Measuring inductor saturation

[Oznog]

What's the best way to measure the saturation current of an inductor? I wouldn't mind making up a PIC circuit or something similar to show it. I've got so many inductors I've got little data on that came from surplus catalogs, and now I realize I can't use them without figuring this out.

Actually, what's the most practical way to measure inductance? I'd like to check up on that rather than rely on the surplus guy's word for it.

Is there any practical way to measure core losses at higher frequencies?

 

[Styx]

Well an air-cored inductor will never saturate.
For a iron-core inductor the best way is to plot a B-H curve on a X-Y channel scope - I have lost teh link but very simple to do, just need a current trasformer.

The way I test inductance is to put a put a pulse of voltage across it (plus free-wheel diode) and then go:

V = L*di/dt

You know V, you know dt and you can measure di.

I think you might be able to use this techneque as well to find teh point of saturation (just look for a knee in the current ramp signalling the saturation point of the core)

Ill have a think and find the B-H test setup

 

[Styx]

I habve found this, it has a good realplayer demo. It still isnt the one I know so will look a bit more

https://web.mit.edu/6.013_book/www/chapter9/9.4.html

 

[Grossel]

Hi. I know this thread is six years old, but I found an interresting link to a site where inductor being tested for saturation using osciloscope with trigger input.

Link: Alan Yates' Laboratory - Inductor Saturation Tester

If anyboy knows different approaches, please let's know

 

[MrAl]

Hello there,


When an inductor saturates it's inductance goes from a relatively high value to a relatively low value, meaning the current rises very sharply and on the scope it looks like a spike of current (using say a current probe). At that point the current is limited by only the series resistance of the coil Rs, so the current would be due to whatever dc voltage is applied divided by that Rs. It can be very very high for power electronics inductors and can blow out transistors unless some means to prevent this is also incorporated into the circuit. Many modern circuits monitor the max inductor current to prevent the power transistor from blowing out, and some even use the inductor max current as a means of regulation.

Oh yeah one more thing worth mentioning is that sometimes the best circuit to use to test an inductor is the actual circuit it is being used in. In other words, check the inductor current in the circuit it is working in presently and see if you can find some mode that makes the inductor saturate. That's the best test.
Just before the inductor 'saturates' the current slope increases, so that's a tell-tale sign that something is going wrong. Many times it will be almost perfectly straight, then curve up near the end of the pulse when something is not quite right.