Re: DC, MOTs & PFCs

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

yes it could, but multi kV capacitors that can take AC tend to be expensive
and/or big and bulky.  

The once popular 4500V transformers from H&R and C&H, for instance, used a
third 600V winding just for hooking up a PFC.  600V run capacitors are
available inexpensively

Tesla list wrote:
> 
> Original poster: "Metlicka Marc by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>
> 
> Tesla list wrote:
> >
> > Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <youngs-at-konnections-dot-net>
> >
> > List,
> >
> > My MOT filtered DC supply with no load benefits from about 135 mFd of PFC
> > capacitance to drop the AC line current.  But I was surprised to discover
> > that at load, the PFC correction actually increased the current!  Why?
> >
> > I think the answer is that with no load, the DC supply filter caps are
> > essentially disconnected from the secondary, via the diode, almost all of
> > the 60 Hz cycle.  But at load, they are effectively in parallel with
the MOT
> > secondary for most of the load cycle.  This capacitance (about a
microFarad)
> > gets reflected back to the primary as a rather large cap and acts as a PFC
> > cap.  So adding more on the primary doesn't help.
> >
> > Engineers - am I interpreting the situation correctly?
> 
> I could be showing some more of my ignorance here, but couldn't an mot
> system use Pfc. on the secondary side?
> Take care,
> Marc M.
> 
> >
> > --Steve