Re: DC, MOTs & PFCs

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

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