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Registered Member #3806
Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259
o: I thought it was 115V in UK... my bad
Do you have your toroidal transformer specs ? If not, do you have a manufacturer/part number that could help you find these specs to see what's the actual primary/secondary insulation voltage ?
Something else, would it be possible to fully unwind your secondary without damaging the wire ? If yes you could then add an insulation layer above the primary and then rewind your secondary. (well I'm not sure about this but that's what I would try to do)
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
not exactly, the wire is quite abit for secondary and its on a small torroid which is a nightmare to wind... hmm, i dont think 3Kv will jump through so much insulation, enamaled wire holds up a fair amouth, it would have to jump through atleadt 4 peiced of enamalled wire and a load of other insulation yeh?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The solution is to use a voltage doubler. Then you can ground both the core and the negative output. Indeed that is why MOTs have one end of the secondary connected to the core, because they are designed for use with a doubler.
You get twice the output voltage, which you may not want, but you can fix that by reducing the input voltage to 120V.
You also have halfwave rectification, but you can fix that by using two MOT/doubler arrangements 180 degrees out of phase. (and maybe connect the primaries in series for 240V operation?)
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
hmm, i guess im on the hunt for a seond MOT then, by the way the GK-71's voltage is acctually 1500v or so but everyone seems to be pushing it to alot more
EDIT: what if i just half-wave rectify it and dont double?
Registered Member #3806
Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259
Steve Conner wrote ... ... You also have halfwave rectification, but you can fix that by using two MOT/doubler arrangements 180 degrees out of phase. (and maybe connect the primaries in series for 240V operation?)
Sounds like the perfect solution to our problem, thanks Steve !
<--- Just ordered a 2nd big MOT similar to the one I already have
Tom Williamson wrote ...
hmm, i guess im on the hunt for a seond MOT then, by the way the GK-71's voltage is acctually 1500v or so but everyone seems to be pushing it to alot more
EDIT: what if i just half-wave rectify it and dont double?
1500V is max voltage for normal operation. Coilers rarely work in the "normal operation" range Well we don't expect the tube to live for years at 24/7 runtime.
With half wave rectification you would get the typical 50Hz buzz as the coil would be off every half cycle. This would probly also affect output look (maybe even no flame at all ? not sure...)
Half wave rectification also leads to MOT's core saturation, resulting in huge current draw (10A @ 250V on my 572B VTTC) and MOT heating quickly.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi,
Sorry to jump in your thread, but seeing as this is your first TC...
I probably should warn you that the RF interference produced by these circuits is huge and can kill nearby electronics. If you don't use a proper RF ground, the RF may even travel through the house wiring.
Always use proper RF grounding, and if you can, put a common mode interference filter on the input. This filter can be as simple as winding the input cable around some larger ferrite a few times. The RF ground can be a large sheet of metal.
The path of RF currents is unpredictable. Be careful to not hurt yourself or damage other electronics. Never touch the flame - not even with a metallic object in your hand - as the full DC plate voltage is present in the output and will kill you instantly if it finds a path to ground.
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
Pinkamena wrote ...
What are you trying to build, Tom?
I, am trying to build a simler HFVTTC to this one here: the schematic i have is apparently the same as the one he is using, i may be mistaken however.
Mr Health And Safety =3 wrote ...
Hi,
Sorry to jump in your thread, but seeing as this is your first TC...
I probably should warn you that the RF interference produced by these circuits is huge and can kill nearby electronics. If you don't use a proper RF ground, the RF may even travel through the house wiring.
Always use proper RF grounding, and if you can, put a common mode interference filter on the input. This filter can be as simple as winding the input cable around some larger ferrite a few times. The RF ground can be a large sheet of metal.
The path of RF currents is unpredictable. Be careful to not hurt yourself or damage other electronics. Never touch the flame - not even with a metallic object in your hand - as the full DC plate voltage is present in the output and will kill you instantly if it finds a path to ground.
Thanks, i did not know some of this, how close would stuff haveto be to get messed up, and if i put it in a cage of chicken mesh or fine mesh will that help? providing i ground that too?
as for the last part, i kind of guessed, how is it unpredictable by the way? i hope it follows V = IR D:
RF currents are exceptionally unpredictable. Items you think of as being insulative may be conductive and conductive items can act as antennae or reflectors.
For example; I have my SSTC on a wooden table, and the wood is partially conductive at the fres of the coil. If I unground the table (wrapped the legs with wire which is RF grounded) you can actually draw a small arc (1 to 2 mm) between the wood of the table and a good RF ground.
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My GK-71 HFVTTC
