To make sure that only masterpieces leave our factory gates, We go through below process
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.
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. Type test like impulse voltage and short circuit are also conducted outside recognised lab when a new design of transformer is manufactured.
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.
Latest amendment and modification as per ISS 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.
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.
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.
The assembly is subject to the drying process is an oven where filtered dried air at 90 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.
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.
To maintain the Transformer within the temperature rise limits specified by the standard, cooling tubes are provided into the tanks.
The fittings are provided as per required standard. Any Additional fitting can be made on request of the customer.
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 or aluminium 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 of aluminium strips, the strips are transposed during winding to avoid unequal voltage induction and circulating current in the conductor.
Tapping and Tappings switches
To compensate the voltage drops in the lones and Transformer itself ration taps are provided on Transformer. Generally tapping are located in the mid of the transformer.
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.
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.