Re: RSG and NST's

["Tesla list" <tesla@xxxxxxxxxx>]

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