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ELETRA

TRANSFORMERS

TRAINING

COURSE

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 Introduction Introduction

ELETRA transformers factory will be one of the biggest transformers

manufacturing companies in the middle east . The factory is

established to meet the increase in demand in power sector. It is the

expected step to complete Alfanar electrical systems perfection .

ELETRA manufactures a wide range of Three-Phase Distribution

Transformers with oil immersed core type and ³Oil Natural, Air 

 Natural´ cooling system (ONAN).The main characteristics of the ELETRA Transformers are:

Rated power: From 50kVA to 10000kVA

Rated voltage: Up to 36kV

with two types of tanks:

Free breathing with conservator 

Hermetically sealed

The standard products items are listed as follow:

Transformer Range

1 300 KVA

2 500 KVA

3 1000 KVA

4 1250 KVA

5 1500 KVA

6 2000 KVA

7 3000 KVA

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22-- T ransformer theoryT ransformer theory

Transformers are devices that transfer energy fromone circuit to another by means of a common

magnetic field.

When an alternating current flows in a conductor ,

a magnetic field exists around the conductor If 

another conductor is placed in the field created by

the first conductor such that the flux lines link the

second conductor then a voltage is inducedinto the second conductor. The use of a magnetic

field from one coil to induce a voltage into a second

coil is the principle on which transformer theory and

application is based.

(Types, Applications, purpose ) ???

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T  ype of T ransformersT  ype of T ransformers

Distribution transformer 

100-5000 KVA

11KV, KV,33KV/side cable box type

Kiosk type transformer 

Corrugated tank type oil transformer 

100-8000 KVA

One Side cable box

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Distribution transformer pad mounted

Primary & secondary side cable box

transformer with galvanized radiators

100-3000KVA

Dry type transformer 

100-1000KVA

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33--Design fundamentals Design fundamentals1- EMF equationThe relation ship between induced voltage and flux is given by the following equation

E= 4.44* F *B* A *N

E Induced EMF

F frequency

B flux density

A core area

  N no. of turns

-turns ratioE1/E = N1/N

E1,E induced voltage for primary and secondary winding

 N1,N no of turns for primary and secondary winding

3-Amper ±turns balanceI1* N1 =I *N

I1, I induced currents for primary and secondary winding

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44-- T echnical data sheet T echnical data sheet S.N.

1 Transformertype2 Installation indoor or Outdoor 3 Rated power (KVA )4 Rated primary Voltage (KV)

5Number of taps and voltage % for Off -Circuit regulation

6 Rated secondary voltage at no load V 7 Frequency (HZ)8 Number of phases9 Connection and voltage group11 Max Ambient temperature °C12 Temperature rise top oil °C1 3  Average winding Temperature rise °C14  Altitude (max) .m15 SC- Impedance voltage %16 No Load losses (W)17 Load losses (W)

20 Type of - Oil21 Parallel operation22 Standard

24Over all dimensions

 Width × Depth × Height (mm )25 Oil Weight ( KG )26 Total Weight (KG )

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5 5 --basic materialsbasic materials

The seven main materials in transformer categorized as follow

A- Cooled rolled grain oriented silicon steel ( CRGO )

B-Copper conductors ( copper foil ,enameled copper wire , paper wrapped copper wire, Bus Bar, etc«. )

C- solid insulating materials (Kraft paper , epoxy DDP, pressboard ,wood , etc««..)

D-Transformer oil

E-steel (mild steel coils and sheet, stainless steel, U channel , tie rods , steel pipes ,etc««)

F- transformer accessories ( tap changer, bushings, oil temperature indicator , drain valve ,winding temperature

Indicator , DGPT, Buchholz relay , dehydrating breather . Etc«)

G- painting materials

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6 6 -- T ransformer constructionT ransformer construction

T he coreT he coreThe purpose of the core is to provide a low reluctance path for the magnetic

flux linking primary and secondary windings. The magnetic circuit in a

transformer is made of steel lamination sheets whose basic constituents are

iron and approximately 3% silicon as an alloy element.

Core laminations are compacted and clamped together using yoke clamps

U channels and by tie-rods locking the top and bottom yoke clamps

together.

W inding W inding The windings consist of the current-carrying conductors wound around the

sections of the core. Copper is the primary material used as conductor 

 because of high conductivity and mechanical strength.

Conductors for low-voltage windings were originally made from foil copper sheet, and the conductor of high voltage winding were rectangle of round

shape depend on the rating and voltage system of the transformer .

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 Active Part  Assembly Process Active Part  Assembly Process

In the previous stage, the main part of the Active Part (core without the top leg andwinding) is finished.The Active Part Assembly is as follows:

1. Insertion of the transformer windings into the iron core. Completion of the magnetic circuit by stacking the upper yokes

3. Insertion of axial wooden rod studs between iron core and internaldiameter of windings for clamping the core and the coil to withstand theaxial and radial forces during short circuit

4. The core assembly will be dried in a vacuum oven This step is necessary

for removal of moisture from windingsT ank Manufacturing ProcessT ank Manufacturing Process

1. First process in making tank is slitting of steel. this the slit is transferred to fin wall machine which forms the steel into corrugated

wall3. The next operation is spot welding to weld all four walls forming the tank .4. Finally tanks are subjected to shot blasting & primer coating to produce tank in its final

form

T anking ProcessT anking Process

1. Transformer core assembly will be inserted into the tank 

. impregnated with oil by means of vacuum . Oil is supplied from the oil filtration plant

3. Finally ,top plate ,insulators & accessories are added to the final assembly after tanking

takes place followed by final testing

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88--testing of transformer testing of transformer 

Transformer tests are classified into three categories Routine Tests, Type Tests and Special Tests as described below:

 Routine T ests Routine T ests

Following tests are performed on every transformer in accordance with IEC 60076 standard:

- Measurement of winding resistance

- Measurement of voltage ratio and phase displacement check 

- Measurement of short-circuit impedance and load loss

- Measurement of no-load loss and current

- Dielectric routine tests (separate source AC voltage withstand test and short duration induced over voltage withstandtest)

- Measurement of insulation resistance to earth of the windings.

T  ype T estsT  ype T ests

For transformers of new type or design, ELETRA carries out the following Type Tests on at least two units:

-Temperature-rise test (in accordance with IEC 60076- )

-Dielectric type tests (Lightning impulse test in accordance with IEC 60076-3)

 Special T ests Special T ests

These tests are carried out after signing a contract with a client:

-Measurement of zero-sequence impedance(s) on three-phase transformers

-Short-circuit withstand test* (as per IEC 60076-5)

-Determination of sound levels (as per IEC 60076-10)

-Measurement of the harmonics of the no-load current

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99-- Information Required with Order  Information Required with Order 

To fulfill a customer¶s exact requirements, the following information along with orders requires :�Transformer specifications

�Kind of transformer (For example: Separate winding transformer, auto transformer, etc.)

�Single or three-phase

�Connection symbol

�Frequency

�Type of oil (mineral or synthetic insulating liquid, and its class)

�Indoor or outdoor type

�Type of cooling

�Rated power �Rated voltage

�Number of tapings; tapping range or tapping step (if tapping range is more than 5%, the voltage

variation type and the location of the maximum current tapping)

�Highest voltage for equipment

�Insulation level for each winding

�Connection symbol

�Impedance voltage at rated current

�No-load losses

�Load losses at reference temperature�For transformer with cable end box degree of protection according to IEC 605

�Neutral terminals, if required for any winding

�Fittings required; and indication of the side on which meters, rating plates and oil-level indicators are to

 be fitted

�Accessories required

�Type of oil preservation system

�Temperature limits and atmospheric conditions