[SOLVED] INDUCTORS inductance change with current

[Anna Conda]

Yes but tricky for low freq inductors, where there will be a lot of core loss if subject to a switcher, and a lot of eddy current loss in the lams on the edges...

 

[Warpspeed]

If its a "tricky" low frequency inductor, the applied switching frequency and voltage can be kept suitably low.

The test "range" needs to be made appropriate for the type of inductor as with any type of measurement.

Even the "resonance" method of inductive measurement you need to use common sense when choosing a suitable resonating capacitor.

 

[andre_luis]

Taking a search on the Web, I could find this interesting document presenting a design case which according to the figure 1, it is clear the effect due to vary DC bias current through the inductor.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19640013113.pdf

 

[Warpspeed]

Great stuff Andre.
That article was written in 1964, and there are now some very good software tools for doing all that.
Check out the Micrometals website.
**broken link removed**

There are several things you need to think about, but with most toroidal chokes the problem is one of core losses due to ac induction, which rises steeply with frequency and ac flux density.
But the magnetization curves and loss curves are all there for various core materials if you wish to go through the whole long iterative design process yourself.

The Micrometals design software allows you to punch in some numbers and it will give you a whole range of possible solutions.

These toroids are both economic and excellent where the ratio of dc current to ac voltage is quite high.
But they make very lossy ac inductors at high frequencies and for high applied ac voltages.

 

[FvM]

I think that the original question has been well answered and the thread should be marked as solved.

You really don't need to decide which measurement setup "is better", small signal AC with bias-T (including the inductor pair configuration suggested by Anna Conda) or large signal pulse method. Both are valid and have their advantages and disadvantages.

The inductor design point is, strictly spoken, off-topic.

 

[Warpspeed]

Hi Guys,

Quick question, how can I work out the change of an inductors inductance with the amount of current flowing through it, is there an easy way to test this?

Cheers

The original question as posted was in two parts.

How to WORK OUT the change.
That involves some theoretical inductor design, and the use of magnetization curves, and perhaps Hannah curves for the particular core material being used.

The second part of the question is on practical testing, and is a different thing altogether.
And I agree that part has been covered rather thoroughly.

 

[bowman1710]

Thanks guys,

Didnt expect to start a huge debate over the correct way to test it though

I think i will try what both have suggested and see for myself what i find issues with etc.

I have marked this as solved, thanks once again.