enormous drum core

This "electric motor" gives you the ICE-revving experience and doubles as a degausser:

It occurs to me that we'll have a relay close to two of these inductors in parallel. We'd better check that the mag field from the cores doesn't mess up the relay.

Not really enormous, Renco makes bigger.

If you need shielding, consider a big ugly powdered iron:

I think Bourns makes toroidial inductors of similar values, of course if you end up needing more, you're into specialty or custom territory regardless of the shape.

Could also put ferrite plates beside it, but mind the increase in inductance, and possible saturation.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

I have a MicroMetals sample kit, with some really big ones; you can pass your hand through the ID. But they need to be wound, and don't fit on PC boards very well.

Two of these Bourns in parallel, with a bit of air flow, should work.

Antiparallel would minimize field leakage, but there's no obvious way to know how to install them. We'd have to test each one and mark it, I guess.

If they don't try to crash into each other you did it wrong?

Mark L. Fergerson

" snipped-for-privacy@bid.nes" wrote in news: snipped-for-privacy@googlegroups.com:

Biggest drum core...

Actually, China now has built an entire building that looks like a huge drum...

I guess we'll bolt them to the underside of the PCB, with a screw through the center hole. That should hold them down. I'm thinking a stainless screw won't affect the electricals much.

I wonder how an unshielded drum inductor interacts with a PCB ground plane. I'll experiment. I recall that a sheet of 1 oz FR4 has a magnetic eddy-current time constant, but I don't remember the value. A few artistic slits in the plane could change that.

There will be a biggish fan on the underside of the board, cooling everything. Bourns rates the 1 mH part for 3.6 amps, but it looks good for a lot more with a little air flow.

Component thermal ratings are really suggestions, starting points.

Looks like I should hack the ground plane somehow.

I think one could couple some serious power over a pair of these, with a lot of high voltage clearance.

In image 4 it looks to me like the blue wire goes to the end of the winding and the yellow wire to the start.

If that's consistent, we could spot the difference visually and add a color dot somewhere that will be visible after assembly, for inspection.

Or build some sort of field sensing rig.