To minimise the burden

To maintain constant output

To prevent high static shield

To minimise the error in reading

Using thin laminated core

Providing long magnetic path

Using high flux density material

Providing good quality core material

To disconnect the tappings from neutral point

To disconnect the moving contact of the diverter

To avoid heavy sparking at the contact points

To provide an electrical isolation for the windings

Nature of load

Type of cooling

Phase sequence

Class of insulation used

Use of laminated core

By reducing core thickness

By using grain oriented core

Use stepped core arrangement