Hi Bert,
It looks like I will probably have to "settle" for my single 106 uF, 22 KV, 24 KJ capacitor (ha ha). The E-Bay vendor that is offering an identical capacitor, which I planned to parallel with mine, will not sell it to me. They will only sell to a business, government entity, or educational institution. This kind of makes me angry because I bought an identical capacitor from them on E-Bay about 5 years ago, no questions asked. I even told them that they sold me an identical capacitor 5 years ago. I informed them that I was a retired electrical engineer with a master of science degree in an attempt to convince them that I knew what I was doing. I even offered to sign a liability waver but they weren't interested. Given the extremely limited market for such a device and their restrictive sales policy, I think that they are going be sitting on it for a very long time.
My initial thoughts for the design are:
* Aerovox capacitor (106 uF, max 22 KV)
* 15 KV, 60 ma NST transformer with full wave bridge for a charger
* 10 Kohm charging resistor
* 50 Kohm discharge resistor
* appropriate safety features and interlocks
Any thoughts? Sorry that this is not strictly tesla coil related but it does involve energy discharge capacitors and high voltage.
Steve
----- Original Message -----
From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, June 18, 2018 1:57:16 PM
Subject: Re: [TCML] Need Energy Discharge Capacitor Information
Hi Steve,
Sounds like good plan.
Consider building a relatively large volume blast shield around the
region of activity if you plan to run at higher energy levels. The
internal volume of mine is about 0.4 cubic feet, but I never run it
above 8 kJ. I initially used 1/2" Lexan sheet on my blast shield, but I
quickly discovered that I needed to reinforce it with steel in the
regions directly impacted by coil fragments. Prior to this, I began
fracturing the Lexan at 8500 joules from wire fragments and the shock
wave when the work coil exploded.
I've been using abrasion-resistant (AR400) steel on the inside surfaces
of the blast shield. No problems after over 7,000 shots. Another coin
shrinking experimenter uses an old safe for his blast shield. And, many
years ago, some Texas coin shrinkers used a large diameter 1/2
thick steel tube (the base of a large outdoor sign), topped by a
comparably thick steel plate that was then weighed down with several
hundred pounds of sandbags. However, higher-energy shots (over 20 kJ)
still lifted the top plate sufficiently to allow fragments to escape
into the lab. 48 kJ packs the energy equivalent of ~35,400 foot-pounds
or energy, and exploding coil fragments have been measured at over Mach
4.4.
Plan accordingly.
Bert
Steve White wrote:
I originally tried to get information from Aerovox about my unit. They said that they had no record of it because it was made in 1992 (I presume from the serial number). I assumed that they would have records of all such huge capacitors but I guess not.
I am think of buying another one of the Aerovox capacitors (PM-series, 102 uF, 22 KV) and connecting it in parallel with the one that I already have. This would give me a combined maximum energy of 48 KJ for mayhem. My primary reason for doing this though is to get the same energy by charging to a lower voltage to minimize VR and thus extend capacitor life. The same E-Bay seller that I bought my current unit from is offering another one. Any thoughts?
Steve
----- Original Message -----
From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, June 18, 2018 9:51:22 AM
Subject: Re: [TCML] Need Energy Discharge Capacitor Information
Hi Chris,
These are also heavy-duty energy discharge caps, using a kraft
paper-foil dielectric system. The Aerovox PM series are all rated at 20%
voltage reversal, and no self-healing.
The low capacitance and dielectric system for your caps limit their use
to low pulse-rate, very high-voltage applications, such as flash X-ray,
Marx generators, exploding wire, or rock fragmentation work. The
dielectric system will be fairly lossy for lower-voltage oscillatory
applications, and the stored energy is limited for coin shrinking since
work-coil flashover limits maximum cap voltage to 20-25 kV.
You might be able to get more information by directly contacting the
folks at Aerovox. Unfortunately, many of their energy discharge caps are
custom designs. This often binds Aerovox to non-disclosure agreements
with their customers, preventing them from releasing even basic
capacitor specs...
Best wishes,
Bert
Chris Reeland wrote:
Okay, to get back on track to the topic, I have been following this with
interest.
I also have a pair of energy discharge caps that I have picked up last year
for a future project that I can't find any info either. Any info would be
appreciated.
Aerovox:
PM104YW003D04
3.110 uF and 3.364 uF
100,000VDC
15K Joules
They are in a stainless steel case.
A couple of pictures also if I made a typo...
https://photos.app.goo.gl/wPq4WEvYLuGbXKqM9
https://photos.app.goo.gl/jTgwWWiTbqaEA9ph7
https://photos.app.goo.gl/LHnuy85eBTaSZUP38
Thanks,
Chris
Sent from my LG V20
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