CRGO i.e. Colled Rolled Grain Oriented. A core of a transformer is similar to the heart to a living being. Considering the importance of coil, many issues are kept in mind while their designing, like manufacturing functional reliability, longer service life, economy etc. Due weight age is given for the careful selection of proper material & optimization of the shape of this unit as the efficiency of the Transformer depends entirely on this crucial component.
The Windings allow the flow of oil around the conductor in-between sections. These Windings are made of high grade electrolytic copper, which are designed to optimize thermal, mechanical and electrical stresses depending upon the current & voltage requirements. Spiral, Cross-over, Helical and Continuous Disc winding with multiple copper conductors are usually adopted for transformers. The coil is lowered on the core legs. The machines for windings are equipped with different speed gears to ensure that proper tension is maintained on the windings. In order to give extra strength to the windings & for axial cooling of the ducts, dove tail key spaces are maintained.
This plays a major role in several processes like space utilization, compactness, ease of transportability, handling & installation. Care is taken in every respect for judicious space utilization and that too without compromising with the functional efficiency. Establishing a proper production line in assembly shop always helps in obtaining high production rate.
Virginity & purity of oil used in transformers is of paramount importance. The contamination, inclusion of foreign particles, even of microscope level or water particles, causes harmful effects on proper functioning of the transformer. These further affect the desired functional characteristics. Thus, these harmful elements are kept at bay by filtering the oil.
Tank & Final Assembly
After ensuring that the active part is fully dry & moisture free, it is lowered inside a suitably designed & fabricated mild steel tank. These tanks are thoroughly cleaned & painted before testing and are filled in with freshly filtered oil. The connections to LV & HV terminals are made as per drawings & all relevant parts are fitted in before the Transformer is sent for testing.
Tank Fabrication & Sand Blasting
The corrosion due to presence of moisture in the environment, brittleness of material due to influence of various gases, the formation of rust flakes, etc is not desirable on the surface of the transformer tank. These will have adverse effects on surfaces & ultimately lead to shortening of service life. The sand blasting is an effective process which helps in removal of harmful rust flakes. The proper painting gives aesthetic look of assemblage. It increases the service life of the Transformer by insuring protection against undesirable influences of the environment.
Drying / Ovening
We take care for drying individual coil and insulation components to ensure that they match the duty cycle and short circuit forces, which the winding may encounter in service.
The core and coil assembly is dried through a very efficient drying oven, which ensures extraction of moisture to zero level. After drying process, winding, clamping and connection are checked and tightened before lowering into tank. Filtered and degassed oil is then filled into the tank under vacuum and this oil is circulated through the vacuum filter plants until the required insulation level is achieved.
Ready to Dispatch
During final assembly all pipe work, bushings and radiators are fitted to the transformer.