Comparison between Auto-transformer and Conventional Transformer

S.no	Auto-transformer	Conventional transformer
1	It has only one winding, wound on a laminated core.	It has two separate windings, i.e., primary and secondary windings.
2	The windings are not electrically insulated.	The windings are electrically insulated.
3	The size of this transformer is small.	The size of this transformer is large.
4	The primary and secondary winding circuits are connected magnetically and electrically.	The primary and secondary winding circuits are connected magnetically.
5	It is more efficient and has better voltage regulation.	Efficiency and voltage regulation are less when compared to an auto-transformer.
6	Has low leakage flux and resistance.	Has high leakage flux and resistance.
7	Since the copper material required is less, it is very cheap and more economical.	Since the copper material required is high, it is very costly and less economical.
8	Loss is low.	Loss is high.
9	Generates variable output voltage.	Generates constant voltage.
10	It is mostly used as a starter in an induction motor.	It is mostly used to step-up or step-down the voltage in the power system.
11	Also called as VARIAC.	Also called as two-winding transformer.