Re: DC power

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Chris Swinson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>

Hi Kevin,

> OK, using a 200K series resistor with a DC supply is not going to work
> The purpose of the resistor is to protect the rectifier diodes not the
> transformer.  Take a look at the Max surge current for your diodes
> and limit the current relative to that and the maximum sustained
> power you want to run.  Try 40K or 20K ohms to begin with.


 Right, will see what I can find to do that job...



> How are you checking to see that the rectifier is functional and
> operating properly? Do you have an HV probe or HV meter of
> some kind?  You could have bad or improper diodes.

No HV probe, I just take it as about 15KV since I can open up my gaps wider
than I could with AC.  First of all it fired at the same gap spacing as I
ran for AC so it should be good for 9 or 10KVAC. i'm pretty sure the 15KVDC
is there....

>
> Also, it would help all of us (to help you) if you draw a picture or
> take a photo of exactly what your system looks like now and the
> values of the components.  Debugging Tesla coils long distance
> is a remarkably difficult task when minor things like the gauge of
> the hookup wire you are using can make a significant difference.

Its almost the same as the one on your site. appart from I have a 2MFD
smoothing cap across the Dc level, I also tried a 16nf cap and there was not
much difference so the worry about it overloading the NST should be ok....


>
> At low RPM (<2 BPS) and long dwell times, DC coils tend to power arc
> (fire multiple times at a single gap presentation).  Also, as with AC,
> keeping the spark gap cool with a reasonable air flow is important.
>
> You don't need to run the rsg at high speeds ... although I don't know
> what it looks like (maybe take a pic?) or how many poles it has so I
> don't know what BPS you are trying to run at.
>


TBH neither do I, I would guestimate 100BPS as normal for AC op.  it will
run at that for DC but it really gets going way faster maybe 300 or
400BPS.... im really pushing the gaps. Theres pics of it on my website....

http://www.mega-disczine.freeserve.co.uk/room/rsg.htm


> If you try to run the RSG at a speed that is faster than the recharge rate
> of your tank cap you will get an odd stuttering discharge sound but
> really never get more BPS.
>

yeah it does start to do that, but it does give a nice flame like arc.

> It takes real power to run a DC coil at more than a few 100s of BPS ...
> remember that in AC systems you are typically running at 60 BPS
> or 120 BPS.
>
> I definitely know that small NST DC driven coils are simple to build
> and a lot of fun, although with limited power the sparks will be much
> more discrete (zap, zap, zap) than the 60Hz sizzle that we normally
> hear with AC systems.  My friend Mike down in Southern California
> has been running a very basic 60ma rectified NST driven coil for
> several Halloweens and it's quite impressive (and scary for the
> kids!) for such a simple little system.
>

cool, it sounds a bit better than AC, sure aint as loud for a start :)

Chris



> Kevin
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