1. Output of Transformer Let, Ø m = main flux, Wb ; B m = maximum flux density, Wb/m 2 ; δ = current density, A/m 2 ; A gi = gross core area, m 2 ; A i = net core area, m 2 = stacking factor * gross core area A c = area of copper in window A w = window area, m 2 ; D= distance between core centers, m; d= diameter of circumscribing circle, m; K w = window space factor; F=frequency, h z ;

2. E t = emf per turn, v; T p,T s = no. of turns in primary & secondary winding respectively; V p,V s = terminal volt. In primary & secondary wdg. respectively, V; I p,I s = current in primary & secondary wdg. respectively, A; a p,a s = area of conductor of primary & secondary wdg. respectively, m 2 ; l i = mean length of flux path in iron, m; L mt = length of mean turn of x’mer windings, m; G t =weight of active iron, kg; G e =weight of copper, kg; g t =weight per m 3 of iron, kg; g e =weight per m 3 of copper, kg; p i =loss in iron per kg, W; p e =loss in copper per kg, W;

3. Single phase Transformers The volt. induced in a x’mer wdg. Wth T turns & excited by a source having frequency f H z is given by: Voltage per turn E t = E/T=4.44f Ø m. The window in a single phase x’mer contains one primary & secondary wdg. Therefore, Total copper area in window A c = copper area of primary wdg. + Copper area of secondary wdg. = primary turns × area of primary conductor + area of secondary conductor = T p­ a p +T s a s.

4. Taking the current density δ to be the same in both primary & secondary wdg. a p =I p / δ & a s =I s δ Therefore, Total conductor area in window A e =T e. I p / δ +T s. I s =(T e I p +T s I s )/ δ = 2AT/ δ As T e I p = T s I s =AT if we neglect magnetizing mmf.