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Transformers are used to transfer electrical energy from one circuit to another through electromagnetic induction. These are used to increase or decrease the voltage level. A transformer is made up of many different parts that work together in different ways to improve the overall operation of the transformer. These include core, windings, insulating materials, transformer oil, tap changer, conservator, breather, cooling tube, Buchholz relay, and explosion vent. The core, windings, insulating material, and transformer oil are seen in almost all transformers, while other components are seen in transformers larger than 50 kVA.
The transformer core is used to support the windings. It is made of soft iron to reduce eddy current losses and hysteresis losses and provides a low reluctance path for the flow of magnetic flux. The diameter of a transformer core is directly proportional to the losses in copper and inversely proportional to losses in iron.
The windings consist of many turns of grouped copper coils, each bundle connected to form a complete winding. Windings can be based on input-output supply or voltage range. Depending on the supply, the windings are classified into primary and secondary windings, that is, the windings to which the input and output voltages are applied respectively. On the other hand, depending on the voltage range, the windings can be classified into high-voltage and low-voltage windings.
Insulating materials such as paper and cardboard are used to separate the primary and secondary windings from each other, as well as from the transformer core. Due to copper's high conductivity and ductility, these windings are made of copper. The high conductivity reduces the amount of copper needed and minimizes losses. Additionally, the high ductility results in easier bending of the conductors into a tighter winding around the core, which also reduces copper volume and winding volume.
It is the transformer oil that insulates and cools the core and coil assembly of the transformer. The transformer core and windings must be completely immersed in oil, which normally consists of hydrocarbon mineral oil.
The conservatory is a hermetic metal cylindrical drum mounted on top of the transformer that holds transformer oil. It is flanged at the top and is only half filled with oil to allow for expansion and contraction during temperature variations. However, the main tank of the transformer to which the conservator is connected is completely filled with oil through a pipe.
The breather is a cylindrical container filled with silica gel, used to allow air into the tank without moisture. This is because insulating oil reacting with moisture can affect the insulation and cause internal failure, so it is essential to keep the air free of moisture. In ventilation, when air passes through the silica gel, the silica crystals absorb the moisture content.
Tap changer Tap changers are used to balance voltage variations within a transformer. Know more about the two types of tap changers,, first one is the on-load and the second one is off-loaded. On load tap changers, the tap can be changed without disconnecting the transformer from the supply, while on non-load ones, the transformer must be disconnected from the supply.
As the name suggests, the cooling tubes are used to cool the oil in the transformer. The circulation of oil inside the transformer can be natural or forced. In the case of natural circulation, when the oil temperature rises, the hot oil rises naturally and the cold oil falls, while in the case of forced circulation, a perpetual motion pump is used.
Placed in the connecting pipe from the main tank to the conservator tank, the Buchholz relay detects faults that occur within the transformer. It is operated by gases released due to the breakdown of transformer oil during internal faults. Therefore, this device is used to protect the transformer from internal faults and, in turn, to detect them.
Boiling transformer oil is drained during internal faults through explosion vents to prevent transformer explosion. Usually, it is placed above the level of the greenhouse tank.