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How do I make my HV chokes?




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From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Monday, February 23, 1998 3:19 PM
To:  Tesla List
Subject:  Re: How do I make my HV chokes?

Tesla List wrote:

> > > What's an L-diode filter?
> >
> > It's like an L-C filter, except with a diode
> > in place of the C:
> >
> >            + --CHG--+--RFC---
> >                     |
> > HVDC supply<        D        >to pri ckt
> >                     |
> >            - -------+--------
> >
> > The diode clamps any negative excursions
> > that make it back thru the RFChoke, thereby
> > protecting the CHarGing reactor.  Positive
> > excursions do not pose a problem, as they
> > are never higher than the HVDC supply.
> >
> > It's much more effective at attenuating RF
> > than a standard L-C, and does not have any
> > self-resonant properties to worry about.
> > Both of my present coils use this scheme,
> > and the measured negative excursions stay
> > well below 100V.
> >
> > -GL
> >
> Thanks for the explanation.  This is fine for a DC power supply.
> Wouldn't do anything for someone trying to protect an NST or OBIT.  I
> can see how it would be great for clamping negative kickback, but how
> is it superior for attenuating RF?  The diode diverts RF better than
> a cap?
> 
> GH

Sure, since the L-diode arrangement does not 
introduce a freq rolloff or exhibit self-resonance.
All AC frequency components kicked back from the 
pri are clamped equally, up to and limited by 
the reverse recovery time of the diode stack.
(500nsec, which works OK for TC purposes) 

Converting the prime power to DC makes the charging,
filtering and isolation tasks much easier, for the 
primary HVDC as well as for the rotary gap motor drive.


-GL