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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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