Thanks Glort, they will be relatively small values and not high enough current for welding. a 3000 watt inverter with 230vac output will have filtering chokes for 15-30 amps. The needed 150amp or better for a 24vdc welder is going to make for big wire and a big core. Expensive commercially because of size and weight in electrical steel and copper. Since there will be a strong stray magentic field from an E-I core, with changes in current, I'll stick to the tedious gapped toroid, wound in two layers for better self cancelling. If I ordered one to be made, I'd be out near $1000. I can make it with a surplus core for about $70 worth of copper. I might be able to get a puny 250 uh without saturation at 150a.
I have doubts about the project- no telling if the welding fumes will be more than I can handle, or if the variations in welding current which the researcher noted are rapid and will cause substantial AC magnetic field. I hate failed expensive projects, though often much more is learned.