Re: [TCML] PFC Question (again)

[FutureT@xxxxxxx]

In a message dated 5/27/2008 9:05:58 P.M. US Eastern Standard Time,  
drieben@xxxxxxxxxxx writes:

>Hi John,

>Yes, I would agree that one would almost have  to run LTR to run
>EFFICIENTLY at ONLY 120 BPS and we do know that  Kevin
>is runing his rotary at just 120 BPS. However, just from the  sheer
>power levels that Kevin runs (up to 55 kVA & 21.6 kV  according 
>to the Youtube vids - that's over 2.5 amps!!), the  transformer's 
>natural (Z) impedance would dictate closer to .7 uFd, at  60 hz mains, 
>as Bart stated, for it to be LTR. Of course with 400 amp  service and 
>running  >50 kVA, who needs to worry about running  efficiently ;^)

>David Rieben


Hi David,
 
Please also see my other posting "PFC Question (again) --  more.
 
When Kevin built his coil, I saw it as possibly an excellent  
platform for studying these issues.  My theory at the time  (and
possibly still), is that 120 bps operation should give better  
"efficiency" than higher break-rates, even for a large coil.  
Unfortunately Kevin's ballast at the time was extremely  lossy,
and burned up a lot of power and ran very hot.  So Kevin  was
not able to determine the true power or KVA draw of the coil.  
We couldn't really determine if it was efficient or not.  I  think
he eventually replaced the ballast with something more
efficient, but I don't remember the details.  
 
Also for pigs and PT's, one cannot think in terms of
the natural impedance of the transformer for determining LTR
values.  These transformers have a very low internal  impedance,
so they are always ballasted.  It's the ballast and the power
capability that determines the needed cap value for resonance,
LTR, etc.  My other posting explains this is more detail.  It's  a
whole different ballgame than NST coils in regards to LTR,
STR, resonant mode, etc.  An NST coil is a special situation
because of the built-in and fixed value of leakage reactance.
 
The end result of all this is that whether Kevin's coil is running
resonant depends on the setting of the ballast.  Regarding
forcing power into the coil, it can't be done if the cap value is
too low at 120 bps.  The coil simply will refuse to draw  enough
power, even if minimal or no ballasting is used.  Actually in
resonant mode, a ballast doesn't limit the current, it actually
increases the current draw.  But it does limit the current 
while the gap is shorted, as it should.  
 
Cheers,
John









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