I want to build a step-up trafo that should have an input voltage of 12V and output of 350V.The power should be 175W in,150W out. How many coils,how thick should the wire be and other questions like this could your answers. The core is a ferrite core,ETD29 3C90 from ferroxcube,with a Ve=5460mm^3,Amin=71mm^2,Ae=76mm^2. I got some advice that Bmax should be around 0.2T(2000Gauss) and J=2.5A/mm^2. Where could i find formulas to resolve this design? Thank you for your tips.