Re: Charging inductors for resonant charging

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

Original poster: "Robert Jones" <alwynj48-at-earthlink-dot-net> 

Hi Bert,

 > Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net>
 >
 > Hi Jimmy,
 >
 > Yeah, I still think it's a problem...
 >
 > In theory, if the system is operated in a mode where the firing rate is
 > always at or below 2X the resonant frequency of the charging inductor and
 > the tank cap, then the inductor the current should return to zero on each
 > cycle.
 >
 > In practice, residual magnetism will bias the core since the de-Q'ing
diode
 > prevents reverse current flow, and we begin walking our way into
 > saturation. Using an ungapped core MIGHT work with if we removed the
 > de-Q'ing diode AND we set the BPS to 2X the inductor/tank cap resonant
 > frequency. In this case, reverse current can flow through the inductor for
 > part of the cycle and this may be sufficient to prevent a saturation
problem.
 >
 > -- Bert --
 >
 >
I have never understood the "walking in to saturation" thing. perhaps you
can explain it in more detail.

I do understand why you need a blocking capacitor when you drive an inductor
with signal with a DC offset. i.e. the offset drives a current through the
inductor limited by only the R.
Is this what you call "walking in to saturation"?

If there is no offset current (average =0) I can't see how saturation can
occur even with some residual magnetism.

I had always understood the reason for air gaps in inductors  with a DC
current was to reduce saturation by the DC current  while still maintaining
reasonable inductance to the AC current. Particular relevent in power supply
chokes when the DC may be much higher than the AC current.  Is this also
what would be called "walking in to saturation".

Bob