Process
To make sure that only masterpieces leave our factory gates, We go through below process
Core
The core assemblies are built up from non againg cold rolled grain oriented silicon steel lamination with very low magnetisation losses. The core limbs and yoke are of the stepped selection and provided with the liberal oil ducts. Mitred Construction is adopted to join core legs with the top and bottom yoke to reduce the iron losses and magnetisation current. The core lamination sheet is coated on both sides with a very thin film of carlite insulating materials to minimise the excitation losses.
Coil
The coils are made of EC grade copper phase relationship, impedance voltage load losses, No load current, insulation resistance, induced over voltage withstand separate sources voltage withstand. Acceptance tests like temperature rise is conducted, if required by the customer.
Testing
The aim of testing is to prove the technical data and to find the higher efficiency and operational capacity of the Transformers are subjected to all routine and quoted in international standard.
Modification
Latest amendment and modification as per NEA and international standards are constantly watched and alternations are done accordingly. Technical data’s are subjected to change as per amendment in drawings and designs.
Assembly
Proper insulation is provided between the coils and core and the coils and yokes during assembly. Assembly is clamped properly to avoid possible slackness in any part of the core and coils. To ensure that specified short circuit withstand levels, full axial and radial bracing of the cold assemble is of utmost important. The phase leads are separated from tapping leads by adequate press board barriers. Leads bare joints are brazed/crimped and insulated properly.
Tanking
High assembly M.S. Plates are used to fabricate the tanks which are cleaned properly inside and outside to remove scale and rust. For ensuring that they leakfree, tanks are hydraulically tested, The inside of the tank is coated with oil resisting paint while the outside is coated with a priming coat followed by two coats of high quality enamel paint.
Processing
The assembly is subject to the drying process is an oven where filtered dried air at 75 C to 100 C is circulated as assembly contains good quality of moisture. The degree of dryness is monitored carefully with a view to bring moisture content in the assembly to the minimum limits.
Impregnation
The core and coil assembly in Transformer is put in its own tank while still hot and the flooded with hot filtered Transformer oil. Previously dried and degassed oil is fed through a valve at the bottom the vacuum is maintained in the tank during filling to draw out of any bubbles of air that may have been trapped.
Cooling System
To maintain the Transformer within the temperature rise limits specified by the standard, cooling tubes are provided into the tanks.
Fittings
The fittings are provided as per required standard. Any Additional fitting can be made on request of the customer.
Quality Control
Quality Control of incoming materials at all stages of manufacture are carried out to ensure total quality assurance of finished transformer. Every transformer is subjected to the following routine tests before dispatch. The routine test comprises measurement of winding resistance, Voltage ratio, Polarity and conductors suitably with high grade enamel or Kraft paper as required for any specific application. The high voltage coils of Distribution Transformers are buil up of round conductor of small cross section. The full high voltage is subdivided into a number of sectional coils. Low voltage winding are would in the form of spiral coils of rectangular copper strips, the strips are transposed during winding to avoid unequal voltage induction and circulating current in the conductor.
H.V. Windings
The off load tap changer is provided to change the tap with numbering identification and locking mechanism to be operated from outside of the tank as well as when the core coil assembly is out of tank.
Insulation
Special care is taken for providing insulation system to high voltage Transformer to sustain the operating stresses in service. The insulation system is chosen very carefully which is dried and preshrunk enabling the robust and stable assembly. To minimise the total capacitance and increase the series capacitance of the winding and to achieve a good uniform voltage Distribution, Static End rings are provided in coil assembly to Transformer.