Phil et al.
Here is my take on the equidrive circuit based on discussions and
brainstorming with R. Hull about 10-20 years ago. This was/is
an attempt to determine scientific advantages (if any) over this
topology and just the old "parallel feed" capacitor system
With an equidrive (or series feed/parallel SG system)...
1. AC transformer is shunted during SG commutation. This stores
energy in transformer (Ldi/dt) that would not normally be stored
in transformer, in a parallel C configuration. This I is released
when the gap quenches "possibly" allowing faster C recharging.
I do know that equidrive systems can be run with much higher break
rates then a parallel drive system (30-50% faster if my memory
is correct).
2. The SG shunting the tank circuit removes the AC line and transformer
impedance as a parallel parasitic tank load. This is probably
the most compelling reason for using a series feed/equidrive
configuration, IMO. You also reduce HV/RF transients from HV
transformer windings (by SG shunting with operation).
3. Equidrive allows input voltage to be divided between two sets
of independent tank capacitors. This is probably the main reason
Tesla used it in Colorado Springs, his dielectric materials frankly
"sucked", and he was stacking the deck as best he could. He still
had to reduce the transformer voltage (by reconnecting the HV
windings in parallel), and still run equidrive to keep from having
catastrophic capacitor failures. This is a reasonable reason
to use it today, to improve system robustness.
With modern materials and MMC technology, much higher tank
voltages can be run then previously used. This would
allow C size reduction for same energy (0.5*C*V^2) and a large
value primary L for a given frequency, which would tend to reduce
SG losses, and increase primary tank Q.
4. Two independent capacitor banks would maximize tuning
flexibility and would allow fine tuning (even with non-perfect
equal values on each leg, realizing voltage division will not
be perfect in that condition), and would reduce V stress on each
capacitor
I also admit that all machines that I build are equidrive machines,
with C bleeders.
Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield VA. USA
-------------- Original message ----------------------
From: "Tesla list" <tesla@xxxxxxxxxx>
> Original poster: FIFTYGUY@xxxxxxx
>
> In a message dated 4/30/07 12:47:05 A.M. Eastern Daylight Time,
> tesla@xxxxxxxxxx writes:
>
> >I believe Hull's hypothesis was
> >that blocking the 60Hz on the primary, via a capacitor on each
side, would
> >make for a more pure ringdown. > > I *still* don't see how the "Equidrive" could affect even 60 Hz on the > primary. If you have just one cap in series with the primary, > wouldn't it block 60 > Hz current just as well? > Is there some stray significant coupling to ground that I'm overlooking? > > > Without bleeder resistors on each cap, there > >is a chance that the capacitors will be in a charged or partially charged > >state when the power is removed. > > Yet again, I *still* don't understand why there's a difference with the > "Equidrive". The two caps are tied together by the primary, and the > transformer's > secondary completes the circuit. > > >We found no measurable difference in arc length or RF output> >characteristics. We did find that a cap would occasionally be left charged
> >and for that, we abandoned the Equi-Drive topology. > > Thanks for the anecdote! > Obviously, it must be *possible* to end up with a charged cap. I know > I'm sounding like a broken record, but I'd just like to know *why*? > > -Phil LaBudde > > > >> ************************************** See what's free at http://www.aol.com.
> >