Hello guys with the welder transformer everything is working fine and now i want to wind my own transformer.. I started with this document "slup229" but i have an problem that i'm not understanding the part where they calcolate the primary turns can anybobdy help me ? It's on 3-8 pdf's page
The flux swing in the core is determined by the volt microseconds on the primary. The higher the voltage, or the longer the primary voltage is applied, the more turns that will be required for any given flux density.
The hardest operating condition the core sees, will be at maximum full duty cycle, which should only occur at minimum supply voltage and absolute maximum load.
At less than full load, or at higher input voltages the duty cycle will be much reduced, so its less stressful.
So what you design the primary turns for is lowest input voltage, and maximum full duty cycle at the switching frequency of your choice.
Np = (primary voltage x microseconds turn on) divided by (flux swing in Teslas x core cross section in mm squared).
Its pretty straightforward apart from choosing a suitable flux swing.
Above about 30 Khz core losses start to climb, and acceptable temperature rise of the core is what you need to think about.
Basically, if its burning up under no load, you need to reduce the flux swing by adding more turns.