An auto transformer is a electrical transformer having only single winding which acts as both primary and secondary,so in input and output connected to shared single winding.
Why we need to go for Auto Transformer ?
We have some advantages of auto-transformer over normal two winding transformer.
1.Auto transformers usually smaller in size,because one winding is eliminated.
2.as size is small cost also low(so cheap in cost)
3.as the winding is same so leakage reactance will be less.
4.increased kVA rating.
Construction, Principle of Operation Of Auto Transformer:
Copper Savings in Auto Transformer:
If we compare conventional two winding transformer and auto transformer the amount of copper needed for auto transformer is less.weight of copper of any winding depends upon its length and cross – sectional area.and length depends on no.of turns,cross – sectional area varies with rated current.
Let’s assume, Wa and Wtw are weight of copper in auto transformer and two winding transformer respectively,
∴ Saving of copper in auto transformer compared to two winding transformer,
∴ Wtw -Wa=kWtw