Re: rotary bps

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Colin,

How fast the caps will charge is a function of the total capacitance
(66nF?) and power supply (12kV 500mA
MOT). Yes, at 400 bps, the electrodes will align every 2.5ms. But this is
simply the time between
alignment. The charge time in it's simplist form can said to be at 99.99%
of full charge in 5 time
constants where Z x C is 1 time constant.

I'm not sure on the MOT specs, but assuming 120Vin, 12kV out, 500mA, then
transformer output impedance is
12000 / 120 = 24000 ohms.

Then, Z x Cp x 5 = 24000 x 66nF x 5 = 7.92ms (full charge time).

At 400 bps, your firing every 2.5ms and achieving a time constant of 1.6
which is about 75% of Vp (it's
not linear). This actually is not bad and could easily run at 400 bps, but
nevertheless, if the specs I
assumed are correct, then you could probably benefit from halving the bps.
At 200 bps, charge time between
bangs would climb to 96%.

This basically comes down to cap energy. Typically, just on specs you would
calc about 9.5 joules.
However, cap energy at the time of conduction is based on Vp at the time of
conduction. So at 400 bps your
looking at 5.34j and at 200 bps at 8.76j. This is why I think you could
benefit from halving the
breakrate.

Regardless of individual cap specs (MMC or otherwise), you have to look at
the total cap value and apply
it to your charge and break system.

BTW, JavaTC will show you all these values in the Spark Gap Design area.
Something to play around with.
You can simply put in the cap value in the primary design, then go down to
the transformer and gap specs
if this is all you need to look at.
http://www.classictesla-dot-com/java/javatc.html

Take care,
Bart


Tesla list wrote:

> Original poster: "colin.heath4 by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <colin.heath4-at-ntlworld-dot-com>
>
> hi bart i worked out the time between bangs to be 2.5ms well the rise time
> of my arcotronics caps is 1800v/us so this gives plenty of time to charge
> one but how does this figure change with an mmc? i assume it will take a sum
> of the 40caps to charge making still plenty of time
> im no expert on this and would appreciate correcting
> many thanks
> colin heath
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, March 31, 2002 2:05 AM
> Subject: Re: rotary bps
>
> > Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
> >
> > Hi Colin,
> >
> > You don't mention the cap size or transformer size, so it's difficult to
> > say. At 400 bps it's likely that
> > your caps are not charging completely. If so, 200 bps should be
> beneficial,
> > but you will probably need to
> > phase it for the change. The gain in sparklength is dependent on more than
> > just the charging circuit, so
> > there's no way to really say how much. The best way to tell is simply give
> > it a try and see what happens.
> > With the 200 bps setting, you will probalby need to phase it about 30% off
> > peak.
> >
> > Take care,
> > Bart
> >
> > Tesla list wrote:
> >
> > > Original poster: "colin.heath4 by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <colin.heath4-at-ntlworld-dot-com>
> > >
> > > hi all,
> > >         iv run my sync rotary spark gap tonight with good results with a
> > max of
> > > 4'
> > > the gap is running at 400bps this is with a mot supply
> > > will power increase with 200bps as the caps have longer to charge?
> > > many thanks
> > > colin heath
> > >
> <http://www.geocities-dot-com/colinheath2002/>www.geocities-dot-com/colinheath2002/
> > >
> >
> >
> >