Re: How to rise the secondary? (fwd)
---------- Forwarded message ----------
Date: Sat, 18 Jul 1998 10:00:03 -0500
From: "Barton B. Anderson" <mopar-at-uswest-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: How to rise the secondary? (fwd)
Coupling is two-fold. First, coupling is a coefficient of magnetic flux linking
inductors resulting in some amount of energy transfered.
Secondly, coupling should also be realized as a very real physical energy transfer.
What is it were coupling? Well, a voltage potential producing current in the primary
causing a magnetic field to be generated thus coupling the secondary. Remember, it
is a magnetic field we are coupling, and magnetic fields move in "size and density"
*with and by* the AC component (em field).
An em field produced in the primary will have a varying size , position, and
density. Current determines these parameters of the em field once the primary and
secondary are in place, and quenching determines the amount of current transferred
By *theory*, if we are "over-coupled" (too close, too much current, large em field),
the em field flux lines of force "does not" engage optimally and there is less
energy transfered than what could be. If we are "under-coupled" (too far away, not
enough current, small em field), the em field flux lines of force "does not" engage
optimally and again there is less energy transfered than what could be.
With TC's, I theorize that regardless of under of over coupled conditions, distance
of Pri to Sec arcing is set to prevent a *voltage* determined occurance. This does
not mean we are favorably coupled. It only means the Pri is far enough away from the
Sec to prevent arcing based on *current* and *quenching* conditions. Raising and
lowering the secondary *does* change the coupling due to the positioning within the
It is very possible, that due to the voltage level on the primary, our maximum and
most efficient K is beyond our reach with present design. Because quenching (energy
transfer) changes the current/time occurrance, it also changes the em field and flux
density. This may explain racing sparks along the secondary at low power levels vs.
high power levels and why changing the secondary vertical positioning can elliminate
or minimize this condition and produce sometimes longer, sometimes shorter arc
Until a program can take into account the em field parameters (sparkgap quenching,
current/time, etc..), coupling is a hit and miss condition. With a system designed
to just beyond the Pri to Sec arc distance, raising the secondary *can* provide a
better *coupling*, it may also reduce coupling depending on the em fields
relationship to the secondary.
At some point in our TC technology, we must begin research to best shape the em
field. This is where programs such as SPICE will play a large roll.
Sorry to respond so late to your first post. My life got real busy here lately. BTW,
I did review all the other posts.
Tesla List wrote:
> ---------- Forwarded message ----------
> Date: Mon, 13 Jul 1998 05:27:53 +0000
> From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: How to rise the secondary? (fwd)
> Barton, All -
> Coupling is not a critical adjustment for Tesla coils and exact coupling
> is not necessary. In fact, when the secondary is raised if only the
> coupling changed the only change would be a reduction in the TC output. The
> reason the output does change is because the tuning changes and this is very
> important and must be precisely set to obtain maximum output from the TC.
> The problem with raising the sec to prevent sparking and change the tuning
> is that there is a better way to design and build Tesla coils. When a TC is
> correctly designed, built, and tuned, raising the sec will only reduce the
> output until it is zero. A correctly designed TC requires that the pri to
> sec clearance be adequate to prevent sparkovers. This is not a critical
> parameter because classical Tesla coils operate over a wide range of
> couplings from about 0.10 for large coils to about 0.30 for small coils.
> If an exact coupling is desired it cannot be done by raising the sec because
> chances are the tuning will not be correct. This is not true when the
> primary is used to tune the coil.
> Coupling or K factor is only a numerical ratio like pi. With Tesla coils
> the coupling is a ratio of inductances. Changing the coupling changes the
> inductances which changes the tuning when raising the sec. This does not
> happen when the tuning is changed by changing the primary coil. Quenching is
> not changed by coupling but it may be changed by tuning and other adjustments.
> It is important to know that raising the sec can be used to "tweak the
> tuning" but there is a better way. That is to design the primary with
> sufficient clearance to prevent sparkovers instead of having to raise the
> sec. The necessary clearance data has been obtained by empirical means by
> many coilers in the past. I have incorporated this data into the JHCTES TC
> computer program and it appears to be working. The data can only be verified
> when other coilers make similar programs for comparison.
> John Couture