Slitted cores are then taken into the core wrapper machine for cutting and wrapping to precisely designed shape and size which ensures low core losses and consequently low noise generation. The core wrapper machine is imported from Atlanta Grotones, USA.

 

ACTIVE PART (CORE COIL ASSEMBLY):

The coils are inserted into the core limbs. Insulation to the core. Yoke insulation. Lead wire insulation and clamping structures are assembled at this stage.

CORE ANNEALING:

Annealing of the wound core takes place in a Bell-type Annealing Furnace where the temperature is maintained as per the relevant temperature cycle. This ensures that the mechanical stresses, if any, induced during slitting, cutting, and forming operations are relieved from the core, and the specific loss values are improved.

COIL WINDING & INSULATION:

The high and low voltage coils are of copper. They are wound on variable speed machines. Spiral, cross over or continuous disc coils are used depending on voltage class and rating of the winding. The Wound coils are dried and pressed to predetermined stack Height prior to assembling on the core.

DRYING AND TANKING:

The core-coil assembly is subjected to Controlled temperature cycles to drive out the moisture. Coil clamping is done at this stage so that preset compression is given to the dried and compressed coil assembly. Once the drying and tightening process is completed the core coil assembly is tanked and filled with degassed oil under vacuum.

 

TANK FABRICATION:

Tanks, covers, and fittings are designed to withstand the specified pressure and Vacuum levels. Welded tanks are tested for leaks after fabrication. Mig welding sets are used for welding.

TANK CLEANING:

Seven tank chemical treatment Procedure is followed for tanks & accessories surface treatment to give a phosphate coating before painting. A single coat of powder coating is applied finally.

TESTING:

Apart from section wise testing of components and sub-assemblies, the fully assembled transformer undergoes tests as per applicable standard including insulation and Continuity tests. Voltage ratio, polarity, victor group, Excitation current, and No-load loss, Winding resistance, Load loss Impedance, Induced Overvoltage Test (DVDF), and separate source voltage withstand test, Breakdown voltage. Tan delta measurement of transformer oil.

Type tests and special tests including Temperature rise test, impulse test, Dynamic shot circuit test, Noise Level measurement, Zero sequences impedance measurement, etc. can be conducted as per requirements.

Apart from section wise testing of components and sub-assemblies, the fully assembled transformer undergoes tests as per applicable standard including insulation and Continuity tests. Voltage ratio, polarity, victor group, Excitation current, and No-load loss, Winding resistance, Load loss Impedance, Induced Overvoltage Test (DVDF) and separate source voltage withstand test, Breakdown voltage. Tan delta measurement of transformer oil.

Type tests and special tests including Temperature rise test, impulse test, Dynamic shot circuit test, Noise Level measurement, Zero sequence impedance measurement, etc. can be conducted as per requirements.

TECHNICAL SPECIFICATION :