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Re: [TCML] primary voltage
Hi Brandon,
Matt was NOT saying that you CAN'T operate a Tesla coil
with primary voltage in this range, he was simply citing the chal-
lenges associated with using the higher voltages (and he is 100%
correct). Scot (bunykiller) does operate his coil with up to
32 kV primary voltage and he has also cited some of these
same challenges that he had to overcome to operate his coil
like this. If you already have a 36 kV transformer and it is the
major cost of your system, then I would say go ahead and go
for it, assuming that you can also obtain/purchase capacitor(s)
that will handily withstand that much voltage. Just be aware
of the difficulties involved with using primary circuit voltages
of >20 kV.
David Rieben
----- Original Message -----
From: "Brandon Hendershot" <mrbrandman@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, January 07, 2010 5:32 PM
Subject: Re: [TCML] primary voltage
Hi Matt,
Reading your post was kind of disturbing! You said all that happens
somewhere inbetween 30 and 100 kV?Is there a tighter more precise
range you know of? Because my coils primary circuit voltage will be
hovering around 36kV. Should I be too worried about insulating every
little point and wire? If it matters at all, I'm installing a Terry
filter too. Those chunky resistors won't affect the issue much I assume?
Thanks,
Brandon
On Jan 7, 2010, at 1:13 PM, mddeming@xxxxxxx wrote:
Hi Kevin,
While some people have experimented with primary voltages in to
30-100 kV range, there are several distinct problems with primary
voltages much above 15 kV (rms).
1) Costs: The number of caps in an MMC goes up as the square of the
voltage (twice V = 4 x number of caps). Above ~15 kV you are also
talking custom-made transformers: Cost and weight increase
exponentially with voltage.
2) Corona problems: above about 20 kV, every point, twist, kink,
bend, or screw head in the primary wiring becomes a source of corona
leakage which is power lost.(but the blue glow looks "cool".to
some). These losses increase rapidly with voltage level.
3) Insulation breakdown: most HV wire tops out at 30-40 kV then you
start needing to get into X-ray equipment cables, or custom, or home-
made cables made from coax. Even wire run through plastic tubing
starts to have problems at higher voltages.
4) Unintended Coupling: as voltages go up, there is an ever
increasing tendency of currents in the wire to couple capacitively
or inductively to nearby objects and power, telephone,etc. lines,
charging them to "unpleasant" levels and wasting spark energy doing
it.
In short, it is much more cost, weight, and safety efficient to keep
primary voltages at the level of mass-produced transformers and
minimize the number of caps needed to still keep a good working
margin.
Hope this helps,
Matt D.
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