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Registered Member #2591
Joined: Fri Jan 01 2010, 11:58AM
Location: netherlands
Posts: 76
hello coilers,
I have a secondary coil, fres is 770 khz without topload, is it possible to lower the fres by using a hv-capasitor instead of a toroid, with a toroid of 7 pf i have a fres of 412 khz, but i need to go below 200khz.
it is a small coil: 140mm long 50mm diameter 1000 turns @ awg38
Registered Member #2591
Joined: Fri Jan 01 2010, 11:58AM
Location: netherlands
Posts: 76
because it has to be small, the sec. voltage output is 30kv so I toucht just put a high voltage cap to the output, but I think this will not work because it is in serie with the topload of 7 pf and than: 1/ (1/c1+1/c2)=total and is less than 7 pF
I think it is verry differcult to make a small coil like this to lower the fres below 200Khz
maybe an capacitive earth shield around the sec. coil will do with some distance and isolation of course, but I think that is a bad idea.
a long small ferrite in the center of the sec. is allso an idea, but than it is not a tesla coil anymore
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I think you'll have to wind a new secondary using thinner wire! But seriously, I don't see why 400kHz is a big issue. I've made coils which run at both 500 and 600kHz, using common components in a half-bridge and fullbridge, without issues.
Registered Member #2591
Joined: Fri Jan 01 2010, 11:58AM
Location: netherlands
Posts: 76
Uzzors wrote ...
I think you'll have to wind a new secondary using thinner wire! But seriously, I don't see why 400kHz is a big issue. I've made coils which run at both 500 and 600kHz, using common components in a half-bridge and fullbridge, without issues.
also at cw-mode ?
edit: thinner wire is a hell to wind... i am seeking for alternative things, maybe a hv cap across the full secondary will do...
edit2: yes it does, 50 pf will drop my res.freq. to 180 khz, so I am going for a try to build this cap, I have a lot of 2KV/100pF caps, and they are small enough to put them inside the coil, I don't know if they like it inside this coil but I give it a try
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
tritium wrote ...
Uzzors wrote ...
I think you'll have to wind a new secondary using thinner wire! But seriously, I don't see why 400kHz is a big issue. I've made coils which run at both 500 and 600kHz, using common components in a half-bridge and fullbridge, without issues.
also at cw-mode ?
Yes. Streamers aren't too impressive, but I built it to last, meaning very little stress on components.
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sstc topload
