Transformer

Power and distribution transformer cores are built with CRGD (Cold-Rolled Grain-Oriented) low-loss silicon steel laminations. HIB Grade and laser-scribed laminations significantly reduce no-load losses and noise levels. Well-executed core slitting and cropping delivers stress-free laminations without burrs for fully aligned core building. Specially dimpled sheets provide space between laminations for highly effective cooling. Step-lap or mitered joints at core corners ensure a streamlined magnetic flux path. Core limbs are held with resin-bonded glass bands to eliminate limb boards. Yokes are clamped with solid mild steel plates and yoke studs, ensuring high rigidity for withstanding mechanical shocks during transportation and short circuits.

Electrolytic-grade copper or super-enamel wire is used for optimal winding performance. Windings are produced on vertical winding machines by well-experienced craftsmen in a clean, pressurised environment ensuring superior reliability. High-quality pre-compressed insulation, pre-shrunk by a specially designed process, ensures long service stability — including capacity for emergency overloading beyond nameplate rating. Axial and radial cooling ducts ensure effective heat dissipation, eliminating hot spots. For high-voltage windings, disc coils with excellent mechanical strength are used. A special interleaved or shielded construction provides the most uniform voltage distribution against system transients.

Windings are rigidly supported by common pressure rings of densified wood at the top and bottom for precise alignment. Oil-profiled alignment rings are placed between HV and LV windings to reduce voltage stress levels. Tapping leads of all windings are connected by special extra-flexible insulated copper cables, rigidly brazed in position. In oil-forced units, oil is circulated inside the windings by specially designed insulating material pipes. High mechanical rigidity is achieved by hydraulic pressing at calculated force and tightening all special screws before the core-coil assembly is seated in the tank with locating arrangements.

The tap changer is made from high-quality homogeneous insulating board or synthetic resin mould, mounted below oil level for changing connections of taps in the primary winding. Tapping is adjusted by an off-circuit tap changer for distribution transformers of 11 KV class, assembled on the top of the core-coil assembly.

The conservator tank is detachable via a flange at its connection point to the tank cover. The connection to the main tank cover is at the highest point to prevent air trapping in the conservator tank, which shall be detachable to facilitate cleaning.

Tank: Fabricated from steel sheet and covers by welding; pressure-tested for leak detection. Steel parts are shot-blasted and sandblasted to remove weld splatters and mill scales. Tank finish consists of three coats: one anti-corrosive zinc chromate primer and two coats of weatherproof finish paint, each applied uniformly and cured at even temperature.

Radiator: Pressed steel radiators specially made from "D" grade CRCA sheets with profile-formed elements resistance-welded with seam/arc welding. Each individual element and assembled radiator is tested with air pressure of approximately 3 kg/cm².