Calculating windings of pulse power transformer

In old magazine (Radio – Радио) I found small article about calculating PWM power transformers. The formulas are for toroid core transformers, but I think, they are usable in standard E core transformers too.

1. Calculate the power of transformer: P_t=1.3*ΣP_n , W. The power of transformer is sum of all output powers multiplied by 1.3.

2. The core max power: P=S_c*S_o*f*B_max/150 , W. f=Hz, S_c=area of core section in cm², S_o=area of the “hole” in cm². B_max= max induction in Teslas, from core datasheet.

3. Number of turns in primary winding: w₁=0.25*10⁴*U₁/fB_maxS_c , in turns.

4. Max current in primary winding: I_1max=P/ηU₁ , A. (η = ~0.8)

5. Diameter of wire: d₁=0.6*√I_1max , mm. diameter is equal 0.6 multiplied by square root of max current.

6. Secondary (ant other) winding: w₂=w₁*U₂/U₁ , in turns.