Multilayer Helical Winding of Transformer and Types of Transformer Winding

Q. Draw neat sketches and discuss the special features of following winding used for 3 phase transformer : Cylindrical winding, Helical winding, Crossover winding, Disc winding. List the typical voltage and current ranges over which they are used.

• Different type of winding are used depending upon voltage, current and capacity of transformer.
• Transformers with core type construction uses concentric type of winding. Both primary and secondary winding coils are wound on the limb concentrically. Generally LV winding is placed near the core (Due to less insulation requirement).
• Depending upon voltage, current, temperature rise, short circuit strength following types of winding are used for core type of transformer :

Types of Transformer Winding
     1. Cylindrical winding of Transformer
     2. Helical winding of Transformer
     3. Double helical winding of Transformer
     4. Multilayer helical winding of Transformer

• winding is used in high voltage >132 KV winding of high capacity transformers.
• As shown in Figure several cylindrical layers are wound. Concentrically and are connected in series. Layers are separated from each other by the insulating paper also depending upon number of layers vertical oil ducts are created with the strips of insulating papers. The number of layer are increased as voltage increases.

• As this winding is used for high voltage winding, capacitance effect is prominent and needs to be given proper attention. This capacitance controls the surge behavior of transformer.
• To improve the surge behavior of transformer, capacitance should be distributed uniformly, which is done by making outer layers shorter. However, it is to be noted that this reduces mechanical strength as well as leakage reactance.

     5. Cross over winding of Transformer
     6. Disc and continuous disc winding of Transformer