Question

Compare auto transformer with two winding transformer.

Answer 1

Two winding transformer	Auto-transformer
There are two windings in this transformer for primary side and secondary side.	There is only one winding in this transformer for primary side and secondary side.
Both windings are electrically isolated.	Winding is not electrical isolated.
If number of turns on secondary side is more than primary side it acts as step up transformer.	If the winding for output have more number of turns than the input it acts as step up transformer.
There are two separate windings for primary and secondary.	Only one winding, part of the winding is common for primary and secondary.
No movable contact between primary and secondary	Movable contact exist
Electrical isolation between primary and secondary windings.	Electrical connection between primary and secondary.
Comparatively more losses	Comparatively lower losses.
Efficiency is less as compared to autotransformer.	Efficiency is more as compared to two winding transformer.
Copper required is more.	Copper required is less, thus copper is saved.
Core type or shell type core construction	Spiral core construction
Most of the general purpose transformers where fixed voltage is required.	Special applications where variable voltage is required.
Cost is more	Cost is less
Poor voltage regulation	Better voltage regulation