Core Type Transformer

In the core type of transformer, the winding’s are placed on both of the limbs of a core. The core is of rectangular shape. In this type, the winding’s surround the most part of the laminated core.

The core type has a single magnetic circuit and the shape of coils used are cylindrical in shape. A core type transformer is shown in the diagram below. 

Core Type Transformer Diagram:

core type transformer diagram

We can see that the primary and the secondary winding’s are at the different limbs of the core.

But practically, in a core type, a part of primary winding is on one limb of the core and other is on the other limb of the core. The secondary winding also has a similar winding as the primary. We can understand this by looking at the construction diagram. 

Construction of Core Type Transformer:

construction of core type transformer

Why is this so?

Because if the primary and the secondary winding’s are both apart as shown above in the first figure then the flux leakage would be too high. So in order to avoid this leakage, this arrangement is made. In short, maximum linkage is provided in order to avoid the flux leakage between the primary and the secondary winding’s.

The typical arrangement of the transformer is shown as: 

core type transformer

In the following diagram the low voltage winding is closest or adjacent to the iron core instead of the high voltage winding. The reason for placing LV winding near to the iron core is that it is easy and cost effective as compared to placing HV. Less insulation is required between iron core and winding.

If the HV winding is placed near to the core instead of LV winding, then a high voltage insulation is required. Here note that either in both the cases i.e. HV near to core or LV near to core, the insulation between the HV and LV remains the same.

3 phase core type transformer:

By stacking together the single core type transformers, the three phase core type transformer is formed.

The transformer is shown as:

3 phase core type transformer

The 3 phase transformer core consists of three limbs. Each limb consists of both winding’s of one phase. The coils used in the winding of 3 phase are cylindrical in shape. 


  • The core design is more economical.
  • This is more easy to manufacture as compared to others.
  • Less insulation is required compared to shell type so less insulation cost.
  • Less iron is used in the core compared to other types.
  • It has more effective cooling.
  • The cylindrical coil gives high strength.
  • This is more efficient in high frequencies.


  • More copper wire is used in the winding’s.
  • Have some less mechanical strength as compared to shell type.
  • The winding is not easy.
  • The transformer can be noisy.


The application of core type transformer is preferred for high voltage ratings as they are more economical.

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