RE: [TCML] 1 Mhz ,1 kw

["Lau, Gary" <Gary.Lau@xxxxxx>]

I think it's important to understand the real reason (IMHO) that ARSG's _might_ cause NST failures.

That zero-voltage crossings can occur is not in itself a problem.  They happen all the time with static gaps.

The problem is when users don't have a properly set safety gap in parallel with the RSG, AND they have a speed control on the RSG motor and run it significantly below 120BPS (or forget to turn the motor on before the NST is on).  Under these conditions, yes indeed, mains resonance will cause the cap voltage to ring up to voltages that will damage the NST and/or cap.

But the solution is easy - ALWAYS have a properly set safety gap in parallel with the main gap, for when things go wrong.  The safety gap in a Terry filter (or the MOV's) will accomplish this as well, though I prefer to have a separate 2-terminal safety gap built right onto my RSG (see http://www.laushaus.com/tesla/sync_gap.htm; it's a sync gap but same reasoning).  If one has a properly set safety gap, I don't believe that ARSG's are any more likely to damage an NST than anything else.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Monday, March 23, 2009 9:54 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] 1 Mhz ,1 kw
> 
> Hi Dex,
> 
> One other thing regarding the ARSG. It's not good for NST's. Breakdown
> will occur throughout the 60Hz charging waveform and it will breakout
> whenever the cap reaches the breakdown voltage. Zero crossing occurs in
> the ARSG and the voltage is allowed to climb to the next break, at which
> point the cap (especially if STR) is allowed to charge to a higher
> potential than the transformer output voltage. That extreme voltage can
> be lethal to the secondary windings inside an NST which simply doesn't
> handle excessive high voltages well. So again, a potential transformer
> would be a better choice here if you build an ARSG.
> 
> Take care,
> Bart
> 
> Dex Dexter wrote:
> > Thanks for the photo.
> > I think power source for the coil I want to build is a potential transformer.
> > And I'm thinking of use ASRG with 300-400 PPS.Cp about 10 nF.
> > Still thinking of how to realize good 40 kV capacitor bank for the purpose.
> >
> > Dex
> >
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla