Shell Type Transformer

There are two types of transformer depending on the construction of its core, and these are shell type transformer and core type transformer.

Shell type transformer is such a transformer where the core completes its magnetic path outside the windings.

Core type transformer is such a transformer where the magnetic core completes its path through the axis of transformer windings.

We shall discuss here the shell-type transformer. In a single phase shell type transformer, the magnetic core has three limbs. The core has two windows.

Shell Type Core
Single Phase Shell Type Core

We wind both primary and secondary windings on the central limb alternatingly. That means some portion of one winding is placed first then some portion of the other winding gets placed. Primary and secondary windings get sandwiched to each other. Hence, this type of winding is called sandwich winding. Each section of the windings on the central limb looks like a disc, and that is why it is also known as the disc winding.

Shell Type Transformer
Shell Type Transformer

There is required insulation inserted in between two adjacent sections or discs of the windings. We provide insulation between core and discs.

During designing and constructing a shell-type transformer, the disc of low voltage winding is first kept nearest to the yoke. Then high voltage winding discs are kept alternatingly with low voltage disc between two low voltage end winding discs. This arrangement makes the transformer economical as it saves insulation costs because the core is at ground potential. So the potential difference between core and lv winding is lower than that between the core and HV winding.

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