RE: Ed Wingate's Teslathon (async RSG & NST's)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

At 05:18 PM 8/24/2004 -0600, Tesla list wrote:
>Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
>Hi Ed:
>
>I too have often wondered about the origins of advising against the use
>of async rotaries with NST's.  I've not been able to simulate nor think
>of a scenario that would cause a hazardous voltage to occur, as long as
>a gap fires at least once per mains half-cycle.

I think this is the scenario that is the problem: a misfire, leading to a 
resonant rise.  (of course, a safety gap would completely eliminate the 
problem, no?)




>   The oft-cited rationale
>is that the more fragile NST's can't stand high break rates, but this
>seems backwards to me.  Higher break rates, at least with NST's, imply
>smaller bangs (which shouldn't be more stressful to the NST in any
>case).  More importantly, higher break rates would guarantee that the
>cap is discharged at least once per mains half-cycle.  It is conceivable
>that at low break rates, gap presentations may occur at or near
>zero-crossings and not fire, permitting mains resonant rise across
>half-cycles.  Since async gaps are typically used with a variable speed
>control, if the speed was set below 120 BPS, there would be problems.