Core of Transformer and Design of Transformer Core

               In a electrical power transformerthere are primary, secondary and may be tertiary windings. The performance of a transformer mainly depends upon the flux linkages between these windings. For efficient flux linking between these winding one low reluctance magnetic path common to all windings, should be provided in the transformer. This low reluctance magnetic path in transformer is known as core of transformer.

                               

Influence of Diameter of Transformer Core

Let us consider, the diameter of transformer core be ′D′

Then, cross-sectional area of the core,

Now, voltage per turn

E = 4.44.φ_m.f

= 4.44.A.B_m.f

Where B_m is the maximum flux density of the core.

E is proportional to D²

Therefore voltage per turn is increased with increase in diameter of transformer core
Again if voltage across the winding of transformer is V

Then V = eN, where N is the number of turns in winding

If V is constant e is inversely proportional to N. And hence D² is inversely proportional to N. So diameter of the core is increased, the number of turns in the transformer winding reduced. Reduction of number of turns, reduction in height of the core legs. In-spite of reduction of core legs height, increased in core diameter, results, increased in overall diameter of magnetic core of transformer. This increased steel weight ultimately leads to increased core losses in transformer. Increased diameter of the core leads to increase the mean diameter on the winding. In – spite of increased diameter of the winding turns, reduced the number of turns in the winding, leads to less copper loss in transformer.

So we go on increasing diameter of the transformer core, losses in the transformer core will be increased but at the same time load loss or copper loss in transformer is reduced. On the other hand if diameter of the core is decreased, the weight of the steel in the core is reduced which leads to less core loss of transformer, but in the same time this leads to increase in number of turns in the winding, means increase in copper weight, which leads to extra copper loss in transformer. So diameter of the core must be optimized during design of transformer core, considering the both aspect.