Re: [TCML] primary voltage

[mddeming@xxxxxxx]

Hi Kevin,

Corona effects start somewhat above 20 kV and become quickly worse as you go higher, as do weight and cost. There is no sharp cut-off point. As long as you're under about 20-25 kV the effects are usually acceptably low. To use a plumbing analogy, as the "pressure" goes up, more and more "joints" will start to show "leaks" that didn't show at lower pressure.

Matt D




-----Original Message-----
From: Brandon Hendershot <mrbrandman@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thu, Jan 7, 2010 6:32 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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> 
> -----Original Message----- 
> From: makinglightning@xxxxxxxxxxx 
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> 
> Sent: Thu, Jan 7, 2010 12:27 pm 
> Subject: [TCML] primary voltage 
> 
> 
> 
> What is the practical upper limit on the primary tank circuit? 
> 
> What is the highest primary tank voltage that people have used? 
> 
> Kevin 
> 
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