have an excellent Stepper motors are less efficient than

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Weight/Size ratiopower to weight ratio given their

efficiency.

servo motors which usually means a

smaller power to weight/size ratio.

Efficiency

Servo motors are very efficient.

Yielding 80-90% efficiency given

light loads.

Stepper motors consume a lot of

power given their output, much of

which is converted to heat. Stepper

motors are usually about 70% efficient

but this has some to do with the

stepper driver.

Flexibility in

motor resolution

Since the encoder on a servo motor

determines the motor resolution

servos have a wide range of

resolutions available.

Stepper motors usually have 1.8 or 0.9

degree resolution. However thanks to

micro-stepping steppers can obtain

higher resolutions. This is up to the

driver and not the motor.

Torque to Inertia

Ratio

Servo motors are very capable of

accelerating loads.

Stepper motors are also capable of

accelerating loads but not as well as

servo motors. Stepper motors may

stall and skip steps if the motor is not

powerful enough.

Least Heat

production

Since the current draw of a servo

motor is proportional to the load

applied, heat production is very low.

Stepper motors draw excess current

regardless of load. The excess power

is dissipated as heat.

Reserve Power

and Torque

A servo motor can supply about

200% of the continuous power for

short periods.

Stepper motors do not have reserve

power. However stepper motors can

brake very well.

NoiseServo motors produce very little

noise.

Stepper motors produce a slight hum

due to the control process. However a

high quality driver will decrease the

noise level.

Resonance andVibration

Servo motors do not vibrate or haveresonance issues.

Stepper motors vibrate slightly andhave some resonance issues because

of how the stepper motor operates.

Availability

Servo motors are not as readily

available to the masses as are stepper

motors.

Stepper motors are far easier to find

than quality servo motors.

Motor Simplicity

Servo motors are more mechanically

complex due to their internal parts

and the external encoders.

Stepper motors are very simple in

design with no designed consumable

parts.

Direct Drive

Capability

Servo motors usually require more

gearing ratios due to their high RPM.

It is very rare to see a direct driveservo motor setup.

Stepper motors will work fine in direct

drive mode. Many people simple use a

motor couple and attach the motor

shaft directly to the leadscrew or

ballscrew.

Recirculating Ball ScrewsTransform rotational motion of the motor into translationalmotion of the nut attached to themachine table.

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Advantages

Inexpensive & Low Power Use

Low Maintenance & High Accuracy

High Repeatability & High Efficiency

High Load Capacity

A Typical single axis CNC working diagram:

CNC Controller and PannelThe CNC controller is the brain of a CNC system. A controller completes the all important linkbetween a computer system and the mechanical components of a CNC machine. The

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controller's primary task is to receive conditioned signals from a computer or indexer andinterpret those signals into mechanical motion through motor output. There are severalcomponents that make up a controller and each component works in unison to produce thedesired motor movement.

The overall CNC controller architecture is to break the controller into a motion board and

buffer board.

Motion Board

The motion board is controlled via a standard PC parallel port using step anddirection commands to control the motion of up to 4 stepper motors. The step anddirection commands are sufficiently standardized that alternative motion control

systems (e.g. [Camtronics] or [Gecko]) can be substituted in without breaking theoverall architecture.

Buffer BoardThe buffer board contains a dedicated microcontroller that talks to a high speedserial port (or SimpliciNet hub; see below) and provides some command buffering.If there is enough buffering, it should be possible to run the CNC equipment from astandard desktop operating system without requiring something as specialized asreal time Linux [RTLinux].

There are a total of three configurations:Parallel Port Mode

In parallel port mode, the motion board is directly connected to the parallel port ofthe host processor.

Serial Port ModeIn serial port mode, the buffer board is connected to the host processor via a highspeed serial port and the motion board is connected to the buffer board.

SimpliciNet ModeIn SimpliciNet mode, the buffer board is connected to the high speed serial port ofthe host processor via a SimpliciNet hub [SimpliciNet] and the motion board isconnected to the buffer board as before.

CNC G-CODE Programming

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2. CNC machines are programmed with a design which can then be manufacturedhundreds or even thousands of times. Each manufactured product will be exactlythe same.

3. Less skilled/trained people can operate CNCs unlike manual lathes / milling

machines etc.. which need skilled engineers.

4. CNC machines can be updated by improving the software used to drive themachines

5. Training in the use of CNCs is available through the use of virtual software.This is software that allows the operator to practice using the CNC machine on thescreen of a computer. The software is similar to a computer game.

6. CNC machines can be programmed by advanced design software such asPro/DESKTOP, enabling the manufacture of products that cannot be made bymanual machines, even those used by skilled designers / engineers

.7. Modern design software allows the designer to simulate the manufacture ofhis/her idea. There is no need to make a prototype or a model. This saves timeand money.

8. One person can supervise many CNC machines as once they are programmedthey can usually be left to work by themselves. Sometimes only the cutting toolsneed replacing occasionally.

9. A skilled engineer can make the same component many times. However, if eachcomponent is carefully studied, each one will vary slightly. A CNC machine willmanufacture each component as an exact match.

Disadvantages1. CNC machines are more expensive than manually operated machines,

although costs are slowly coming down.

2. The CNC machine operator only needs basic training and skills, enough tosupervise several machines. In years gone by, engineers needed years oftraining to operate centre lathes, milling machines and other manually operatedmachines. This means many of the old skills are been lost.3. Less workers are required to operate CNC machines compared to manually

operated machines. Investment in CNC machines can lead to unemployment.

4. Many countries no longer teach pupils / students how to use manuallyoperated lathes / milling machines etc... Pupils / students no longer develop thedetailed skills required by engineers of the past. These include mathematicaland engineering skills.

1.CNC Deep Hole Boring Machine specification Max. Solid drilling diameter 200 mm Max. Trepanning diameter 350 mm Max. Counter boring diameter 350 mm

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Max. Boring depth 12000 mm Swing over bed 1400 mm Mx. Wt. Job 15 MT

2.CNC 3-Axis Gear Shaper

3.CNC Horizontal Boring Machine specification Boring spindle diameter 100 mm

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Max spindle travel 900mm Head stock vertical travel (Y-axis) 1120 m

4.6 Axis CNC Double Column Vertical Turning & Milling Machine (BV 40 / 50 NM)

supplied to Vikram Sarabhai Space Research Centre

EOT Cranes & Drive System

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Conventional AC operated electric overhead travelling (EOT) cranes uses slip ring

induction motors whose rotor windings are connected to a power resistance. Speed

control is performed by changing the rotor resistance in 3 to 4 steps by power

contactors. Reversing is performed by changing the phase sequence of the stator

supply through line contactors. Braking is achieved by a plugging operation.

A crane control system has been developed using a variable voltage variable frequency

drive and a programmable controller which has the advantage of continuous speed

control; reversing is achieved by changing the phase sequence through an inverter.

The main advantages of this system are precise positioning, energy saving and

increased motor life.

Capacity:400 /60 T, Span : 32 M installed at a height of 46 M to handle GSLV and PSLV at ISRO, Sriharikota.

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Understanding Vector Control Drive Technology

Vector control, also called field-oriented control (FOC), is a variable frequency drive (VFD) control

method which controls three-phaseAC electric motoroutput by means of three controllable VFD

inverter output variables.

Voltage magnitude

Voltage angle

Frequency.

FOC is a control technique used in brushless DC andAC induction motorapplications that was

originally developed for high-performance motor applications which can operate smoothly over the

full speed range, can generate full torque at zero speed, and is capable of

fast acceleration and deceleration but that is becoming increasingly attractive for lowerperformance applications as well due to FOC's motor size, cost and power consumption reduction

superiority.

Not only is FOC very common in induction motor control applications due to its traditional

superiority in high-performance applications, but the expectation is that it will eventually nearly

universally displace single-variable scalarvolts-per-Hertz (V/Hz) control.

In vector control, an AC induction or synchronous motor is controlled under all operating conditions

like a separately excited DC motor.That is, the AC motor behaves like a DC motor in which the field

flux linkage and armature flux linkage created by the respective field and armature (or torque

component) currents are orthogonally aligned such that, when torque is controlled, the field flux

linkage is not affected, hence enabling dynamic torque response.

Vector control (see Indirect FOC Block Diagram) accordingly generates a three-phase PWM motor

voltage output derived from a complex voltage vector to control a complex current vector derived

from motor's three-phase motor stator current input through projections orrotations back and forth

between the three-phase speed and time dependent system and these vectors' rotating reference-

frame two-coordinate time invariant system.

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(d,q) Coordinate System Superimposed on Three-Phase Induction Motor:

Such complex statormotor current space vector can be defined in a (d,q) coordinate system withorthogonal components along d (direct) and q (quadrature) axes such that field flux linkage

component of current is aligned along the d axis and torque component of current is aligned along

the q axis.[21]The induction motor's (d,q) coordinate system can be superimposed to the motor's

instantaneous (a,b,c) three-phase sinusoidal system as shown in accompanying image (phases a &

b not shown for clarity). Components of the (d,q) system current vector, allow conventional control

such as proportional and integral, orPI, control, as with a DC motor.

Projections associated with the (d,q) coordinate system typically involve.

Forward projection from instantaneous currents to (a,b,c) complex statorcurrent space vector

representation of the three-phase sinusoidalsystem.

Forward three-to-two phase, (a,b,c)-to-( , ) projection using the Clarke transformation. Vector

control implementations usually assume ungrounded motor with balanced three-phase currents

such that only two motor current phases need to be sensed. Also, backward two-to-three

phase, ( , )-to-(a,b,c) projection uses space vector PWM modulator or inverse Clarke

transformation and one of the other PWM modulators.

Forward and backward two-to-two phase,( , )-to-(d,q) and (d,q)-to-( , ) projections using

the Park and inverse Park transformations, respectively.

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However, it is not uncommon for sources to use three-to-two, (a,b,c)-to-(d,q) and inverse

projections.

While (d,q) coordinate system rotation can arbitrarily be set to any speed, there are three preferred

speeds or reference frames.

Stationary reference frame where (d,q) coordinate system does not rotate;

Synchronously rotating reference frame where (d,q) coordinate system rotates at

synchronous speed;

Rotor reference frame where (d,q) coordinate system rotates at rotor speed.

Decoupled torque and field currents can thus be derived from raw stator current inputs for control

algorithm development.

Whereas magnetic field and torque components in DC motors can be operated relatively simply by

separately controlling the respective field and armature currents, economical control of AC motors

in variable speed application has required development of microprocessor-based controls with all

AC drives now using powerful DSP (digital signal processing) technology.

Inverters can be implemented as eitheropen-loop sensorless or closed-loop FOC, the key limitation

of open-loop operation being mimimum speed possible at 100% torque, namely, about 0.8 Hz

compared to standstill for closed-loop operation.

There are two vector control methods, direct orfeedback vector control (DFOC) and indirect

orfeedforward vector control (IFOC), IFOC being more commonly used because in closed-loop

mode such drives more easily operate throughout the speed range from zero speed to high-speed

field-weakening. In DFOC, flux magnitude and angle feedback signals are directly calculated using

so-called voltage or current models.

In IFOC, flux space angle feedforward and flux magnitude signals first measure stator currents

and rotorspeed for then deriving flux space angle proper by summing the rotor angle

corresponding to the rotor speed and the calculated reference value ofslipangle corresponding to

the slip frequency.

Sensorless control (see Sensorless FOC Block Diagram) of AC drives is attractive for cost and

reliability considerations. Sensorless control requires derivation of rotor speed information from

measured stator voltage and currents in combination with open-loop estimators or closed-loop

observers.

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Application Recap

1.Stator phase currents are measured, converted to complex space vector in (a,b,c) coordinate

system.

2. Current vector is converted to ( , ) coordinate system. transformed to a coordinate

system rotating in rotorreference frame, rotor position being derived by integrating the speed by

means ofspeed measurement sensor.

3. Rotorflux linkage vector is estimated by multiplying the stator current vector with magnetizing

inductance Lm and low-pass filtering the result with the rotor no-load time constant Lr/Rr, namely, the

rotor inductance to rotor resistance ratio.

4. Current vector is converted to (d,q) coordinate system.

5. d-axis component of the stator current vector is used to control the rotor flux linkage and the

imaginary q-axis component is used to control the motor torque. While PI controllers can be used to

control these currents, bang-bang type current control provides better dynamic performance.

6. PI controllers provide (d,q) coordinate voltage components. A decoupling term is sometimes

added to the controller output to improve control performance to mitigate cross coupling or big and

rapid changes in speed, current and flux linkage. PI-controller also sometimes need low-pass

filtering at the input or output to prevent the current ripple due to transistor switching from being

amplified excessively and destabilizing the control. However, such filtering also limits the dynamic

control system performance. High switching frequency (typically more than 10 kHz) is typically

required to minimize filtering requirements for high-performance drives such as servo drives.

7. Voltage components are transformed from (d,q) coordinate system to ( , ) coordinate system.

8. Voltage components are transformed from ( , ) coordinate system to (a,b,c) coordinate

system or fed in Pulse Width Modulation (PWM) modulator, or both, for signaling to the power

inverter section.

Significant aspects of vector control application:

Speed or position measurement or some sort of estimation is needed.

Torque and flux can be changed reasonably fast, in less than 5-10 milliseconds, by

changing the references.

The step response has some overshoot if PI control is used.

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http://en.wikipedia.org/wiki/Rotation_(mathematics)http://en.wikipedia.org/wiki/Rotation_(mathematics)http://en.wikipedia.org/wiki/Rotor_(electric)http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Flux_linkagehttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Bang-bang_controlhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Pulse-width_modulationhttp://en.wikipedia.org/wiki/Step_responsehttp://en.wikipedia.org/wiki/Overshoot_(signal)http://en.wikipedia.org/wiki/Rotation_(mathematics)http://en.wikipedia.org/wiki/Rotation_(mathematics)http://en.wikipedia.org/wiki/Rotor_(electric)http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Flux_linkagehttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Bang-bang_controlhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/Pulse-width_modulationhttp://en.wikipedia.org/wiki/Step_responsehttp://en.wikipedia.org/wiki/Overshoot_(signal)


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The switching frequency of the transistors is usually constant and set by the modulator.

The accuracy of the torque depends on the accuracy of the motor parameters used in the

control. Thus large errors due to for example rotor temperature changes often are

encountered.

Reasonable processor performance is required; typically the control algorithm has to

calculated at least every millisecond.

Although the vector control algorithm is more complicated than the Direct Torque Control (DTC),

the algorithm is not needed to be calculated as frequently as the DTC algorithm. Also the current

sensors need not be the best in the market. Thus the cost of the processor and other control

hardware is lower making it suitable for applications where the ultimate performance of DTC is not

required.

Block diagram for Vector Control of Motor:
http://en.wikipedia.org/wiki/Direct_Torque_Controlhttp://en.wikipedia.org/wiki/Direct_Torque_Control

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