As per construction, transformers are usually classified as,
1. Core type
2. Shell type
3. Berry type
The most commonly used transformer is core type.
The core type transformer has windings encircling the core.
The H.V. & L.V. both are placed on same limb concentrically.
Observe following figure:
L.V. is placed near to core.
The advantage of such transformer is:
1. Maintenance and repair is easy.
2. Ventilation & cooling of transformer windings is easy.
3. Less leakage flux, as windings are placed concentrically.
4. Higher efficiency and better regulation.
Mostly, power and distribution transformers are of core type.