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Re: [TCML] Need Energy Discharge Capacitor Information



Hi Steve,

I had the same question and spent some time discussing this with a GA capacitor engineer. It is an operational spec. The caps can be stored below 14F as long as they have a chance to fully "thaw out" before being charged. The root of the problem is that, at low temperatures, a small amount of water (that was previously harmlessly in solution within the caster oil) comes out of solution and is absorbed by the kraft paper, reducing its breakdown voltage. Once the oil fully thaws out, the water goes back into solution and the capacitor recovers its full dielectric strength.

Since my caps are in an unheated patio, I now use silicone strip heaters to keep them toasty during the worst part of Chicago-area winters.

Bert

Steve White wrote:
Bert,

I have a question about the temperature specs. Is the minimum temperature a storage and operational temperature or is it operation only? I ask because before I knew about this I am certain that these caps may have experienced storage temperatures below 14 degrees F at some time (I live in Iowa). They have never been operated below 14 degrees F.

Steve

----- Original Message -----
From: "Bert Hickman" <bert-hickman@xxxxxxxxxxx>
To: "Tesla list" <tesla@xxxxxxxxxx>
Sent: Saturday, June 16, 2018 3:17:41 PM
Subject: Re: [TCML] Need Energy Discharge Capacitor Information

Hi Steve,

Steve White wrote:
I have two energy discharge capacitors for which I am seeking additional information. I have searched the internet and sent questions to the manufacturers to no avail. This is what I know about the two capacitors from the nameplates.

Capacitor #1:

* Manufacturer: Maxwell
* Catalog Number: 33504
* Capacitance: 106 uF
* Maximum Voltage: 10 KV
This is a kraft paper-foil energy discharge capacitor with castor oil
dielectric as the fluid. The other specs for this cap follow:

Rated %VR:  80%  (Most energy discharge caps are only 20% VR)
Max %VR:   100%
Rated Id:  150 kA
Max Id:    300 kA
Irms:       75 A
Inductance: 40 nH
Design Life at rated V and I: 10,000 shots  (90% survival)
DC Life:     75 hours
Max/Min T:  40/-10 Degrees C


This is one of the big orange units that I have seen others use in various HV pulse discharge projects. I have a section of an old Maxwell catalog but this particular model is not listed.

Capacitor #2:

* Manufacturer: Aerovox
* Catalog Number: PM223YW099D01
* Capacitance: 102 uF
* Maximum Voltage: 22 KV

This cap also uses a kraft paper-foil dielectric system with castor oil
dielectric fluid. This cap (as are all Aerovox in the PM series) is
rated for 20% VR. I don't have any other specs, but looking at the cap
and its massive terminals, it's good for at least 100 kA. Keep voltage
reversal below 20% and either cap should outlive you.

Neither cap is self-healing, but they're both excellent caps for quarter
shrinking or can crushing. Don't let either stay below 14 F for any
extended time though. The castor oil starts clouding (solidifying) and
the cap will fail when being charged. Ask me how I know... :)

Good luck and play safely!

Bert


This is one of the big gray blocks that I have also seen. I have also seen similar Aerovox units used in HV pulse discharge projects.

Primarily what I am seeking is maximum number of shots and maximum allowable voltage reversal. I know that these capacitors are not suited for tesla coil use. I am going to use them to build a quarter shrinker and a ring launcher. Please, I don't need any safety warnings or such. I have been building tesla coils for many years. Any additional information about these capacitors would be greatly appreciated.

Steve
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-
Bert Hickman
Stoneridge Engineering LLC
http://www.capturedlightning.com
+1 630-964-2699
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