Making your own ferrites?
Posted: Tue Oct 18, 2011 10:56 am
I've recently been planning high frequency switching circuits, a bit like the ones I have made already (500V/6MHz/1A) but at lower frequency/high current. This is both for my own stimulation, and also, hopefully, I'll get some useful power supplies at the end of it.
The subject I have bumped into along the way is the use of transformers and inductors. Figuring I don't really know much about these suckers, I took a look on ebay for a power transformer to test things with, and found a guy selling 13 of them, bobbins stripped from switch mode supplies. I bought those, and a stack of other inductors the guy had collected. Around 4 kg of ferrite altogether, I'm told. It is on its way.
So this will hopefully be my 'fast track' dive into the world of high frequency magnetics, and I plan to figure out how best to measure inductance and B-H curves, and the like.
One thing I have figured so far is that the majority of ferrites seem to be actually too high permeability for the intended power/frequency range I am looking at. My basic calcs show that in the range I want to experiment in (500kHz to a meg, or so - hence I put it here in the 'RF'), most ferrite is too lossy and the reactances too high anyway.
So, [if I didn't already have enough projects already] I am considering buying a kg of iron oxide, one of manganese oxide, and some hard-setting gypsum, and mixing them to cast my own ferrite. I want big pieces of ur=~50 or so, to try in this HF range, so I can make smaller coils than air-cored, but less lossy that regular ferrite with air gaps.
Well, that's the punch line. Is this an interesting experiment to try, or is there info out there that already shows this is a crash-and-burn route to a waste of time (probably quite messy, too!!)?
The subject I have bumped into along the way is the use of transformers and inductors. Figuring I don't really know much about these suckers, I took a look on ebay for a power transformer to test things with, and found a guy selling 13 of them, bobbins stripped from switch mode supplies. I bought those, and a stack of other inductors the guy had collected. Around 4 kg of ferrite altogether, I'm told. It is on its way.
So this will hopefully be my 'fast track' dive into the world of high frequency magnetics, and I plan to figure out how best to measure inductance and B-H curves, and the like.
One thing I have figured so far is that the majority of ferrites seem to be actually too high permeability for the intended power/frequency range I am looking at. My basic calcs show that in the range I want to experiment in (500kHz to a meg, or so - hence I put it here in the 'RF'), most ferrite is too lossy and the reactances too high anyway.
So, [if I didn't already have enough projects already] I am considering buying a kg of iron oxide, one of manganese oxide, and some hard-setting gypsum, and mixing them to cast my own ferrite. I want big pieces of ur=~50 or so, to try in this HF range, so I can make smaller coils than air-cored, but less lossy that regular ferrite with air gaps.
Well, that's the punch line. Is this an interesting experiment to try, or is there info out there that already shows this is a crash-and-burn route to a waste of time (probably quite messy, too!!)?