Re: ARSG Motors (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 26 Aug 2007 10:28:36 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: ARSG Motors (fwd)

Hi Phil,

The cap is charged at a specific rate (60Hz). ALthough the ARSG has a 
specific rpm, will not be synchronous with the cap charge timing (and 
this is what counts). This causes the voltage required to arc the gap to 
constantly vary. The timing of the arc fires at points all along the 
60Hz line, through zero crossing, etc.. The charge cycle is constantly 
varied with the charging frequency. In the end, the result is a varying 
voltage. NST's are quite sensitive to overvolting, so it's easy to see 
why ARSG's are not recommended. Pigs and PT's seem to handle the 
variation fine.

SRSG's are recommended for NST's as it simply helps maintain a constant 
voltage at the time of arc (and even that's not perfect). LTR certainly 
is recommended for such operation.

I think when it comes to performance, it's really difficult to compare 
the two (apples and oranges). Of course, variable speed gaps (such as a 
VFD or DC motor) adds an adjustment capability to bps. But, just like 
the ARSG, the varying voltage is an issue to keep aware of if one is 
thinking on running an NST with it.

Take care,
Bart

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Sun, 26 Aug 2007 11:17:50 EDT
>From: FIFTYGUY@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: ARSG Motors (fwd)
>
>While we're on the subject, here's something I thought of the other  day:
> 
>    If you run an ARSG, by definition it's asynchronous  to the power line 
>frequency. However, when you run it at exact multiples or  fractions of the line 
>frequency, it *is* synchronous at that setting. 
>    However, the phasing relative to the line frequency  will be variable, 
>depending on circumstances preceding the synchronous setting. 
>    In other words, for a 60 Hz line frequency: If  you run the motor at 1801 
>rpm, then drop it to a synchronous 1800 rpm, the  phasing will depend on the 
>physical rotor position at the instant the rotor  spins at 1800 rpm. If you 
>come off that synchronous setting, and then return,  the phasing will probably 
>be different every single time.
>    So for those of you who run ARSG's, my question is  this:
>    If we make such a big deal out of phasing for  SRSG's, then obviously 
>phasing at (at least) the synchronous speeds is  important. Have you guys noticed 
>a performance change when sweeping through the  synchronous speeds, or when 
>setting to a synchronous speed, depending on the  arbitrary phase relationship? 
>Do you sometimes have to come off synchronous a  tad, then return to it to 
>"hunt" for a particular "sweet spot" in the phase  relationship?  
>    Does anybody run a "phase control" or do phase  adjustments with an ARSG? 
>Does it make a performance difference? 
>    Or does running an ARSG just give you "beats" of  good performance, and 
>it takes a bit of fiddling to obtain and maintain a "good"  setting?
> 
>    I'm following Bart's lead by putting together a  3-ph VFD setup for my 
>RSG. I already had a 3/4 hp single-phase motor I modified  for a SRSG, but so 
>many folks advocate the ARSG for pig setups that I figured  I'd give it a try. I 
>think another important advantage is the control over  the motor's accel to 
>speed, so as not to mechanically shock the rotor system  when starting up.
> 
>    Thanks!
> 
> 
>-Phil LaBudde
>Center for the Advanced Study of Ballistic  Improbabilities
>
>
>
>************************************** Get a sneak peek of the all-new AOL at 
>http://discover.aol.com/memed/aolcom30tour
>
>
>
>
>
>  
>