Source for large (30mH+) inductors?

[MarcE]

Hi! I'm looking for a 30mH coil for a use in a conjugate. I noted on Erse's website that they do make such a beast (even as an air coil) but I cannot find them readily at their distributors. I assume this would be a custom order item. Does anyone have any experience ordering this type of item from one of their distributors? Any other recommendations?

[mazurek]

I think plitron will do custom wound stuff, don't know about pricing or minimum quantity

[MarcE]

Heh, I've spent far too much cash with Plitron this year. I just ordered a custom toroid and anything from them that is custom is very expensive. Thanks for the suggestion though!

[dawaro]

For something that large you might want to look at building your own. Someone on here posted a message to Jon about having some left over 10ga wire but I cant remember who it was. Maybe someone else will chime in and know who it was. If you can get the wire there are several online calculators you can use to get the # of turns.

[Dennis H]

I've heard Madisound will do custom coils. Realistically, you're probably looking at a steel core to get to 30mH at any reasonable price and DCR. It might be worth calling them.

[Piotr]

http://www.mundorf.com/english/bauteile/frspule.htm

/Peter

[JonP]

For something that large you might want to look at building your own. Someone on here posted a message to Jon about having some left over 10ga wire but I cant remember who it was. Maybe someone else will chime in and know who it was. If you can get the wire there are several online calculators you can use to get the # of turns.

That was me... It was kind of a joke.. they were talking about 18" drivers for the Isirus (sp?) and I kind of had this crazy vision of Jon with a passive 40Hz low pass or something. Thought I'd freak him out with the beasts...

We had made these giant coils for a magnetic field test, out of 10ga magnet wire. They are about 70-90mH each, I forget now. About 18" in dia, about 3" thick as well as wide, just the winding part, they're on heavy wooden spools. I posted pics for the full joke effect... Haven't weighed them, but I'd guess the pair weigh 50-60lbs or more. And, we have about half a spool of unused wire left!!! 8O

Anyway, are you thinking about iron cores yet?? :rofl:

[MarcE]

yeah, I'm thinking I'll need an iron core. Funny that Erse lists them on their website, but none of their distributors will special order them for me. Probably the cheapest one would be:

IXQ Xtreme Laminated I-Core Coil
ELC55-20-30000
20 Ga.
30.00 mH
2.202 Ω

Any good sources for cores?

[MarcE]

looks like I have a bite! Meniscus Audio is going to wind some for me, for a great price! I'll let you know how they turn out. Has anyone ever measured where hysteresis distortion / inductive reactance begins on an inductor?

[Jed]

I was going to suggest using (2) 15mH in series.

[Piotr]

MarcE, did you check the "zero-ohm-coils" at the Mundorf site?

You mentioned 2.2ohm for a 30mH coil... can you live with that resistance?

Hysteresis distortion depends on type of core and material.

Inudctive reactance = inductance and that depends on how big the coil (diameter, number of turns and layers) is and if it is an air coil or iron cored coil.


/Peter

[Gir]

Like Jed said, you can just add inductors in series for equivalent inductance. Just make sure you take care with the placement of the inductors; normal rules apply.

[Piotr]

One should be aware though that two coils in series will give higher resistance than a single coil with the same inductance.

Also what is "normal rules" when it comes to placement of coils? In a crossover where you may wish to minimize coupling between parts of the crossover you need to separate the coils by some distance and angle them 90degrees from eachother. When you seek to maximise inductance for a given length of wire in two coils you want the opposite.


/Peter

[Irwin AR]

considering the size (30mH) and if it must be a steel cored one, go
for the mundorf for a better lamination process and material.
And for me considering you may have to order direct from Germany,
go for the adjustable coil setup (google for the 2006 catalog/prices where
there's pictures of the thing.2007 catalog doesn't show them) available for round or even flat coil wire.

I almost ordered those setup too.But still holding it back as i'm more
interested in a series coil configuration (say 15mh+15mh but on a single core) but adjustable!
It would be great if mundorf could make them for me.We'll see.Haven't
pushed them those disturbing email yet.

[69Stingray]

One should be aware though that two coils in series will give higher resistance than a single coil with the same inductance.
/Peter

If you have two 15 mH coils, each with 0.50 DCR, then in series, you have a 30 mH coil with 1.0 DCR? Correct?

[BobEllis]

If you have two 15 mH coils, each with 0.50 DCR, then in series, you have a 30 mH coil with 1.0 DCR? Correct?

That depends. The DCR will be 1R, but the inductance depends on the mutual coupling of the coils, if any. Stack them together with the windings in the same direction you'll get more than 30 mH. Flip one coil over, the inductance will be less than 15 mH, approaching 0 with perfect coupling. Keep them well away from each other and oriented so that they don't interact, then your assumption is correct.

[Gir]

Also what is "normal rules" when it comes to placement of coils? In a crossover where you may wish to minimize coupling between parts of the crossover you need to separate the coils by some distance and angle them 90degrees from eachother. When you seek to maximise inductance for a given length of wire in two coils you want the opposite.

If you buy two 15mH inductors to make a 30mH inductor, then you don't want any coupling. If you have the equipment to measure inductance (such as a capacitor and oscilloscope), you could buy two lesser inductors and play around with them and see how they couple.