For Medium and Large Capacity transformer Circuit coils are used because they are mechanically stonger. It is more economical to use circular shape coil around the stepped core for the same area of the iron core, Required by Magnetic flux the diameter of the circumscribing circle (d) get Reduced with an increase in the Number of steps. Reduction of diameter (d) will reduce the mean length turn of the winding around the core. Thus lesser copper (mean turn wise) will be used and the cost will reduce. The core area also and the cost will Reduce. The core area also can be better utilized for cooling Purpose and Mechanically the core structure will be stable with stacking intact.