Or to put it another way - a copper cable to carry 200A needs to have a cross-sectional area of about 70 mm^2
Roughly 8.5 x 8.5mm of copper, if it were square.
Just an insulated connecting wire is going to be as thick as your little finger.
https://docplayer.net/docs-images/43/16516288/images/page_6.jpg
That's not allowing for skin effect, which means larger cables at higher frequencies..
https://en.wikipedia.org/wiki/Skin_effect
At just 10KHz, the majority of current flow occurs within the outer 1mm of the conductor, no matter how big it is.
That "skin" region has got to have enough cross-sectional area to carry the current without excess heat production.
You are in to the realms of litz wire, which is very expensive, especially in large sizes.
**broken link removed**
Any high-current, high-frequency inductors would need to be wound with that type of wire
High current systems are a specialised field.
High frequency systems are another specialised field.
Combining the two successfully requires a
lot of experience with both.
You absolutely need decent test equipment as well, such as a reasonable oscilloscope and a good multimeter - plus preferable a clip-on current probe for the scope, when working with high power switching supplies, so you can directly view current waveforms as well as voltage.
Don't give up the idea, but start small!
You _will_ destroy a lot of parts experimenting with switched-mode circuits, so use small cheap ones initially, that do not matter much and don't cause life-threatening explosions...
[And as Ron says, you need a bit bigger iron when working with large high-current cable & component joints.. The "small" one in the photo is one of our standard 50W temperature controlled bench irons..]