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Re: additional transformers [rotary gap]
From: Mad Coiler[SMTP:tesla_coiler-at-hotmail-dot-com]
Sent: Thursday, August 07, 1997 11:02 AM
To: tesla-at-pupman-dot-com
Subject: Re: additional transformers [rotary gap]
>From: Robert W. Stephens[SMTP:rwstephens-at-headwaters-dot-com]
>Reply To: rwstephens-at-headwaters-dot-com
>Sent: Thursday, August 07, 1997 12:21 AM
>To: Tesla List
>Subject: Re: additional transformers [rolled caps]
>
>>
>> From: richard hull[SMTP:rhull-at-richmond.infi-dot-net]
>> Sent: Friday, August 01, 1997 5:52 PM
>> To: Tesla List
>> Subject: Re: additional transformers [rolled caps]
>>
>> A
>> >> > >
>> >> > >Peter,
>> >> >
>> >> > I recommended leaving a full 2" edge separation metal to edge of
dielectric
>> >> > in all rolled capacitors!
>> >> >
>> >> > Richard Hull, TCBOR
>> >>
>> >> Thanks for the info on that, I will go 2" on my future overlaps.
It
>> >> seems strange to me that sparks seem to travel much further along
the
>> >> surface of an insulator, no matter how clean it seems to be. Maybe
this
>> >> is due to microscopic impurities on the surface of the plastic?
>> >>
>> >> Another little trick that you probably have already figured out is
to
>> >> insulate the input connections to the plates by rolling a few
layers of
>> >> poly around them.
>> >>
>> >> Cheers, Peter E.
>> >>
>> >Peter, Richard, All,
>> >
>> >I had the same problem with a rolled poly cap I made once, and I
>> >*was* using a 2 inch surround from the foil to the edge of the poly.
>> >Dismantling the cap after the failure showed these burns distributed
>> >all along the edge of the foil outwards into the poly.
>> >
>> >I had a chat with a capacitor engineer at Condesnser Products about
>> >this phenomenon and was told that this is why HV capacitors are
>> >generally not successful when one tries to apply more than 8-10 kV
>> >across a single stage. He explained that the energy exchange
between
>> >the plate and the local surface of the dielectric becomes too
violent
>> >and just completely overstresses the dielectric causing it to
>> >break down. Placing additional thickness of poly does not
>> >significantly reduce this violent surface area exchange so you will
>> >still get failures no matter what you do if you try to run a single
>> >stage cap at 15 or 20 kV.
>> >
>> >FWIW
>> >rwstephens
>> >
>> >
>> >
>> >Robert,
>>
>> This is the very reason I have stated even in tape #3 where the big
rolled
>> jobs are made that one should never run them at over 10KV. Series
for more
>> volts. In tape #8 where we build another type of poly cap, I note
that 7-8
>> KV is the max on the single unit. Nonetheless, many never headed my
>> warning and blew out there caps almost immediately. Too many coilers
rush
>> to the 15,000 60ma neons and use a single capacitor unit. They will
lose it
>> sooner or later.
>>
>> The two inch boarder is minumum on caps used over 5KV per unit. Once
aged
>> and all the air is out I have run my single, big, rolled oil caps
with 12KV
>> neon transformers and luckily have never lost one. When working on
maggeies
>> #1-8 from 1990-1995 I used two of the big rolled jobs in series with
a
>> 14,400 volt potential transformer and never suffered a break down,
but the
>> stress was reduced on each unit by series stringing them.
>>
>> Since then I have used only professionally produced discharge caps.
The old
>> 1990 built rolled caps are still kickin' and are often used in snap
setups
>> for visitors, etc.
>>
>> Concomittant with the use of homemade caps is a sense of power input
>> limitation in the form of break rate. Lots of folks kill these
spartan
>> units with 15,800 rpm 24 point rotary gaps!!!! Even 2 KV might blow
them at
>> that rate of delivery. Newbies always want the 20,000 volt
transformers and
>> turbine speed rotaries and wonder at the ease of destruction of their
>> capacitors.
>>
>> There is rarely a real viable need for break rate over 360/second
(maggies
>> can handle more). If a rotary gap has more than 8 points, it will be
a bear
>> to quench well with out super high speed and attendant cap
destruction.
>>
>> I have no way of knowing, but I suspect a lot of Good CP caps fell to
the
>> turbine rotary effect.
>>
>> Richard Hull, TCBOR
>>
>Richard,
>
>You have shared some valuable pointers again for newbies here and
>safety reminders for the rest of us. I can really appreciate how a
>turbine break rate will destroy the best commercial capacitor but I
>just wanted to say in reference to your 360 BPS suggestion that I
>have personally found ~ 402.5 BPS (14 stud rotary wheel on a 1725 RPM
>non-synchronous motor) to be really sweet. A wheel with 12 studs
>yielding ~345 BPS was significantly less impressive in my MTC unit, all
>things else being identically equal. I guess there is an ion channel
>lifetime effect difference happening here that is better at the
>slightly higher break rate of 400, but suspect a supply sinewave
>filling factor or synchronizing benefit also as the break pulses 'walk'
through
>the 60 cycle mains phase in a slightly more concentrated manner.
>
>The Twin system which I have recently built really comes alive in
>this 400 PPS regieme, and is noticeably less remarkable at slower
>rates, including attempts to set the non-sync DC rotary break motor
>to run synchronously at 120 BPS (due to large wheel inertia and
>variac control I can successfully ride the crest of the sinewave peaks
for a few
>seconds at a time). I subsequently have no intention to operate the
>Twin at 120 BPS synchronous, nor any need to operate it's break rate
>exceeding 402 PPS.
>
>rwstephens
>
>
I am still a little fuzzy about the synch/non-synch rotary gaps. I
understand the basics of the synch gap-but how is the non-synchronous
gap advantageous?
The confused, bewildered, and vexed
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