Re: Paralleling Inductors and Resitors

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

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Ryan!

Date: 31 January 2001 19:45
Subject: Paralleling Inductors and Resitors


>Original poster: "Ryan Ries by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <spud-at-pureinsanity-dot-net>
>
>
>I'm really just asking this for the fun of it, but in
ballasting a large
>transformer, would there be any strange effects in placing
resistors in
>parallel to inductors?  Considering how inductors work, and
the fact that
>resistors drain the supplied voltage, I was wondering about
this, but never
>tried it out for myself.


Simulations done by Terry and Deano have supported what an
electrical engineer by the name of G.W. Carter published in
1945, that a resistor in parallel with a coil provides
excellent damping of oscillations. (Carter was writing about
ways to prevent damage to mains power distribution
transformers in the event of lightning strikes on the power
lines, which can generate large amplitude oscillations as
the inductance of the power line resonates together with the
capacitance of the transformer like a TC primary circuit.)

Various postings on this topic have included the following
references:

http://hot-streamer-dot-com/temp/Dfilter.gif
http://hot-streamer-dot-com/temp/Dunckx.sch (if you have
microsim)
http://hot-streamer-dot-com/temp/Dunckx.gif
www.corridor-dot-net/deano/NewFiltr.zip
http://hot-streamer-dot-com/temp/transients.zip (excerpt from
G.W. Carter's book)

I imagine that G.W. didn't invent this (and I simply pinched
the idea from him) but that it was standard technology at
the time - his book was based on a lecture course he gave to
engineers of the British Thomson-Houston Co. Ltd. (BTH)
which is located just up the road from me at Rugby, or was -
I don't know if they're still in business.  They are/were
heavyweight electrical engineers anyhow.  Perhaps those list
members who have modern power distribution experience might
like to comment on how lightning-induced oscillations on the
line are suppressed today.  Maybe it hasn't changed!  There
could be other take-home lessons for transformer and mains
supply protection which we could benefit from.  TCBOUK is
currently trying to organise a visit to a large substation
in the UK this summer and I'm rather looking forward to it -
might be some good ideas to pick up on.  What's good enough
for the pros is generally good enough for amateurs, scaled
if need be.

On this basis, I would expect that say a pole pig with
inductive ballast and which was experiencing surging
troubles would have its problems cured by putting e.g. a
heater element or two in parallel with the inductive
ballast.  It wouldn't surprise me if one or more of the "pig
farmers" on the list have experience with this . . .

Dunckx