Types of Transformers

The classification of the transformers is based on the relative arrangement or disposition of the core and the windings. There are three main types of the transformers which are:


  1. Core Type
  2. Shell Type
  3. Berry Type


 Core Type Transformer

Core Type Transformer has single magnetic circuit. The core is rectangular having two limbs. The winding encircles the core. The coils used are of cylindrical.The coils are wound in helical layers with different layers insulated from each other by paper or mica. Both the coils are placed on both the limbs. The low voltage coil is placed inside near the core while high voltage coil surrounds the low voltage coil. Core is made up of large number of thin laminations.

As the windings are uniformly distributed over the two limbs, the natural cooling is more effective. The coils can be easily removed  by removing the laminations of the top yoke, for maintenance.



Shell Type Transformers

Shell Type Transformers has a double magnetic circuit. The core has 3 limbs. Both the windings are placed on the central limb. The core encircles most part of the windings. The cols used are generally multilayer disc type or sandwich coils. Each high voltage coil is in between two low voltage coils and low voltage coils are nearest to tip and bottom of the yokes.


Berry Type Transformer

These type of transformer are generally kept in tightly fitted sheet metal tanks. The tanks are constructed of specific high quality steel plate cut formed and welded into the rigid structures. All the joints are painted with a solution of light blue chalk which turns dark in the presence of oil, disclosing even the minutest leaks. The tanks are filled with the special insulating oil. The entire transformer assembly is immersed in the oil. The oil served two functions.

  • keep the coils cool by circulation
  • Provides the transformers an additional insulation



This topic is shared from book: Electric Machines by U.A.Bakshi, V.U. Bakshi.

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