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Re: LTR&MMC



Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 1/24/01 2:26:59 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> I haven't been following the tesla list for some time, so I was
>  wondering if there have been any recent developments about the tank cap
>  size. Last time I subscribed to it, people talked about LTRs. How much
>  bigger should the primary cap be compared to the resonance value?
>  
>  I will be using two grid transformers (got them for free, I'm lucky),
>  100v->6kV, 800VA each (that's what the datasheet says), I will connect the
>  primaries in series and secondaries center tapped, and drive the primary
>  0-230V (that's the voltage where I live) through a variac. That would be
>  0-13.8kV 1.6kVA.
>  
>  I will use a MMC. How many strings of caps would be the best? Cheapest
>  option would be to use 3 strings, but should I use more? I'll be using
>  WIMA FKP-1 (I think) pulse caps.
>  
>  Regards,
>  Tero Ranta (Finland)

Tero,

If those transformers are not current limited, then you'll have to use
a ballast to limit it, and the L value of the ballast, in relation to the
cap size, will determine if it is LTR or not.  When running at 120 
bps with a non-limited transformer, I do use slight LTR cap size.
I turn my ballast so the natural resonant freq of ballast/cap combo
is about 20% lower than 120bps, which effectively makes it LTR.

AT higher bps, folks often run STR it seems.  LTR hurts the
power factor, at least at 120 bps (100 bps).  The more LTR, the 
worse the power factor.  

John