Why helical windings are preferred for high rating transformer?

Helical windings are used for low voltage and high capacity transformers, where the current is higher and at the same time the winding turns are lesser. The output of transformer in this case varies from 160 to 1000 kVA from 0.23 to 15 kV.

Why are two coils used in a transformer?

In real transformers, the two coils are wound onto the same iron core. The purpose of the iron core is to channel the magnetic flux generated by the current flowing around the primary coil, so that as much of it as possible also links the secondary coil.

In what type of transformers sandwich coils are used?

Figure 1.15 shows sandwich windings used in shell-type transformers. The high-voltage and low-voltage windings are split into a number of sections where each high-voltage section lies between two low-voltage sections. In sandwich coils, easily leakage can be controlled.

What is the purpose of providing iron core in a transformer?

The purpose of the iron core is to channel the magnetic flux generated by the current flowing around the primary coil so that as much of it as possible also links the secondary coil. The iron core is also used to decrease the magnitude of magnetizing current.

Why is the stepped core used for the transformer?

Stepped core reduces the area of the core and more of the limb can be utilized for placing the windings. Thus lesser copper (mean turn wise) will be used and cost will reduce. Hence I2R losses can be reduced.

What is the function of CT and PT?

The current transformer and potential transformer (also called voltage transformer) are both measuring devices. A CT lowers the current signals for measurement purposes, while a PT lowers high voltage values into lower ones. The transformers are designed to measure whether power systems are both accurate and safe.

Why are helical coils used for high voltage applications?

Helical coils are basically used for LOW voltage side that is it has to carry high current so its spiral with less number of turns.Thus helical is most effective for high capacity. Also I would like to add that the high voltage windings are shaped in a disc form because they are effective for the high voltage stress due to the HV wimding.

What are helical windings in Transformers?

Helical windings are used for low voltage and high capacity transformers, where the current is higher and at the same time the winding turns are lesser.The output of transformer in this case varies from 160 to 1000 kVA from 0.23 to 15 kV.

Can a transformer coil be wound vertically?

Coils can be wound in an upright, vertical orientation, as is necessary with larger, heavier coils; or they can be wound horizontally and placed upright upon completion. As mentioned previously, the type of winding depends on the transformer rating as well as the core construction.

What is a spiral coil used for?

Figure 1.11 shows double-layer spiral coils, which are wound on solid insulating former, and hence are mechanically strong. These coils are wound in the form of helix, which are generally used for low voltages 11 kV to 33 kV for large transformers.