What is Core Type Transformer
The core of single phase core type transformer is of single window core type. This means that it has two limbs as shown in the figure below.
In this type of transformer, both the LV and HV windings are wrapped on both limbs, usually both windings are divided into parts and one part of both windings is wrapped on one limb and the other part of the core on the other. Is wrapped on the limb.
The LV winding is first wrapped on the surface of the core limb with sufficient insulation between the core body and the winding.
The HV winding is then wrapped with adequate insulation between the LV winding and the HV winding.
In this way, both the limbs are wrapped first to the LV and then to the HV winding.
This arrangement makes the transformer economical. Since the potential difference between the grounded core and HV winding is maximum, the insulation value between them is also kept to a maximum. LV windings are kept close to the core to avoid this insulation cost.
Small-type core type transformers use square or rectangular cross-section cores. Because it is easier to construct a laminated square or rectangular cross-sectional core.
It is also not difficult to wrap the windings on that square or rectangular rectangular cross-sectional core limb. This process can reduce the cost of manufacturing small transformers.
But it is not easy to wrap large transformer winding conductors in square or rectangular forms.
To optimize the use of copper conductors, round cylindrical shaped windings are the best option.
But round cylindrical winding on a square cross-sectional core limb leaves unused space between the windings and the core, which is not appropriate.
This is not a good approach for large transformers because the size of the transformer matters. To minimize these unused spaces, phased cross-sectional cores are used where laminations of different dimensions are carefully staged to form nearly spherical cross-sections.
The cross section can be one-step, two-stepped and multi-step depending on the size, design and economical optimization of the transformer.
The main disadvantage of a core type transformer is leakage flux. In this arrangement leakage flux is higher than that of shell type transformer.
This affects the performance and efficiency of the transformer but still this arrangement is the best approach for large size transformers due to the best approach to winding during maintenance.
If there is any permanent damage to the internal winding, it can only be corrected by removing the outer winding which is not so easy in the case of shell type transformers.