User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1
Doug,
It's polite to change the subject of a thread if you are going to a
different topic.
There is no way to predict the voltage rating of your cap without
knowing the thickness and dielectric ratings of the plastic material of
the food tubes that you are using.
If the cap works and doesn't show signs of puncturing, then it's
apparently rated high enough for your application. How long it will
continue to work is unpredictable.
The buzzing indicates that the foil electrodes are not firmly attached
to the dielectric material. The metal flexes as the potential changes
across the capacitor, making the noise.
To eliminate the buzzing, you want to use a uniform layer of adhesive to
glue down the dielectric on both the inside and outside of the tube.
Air bubbles under the foil will permit the development of corona
discharge which will attack the dielectric material and eventually lead
to its failure.
People who have built their own capacitors have used rolled layers of
Mylar Teflon, or polypropylene dielectric sheet and aluminum foil coated
liberally with mineral oil, and tightly compressed to exclude air
bubbles. It's a messy and difficult process to make caps that will last
for any extended period of operation.
I'm pretty sure that your capacitance value is overly optimistic. 14 uF
would be a very high value of capacitance for the sort of device that
you have described, unless I'm missing something. A value like 0.0014
uF might be more in the ball park, would be my guess.
Dave
On 10/19/2018 3:15 PM, doug11642@xxxxxxxxxxx wrote:
I have been experimenting with home rolled Caps and would like some
help with values please?Using food saver tubes as the dielectric,
dielectric is 36" X 8", foil inserted in the food saver tubes is 32" X
6", uf measures 14uf as rolled. What would be the voltage rating? So
far I have used one in a small TC [7.5k NST] and have not destroyed
it! All-tho it buzzes loudly.Doug J.