Auto Transformer is a laminated core transformer with only one winding on it. An Auto Transformer is similar to a two-winding transformer, but the primary and secondary windings are connected differently. Both the primary side and the secondary side share a portion of the winding. When the load is turned on, part of the load current is taken directly from the power supply, while the rest is obtained through transformer action. The voltage regulator is an Auto Transformer.

　　Advantages of Auto Transformer:

　　cheaper and more efficient;

　　There is less leakage inductance between primary and secondary, so there are fewer losses;

　　Simple construction for OEM;

　　Smaller footprint for the same VA rating.

　　The main purpose of an Auto Transformer is to adjust the voltage of the transmission line, which can be used to transform the voltage. The Auto Transformer has only one winding and can automatically adjust the voltage according to the load. These transformers require AC power to function properly and cannot use DC power.

　　Applications of Auto Transformer include:

　　Used as a starter, supplying up to 50 to 60% of the full voltage to the starter of squirrel cage induction motors during starting;

　　For small lifts on distribution cables to correct for voltage drops;

　　used as a voltage regulator;

　　It is used in power transmission and distribution systems, audio systems, railways, etc., and simply acts as a voltage converter.