[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Is this 2,3kW Triode suitable for a VTTC?
That depends also by the cap used in the doubler.
My oppinion is that the doubler schema allows the resonant rise of the voltage for some well chosen cap values (the doubler schema allows AC passing through the cap, 1/2 cycle through the HV diode and cap, the other 1/2 AC cycle, through MOT-cap-load, giving DC pulsed current). Well, maibe resonant rise is not the right word, I would better say the maximum charging current for the doubler cap.
And this can be proven by some calculations and the best cap values observed from my practice (2 microF in a doubler with a single MOT or 1 microF cap in a doubler fed with 2 MOTs in serie).
For f (frequency) = 50 Hz (our AC system) and a MOT inductance L = 5.5 Henry (I found this value on the net), starting from equation : 2*pi*L = 1/(2*pi*C) we found the values:
For 1 MOT (5.5 H) the best C is 1.844 microF (around 2 microF)
For 2 MOTs in serie (11 H), the best C = 0.922 microF (around 1 microF)
One more thing I believe is that the filter cap is not just for filtering but acts also as a charge reserve for the VTTC (something like the bus cap in a drsstc). Thats why I think that the filter cap has to be at least 10 times bigger than the primary cap (Dr. Spark recomandation). I am using more than 30 times bigger in my GU5b VTTC with good results ( http://www.youtube.com/user/teslina#p/u/3/H_hNd1exC60 ). Bigger is better I suppose.
vasil
>
>
--- On Sat, 1/15/11, Futuret <futuret@xxxxxxx> wrote:
> From: Futuret <futuret@xxxxxxx>
> Subject: Re: [TCML] Is this 2,3kW Triode suitable for a VTTC?
> To: tesla@xxxxxxxxxx
> Date: Saturday, January 15, 2011, 8:28 PM
> Hi Stefan,
>
> It's possible that when I changed from MOT doubler to
> plate
> transformer without doubler, I may have had to re-adjust
> something
> on the VTTC such as the grid resistor or tuning, etc.
> I don't really
> remember. I'd have to look back at my notes.
> But you may be
> running into something like that. The doubler method
> in some
> cases does tend to give a quick spike of voltage at the
> beginning
> of the mains AC cycle, which then tapers off. So the
> overall
> efficiency of the doubler system can be higher. This
> however
> may only offset the general inefficiency of MOTs, so the
> overall
> efficiency might be about the same.
>
> I generally prefer operation with the doubler. The
> tube may run
> cooler because the high voltage is not sustained as long
> during
> the mains AC cycle. It's sort of like using what I
> used to call
> "duty cycle control".
>
> John
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: Teslalabor <teslalabor@xxxxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Sat, Jan 15, 2011 11:58 am
> Subject: Re: [TCML] Is this 2,3kW Triode suitable for a
> VTTC?
>
>
> Hi John,
>
>
>
> in my doubler, I'm using a 2kV MOT which is doubled to 4kV.
> The doubler is
>
> regulated by a variac so I can adjust voltage from
> 0-4000V.
>
> So what I meant was, that I fed the VTTC with 2kV from this
> doubler circuit
>
> where it makes good sparks, and than, I removed the doubler
> and only put a
>
> 2kV MOT in place, where the sparks were not good, at the
> same voltage. This
>
> I don't understand. But I read in the web that also other
> folks recognized,
>
> that the VTTC only runs on a doubler and with a normal
> plate transformer
>
> not. So I'm surprised you got the same results in both
> cases. This tells me
>
> that the transformer-type maybe is an important factor when
> running a VTTC
>
> on AC.
>
> Have to check it tomorrow with a big plate transformer
> instead of the MOT.
>
> Regards
>
> Stefan
>
>
>
> ----- Original Message -----
>
> From: "Futuret" <futuret@xxxxxxx>
>
> To: <tesla@xxxxxxxxxx>
>
> Sent: Saturday, January 15, 2011 5:08 PM
>
> Subject: Re: [TCML] Is this 2,3kW Triode suitable for a
> VTTC?
>
>
>
>
>
> Hi Stefan,
>
> In the past, I compared my VTTC operation using 4.2kV, from
> a
>
> doubler, and from a plate transformer. Both methods
> gave the
>
> same spark length. The difference was that in
> staccato mode,
>
> I got better sword sparks using the doubler. I don't
> know why
>
> you're seeing such a big difference.
>
>
> snip
> John
>
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla