# Re: [TCML] Question on Dummyload-Testing in DC Resonant Chargingcircuit, similar pursuit

```Hi Stefan,

Wow! (20) 500 watt halogens? That's a heckuva dummy load. I'll bet you can heat a decent sized room with the heat these would give off while testing your circuit, once it's properly tuned ;^) I've never personally tried the dummy load tuning approach, but from what I've heard from others, I thought one or two halogen bulbs was the typical dummy load setup for tuning a coil, at least for a small or medium sized one. Of course, I'm also on the North American side of the big pond, in 120 VAC, 60 hz land instead of 240 VAC, 50 hz, so the ohmic resistance of our halogens of a given wattage would necessarily be half of what it would be in Europe. Hmm, but that means we would need 2x more bulbs to accomplish the desired ohmic value with 1/2 the voltage rating per bulb. Does the total wattage rating really need to be in the multi-kilowatt range for the dummy load tuning approach to work?

David Rieben

On Sunday, June 8, 2014 6:08 AM, Teslalabor <teslalabor@xxxxxxxxxxx> wrote:

Hi Jim,

you can not run such a circuit only with a primary in place without a
secondary. The result would be extreme currents through your transformers,
spark gap and capacitor, which would mean total failure of this components.
So I did some calculations concerning the dummyload with the result, that
the halogen dummyload testing is absolutely okay and the very best method
for testing such a circuit without messing arround with sparks... ! In my
case it consists of 20 halogen bulbs, each is 240V 500W.
10 of them are connected in series and 2 of this groups in parallel, giving
a 10kW Dummyload. The resistance of one bulb is 100Ohm when glowing, so 10
of them in series is 1kOhm, 2 groups in parallel giving 500Ohm total of my
The dwell time of the spark gap is arround 500us, so this is enough time to
empty my 50nF capacitor during each bang.

Jim, I think you need another charging reactor, the Burnett-Equations will
show you. This 150H inductor, built into your HVDC Supply, is not suitable.
It's inductance is much to high, I think it is not possible to build a
properly resonant charger with this. Also 24kV could mean some trouble,
remember that the tank cap is charged to twice that voltage, in your case
48kV !

Some short facts about my coil: The system is designed (by using the
Burnett-Equations) for running 7kW full power @ 400bps. I am actually
testing it with my 3000rpm Schraner-Style SRSG (Hello Kurt :-) ), running @
only 300bps fixed (it is not variable in speed). The variable speed rotary
is still in progress...  System is 3-phase powered, with a 6-pulse
rectifier, DC Charging voltage is 13,3kV. The tank cap is 2 Maxwell Caps in
series, each 40kV/100nF, giving me 80kV / 50nF. My charging reactor is 12,4
Henries. The energy is fired into the 10kW dummyload, mentioned above. The
performance seems to be amazing. Primary and Secondary coils will be build
later...

Regards,
Stefan

----- Original Message -----
From: "Jim Mora" <wavetuner@xxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Sunday, June 08, 2014 4:18 AM
Subject: Re: [TCML] Question on Dummyload-Testing in DC Resonant
Chargingcircuit, similar pursuit

> Hello Stefan,
>
> Why not get some heavy gauge wire and simulate the calculated turns? Now
> you
> have introduced the inductance albeit the R is off rather than purely
> resistive load which seems reasonable to me as R is so small anyway. I
> know
> people have tuned traditional coils ahead of time this way. That was a Dr.
> Resonance trick I believe.
>
> I too am starting on a DC resonate coil. I have a huge Choke in my
> changing
> circuit which can not reasonably be altered. I have the ability to add a
> de-queing diode easily enough, but there is not one in the old charger
> from
> the military. This one outputs 24KV and is full-wave 3P tube circuitry 6x
> GL
> 8020's. The inductor says it is 150H ! Plugging in Richie Burnent's
> equations, if I performed the math correctly, I am limited to 116 BPS with
> a
> .05UF Tank cap (I have 2 .1uf's) It drops to 82 BPS @ .1 uf. So that's not
> too ideal and I wonder about quenching and Tungsten size in the rotor.
> Anyone?
>
> The equations also reveal my max power will be 6.7KW at 116BPS which is
>
> Thanks,
> Jim Mora
>
> Sorry to hijack your thread Stefan, we may be talking more ;-^) What size
> is
> your coil going to be?
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
> Of Teslalabor
> Sent: Friday, June 06, 2014 10:14 AM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Question on Dummyload-Testing in DC Resonant Charging
> circuit
>
> Hello all,
>
> I just finished the DC resonant charging circuit for a planned medium
> tesla
> coil project. It is 3-phase powered and today I started testing it with
> reduced power and a dummyload in place of the primary coil, which will be
> installed later. The dummyload consists of several 240V 500W halogen
> bulbs,
> which are glowing very nice and smoothly :-) So on the first glance, it
> seems to work well for testing.
> But the question is, how does such a dummyload with a high resistance
> (let's
>
> say 500-1000Ohms when glowing) influence the behavior of the charging
> circuit? My guess is, that the capacitor never can discharge completely
> into
>
> this dummyload during each bang and still have much of its charge after
> each
>
> bang... So the drawn power should be much higher, when using the real
> tesla
>
> Regards,
> Stefan
>
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>
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