Re: RSG and NST's

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi David,

I think 1.66:1 is too small for a RSG and the inductive kick could easily
double the voltage from the NST rating.  Simulation for a SRSG at 120pps and
with 1.6*Cres shows about 30KV being generated.  I run my SRGS at 2.5*Cres
and get 24KV.  Certainly you have an ARSG at a higher pps, but if it was
still spooling up, 120pps could have kill it.  Just a thought.

Gerry R.

> Original poster: DRIEBEN@xxxxxxxxxxxxxxx
>
> Gerry,
>
> I think I already addressed some of these questions in a response
> to Gary Lau? but I'll try again. First, I'm reasonably sure that
> the motor had been brought up to speed, but it's been around 5 years
> ago and I didn't document any of the results. Just going from memory.
> As far as the Terry filter, no, I never had even heard of one at that
> time! I'm sure that't the big thing that contributed to failure! For
> the Cp/Cres ratio, let's see, I was using about 83 nFd and the approx
> Cres for a 15/30 NST is about 5 nFd, and I was paralleling 10 (that's
> right, I had 10, not 6 15/30 NSTs paralleled, my mistake) so that should
> translate to approximately 50 nFd for Cres. As I said, I was using
> 83 nFd, so the Cp/Cres ratio would have been around 83:50 or ~ 1.66:1.
>
> David
>
>
> David Rieben
>
> ----- Original Message -----
> From: Tesla list <tesla@xxxxxxxxxx>
> Date: Thursday, December 2, 2004 9:07 am
> Subject: Re: RSG and NST's
>
>  > Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>  >
>  > Hi David,
>  >
>  > Did you bring the RSG up to speed before you power up the NSTs???
>  > Also, do you have the protection circuit (Terry's filter) in place
>  > in case
>  > of runaway overvoltage due to ferroresonance and misfiring???
>  > What was the
>  > Cp/Cres ratio???
>  >
>  > Gerry R.
>  >
>  > > Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>  > >
>  > > Hi Gary, Dr,
>  > >
>  > > I'm not too sure which one of you are "right" on this ;^) I have
>  > > experienced near cascading failure of an NST farm when try-
>  > > ing to run an asynch rotary gap with them! I'm not too sure
>  > > what the BPS rate was but I think it was in the 300 to 350
>  > > range - 6 rotary electrodes on a 3450 rpm motor. Anyway,
>  > > I had (6) 15/30 NSTs in parallel and almost as soon as I
>  > > fired it off, the output quickly went down to almost zero. In-
>  > > spection revealed that one of the transformers had failed.
>  > > Once this transformer was removed and I was operating
>  > > on 5, the same thing happened again almost immediately
>  > > after power up. So now I had 4. Didn't take long to figure
>  > > out that this was NOT going to work :^O I don't think 300
>  > > or so bps would be considered LOW bps. One thing that
>  > > I am pretty sure of is that whether or not high bps is more
>  > > stressful on the transformer from resonant rise or whatever,
>  > > it is more stressful on the primary capacitor due to higher
>  > > RMS currents. This particular .083 uFd, 84 kV cap was
>  > > quite robust though and never even "hiccupped" then or
>  > > for the next several years after that after I had finally upgraded
>  > > the transformer(s) to a single 10 kVA, 14,400 volt pole
>  > > pig and got bright, thick 8 to 10 ft. sparks for runs of se-
>  > > veral minutes of non-stop operation at a time. So for me,
>  > > NSTs are just too fragile for serious coiling and since
>  > > using pole pigs, transformer failures have ceased , with or
>  > > without any type of protection/filter circuitry ;^)
>  > >
>  > > David Rieben
>
>