Looking for formula to calculate gapped inductor

Le Wed, 15 Aug 2007 05:09:36 -0700, w2kwong a écrit:

Could you give me the money your customer is paying you. I don't want to mess with marketing and such, all I need is the bank transfer, and preferably in Euros. Thanks for paying ^_^

I can't give you SI units but you can convert. A gapped inductor is worth about:

Y = 43.2 + 1.7*G + 53*W

Where: Y = How much it is in US dollars G = The number of faces that you need to grind W = The weight in pounds

I hope this helps.

I take paypal :)

D from BC

What the hell is a gapped inductor?

Jim

-- "If you think you can, or think you can't, you're right." --Henry Ford

You really should "mess with theory" at some point...

But in the interest of answering your question... it's easy to compute the inductance of a gapped core vs. an ungapped core; the result is:

L_gapped/L_ungapped = L_e/mu_r / (L_e/mu_r + L_gap)

...where L_e is the effective length that the flux traverses, mu_r is the relative permeability of the of the core, and L_gap is the length of the gap. L_gap, of course, has to have the same units as L_e.

Notice that for large values of mu_r, the gap length alone starts to dictate the entire inductance.

---Joel

Ummm...for instance, an inductor made on a toroidal or similar "closed" core shape, but with a slot cut through the core material. Think of a tape-recording head.

Bob M.

Iiiim, sorry. I call those gapped core. I thought he was winding an inductor with spaces between the windings.

Jim

-- "If you think you can, or think you can't, you're right." --Henry Ford

Yeah, "gapped core" would be more common, but I'm pretty sure that's what the OP meant.

Bob M.

Mates may I apologies for my poor expression, since English is not my first language. Tolstoy your link has been useful, thanks

I'm still a UG student and don't get money for doing my thesis project. Instead I myself 'm paying thousand bucks to buy my own equipments, blown chips etc, and it's unlikely that I will be able to claim these cost from supervisor.

You're an idiot. Almost ALL core manufacturers provide gapped cores per customer spec.

I hope you get help.

You have to actually possess the capacity to provide the required services before you would deserve a dime...

Unless, of course, you are a doctor... Then you can shuffle folks in and out of your office all day, taking only vital signs, and billing insurance companies out the ass for near zero actual performed services.

I already knew that this was your latest nym. You didn't have to prove it with yet another example of your stupidity, but here we have such a fine example that I feel I should respond and fully quote what I said and how you responded so that others may enjoy a good laugh at your expense. Even those who have kill filed you, I am sure, will have a good giggle. You really didn't get it did you?

Beware that at large sizes of gaps, this equation is inaccurate. It assumes that the lines of force pass as straight lines from one face to another.

"Large" is a fairly ambiguous choice of terms here.

Yes, good point. Another one I forgot to mention is that with cores that have mating surfaces (e.g., pot cores) the tiny spaces between the two touching halves can be enough such that there's sometimes already a non-negligible gap that makes the mu_r listed on the data sheet more of an "effective" value rather than the true bulk material value. This of course causes the equation listed to be somewhat inaccurate as well.

Hopefully this guy measures the inductance he ends up with prior to using the device in a circuit...

messagenews: snipped-for-privacy@news.supernews.com...

Toroids actually have a "gap" as well but it is distributed though the core material without actually seeing a physical gap. With non - toriods like E-E cores for example, you need to gap the cores by putting a thin spacer in between the two Es or grinding down the center leg. This gives you the ability to chose the gap. Toriods come in a fixed gap with various discrete values.

messagenews: snipped-for-privacy@news.supernews.com...

if, and only if, its a distributed-gap core, e.g. iron powder, koolmu etc.

for ferrite toroids, this statement is entirely incorrect.

With non -

conversely, this is only true for non-distributed-gap cores e.g. ferrite, metglass etc.

Cheers Terry