Re: Freau's efficiency theory=Success!

["Tesla list" <tesla-at-pupman-dot-com>]

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

In a message dated 6/6/01 7:14:44 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<R.
> E.Burnett-at-newcastle.ac.uk>
>  
>  
>  Hi John, all,
>  
>  > I thought that adding PFC would stop the NST's (over-current) suffering. 
 
>  
>  I believe this is not the case.

Hi Richie,

I see what you're saying.  I had never given it that much thought before.
(I wonder what other things I haven't given enough thought?)  I guess
the NST primaries are destined to always be abused in common usage.
I too like the idea of designing large systems for a good power factor
without PFC.  I guess the thing with those NST's is to not let them
get too hot (among other things, ho ho).

Cheers,
John Freau

--
>  
>  A PFC capacitor connected across the primary of an NST draws a reactive
>  current from the supply which is 180 degrees out of phase with the
>  reactive part of the NST current.  The supply current is the sum of these
>  two currents.  So the inductive part of the NST current is cancelled by
>  the capacitive current drawn by the PFC.
>  
>  This reduces the overall current drawn from the supply line,  but the 
>  windings of the NST still see the same total current with or without
>  PFC.  It is only the line current which is reduced by cancelling the
>  reactive contribution.  However, PFC is still worthwhile as reduced line
>  current makes life easier for the Variac, circuit breakers and wiring.
>  
>  This is one of the reasons why I believe that larger systems should be
>  designed with high PF in mind from the outset.  A poor power factor in 
>  a large system burdens the transformer and ballast,  and requires a lot of
>  PFC capacitance to make a significant improvement in the power factor.
>  
>                           Cheers,
>  
>                           -Richie,
>