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Re: Stand construction



Original poster: "Nicholas Field by way of Terry Fritz <twftesla-at-qwest-dot-net>" <nick.field-at-hvfx.co.uk>

Hi Ralph

Tuning a twin coil is very similar to tuning an ordinary coil, but for one
key
difference, it takes about four times as long!  The problem is that every
adjustment to one primary must be matched by an adjustment to the other
to maintain overall system tune.  Something I have noticed on our relatively
small twin, Isis, and that Bill Wysock echoes in his Model 12 paper is that
the
two coils can be 'tuned' independantly to a certain degree by shifting
inductance
between the two primaries.  For example on a recent job we were running
with one of the coils in relatively close proximity to a black stretched
over
a metal frame, while the other was in clear space.  A substantial retuning
was
needed to 'balance' the two resonators, due to the proximity capacitance
effects of the metal frame.

While at first sight this may seem odd  I suspect it is not in fact a tuning
process but a variation of the coupling of each resonator that allows some
compensation for imbalance, such as added capacitance.

A twin is almost certainly more of a challenge both to design and operate
than a conventional monopolar coil, the reward is there, as our Isis system
shows - 8 feet from 2.7kVA.

Safe Coiling
Nick

_______________
Nicholas Field
Director,  HVFX
www.hvfx.co.uk


> Mike,
> I am working now on a twin coil that has evolved from my 48 inch bipolar.
> Each resonator is 24 inches of # 28 on a 4.5 inch OD form. The topload is
> 4 x 17 heater duct. The primary coils are each 8 turns of 3/16 copper. The
> power input is
> 2.25 KW and Cp is 0.039 uF. I can get 60 inch sparks but I want more for
the
> 2.25 Kw
> I'm pouring into the beast. I managed a 65 inch spark just before the fire
and
> the 30 amp fuse blew.  :-))
>
> I am finding the tuning of the twin resonators kinda tricky. I would like
to
> learn about your twin, and especially any info on how you tuned the twin
> resonators.
>
> Happy day,
> Ralph Zekelman
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