Power Transformer Construction Part Explained | EduVids

Power transformers has become an integral part of the power system. Without this, transmission of alternating current can never be possible. Most of the power transformers we use today is of oil cooled type, in which transformer oil is used to cool the windings. Transformer consists of copper windings, wound on the core. The core is made up of laminated silicon steel. The thin laminated sheets are of thickness 0.5 millimetres, which reduces Eddy current losses. Whereas silicon steel used to reduce Hysteresis losses.

There is three input and three output for the transformer. The winding which carry high voltage is called HV winding, on the other hand the winding which carry low voltage is called LV winding. The primary side of the transformer can either be HV or LV, which depends on whether the it is step up or step-down transformer.

The HV is always wound first on the core, then LV is wounded on HV windings. This is because the insulation required for the core is less when we wound the HV winding primarily on the core. The bushing, which is generally made up of porcelain, controls the shape and strength of the field produce by the transformer windings and reduces the electrical stresses in the insulating material. The tap changer, regulate the output voltage of a transformer by changing the turns ratio.
Oil cooled transformer can be recognized by the conservator tank. It acts as a reservoir for transformer insulating oil. Conservator is provided with the breather, which consists of silica gel inside it. Silica absorbs the moisture from the air produced in the conservator. Silica gel turn form blue to light pink colour when it absorbs moisture completely, and indicates, it’s time to replace breather. From the conservator to the transformer, there is one device connected in between, which is called Buchholz relay. Which is used for the protection of transformers from the faults occurring inside the transformer.

The three phase transformers can connect in different fashion either star or delta. From these two arrangements there are four possible combinations can be made for primary and secondary side.

Being a static device, transformers are very efficient machines, unlike rotating machines. Transformers can achieve up to 99% efficiency.

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