Core type Transformers:  in this type of transformer the windings enclose the core (fig .given below).  Both the windings are separated and half of every winding is placed on every limb to make the leakage flux as small as possible.  Since insulation of low voltage winding is every so low voltage winding is placed next to core and then high voltage winding is placed around the low voltage coils. In such an arrangement only single layer of high voltage insulation is needed and removal or repair   of the high voltage winding, which is more liable to faults than the low voltage winding, is simple and convenient.