From: "Terrell W. Fritz"
Date: Tue, 11 Jun 2002 20:00:13 -0600
Subject: Re: [TSSP] Re: Top V Probe Design
Hi,
I got the plastic stuff for the probe and I hope to get started tonight. Been
sort of lazy lately :o))
I am going to run the probe coil (it needs a name) through fiber optics till I
am sure it is safe for direct connection. Protection circuits and the 5100
probe are pretty safe too but the 5100 is like $300 and it protects by melting
itself down if all else fails (guess how I know this - No problem, it was
work's probe :o))). Best not to risk that right now.
Bert's data is great! We used to test transformer oil at the power company and
the test equipment is trivial to make up. I should probably test the oil. I
have my new hand held wand to test under RF conditions too. Be interesting to
see if there is a difference between DC and RF. I could probably also use the
CW coil for real sine wave high voltage if I am carful not to detune it.
So hope to make progress ASAP.
Cheers,
Terry
At 07:49 AM 6/10/2002 -0500, you wrote:
>Paul, Terry,
>
>Was just checking Sarjeant ("High Power Electronics") for insulating
>oils used in high voltage air core tuned transformers for high voltage
>pulsed power applications. On page 288 Sarjeant presents a chart
>comparing dielectric strength versus electrode spacing for various
>dielectric fluids that was originally generated by Sandia National Labs
>for a 1.5 uSec dual resonant pulse shape. While not an exact match, it
>should provide useful comparative data for the voltage divider.
>
>The estimated impulse breakdown strength from the chart follows:
>
>550 kV/cm R-Temp
>500 kV/cm 20 weight motor oil(!)
>400 kV/cm Water white mineral oil (Macrol 2930)
>310 kV/cm Mineral Transformer Oil
>
>The above is for single-shot impulse and assumes that any streamers or
>gaseous byproducts have dissipated between successive impulses. Since we
>want to run repetitively, significant derating should be applied - at
>least a factor of 4-5. So, using a worst case design with a peak stress
>of 60-75 kV/cm should do the trick. In addition to minimizing E-field
>concentration via large radius electrodes and symmetrical geometry,
>another thing to look at is closer matching between the permittivities
>of the solid dielectric and oil to minimize E-field stresses at triple
>points. For example, LDPE would be a better match than PVC or Mylar for
>mineral oil and R-Temp (all above oils have an Er of ~ 2.2).
>
>Best regards,
>
>-- Bert --
>--
>Bert Hickman
>Stoneridge Engineering
>Coins Shrunk Electromagnetically!
>http://www.teslamania.com
>
>
>Paul wrote:
>>
>> Terry wrote:
>>
>> > For the Top-V Probe, here is the latest design:
>> > http://hot-streamer.com/temp/HVProbe-2.gif
>>
>> I've been a bit busy with some other stuff for the last week or
>> two, but so far I haven't been able to imagine any probe
>> geometry that's going to be better than these coaxial cylinders.
>>
>> The tricky bit remains finding some dimensions that will
>> stand up to the Vtop without breakdown. I'm not sure it's
>> quite there yet. The wider secondary sure helps.
>>
>> > The 1 inch diameter rod has a breakdown at about 40kV in air
>> > but I figure oil is 10X better so the diameter should be OK
>> > to 400kV.
>>
>> Might only be 5 times better. Any idea what to use for oil?
>> Bit outside my field this, so not sure what to suggest.
>> --
>> Paul Nicholson,
>> --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.