Question

application of core type and shell type transformer

Answer 1

It is a choice made by the designer, mostly. There is no hard and fast rule. But there are some trends that we see are based on mere practicalities.  

Mostly, 

Core type transformers are popular in High voltage applications like Distribution transformers, Power transformers, and obviously auto transformers. reasons are,High voltage corresponds to high flux. So, for keeping your iron loss down you have to use thicker core. So core type is better choice.At high voltage you require heavy insulation. In core type winding putting insulation is easier. In fact LV(low voltage) winding it self acts as an insulation between HV (high voltage) winding and core.
Where as, Shell type transformers are popular in Low voltage applications like transformers used in electronic circuits and power electronic converters etc. Reasons are,
At low voltage, comparatively you require more volume for the copper wires than that of iron core. So the windows cut on the laminated sheets have to be of bigger proportion with respect to the whole size of the transformer. So, shell type is a better choice.Here you don't care about the insulation much and insulation is thin and light. So you can put the winding anyway you want in the shell.

Answer 2

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In core type transformer both the primary and the secondary windings are placed on the side limbs whereas, in shell type transformer, the windings are placed on the central limbs of the transformer. The core type transformer has two magnetic circuits whereas the shell type transformer has one magnetic circuit.

Answer 3

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In core type transformer both the primary and the secondary windings are placed on the side limbs whereas, in shell type transformer, the windings are placed on the central limbs of the transformer. The core type transformer has two magnetic circuits whereas the shell type transformer has one magnetic circuit.