Actually goodness factor is an actual SI standard term. It is fairly complicated in mathematical terms but look up the 'Q' of a coil which is often refered to as the 'goodness factor'.

Yes, For a high voltage coil you would wind it as many narrow layers so that the voltage between each layer was minimal. Wave winding also keeps the interwinding capacitance of the winding low so that it absorbs less energy during a rapid flux transition. You just need to be careful with the terminations. This method was frequently used in LOPT's for that reason. For smps transformers it is not used very often as smps transformers tend to have very few turns and so capacitance is very rarely a problem.

Oh ok good to know I had a lot LOPT´s in my hands If you mean the flyback TV transformers. Even the very old ones where you can see the windings. The most problems I have seen is with low load there is corona discharge everywhere. I think this will be my main problem. My problem with these transformers is the low output current othervise I would stick with them. I would like to have more like 100-200mA and I don´t believe they will hold up that continuous on the secondary. Because of these currents flyback is not the way to go also more half or full bridge design at 325VDC.

@@Telectronics You will not be able to use a LOPT in a switching supply as they work in a very different way. For switching supplies you do not need to resort to wave winding as the transformers in a supply have very few turns and so straight winding is fine. Wave winding in a LOPT (and RF coils) is a good option due to the need to minimise energy being absorbed by the coil and stored in the interwinding capacitance as that lowers the output in a LOPT and creates a parasitic tuned circuit in an RF coil. Corona discharge is normally a sign that the insulation is breaking down. Sometimes it can be resolved by doping the windings but I generally just rewind them (as I have a winding machine :) ).

@@JerryWalker001 My first guess was to just use a normal narrow winding with a lot of layer insulations to limit the voltage and corona stress through the whole coil like a pancake If you want to call it like that. The neon transformers for 50Hz as an example make two coils with a middle point ground to save insulation against earth could I do the same with a switch mode high voltage transformer ? I have been searching for plans like that in the internet but could not find a lot about building your own high power high voltage smps power supply like it´s too special knowledge?! The only thing I know that they use a multiplier If the voltage gets very high and not much information about how the pros build it.

It reduces inter-winding capacitance so that the coil acts more like a pure inductance. For example in a LOPT the output voltage would be reduced if the energy was going into the coil capacitance but with wave winding there is less capacitance so the output voltage is higher. With normal parallel winding the coil acts a bit like a coil with a capacitor across it. Wave winding is also used in tuned coils where just inductance is required.