Re: ARSG Motors (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- 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