Re: Condenser Products Caps and max BPS??

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dave,
         That's some really interesting information:

On 24 Jul 2002, at 16:22, Tesla list wrote:

> Original poster: "Dave Hartwick by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>
> 
> I've got 2 Condenser Products, TC503-34-300 0.05 mfd 20,000 VAC capacitors
> (300$ each iirc). Purchased about 7 years ago, these units were designed
> specifically for coil duty.
> 
> They've not been used in 5+ years and have been sitting in the same
> horizontal position. Concerned about oil penetration after such extended
> none-use, I talked to CP. Engineer Gene said to rotate them occasionally and
> then bring the voltage up slowly. Sounds logical. Do you guys have any
> experience with this?

I was told the same thing re storage. I admit that mine have been 
shelved for an extended period without rotation too. You can hear oil 
sloshing about in the air gap when you move them.
 
> Most interestingly, he told me that those caps are rated for a max break
> rate of 120 BPS. I was not told this at the time of purchase. The problem is
> that I had been using an air-blast gap and the break rate was/is unknown to
> me. Gene suggested that the caps very well may have been compromised because
> of possible excessively high break rates, as much as 4-5 cycle for that type
> gap.

That is *really* interesting. I understood from the maker's specs 
when I bought mine as part of the group purchase that the maximum 
breakrate was also 120/s. I once saw Richard Quick thrashing a couple 
of 0.1's (also CP) with an async gap and pole pig on a video. I 
wonder if his were similarly rated??
 
> I wonder if this is the case? They were only fired for a total of maybe 20
> minutes at about 3 KVA (5KVA 14.4 kV pole pig). I noticed no deterioration
> in performance, but he suggested that any excessive internal
> heating--related to the "Tab" configuration connecting multiple internal
> series caps--could have resulted in damage that may not show up until one
> fails catastrophically and explodes.
> 
> The 2 caps were run in balanced series config at < 100 KHz, the coil
> producing about 5' sparks. Not very efficient for 3 KVA, at least measured
> against the current Coiling state-of-the-art.
> 
> So what do you guys think of this potential damage problem? The only thing I
> can do is try them again with a great deal of care. I guess I'll have to
> encase them in a blast proof container of some sort. My hunch is that Gene's
> caution was a bit overblown, but who knows?

My guess (and it is just a guess!) is that they're probably OK thanks 
to having been run in series with a relatively high inductance 
primary. But you never know. If I ever use mine in anger they will be 
encased in HDPE pipe.

> I really thought these caps were supposed to be quite durable. They really
> should have included literature specifically stating the operational
> limitations, don't you think? Maybe I'll just go back to polyethylene salt
> water caps, which surprisingly seemed to work nearly as well.
> Dave Hartwick
> Chambersburg, PA

These days, I run exclusively MMC with conservative current ratings. 
Much better than worrying about potentially explosive oil-filled 
containers.

Regards,
malcolm