The transformer is made of body, transformer oil, oil tank,cooling installation, protector and outgoing sleeve. The iron core is the main magnetic circuit of transformer. It is usually made of hot-rolled or cold-rolled silicon steel sheets with high silicon which cover with insulation paint. The iron core divide into 2 parts that is core limb and horizontal slice. The core limb is covered with windings, and the transverse piece is used for closing the magnetic circuit. There are two basic forms of core structure: core type and shell type.
The winding is circuit part of transformer which is made of double silk-covered insulated flat wire or enameled round wire. The function of winding is the carrier of current to produce magnetic flux and induce electromotive force. According to the relative position of transformer high voltage winding and low voltage winding, the winding of transformer can be divided into concentric type and overlapping type. The difference between the two is the high concentric winding, the low-voltage winding with the core set on the column, and the overlapping winding are made into a pie. High and low voltage windings are placed up and down alternately.
Transformer shell is the main structure and oil holding device of the whole transformer. The iron core and windings are placed in the shell of the oil-immersed transformer. According to the size of transformer capacity, the outer cover basically has two types of core type and hanging cover type. With the development of transformer technology, the performance and reliability of the transformer has been greatly improved. More and more large transformers adopt all-welded structure, which can reduce the leakage point of the transformer and facilitate operation and maintenance.