A Transformer, in which a part of the winding is common to both the Primary and Secondary circuit is called an Auto Transformer. It shall be noted that in Two Winding Transformer, Primary and Secondary windings are electrically isolated but in Auto Transformer, the two windings are not electrically isolated. A simplified diagram of a Step-down Auto Transformer is shown in figure below. As shown in the figure above, N 1 and N 2 are the number of turns between winding AB and AC respectively. If a voltage V 1 is applied across AB, an exciting current will start flowing through the full winding. Therefore, voltage per turn in winding AB is V 1 /N 1 and hence voltage across CB is (V 1 /N 1 )N 2 . As the load current is I 2 and the current taken from the source is I1, neglecting losses Input Power = Output Power V 1 I 1 CosØ 1 = V 2 I 2 CosØ 2 ………………….(1) Assuming internal impedance drop and losses to be negligible, pow...
Comments
Post a Comment