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Re: Solid State
Hari wrote:
>>you were not going to use them as solid state step-up transformers,
were you?
Nope - I hadn't thought of the heat problem though, only the dificulty
in winding them. No I thought they might come in useful for chokes
and possibly FET driver transformers, and current transformers.
Plus the squirrel instinct, plus simple curiousity.
I'm at 205khz by the way. I haven't had a problem with heat in
the cores, but heat in the windings was a real pain. But I'm chipping
away at it - fewer turns, thicker wires. Then replace the thick wires
with multiple strands of enameled wire (I'll twist it myself Litz is
L8.90 for 28g. ($14)
Looking at the catalogues it does seem that the higher grades of
ferrite are only available in the smaller sizes.
Current limiting is still a pain, comes on too soon despite lowering
the resitance to 0.03 ohm (30A peak) seems to turn on at about
the same point regardless of the output transformer ratio - time to
experiment with a current transformer and tighten up the layout.
But if I'm doing all that I may as well go for a half bridge at the
same time.
>I'd suggest earthing the core for safety or not touching it while
>having the power applied.
Definately!!!
>I have desided to stack E-cores for higher power range.
>I think I'll try heading for something like 3-5kW when I get the time.
>2-3 smallish cores should do for that.
I'll store this idea away for later. I am hoping that to get a
FET bridge running at 75v then 150v then try mains with a very
low transformer ratio initially then I should blow fewer FETs.
Malcolm wrote.
> BTW, I said earlier that the voltage gradient was sinusoidal. I
>think that is true if there is no terminal present.
I saw (I think in Byland's book the suggestion of placing at
intervals in the secondary a pair of green/red Led's. To give
some indication of what is happening current wise along
the length of the secondary.Then fibre optic cable to a photo
diode to measure.
Pike wrote
>I've found some IGBT's by International Rectifier and Harris
>that look promising. Faster switching than the Toshiba monsters.
>And they aren't that much more than a quid each.
What are the type numbers? Harris have a lot of their sheets
on the net.
Pike wrote:
>I've read through the TESLA logs back to October. I think I'll go
>through and extract those dealing with solid state and edit them
>for easier reading. It will take a while but I think it will be
>helpful for me to see it all in one place. I'll ask about interest
>in posting to the list or elsewhere when I'm done.
I've had a lot of good answers - I've saved them. I tried to
copy them into a single file with a view to editing them and
posting them to you however compuserve filing cabinet
puts a control Z at the top of each file - bummer. I could
zip them and send them to you as is though.
Alan Sharp (UK)