Re: Rotaries and Neons new question (fwd)

To: tesla-at-pupman-dot-com
Subject: Re: Rotaries and Neons new question (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Fri, 7 Aug 1998 20:57:02 -0600 (MDT)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: Fri, 7 Aug 98 11:36:51 EDT
From: Gary Lau  07-Aug-1998 1059 <lau-at-hdecad.ENET.dec-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Rotaries and Neons new question

>From: Mad Coiler <tesla_coiler-at-hotmail-dot-com>
>I really have no intention of using an asynch rotary on a NST but I 
>would like to learn as much as possible regardless. If you were using a 
>rotary with an NST, and also kept the break rate at 240BPS minimum, then 
>wouldnt that work? With atleast 240BPS you cant miss a gap firing on 
>each half cycle, right? 

Hi Tristan:

You've fallen into the same trap as I once did.

The problem is that while an RSG offers the opportunity to make 240
connections per second, it will only make those connections if the cap is
sufficiently charged to break down the air gaps involved.  The correct
terminology is that it offers 240 gap PRESENTATIONS per second.  It does
not guarantee that the cap will be discharged 240 times per second.

Consider this contrived example.  Maximum charging voltage of the xfmr is
10KV, 60 Hz.  Ignore resonance.  RSG is running 240 presentations per
second (exactly two per half cycle), and gap breakdown voltage at each
presentation is 7.1KV.  If the phasing of the rotor is such that the
presentations occur at 45, 135, 225, and 315 degrees of each cycle (90
and 270 being the peaks), the gaps will never fire, since Vcap is
10KV*sin(45)= 7.07KV at each presentation.

This is obviously a contrived and worst-case example, but it illustrates
the fact that missed presentations will occur if they do not coincide
with mains peaks.

>And if you cap wasnt close to being resonant at 
>50/60Hz than it wouldnt charge to 'dangerously high' voltage levels? You 
>could use half the matched capacitance and twice as high break rate and 
>get the same average energy delivered into the primary? 

If you deliberately avoid mains resonance, you'll be OK as far as the
dangerous voltage levels, but you'll only get a fraction of your NST's
potential resonant-charging power.

>Like I said I  havent tried any of this - just wondering what the flaws are 
>with my thinking.
>
>Tristan Stewart

Regards,
Gary Lau
Waltham, MA USA