There are two basic types of transformer constructions,the core type and the shell type.
CORE-TYPE CONSTRUCTION
In the core-type transformer,the magnetic circuit consists of two vertical legs or limbs with two horizontal sections,called yokes.To keep the leakage flux to a maximum,half of each winding is placed on each leg of the core as shown in fig.The low-voltage winding is placed next to the core and the high-voltage winding is placed around the low-voltage winding to reduce the insulating material required.Thus,the two winding are arranged as concentric coils.Such a winding is, therefore,called concentric winding or cylindrical winding.
SHELL-TYPE TRANSFORMER
In the shell-type transformer fig.,both primary and secondary windings are wound on the central limb,and the two outer limbs complete the low-reluctance flux paths.Each winding is subdivided into sections.Low-voltage(lv) and high-voltage(hv) subsections are alternately put in the form of a sandwich.such a winding is,therefore,called sandwich or discwinding.
The core-type transformer is easier to dismantle for repair.The shell-type transformer gives better support against electromagnetic forces between the current-carrying conductors.These forces are of considerable magnitude under short-circuit conditions.Shell-type transformers provide a shorter magnetic path,and hence magnetizing current is lesser than that in the core-type transformer.The natural cooling is poor in a shall-type transformer due to the embedding of the coils.
CORE-TYPE CONSTRUCTION
In the core-type transformer,the magnetic circuit consists of two vertical legs or limbs with two horizontal sections,called yokes.To keep the leakage flux to a maximum,half of each winding is placed on each leg of the core as shown in fig.The low-voltage winding is placed next to the core and the high-voltage winding is placed around the low-voltage winding to reduce the insulating material required.Thus,the two winding are arranged as concentric coils.Such a winding is, therefore,called concentric winding or cylindrical winding.
SHELL-TYPE TRANSFORMER
In the shell-type transformer fig.,both primary and secondary windings are wound on the central limb,and the two outer limbs complete the low-reluctance flux paths.Each winding is subdivided into sections.Low-voltage(lv) and high-voltage(hv) subsections are alternately put in the form of a sandwich.such a winding is,therefore,called sandwich or discwinding.
The core-type transformer is easier to dismantle for repair.The shell-type transformer gives better support against electromagnetic forces between the current-carrying conductors.These forces are of considerable magnitude under short-circuit conditions.Shell-type transformers provide a shorter magnetic path,and hence magnetizing current is lesser than that in the core-type transformer.The natural cooling is poor in a shall-type transformer due to the embedding of the coils.
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