# RE: RE: Cap question (was H bridge RSG)

```Original poster: "Ray Haynes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ray.haynes-at-home-dot-com>

I was planning on using an H-bridge RSG that alternates connecting the tank
cap first to the storage cap then to the primary coil, kind of like a double
pole double throw switch. The storage cap is connected only to the
rectifiers when the RSG connects the tank to primary coil and the main bang
happens. I know there will be some residual charge left on the tank after
the main bang but if everything is set right it should be only a fraction of
it's original charge. Or am I still missing something.

Also the storage cap that I'm actually going to use is 16uf so it is
actually 1600 times larger than my tank cap.

> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, May 20, 2001 4:11 PM
> To: tesla-at-pupman-dot-com
> Subject: RE: Cap question (was H bridge RSG)
>
>
> Original poster: "David Dean by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <deano-at-corridor-dot-net>
>
> Hi Ray,
>
> The storage cap sees the full tank current while the gap is
> firing. Also the
> storage cap must appear as a short to the RF of the tank so as not to be
> included in, or affect the tuning. Thus the requirement for a very low ESR
> in the storage cap.
>
> Also in your example, "If Cs is 100 times larger than Ct
> (1uf/.01uF) each Ct
> (tank cap) charging will only drain Cs (main storage cap) 1% of it's
> charge." is true for the first presentation when the initial charge in the
> tank cap is 0, however at the end when the gap quenches due to the
> equalization of the voltages on the tank cap and the storage cap, the
> voltage on the tank cap is equal and opposite in polarity to that of the
> storage cap upon the next presentation. That makes the voltage to be
> processed twice as much, and the energy transferred from the
> storage cap to
> the tank cap four times as much.
>
> later
>
> deano
>
> >
> > Original poster: "Ray Haynes by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <ray.haynes-at-home-dot-com>
> >
> > I don't understand LR's comment about needing a "largish storage
> > capacitor,
> > also rated for RF; and the huge voltage reversals, probably +2V
> > to -2V (I'm
> > assuming he meant +/-2KV)". I agree with the largish part but not
> > the rest.
> >
> > Here's my thinking. First I make a fullwave rectified HV supply using a
> > large storage cap (Cs). My tank cap (Ct) is .01uF and RSG with a rate of
> > let's say 600BPS (hoping). If Cs is 100 times larger than Ct (1uf/.01uF)
> > each Ct (tank cap) charging will only drain Cs (main storage cap)
> > 1% of it's
> > charge. And at 600BPS that Cs gets fully charged (ideally) once
> for every
> > five Ct charge cycles; the fullwave rectifier doubles the mains
> > frequency to
> > 120Hz and 600BPS/120Hz = 5. That seems to be roughly 5% ripple
> on the main
> > supply cap which doesn't seem to indicate a need for any RF
> > requirements for
> > the large storage cap. Actually my simulations show more like 2%
> > ripple due
> > to the fact some Ct charge cycles are provided directly by the
> rectifiers
> > (SG closes while mains are at a peak)
> >
> > Is there a flaw in my thinking?
> >
> > > -----Original Message-----
> > > From: Tesla list [mailto:tesla-at-pupman-dot-com]
> > > Sent: Saturday, May 19, 2001 8:02 PM
> > > To: tesla-at-pupman-dot-com
> > > Subject: Re: H bridge RSG
> > >
> > >
> > > Original poster: "LWRobertson by way of Terry Fritz
> > > <twftesla-at-qwest-dot-net>" <LWRobertson-at-email.msn-dot-com>
> > >
> > > Hi Ray and Steve
> > >
> > > A classic coil discharges at some voltage, then
> > > the RF oscillates around zero, approximately. The
> > > H-bridge never stops at zero, but goes straight
> > > from +V to -V, and oscillates there, adding the
> > > RF amplitude to the DC voltage.
> > >
> > > Advantages are very reliable firing, it will never
> > > power arc, and the primary voltage is doubled,
> > > adding some oomph. I would think it should work
> > > well for MOT power supplies. It can be run at any
> > > speed.
> > >
> > > The disadvantages are the necessity for a largish
> > > storage capacitor, also rated for RF; and the huge
> > > voltage reversals, probably +2V to -2V almost.
> > >
> > > At the moment its running on a 8 inch rotary with
> > > a maximum of 240 BPS. I'm (slowly) getting parts together
> > > for a 12 inch which should be good for 360 BPS,
> > > and ultimately hope to make a 22 inch with 24
> > > electrodes. Expensive, though.
> > >
> > > Its a simple enough circuit - I'll be glad to send a
> > > schematic if you want.
> > >
> > > LR
> >
> > snip.....
>
>
>

```