[Prev][Next][Index][Thread]
First light and problems
----------
From: D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Tuesday, June 23, 1998 6:17 AM
To: Tesla List
Subject: Re: First light and problems
to: Marco
We run a similar coil with the 4 inch dia. secondary with 26 AWG. As you
suspected, your problem is overcoupling. We run our sec coil so the first
(lowest) turn is 1 1/2 inches above the horizontal plane of the top of the
primary coil (flat spiral also). The innermost primary turn is 1 1/2
inches away from the secondary coilform. This produces 40 cm sparks with
no flashover problems. Borrow a variac until you get the beast in tune so
you don't injure your caps.
DR.RESONANCE-at-next-wave-dot-net
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: First light and problems
> Date: Monday, June 22, 1998 9:57 PM
>
>
>
> ----------
> From: Marco Denicolai [SMTP:marco-at-vistacom.fi]
> Sent: Monday, June 22, 1998 12:43 AM
> To: tesla-at-pupman-dot-com
> Subject: First light and problems
>
> Last weekend I got my ground and my first TC ready: I had no variac and I
fired
> it up at full power. I had before measure primary and secondary to
resonate
> both at 240 KHz so the primary tap should have been about in the correct
> position.
>
> IT WORKED! I had about 1 meter long sparks running from the toroid into
free
> air, almost perfectly horizontal. After the first minute I run into
problems...
>
> 1. I got 1-2 sparks from the strike rail hitting the middle of the
secondary.
> I suppose my strike rail was too much near the secondary (the sparks made
a
> 10" travel from strike rail to the secondary body).
>
> 2. Then I got some sparks from the inner primary turns to the secondary
base
> and primary to secondary about 3" height from its base. Because it was
day
> and I was (safely) far from the coil, I couldn't notice any corona or
aurea
> effects near the primary base, but I suppose the problem was the well
known
> overcoupling.
>
> 3. One diode from my MOT doubler blow up twice (always the same one).
>
> My coil data:
>
> Secondary 4.33" diameter, 19.7" wind with AWG 26 enamel wire, 7 layers of
> epoxy paint. Toroid 3.15" diameter tube, 11.4" outer diameter, 12.7 pF.
> Mounted 1.6" over the secondary top. The pair resonates at 240 KHz.
>
> Primary 7 turns of 3/16" copper tube, inner diameter 5.3", turn spacing
> 0.3". Flat pancake. Clearance from inner turn to secondary 0.5".
> Secondary capacitor 0.05uF 50KV. Set to resonate also at 240 KHz.
> Primary turns and secondary first turns almost on the same horizontal
plane.
>
> Tank supply made of two MOTs and two voltage doublers, output 8 KVAC,
> almost 0.5A (I believe). A third MOT primary (with shorted secondary)
> was in series with the 2 MOT primaries on the 220V side to work as a
shunt.
>
> Spark gap is a RQ static gap with blower and two series of 3 of 0.275"
gaps
> connected in parallel.
>
> About the following solutions I would like very much some comments:
>
> Problem 1: I plan to rework my strike rail as an open ring about 3" high
> from the secondary base, about 8" horizontal clearance from the secondary
> 4.33" pipe.
>
> Problem 2: rework the primary, increase the clearance between inner turn
and
> secondary to 1", make it a 15 degree upside-down saucer to distribute
better
> it magnetic field and decrease coupling.
>
> Problem 3: the two MOT employed were a 900W and a huge 1500W. The diode
of
> the doubler of the last one keeps on blowing. I replaced the 1500W with
another
> 900W and I hope this will stress less the diode.
>
> Your opinion is really welcome...
>
>
> ________________________________________________________________________
>
> Marco Denicolai Vista Communication Instruments, Inc.
> Hardware Development Manager www.vistacom.fi
>
> marco-at-vistacom.fi Kaisaniemenkatu 13 A
> fax: +358-9-622-5610 SF-00100 HELSINKI
> phone: +358-9-622-623-15 Finland
>
> Remember, Murphy was an optimist! I am not...
> ________________________________________________________________________
>
>