In a simple two-winding transformer, the primary and secondary windings wound on a separate limb or core. The core is made of the soft iron that provides a low reluctance path to the magnetic circuit of the transformer. This magnetic circuit is known as the Transformer Core.
It is designed to provide a low reluctance path for the magnetic flux to flow through the magnetic circuit. And it is necessary to induce the voltage between both windings.
The primary and secondary winding of the transformer is not connected physically. But both windings are connected magnetically. Then also, there is some amount of magnetic loss occurs between both windings.
Therefore, separate limbs are not very efficient. Because it results in a low magnetic coupling and a large amount of leakage of magnetic flux from the transformer.
According to the shape of cores, transformer cores are classified into different types. And these different types of transformer cores are used to overcome these inefficiencies.
The design of the core includes the shape as well as the size of the core. The small size core makes the transformer more compact. It also provides a low reluctance path for the magnetic field.
While designing the core, it must prevent the circulating current within the transformer core. This circulating current is also known as eddy current. The eddy current causes power loss and reduces the efficiency of the transformer. And it is continuously subjected to the alternating magnetic field produced by the external sinusoidal supply voltage.
To reduce the eddy current loss, the transformer core is constructed with the thin steel laminations. The material used to make the core is highly permeable material made from silicon steel. It is made up of thin silicon steel lamination combine in the exact shape of the core. It makes minimum eddy current loss of the transformer.
The thickness of the lamination is approx. 0.25mm to 0.5mm. By thin coating of the insulating varnish, laminations are electrically insulated from each other.
The air gap between the primary and secondary choices wisely. To improve the efficiency of the transformer, both windings are placed as near as possible and make air gap small to improve magnetic coupling. If the air gap is more, it will result in a loss of magnetic coupling between primary and secondary winding. And more flux will leakage through the air gap and it will reduce the efficiency of the transformer.
The transformer core provides a magnetic link between the primary side and the secondary side of the transformer. And it has lots of energy. It is a part of the transformer that forms the magnetic circuit with all other parts like limb, yoke, etc.
As we have seen in the construction of transformer, the limb of the transformer provides housing to the transformer windings. And it is also a part of the magnetic circuit of the transformer. Yoke provides mechanical strength to the internal parts of the transformer. as well as it is also used to complete the magnetic path.
The transformer core is designed with the aim that it creates maximum flux with maximum magnetizing current and minimum core loss.
The factor keeps in mind while designing the transformer core;
- Reduce the iron loss and magnetizing current
- Higher reliability
- Lowering labour cost and material cost
- Diminish of noise level
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