In core type transformers, The LV winding of the Transformer is placed near the core in order to reduce the cost of insulation and the size of the Transformer. If the HV winding of the Transformer is placed near the core, the insulation would have to be thicker leading to higher cost.
Placing the HV winding after the LV winding enables a much lesser thickness of insulation for the HV winding.
In Shell type transformers, the winding is interleaved. That is, the LV and the HV windings are placed alternately to reduce the leakage flux.
