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Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Hello,
I have these 12 toroids I got off ebay, which up until today I thought were regular ferrite. It turns out they are "Molybdenum Permalloy", which Wikipedia says is 81% Fe, 17% Ni, and 2% Mo. I am concerned because I have already used several of these toroids to make CTs and GDTs for my [yet untested] DRSSTC. Will they be okay?
If not, will they be suitable for my ZVS? They are 81% iron, so should be similar to powdered iron toroids. The seller claims 61mH/1000 turns, which would only be 3 or 4 turns for a 200uH ZVS inductor. That would be great because then I could use some fairly thick wire (like 10 or 12 gauge) for higher power operation, and because my current inductor sucks; its only wound with 22 gauge and gets so hot that I can't make full use of all my rewound MOT's power.
I am not sure if "mH" really means "millihenry" or is a crudely abbreviated "microhenry", then again permalloy is supposed to have a high inductance per turn.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
All I can say is... NICE!!
I'm etching a higher power ZVS today; I'll go all the way and break out the 10 gauge wire and wrap like 7 or 8 turns.
Great to hear as well because I put a lot out time into making my GDTs and CTs right, and making them look nice (plus the windings have a layer of superglue keeping them in place!).
Here's a pic (you can see present ZVS in background):
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Oh well, compared to the overall DRSSTC build this is no major setback. I do, however, have several smaller toroids which I know are ferrite. Whether or not they are big enough to avoid saturation is what I am not sure about.
The attached pic shows the ferrite toroids (black) and the MPPs. On top is my new ZVS inductor.
Do you think these new toroids will saturate in GDT/CT use? The coil will run around 70~80 kHz.
For scaling purposes (forgot to include hand/ruler), that is 10 gauge (2.6mm) insulated wire on the inductor.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Just wanted to let everyone know that these toroids KICK ASS as ZVS inductors! 4 or 5 turns on one of these will replace like 30 turns on an ATX core. I am getting like 3 times the Vout I was before with same Vin.
And as I said before, less turns means thicker wire... think of the amp-carrying capability of 10 gauge insulated compared to 20 gauge magnet wire!
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I used quite small cores for my DRSSTC at 100kHz and they are fine. CT's transfer only a tiny amount of power and anything you can fit enough wire onto will do.
Regarding GDT, It's just about fitting enough turns through it. I used smaller core than that and barely fit 6 turns, but it worked happily. Too much turns isn't good either.
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Molybdenum Permalloy Toroids
