Original poster: Jan Wagner <jwagner@xxxxxxxxx> Tesla list wrote:
Original poster: "Herwig Roscher" <herwig.roscher@xxxxxx> I acquired some nondescript and unpainted toroid cores, which I would like to use as gate drive transformers for a SSTC project. Unfortunately I do not know neither the manufacturer nor the mix nor the material. The only value I could figure out is the AL factor. Are there methodes to find out if the cores were made of powdered iron or of ferrite? And of course I would like to know the frequency range of the cores as well.
The best way to find out if the core is ok as a GDT, is to put a couple (10..30) turns of bifilar wound wire (you can keep a pre-made wire handy and re-use it later :-)) on the core, plug it into the pulse transformer driver, with no FETs etc connected. Then check what your oscilloscope shows on the input and output side of the xfmr.
I don't know how to nondestructively /and/ just by looking at it find out if the toroidal core is powdered iron or ferrite...
Quite often the powerdered iron ones that I've seen in e.g. RF balun use have been coated with some glossy paint, or one surface of the toroid has a different color. Ferrite toroids on the other hand quite often have a rough coated surface. You could use those criteria for an initial guess.
There's also some difference in core conductivity, ferrite vs powdered iron, and low freq vs high bandwidth, but it's hard to measure when the toroids are coated.
Since powdered iron is used in high power RF baluns at carrier freqs up to several tens of MHz at still high Q I wouldn't be surprised if these would work fine as a GDT, too. :-)
If you want to know the characteristics for sure, you'll have to use a test jig with with a frequency generator (even a 555 will do :-), scope, etc.
MFG, - Jan