Re: Sync motor question

In a message dated 99-06-06 13:19:36 EDT, you write:

<< Original Poster: Gavin Hubbard <ghub005-at-xtra.co.nz> 
> Hello List
> What is the current wisdom on salient pole motor powered RSG's?
> I understood John has shown no real advantage exists in the synchronous
> system over say a normal fully controlled variable speed rotary. And that
> this is based on actual tests with working coil systems, where a similar
> non-synchronous gap is swapped out after the synchronous gap is run.  
> Thanks in advance for your help,
> Gavin Hubbard >>


I haven't done higher break rate sync vs. non-sync comparisons, for
instance 360bps sync vs. 380bps non sync, but is suspect there
won't be much difference in performance.  I'm seeing the best overall
results at 120bps sync, as far as "efficiency" (input power vs.
spark length) is concerned.  For instance, at 120 bps sync, I can
get 42" sparks using 570 watts.  At higher break rates, I have to
use a lot more power to get the same spark length.  

If you take a typical high break rate TC, and simply replace the gap 
with a 120 bps sync gap, the sparks will probably get shorter,
because 120 bps sync gap systems need a big cap.  Actually a 
properly sized cap.  Non-sync operation lets you vary the break rate
to find the sweet spot in a sense.  In a 120 bps system, the TC has
to be designed to run in the sweet spot.  I posted a method for
designing TC's for 120 bps in the past, that starts out with the 
desired spark length, and works backwards from there to give the
desired toroid size, transformer size, cap size, etc.

NST's generally seem to give the longest sparks using a 120 bps
sync rotary also.  Non-sync rotaries should be avoided when using
NST's generally.

John Freau