Transformers

http://en.wikipedia.org/wiki/Transformer_types

Thanks for the reply. I was looking at this last night and I did not get a good explanation of Regulating transformer. Auto Transformer is easy to understand, but what is a regulating transformer.

http://www.eidusa.com/Electronics_Trans_Regulating.htm

Voltage regulating transformers usually have an additional magnetic circuit and an additional winding connected to a capacitance to form a (quasi) resonant electrical circuit. The added design elements stabilize output voltage under variable source and load conditions. While simple transformers (and auto-transformers) are fairly easy to design and construct, the analysis, design, and construction of regulating transformers is a much more complex project.