Design and Constructional Features
The magnetic core is built up from high quality CRGO Lamination coated with oil and heat resistant insulation. Laminations are free from burrs, generally mitred cut and annealed in continuous annealing furnace for uniform heat treatment to minimize the stresses developed during slitting, cutting and punching. Cores are adequately clamped by steel channels to kept it firm and erect.
Transformer windings are designed to meet three fundamental requirements, such as mechanical, thermal and electrical. They are cylindrical in shape and are assembled concentrically.
The low tension windings are of the helical type, Double paper covered, rectangular shape, copper or aluminium strips are used for LT windings. Single or multiple strips in parallel are used depending upon the current rating of the transformer.
The high tension windings normally consist of cross over coils. Paper covered round conductors are used for cross-over coils. For higher current rating Transformers, continuous disc windings are used and in that case rectangular strip conductor is employed.
Windings are rigidly supported by elephantide washers, electrical grade kraft paper, press board as per IS: 1576 and spacers. Sufficient cooling ducts are provided to reduce the temp. rise of windings, oil and hot spot. All coils are preshrunk as per the seasoning cycle to withstand mechanical forces developed during short time over loads and short circuit conditions.