Hi - I need to find some fairly large inductors. They need to be able to handle around 5A (10A would be better) and have a inductance of about 5mH (20mH would be better). Does such a thing even exist? Would it be just terribly huge/expensive? I couldn't find such a beast in the Digi-key catalog - as soon as inductance went over 1mH current capacity would fall to fractions of an A. Any suggestions? Thanks!
-Michael J Noone
Yes. And, yes.
The size of an inductor is related to the energy stored within. Energy stored in joules is 1/2*L*I^2, so a 10 ampere, 20 mHy inductor stores 2 joules of energy in its magnetic field. To reach that level, there has to either be a lot of size or a lot of flux. The wire also has to look like something you wire a house with. Think E-I laminations and bolted construction that look at home in a big tube amplifier. Something you can prop a door open with.
Here is a catalog page covering something that goes to 10 mHy and 12.5 amperes.
It would look like a transformer. In fact, I might approach this problem by measuring the inductance of individual windings of various transformers, always choosing windings that can carry the rated current or more.
pick picky. First you ask does such an inductor even exist? Then you ask that it come in pint size. Do you need a rating for continuous full current? It's in these fellows nature to have high thermal mass, so low-current-rated chokes can handle high-current surges for quite a long time.
What's your application, maybe there's a work-around.
RL
Check web sites that cater to loudspeaker builders:
see "inductors"
I can't believe noone has yet asked at what frequency you want this inductor to operate?
Line frequency, 10kHz-1MHz, and VHF bands are going to get you vastly different constructions. I'd like to see the air-core version myself.
Good day!
I'm working on a LTC1735 based DC DC circuit - it will take 3 polymer lithium ion batteries in series (so something around 9 -12.6V) and bring it down to 6V at 0-10A or so.
I just wrote out my calculations for the inductor size, and then realized I had accidentally forgotten I was switching in the Khz range, not the hz range (I left out an E3). Argh. I now realize I need something more like 4=B5H at 10A. Oops.
-Michael
In the datasheet
On 27 Aug 2005 04:18:53 -0700, Winfield Hill wroth:
A two-terminal black box that had the characteristics of a large, high current, inductor would be a neat design goal. A high frequency DC-DC converter to charge energy storage caps from the input current and some active circuitry to return that energy to the input at the appropriate, inductor like, time might do the job.
Jim
"Michael J. Noone"
** Yep - with an E & I laminated iron core about the size of a 20 to 30 VA mains transformer. Wound components like this are usually made to order by firms that do small quantity transformer winding and repairs.Such an inductior will have some degree of non-linearity with may or may not matter in your application.
......... Phil
Part number 255-448. 14 gauge wire is rated for 15 amps as AC cable, so 15 guage should only experience moderate heating with 10 amps. Being air core, it should also be quite linear.
Here's a 500mH inductor:
You can even edit the circuit, click component to select, right-click to edit.
saturate at 10A for your design inductance !
Will you please provide a link that points directly to that program or the page that shows it available for download?
I have tried many times to find it, and I think it simply isn't available anymore.
Good day!
It appears to be the very first hit on Google:
Google is
"mc"
** Then you would be making a major blunder.Transformer ( 50/60 Hz types) windings are not designed to be used as power inductors, rather they have very high intrinsic inductance values with low current passing capacity - unless the current flow is induced by a load on another winding.
OTOH, an iron cored inductor is wound and designed to have a particular inductance value and pass a particular maximum current value before core saturation occurs. This is normally achieved by introducing a small air gap between the E and I laminations which are stacked together and NOT interleaved.
Wound steel cores ( toroidal etc) need to be cut with a saw to create such air gaps for use as power inductors.
......... Phil
Lack of minimal adult intrapersonal skills noted.
Whoops. Point well taken.
In fact I am fully formally educated as one, but sometimes my attention to detail is a little slack. Obviously Graham, you have yet to make your first mistake.
Graham to quote a man who is very impressed with himself, you're obviously not an EE. An EE would know that this is just a problem of scale. Air cored is fine, just large and expensive. ;-)
Points well taken. The high DCR was a big tip-off that I missed.
Look at an iron powder core for that.
Graham
Have something to add? Share your thoughts — no account required.
Ask the community — no account required