Autotransformers:

         An autotransformer is a transformer with a single winding.
The primary and secondary form a single, tapped winding. Although they
are connected together, the primary circuit does not include the 
secondary, and the secondary circuit does not include the primary.
Transformer action is the same as explained for conventional
multiple winding transformers.


                0_____________  1
                              |
       Source                 {
      Primary                 {
                              {
                0_____________{___________ 2             
                              {
                              {             Load Secondary
                              {____________3


                 0__________________________1
                               {
        Source                 {
       Primary                 {
                               {
                 0_____________{ 2    Load Secondary
                               {
                               {
                               {
                               {_____________3

       Autotransformers are usually economical only with turns ratios
       no higher than about 4:1. For a given power rating, they can be
       made smaller and more compact than transformers with two windings.
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