My motor's speed is controlled via variac with a maximum speed of about
3200 RPMs. I purchased a new Delta grinder and am using the motor for the
RSG. I'm using .625 diameter brass rod material for the fixed charging
electrodes. I'm using a 5H choke and in the larger coil it is located
about two ft from the rsg and primary coil. On my test setup I'm using a
very heavy duty high voltage/power 5H choke that weighs almost 100 lbs. I
have it about three ft from the coils. I'm also using a string of blocking
diodes in series with the supply and choke.
On Mon, Oct 20, 2014 at 8:33 AM, Teslalabor <teslalabor@xxxxxxxxxxx> wrote:
> Hi Phil,
>
> thanks! You are right, close gap clearances on rotary gaps seem to be
> important, I observed this some years ago on a SRSG, running 200bps @
> 3000rpm. But always was wondering about this, because the arc ignites long
> before the electrodes are coming together.
> The firing voltage on my new rotary will be arround 26kV so maybe close
> gap clearance will not be so important. We will see!
> Yes, the experiments will show, if the brass holders for the stationary
> tungsten electrodes are able to take the heat away properly. If not, it's
> not a big deal to change them for massive copper pieces oder aluminum heat
> sinks.
> Your idea with the air movement control is pretty cool! Will have to keep
> this in mind. But the air movement the disc produces @ 4000rpm is
> incredible :-)
>
> Regards,
> Stefan
>
> ----- Original Message ----- From: "Phil" <pip@xxxxxxxxxxx>
> To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
> Sent: Monday, October 20, 2014 11:07 AM
> Subject: Re: [TCML] Finished: New 600bps Rotary,Power Controller + Variac
> for DC resonant charging TC
>
>
>
> Stefan,
> That's a very nice, sturdy RSG you have built, especially as it is never
> easy getting an outrigger bearing to align easily, but with the revs you
> are
> using it is a good idea! A setup like that should allow some close gap
> clearances as well which I always thinks helps. (I run 10 thou clearance @
> 6
> - 7 Kw 3000 rpm).
> If you do get overheating problems you will find a switch to copper
> electrodes will have a vast difference, as the thermal conductivity of
> brass
> is not very good (copper being about 10 times higher I think). The rotary
> ones rarely get any heat to them, but the stationeries tend to ablate
> mostly, presumably made worse because they are not cooled as much.
> I use approx' 8 inch tall one inch diam' copper bars as terminal posts, and
> recently did some experiments with smoke to find the air movement paths on
> mine, and you may find a carefully sited piece of Lexan to act as a wind
> shield will direct the rotor draft towards the stationary terminal posts.
> (https://www.flickr.com/photos/33962508@N03/15318168107/ The black Lexan
> piece slides across in front of the stationeries and directs the
> substantial
> draft sideways)
>
> Nice to see a motor driven variac in use, but the thought of "overkill"
> comes to mind :-))
>
> Regards
> Phil Tuck
>
> www.hvtesla.com
>
>
>
>
>
> -----Original Message-----
> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Teslalabor
> Sent: 19 October 2014 18:53
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Finished: New 600bps Rotary, Power Controller + Variac for
> DC resonant charging TC
>
> Hello all,
>
> as announced some weeks ago, I now want to show you my current proceedings
> with my DC resonant charging teslacoil. I just finished the rotary spark
> gap, motor driven 3-phase variac which feeds the high voltage transformer
> and also the power control box. Here is a video of it:
>
> https://www.youtube.com/watch?v=wVpRE38UXqE
>
> The rotary is made of a 450W DC Motor with a maximum speed of 12500rpm. The
> speed is controlled by a variac. The disc-diameter is 25cm, equipped with 6
> tungsten rods, each 6mm in diameter. The motor has a tacho generator on its
> shaft, which feeds a speedometer in the control box. So this gives me an
> absolutely precise measurement of both, disc speed AND bps! The meter
> reading, which has a scale from 0 - 10, is just this simple:
>
> x1000 = rpm's
> x100 = bps
>
> The rotary consists of 4 stationary electrodes, mounted to massive brass
> columns, 2 on each side of the disc,
> which results in a total of 4 spark gaps. I think, this in combination with
> the high speed / low dwell times will have some positive effects on the
> quenching properties of the gap and very low speeds will be possible
> without
>
> igniting a firewheel.
> In the video the rotary is accelerated up to 4000rpm (400bps) which is the
> target bps for my system, where the maximum power will be processed, but
> also up to 6000rpm are possible I think. Dwell time at 4000rpm is 252µs, at
> 6000rpm it's 168µs. But I should be aware of the following: Each electrode
> weights 42,736g, so at 4000rpm it's weight rises to 86,7kg, at 6000rpm
> already
> 195,1kg! At the moment I'm happy with 400bps, maybe I shouldn't try more
> rpm's with that calculations in mind :-)))
>
> The 3-phase motor variac can also be controlled with the control-box,
> voltage can be cranked up and down automatically and stopped at every
> voltage.
>
> Regards,
> Stefan
>
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