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A TECHNICAL PAPER

ON

POWERFORMER THE FUTURE ALTERNATOR

y Paper Presented by :-

y I.SRIKANTH & T.SAIPRAKASH REDDY

y E.E.E 2ndYEAR,y VIGNAN INSTITUTE OF TECHNOLOGY AND SCIENCES,

y DESHMUKHI,

y HYDERABAD.


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TWO PERTINENT QUESTIONS

The challenge lies in meeting electrical energy with

with a high degree of RELIABILITY

with a high percentage of EFFICIENCY

in an ECONOMICAL manner

1) Is the Present power-system network capable of meeting the

load demands of the future? If yes,

2) Is the present mode of electrical energy generation the

only capable method of meeting future load demands?

That is, is there no other alternative way of a more reliable

and efficient generation?


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MOVING DEEPER INTO THE QUESTIONS

Why is the power-system network look like the way it is now ?

How has the technology changed over the last few years ?

How can this technology influence the existing system?

How can the existing power-system network accommodate

itself to this changing technology ?

And finally,

What is the technical and economical feasibility of the new

network arising out of change in technology?


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WHY WERE THE TRANSFORMERS BUILT AT ALL?

Large scale electrification started in the industrialized

world more than half a century ago. There was then a lack

of technology for manufacturing very high voltage

generators.

Insulation for such high voltage generating machines was

also a very huge problem.

Step-up transformers using gases, paper and fluidsas insulators and coolants, thus came into existence.


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WHAT ABOUT THE DESIGN OF THE THENGENERATORS?

With transformers available for stepping up voltages,

the generators could do with comparatively low voltage

generation.

However, to generate more power at low voltages, very high

currents had to be generated.

More Copper had to be packed in a given size alternator.

And for this purpose, SQUARE SHAPED CONDUCTOR

PACKING was used.


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THE TRANSFORMER AND ITS DRAWBACKS

Thus we see that, in any generating station, the fundamental

task of a transformer is to be a voltage adapter between the

generator and grid.

Also the transformer has had a great influence on the design

aspects of conductors inside the generator.

But a transformer, consisting of a set of coils and a huge huge

magnetic core,

a) Occupies large spaceb) Adds to the installation cost and

c) Reduces the efficiency and regulation of generating system

d) It also requires hourly maintenance

End of answer to my first Question


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HOW HAS TECHNOLOGY CHANGED OVER THEPAST FEW YEARS ?

Over the past few years, tremendous advancements have

happened in the field of material science.

New materials, their properties have been discovered andutilized for the benefit of mankind.

The discovery of many more carbon compounds and their

applications as insulating materials that can withstand any

sort of thermal, mechanical and electrical stresses has

revolutionized the field of engineering.

The successful landing of the space-shuttle DISCOVERY

is a case where insulating materials withstood tremendous

thermal stresses.

End of answer to my second Question


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BY APPLYING THIS TECHNOLOGICAL CHANGE,CAN WE DO WITHOUT THE TRANSFORMER ?

Yes. Definitely, it is possible.

If a properly insulated alternator itself were to generate a very veryhigh voltage required for transmission (with minimum losses), thenthere would be no need for the transformers. Thus, all the drawbacksassociated with the transformer are eliminated.

This is made possible by using one a part or all of the transformer

material solely inside the generator itself, as armature and core.

This non- conventional generator is named

"POWERFORMER".


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THE BASIC PRINCIPLE BEHIND POWERFORMER

The working principle of a power-former is similar to theordinary conventional alternator

But the new technology is primarily all about a completelydifferent winding in the high-voltage generators stator.

Instead of the traditional square copper conductors, roundhigh-voltagecables are used.

Epoxy resin compound is provided as insulation.

For the first time it is possible, using such cables, to generate avoltage of up to 400 kV.


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POWERFORMER CABLE VERSUS CONVENTIONALREGULAR CONDUCTORS


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POWERFORMER CABLE VERSUS CONVENTIONAL

REGULAR CONDUCTORS

Broadly speaking, the square conductors needed to achieve the

desired high power output have their disadvantages.

The loading from the electrical field is unevenly distributed, withextremely strong fields being obtained in the corners. It wasimpossible for the insulation to cope with them above a certainpower limit. In addition, the heat developed was unevenly

distributed and lay at a high level.

In practice, a high-voltage generator with square conductorscannot give more than about 30 kV.


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THE ROUND CABLES ADVANTAGES

The loading in a round cable with solid insulation will be uniformly

distributed, and the conductor and insulation can be utilized to theirmaximum.

In addition, the electrical field remains inside this type of cable,which results in among other things a lower heat development.

There are no barriers to raising the voltage level. It is only a matterof increasing the number of winding turns and adapting thethickness of the insulation.


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OTHER TECHNICAL ASPECTS

The stator design remains same. The cables

are placed through circular bores in the slots,which extend radially outwards from the insideof the stator in a star-like pattern.

The distance between the cables will then belarge, which reduces the losses and the

magnetizing requirements.

The limitation in rated voltage for this class ofrotating machine is set solely by the ac cabledesign and the cable accessories such asterminations and joints.

End of answer to my 3rd and 4th questions


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IMPLEMENTATION FIGURES

a) EXISTING SYSTEMb) THE NEW SYSTEM


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ADVANTAGES OF THE NEW SYSTEM-1

1) The concept provides the possibility to directly connect a rotating

machine to high voltage power grid.

2) Plant simplicity - no need for step-up transformer, generator breakerand bus-bars.

3) Plant efficiency improved by 0.5 - 2%

4) High reliability, availability and maintainability because there are alower number of components.


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ADVANTAGES OF THE NEW SYSTEM-2

y 5) Lower environmental impact compared with conventional

y generators.

y

y 6) No transformer oil, so risks of leakage are eliminated

y

y 7) Low stresses on the insulating material.

8) And most importantly, it can applied in conjunction with existingsystems also.

-- End of answer to my final question


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THE IMPLEMENTATIONS AND THE CONCLUSIONS

y Power-former is built and is practically being implemented in

Sweden.

y Further tests are being carried out on its economic feasibility in

y Alaska, U.S.A.

THE POWER-FORMER IS DEFINITELY A TECHNOLOGICALBREAKTHROUGH IN THE FIELD OF ELECTRICAL ENGINEERING THATWOULD GO A LONG WAY IN ENSURING A RELIABLE AND EFFICIENTFUTURE

--President of Sweden, 1997.


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FINAL WORDS ANY QUERIES?

y

As the parting words, we dedicate thisslide to everyone here.


19/19

THANK YOU

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