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Re: Pri/Sec coiling
> Date: Mon, 3 Feb 1997 22:25:44 -0700
> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Pri/Sec coiling
> Reply-to: tesla-at-pupman-dot-com
> > Subject: Pri/Sec coiling
> > Subject: Pri/Sec coiling
>
> Subscriber: tom_mcgahee-at-sigmais-dot-com Mon Feb 3 21:47:35 1997
> Date: Mon, 3 Feb 1997 17:26:48 -0500
> From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Pri/Sec coiling
>
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> ----------
> > From: Tesla List <tesla-at-poodle.pupman-dot-com>
> > To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> > Subject: Pri/Sec coiling
> > Date: Sunday, February 02, 1997 8:25 PM
> >
> > Subscriber: Rodney.Davies-at-anu.edu.au Sun Feb 2 17:39:43 1997
> > Date: Sun, 2 Feb 1997 22:16:55 +1100 (EST)
> > From: Rodney Graham Davies <Rodney.Davies-at-anu.edu.au>
> > To: tesla-at-pupman-dot-com
> > Subject: Pri/Sec coiling
> >
> > Hi All,
> >
> > I'm going to ask perhaps a silly and obvious answered question, but when
> > winding your primary and secondary, are the windings in the same
> direction?
> >
> > ie, wind both sec and pri in a clock-wise direction?
> >
> > I should be able to derive this from 1st principles of electromagnetic
> > induction, but can't seem to picture it too well.
> >
> > The reason why I ask this is that in TC circuit diagrams, the coils (if I
>
> > am correct) are back-to-back w.r.t the primary and secondary coils. I
> > interperate this as being that the coils are wound in opposite directions
>
> > to each other.???
> >
> > Then again, this whole idea mightn't really matter...
> > Anyway, my puzzling thought for the day...
> >
> > Ideas, flames, corrections welcome...
> >
> > Thanks guys!
> > Catchya later!
> >
> > Rod
Fr. Tom McGahee wrote:
> Rod,
> whether a coil is wound clockwise or counter-clockwise depends on how you
> look at it :) In other words, if a coil is turned upside down, you have
> effectively reversed the windings, haven't you?
rwstephens: No you haven't. The clockwise or counter-clockwise sense of a
solenoid is the same as viewed from either end. Also, you cannot
change the direction of airflow from a propeller blade by removing it
from the motor shaft and putting it on the other way. Don't feel
like a clone on this one Fr., we've all had daze like this! : )
> As to the effect, I think it does have some bearing, but very minor. The
> only way I see it having a large effect is if the coils are interconnected
> and the secondary has very few turns. Then you have an autotransformer, and
> you want them phased the same. But the difference in most normal coils is
> going to be small. It's one of those things that really doesn't matter
> enough to worry about. But it was a good question!!
>
> Fr. Tom McGahee
rwstephens: The wind direction on Tesla coils is very definitely critical when
building a tandem coil system with a separate secondary in each of the two
primaries, or the same primary with two secondaries suspended within it.
In this case, given that the primaries are wound the same direction, or you use a
single shared primary, then the secondaries will have to be wound
opposite sense from each other to get a 180 degree phase difference
between the top terminals. If you do not do this the two coils will
not speak to each other with hot streamers.
As mentioned by the others, in a classical two coil, or magnifier,
the sense of the coils matters not.
In a vacuum tube TC where a grid tickler coil is employed, the sense
of wind between the plate tank coil and the grid coil is also
critical. You need to drive the grid in 180 degree phase opposition
to the plate signal. If you wind the grid or plate coil the wrong
way however, in this case you can effect repair and obtain operation simply by
reversing the connections to one coil or the other. The reason for
this is that unless the vacuum tube sees *positive* feedback it will
not oscillate. It does not matter what sense the single secondary
coil is wound in, except that this _will_ affect the level of
feedback superimposed on the grid tickler winding, (mutual inductance
of the 3 windings is affected), but that can be compensated for during
initial tuning adjustments. Whether the vac tube oscillator is
operated with the secondary inserted, or removed, or raised and
lowered during K adjustments also effects the amount of grid drive obtained.
Luckily, the grid drive drops with the secondary coil removed, which is after all
the load. Even so, unless you are operating the plate supply transformer up
from zero on a variac, I do not recommend operating a vac tube TC without a
load unless measurements have been made that confirm that the
resultant elevated plate voltage p-p excursions are not going to
exceed the safe voltage capability of the tank circuit capacitor or
the tube(s).
rwstephens