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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 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
> 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.
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, May 19, 2001 9:25 AM
> Subject: H bridge RSG
> > Original poster: "Ray Haynes by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > I'm moving full speed on my MOT powered DC coil and was searching the
> > archives (that's what they're for, right? ;-) ) for information. I found
> > postings about an H bridge RSG. There were some comments about how that
> > approach charged the cap with alternate polarities and that
> this might be
> > hard on the cap. I didn't see any resolution on that.
> > Question (rhetorical?):
> > Since the tank cap forms a resonate circuit with the primary
> and resonate
> > circuits oscillate back and forth charging the cap first one
> way then the
> > other, doesn't that mean all caps used in the primary tank circuits must
> > happy with AC charging? Also this seems to indicate that the alternating
> > charge cycles of an H bridge RSG are not a problem, true?
> > Ray