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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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