Re: Maxwell AC vs. DC ratings

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Edward Wingate <ewing7-at-rochester.rr-dot-com> 

Tesla list wrote:

 >  > Terry,
 >  >
 >  > Commercial pulse caps aren't "fragile", they simply need to be properly
 >  > speced for the intended use and then operated within those specs. I have
 >  > certainly never had a commercial cap fail from "overcurrent" as your
 >  > recent MMC postings seemed to indicate. Actually I've had only one
 >  > commercial cap fail in 15 years and that was due to a manufacturing
 >  > defect in one section. The company built me a new one for free even
 >  > though the warranty period had run out!
 >  >
 >  > MMCs are OK for "playing", commercial caps are for more serious work!
 >  >
 >  > Regards,
 >  >
 >  > Ed Wingate RATCB
 >  >
 > Hey Ed,
 > To be fair,if you're talking about my MMC cap failings.Please keep in mind
 > that my MMC is not "properly speced for the intended use and operated within
 > those specs".I'm using 3 strings of 10 of the Panasonic 1600v .056uf caps to
 > run a 15/60 NST.I use a static gap with a variac turned up to 140v. In three
 > years I've popped 9 caps.I don't have to get the company to build me a new
 > one as I can replace a popped cap and be running again in literally 15
 > minutes tops.I also have 2 extra strings that I can hook up in a couple of
 > minutes if I want to fix a string later.I've run this coil for 20 minutes at
 > a time.My coil is a hobby coil for fun that I "play around" with so for me
 > it's no problem to replace a cap every once in a while.It's certainly cheap
 > enough.My static gap has 6 copper sections that are adjustable so every once
 > in a while I've opened 'em up and let it "goes till she blows"-dot-commercial
 > caps are great, so are MMC's :o)
 > Bill Mck.

Hey Bill,

Easy... don't take it personally. To be fair, I was talking about MMC
failures in general. In the recent past MMCs have been touted on the
list as being the answer to every coilers prayers and folks were pretty
much told not to bother with a commercial cap, MMCs were better. Now it
seems like there have been about as many MMC failures as there have been
in the over stressed commercial cap realm. MMCs are not better, just
different! I wish I'd had MMCs when I was getting started.

In the past 10 years I've popped zero commercial caps, so it's been a
long time since I had to have the "company" build me a new one. I
haven't had to take any minutes to get up and running again from a
failed cap. :^)

The CP caps on my maggy have well over twenty hours of total run time
(actual hour meter) and the break rate on the system is from 750 to 800
BPS! The very same caps had seen extensive duty on several classic coils
before that. During the Teslathon last year I put almost two hours of
run time on the maggy in a single afternoon while people tried out the
"Cage of Death" and the only part of the system that overheated and shut
down was the series rotary gap cooling fan motor (which is necessary
only because of the safety cover over the gap).

All that said, I can't wait to fire up the maggy for the first time this
year after I get the lab open and have one of the aforementioned
commercial caps go up in a blaze of sparks and smoke. :^) That would be
just my luck!

Ed Wingate RATCB