Re: Blown Cap

In a message dated 96-05-24 00:41:58 EDT, you write:

>Hello fellow coilers,
> well I can say that coiling is a learning expierience. Just yesterday
> I blew my newly
>made rolled cap. It was a slight deviation to the standard design we have
>all seen, the difference being an extra layer of 20 mil LDPE for a total
>of 80 mil. This added thickness, I thougth, would allow me to use it in
>service with my 15 KV 120 Ma neon.  Dead wrong! After leting it sit for a
>few days and then breaking it in at 7.5 KV, I wired it up to my Resonator
>with the full 15 KV and only using 30-40% possible gap distance (point
>series with high velocity muffin fan). The first three days no problems (
>average run times: 10-40 seconds, a couple around 60 seconds). So I was
>getting 36-40" sreamers (not to good for a resonator at that power, but
>I'm still working on the design) and then it died! Today I dismantaled the
>cap (a messy job) and located a hole the size of my pinky, it was allong
>the edge of the flashing threw the plastic. I was very carefull in sanding
>and deburring the alluminum and inspected the poly prior to assembly.
>  I would like to say that obviously the standard schools of thought do
>  not apply in TC
>and especially resonator practise. I asumed 600 DC volts/mil breakthrew
>voltage and then divided by three for the TC voltage for 16KV. Now
>I would sugest dividing the DC breakthrew voltage by four, but would
>wonder about that?
> Obvously the way to use homemade rolled caps is to build four and wire
> two in series
>and parrallel them for double the voltage rating. But at around $80 US
>per cap it is probibly wiser to just buy a commercial cap. Has anybody
>had any problems with the Condencer Products caps at 15KV?
> Learning the hard way,
> David Trimmell <dwt-at-efn-dot-org>


I agree.  I have lost two of the 60mil variety.  I think they can only be
used safely up to about 9kv and for anything higher, you must use two in
series.  I calculated my cost at about $90.00 each.  The commercial Condenser
Products caps are around $200.00.  I thought I lost mine but they just
retested it for me and said it is just fine.  I must have problems somewhere

Ed Sonderman