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Re: why 4 Ohms in PARALLEL with trigger coil primary?
Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
Hi all,
I printed the documents out so here are some thoughts on the
matter. First I note that the MOVs have been drawn with constant
current source symbols on the diagram. Hmmmm....*
The resistors as shown in the website diagram are neither across the
mains or the primary of the coil. If they are doing anything, they
appear to be providing a discharge path for the 1uF caps. The circuit
appears to be activated by a current surge through the 1uF caps when
the dimmer fires which would pulse the primary of the coil while
charging the caps, in effect supplying a current spike through the
primary coil. The loading on the dimmer would be rather heavy with 4
Ohms being suddenly connected through it to the mains. I would guess
that firing point would be somewhere near the mains peak which would
limit resistor dissipation somewhat. In fact I wonder why a discharge
path for the caps would even be necessary since the dimmer would
charge the caps with opposite polarity on the next half cycle.
Interestingly, that would significantly increase the triac current as
it would now have twice the voltage applied across it. So why were
the resistors deemed necessary in the first place? To prevent blown
triacs? Maybe by discharging the cap in between firings they are
saving the triac by reducing the charging current through it. Is that
the idea?
Regards,
Malcolm
* Terry may have started using that symbol for MOVs. It's my fault if it's
wrong ;-)
On 18 Oct 2001, at 7:48, Tesla list wrote:
> Original poster: "Barton B. Anderson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
>
> Hi Terry, Ted, Scott,
>
> My guess is these resistors burned open when they were placed across the
> mains if
> they didn't burn up first when they were series'd. I suspect they run
nice and
> cool now. This is probably telling us that R isn't a requirement for
operation.
> Lutron's probably doing all the work.
>
> Bart
> --
> Barton B. Anderson
> http://www.classictesla-dot-com
>
>
>
> Tesla list wrote:
>
> > Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> >
> > Hi All,
> >
> > We have been having some (sort of off list) discussion about the 4 ohms of
> > resistance across the HEI coil's primary in Ted's plans... It seems like
> > these resistors would burn right up. We are a little unsure of what is
> > going on but I thought you all should know about this mystery too incase
> > you try it. If "you" figure it out, let "us" know :-))
> >
> > ---------------------
> > Hmmmmm,
> >
> > If you but 4 ohms directly across the ac line, it will dissipate 3600
> > watts... The dimmer would limit that to maybe 1000 watts... Something
> > strange must be going on there. However, if it works, it works. But I
> > think there is a good chance they are blown open which would probably have
> > little effect. I would leave it for now and maybe when you can play with
> > you coil at length, check into it more. Next time you see the coil, you
> > may want to double check to see that they really are across the neutral and
> > hot wires out of the dimmer and not in series. Check the resistance if you
> > can. I bet it is higher than 4 ohms :-))
> >
> > Cheers,
> >
> > Terry
> >
> > At 12:40 PM 10/17/2001 -0500, Ted Rosenberg wrote:
> > >Hi Terry. Hey, if I can type at 6AM (I work from 7 to 4 :)....
> > >No matter.
> > >
> > >The resistance was based on Marc's picking different low values on his
first
> > >iteration of connections...remember? The 10µF motor run cap and the 10
ohms
> > >etc. It was about the same time you were using the 250W huge reistors? (I
> > >have two...any ideas? They do not make good wind chimes!)
> > >
> > >Then Marc said that 4 ohms would be OK but he was not terribly clear as to
> > >exactly where!!
> > >Well, I didn't have 4 ohms. So two 8's in parallel gave me the 4 <at 40
> > >watts>. Then I put them in series in the line and I almost burned up the
> > >coil from the heat. That's when I got hold of you and you suggested across
> > >the HEI. And that worked.
> > >
> > >Does that clarify? Or should I try and followup with Marc?
> > >
> > >-----Original Message-----
> > >From: Terry Fritz [mailto:twftesla-at-qwest-dot-net]
> > >Sent: Wednesday, October 17, 2001 12:33 PM
> > >To: Ted Rosenberg; 'Scott.L.Hanson-at-seagate-dot-com'
> > >Subject: RE: why 4 Ohms in PARALLEL with trigger coil primary?
> > >
> > >
> > >Hi Ted and Scott,
> > >
> > >I forwarded this to the Tesla list by accident. Sorry bout that... You
> > >may want to write me at:
> > >
> > >terrellf-at-qwest-dot-net
> > >
> > >So the sleepy Terry can't just forward all the morning mail on without
> > >checking who it is addressed to...
> > >
> > >I did not understand why the resistors would be in parallel either :o) I
> > >thought they should be in series. I figured, well, I guess it works for
> > >Ted ok... You may want to check them with an ohmmeter. I wonder if they
> > >blew open in the first second and they are just open now. If they were
> > >open, you may not notice (maybe they don't matter...).
> > >
> > >Cheers,
> > >
> > > Terry
> > >
> > >At 07:02 AM 10/17/2001 -0500, Ted Rosenberg wrote:
> > >>Hi Scott and thanks for the compliment.
> > >>I have some answers for you but please understand, as I said in the
paper,
> > >I
> > >>was the technician. Marc and Terry Fritz deserve the "why" rewards!
> > >>
> > >>I originally had the 4 ohms in-line. the resistors got SO hot that they
> > >>would have burned the wood etc etc. I desparately e-mailed Terry as Marc
> > >was
> > >>unavailable. After some discussion, Terry suggested the new position
> > >>and...it works. I really can't give you a better reason. Sorry.
Perhaps you
> > >>might ask Terry about that. Who knows, I might learn something :))
> > >>
> > >>I do not own an oscope although I can borrow one.
> > >>I had to get this coil into the Hangman's House of Horrors and I was
> > >running
> > >>out of time. So all seriosu tweaking, checking with scope, adding welders
> > >>glass etc, will have to wait until the coil returns home after Oct 31.
> > >>
> > snip...
>
> --
> Barton B. Anderson
> http://www.classictesla-dot-com
>
>
>
>
>