Are these Air core or ferrite core types ?

 

I'm not sure we can tell from just looking, but I took a look at another supplier and see similar devices there that are ferrite core.

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Hello,

They look like the bourns 78F series:
http://www.newark.com/webapp/wcs/st...0016501&showResults=true&aa=true&pf=812083885
But those do not fit the values as the highest in that serie is 1 mH.
Could it be the add is for μH inductors?

Bertus

 

I guess they are ferrite.
Can air core type have that much inductance in that size ?

 

Hello,

For what application would you like to use the inductor?
Coilcraft has a lot of application notes that might be handy:
http://www.coilcraft.com/appnotes.cfm

Bertus

 

It's for a replacement on a PSU I get to fix from time to time.
I was wondering what core it was.

 

Bertus is correct it is micro Henry (uH) Milli is impossible at that size.
many people mix-up M (Mega) or (m) milli while they want to identify micro sign which was not available at the old keyboards so the used the letter u.

 

I am sure it is 2.2mH.
I checked the Schema.

 

Are these Air core or ferrite core types ?

Hello,

Long ago a relative of mine worked in a place that made inductors like that, only higher quality units.
I have a couple samples, and one is 1000uH which as you know is 1mH.
So it is not uncommon to see small inductors with high inductance. The trick is to use very fine wire and high permeability cores. The downside is they can not handle much current at all and the DC series resistance is very high as far as inductors go.
Will they work in a power supply? Only a very low current power supply like that for a 20ma LED, and maybe even not that great for that either. They would normally be used in tuned circuits.
For a true power inductor you need to check not only the inductance but also the max operating current and also the DC resistance. These are all important specs for power supply inductors.

The ones they made back then were 1 percent tolerance.

 

Hello,

Is the original coil of about the same size?
The ones in the link can only handle currents in in mA range.

Bertus

 

I just checked a 3.3 millihenry molded inductor about that size. The inductance dropped from about 3 millihenries to 459 microhenries when I held a magnet to it. Ferrite for sure.

 

I see.
It's used as a filter between main smoothing caps at the primary side, between bridge and the PWM chip ( 7 pin DIL ) with built in FET
The inductor is placed between two 4.7 to 10uf (Varies between supply types) 400V Mains filter caps.

PS. The link shows the same inductor that blows when Chip fails