2. A practical training seminar on

3. Manufacturing of transformer
 Design of core
 Design of LV winding
 Design of HV winding
 Assembly of transformer
 Testing of transformer
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4. Design of core
Core is the most important part of any transformer. There are generally two types of core
used that are as follows
 Silicon steel type core
 Amorphous metal sheet core
 For distribution transformer CRGO (cold rolled grain oriented steel) sheets are
used. these sheets are assembled together in iron channels
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6. Design of LV winding
 LV winding
This is called as low voltage winding .this is wounded on the core.
LV winding is made up of cupper strips. These cupper strips are fully
insulated by the cotton tap and paper insulation and after this it is
wounded on the cylinder made up of press board. The star connection
is made up on the LV winding.
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8. Design of HV winding
HV winding
HV winding is known as high voltage winding. It is wounded after the
LV winding in the distribution transformers. The aluminum or copper
wire is used for making the HV winding. The HV winding is wounded on
the cylinder made up of press board worth the help of machines. After
every layer of winding paper insulation is wounded .the tapings for
the tap changer is also taken out from the HV windings. The delta connection is made
up with the help of HV winding
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12. Assembly of transformer
Now the core assembly is inserted into tank and
transformer oil is filled. Now the other equipment
is equipped on this tank like Radiators, Bushing,
Breather, Conservator, Filling valve, Lifting lugs,
Oil gauge, Tank earthling point, Temperature
meter (O.T/W.T), Drain Valve, Tap-changer ,
Buchloz relay, Explosion vent, Rating plate.
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13. Assembly of transformer
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14. Testing of transformer
 Insulation-resistance test at ambient temperature
This test is done after taking out the assembly of
transformer from the oven for measure the moisture
present in the transformer core. It gives readings in MΩ
and the reading should be greater than 500 MΩ.
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15. Testing of transformer

High voltage test
High voltage test is done for checking the clearance of the
transformer assembly. If there is no gap present in
assembly with the tank then it can cause short circuit to
damage the transformer. There should be gap of 20mm and
40mm in between core assembly and transformer tank.
This is known as clearance.
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16. Testing of transformer
No-load test
In this test we will give supply to the LT side. Now we
will see the ampere metre reading that should be less
than 1 amp. And the power reading should be 121watts.
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17. Testing of transformer
 ON load test
First we will supply the rated current of 1.31 amps (for 25 KVA transformers) by the help of push
button for increasing voltage. Now the reading will observed as followsV = 458.33v
A = 1.31amp
Ws = 579
Room temperature= 400 C
Transformer temperature = 420 C
Ambient temp = 225+42=267(for aluminum)
235+42=277(for cupper)
Slandered factor = 300(for aluminum)
310(for cupper)
Load loss= (WS*S.F.)/amb. Temp.
= (579*300)/267
650.50
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18. Testing of transformer
 6DV-DF (double voltage, double frequency) test
This test is done for the insulation of every phase. In this test 866V supply is
given to the LT of the transformer to be tested. This supply is given by the 3phase induction motor coupling with the generator. This set produce double
voltage and double frequency, hence it is called DV-DF test. This supply is
given for the one minute. Mean while we see the change in the meters
connected for every phase. There is no reading in meter means the insulation is
proper.
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