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Re: [TCML] Voltage - Gap
I think David also remembers the incident and has provided some detail. I was probably exactly on the hairy edge of overvolting, and definitely over current. If you search back in the TCML archives you can probably find my postings about it. It was sometime last year.
As I said, when I paralleled the 37667s I never had another problem with them in my SG coils. So maybe it was overcurrent. Somewhere I have the JTC files and I'll send them to you off list when I can dig them out.
That larger, 50kv rated cap had a very low max - rated reversal rate. Far too low for coil service. I didn't bother reading the specs when I got it on eBay for really cheap. I thought I was lucky. Ah, here's the failure pics <http://www.flickr.com/photos/iceowl/5437138473/in/photostream>
Joe
On Feb 2, 2012, at 5:22 PM, jhowson4@xxxxxxxxxxx wrote:
> That's interesting Joe, hmmmm
> I wonder why some people seem to never have problems with the maxwells and you have had two incidents.
> I would love to run your coil parameters threw my sheet and see how the outputs compare to mine and other peoples coils. If your willing to provide your parameters that is, let me know and I will send you a message with the details I would need.
>
>
>
>
> Thanks,
> John "Jay" Howson IV
>
>
> "Why thank you, I will be happy to take those electrons off your hands."
>
> ----- Original Message -----
> From: "Joe Mastroianni" <joe@xxxxxxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Thursday, February 2, 2012 2:31:29 PM
> Subject: Re: [TCML] Voltage - Gap
>
>> Speaking of maxwells, what is the rms current that these bad boys can
> handle for short runs? I have a 0.15uf 50Kv unit I acquired at a steal
> price. says 25A rms. What do you guys run them at?
>
> Hi Jay
> I don't have my JTC files at hand, but in reading your note I felt to
> provide my cautionary tale of using Maxwell castor-oil filled HV caps in
> TC service.
>
> I have had luck of both kinds - good and bad.
>
> On the bad luck side, I have had 2 of those caps explode rather
> catastrophically, under 2 separate situations. One was in an ARSG coil
> powered by 2 15/60 NSTs, probably running about 1/2 power at around
> 240BPS for 30 secs or so, to a resonator that, as I remember, was an
> 8"x48" secondary with a 6"x24" topload. I don't remember f0 offhand but
> it was something north of 110khz.
>
> I was using a single Maxwell 37667. The cap housing burst, spewing
> oil, though the coil continued to run happily for the two to five
> seconds it took me to realize what had happened.
>
> It is not difficult to exceed the maximum pulse/reversal rate on those
> things, as I came to learn.
>
> Some time later, the same thing happened while I was running my pig
> powered coil using one of those 0.15uF 50kv rated maxwells. Cant
> remember the number, though I did post info on the failure here at
> TCML. After 20 seconds or so at less than full input power (maybe no
> more than 3kva? and probably a 300bps break rate) the cap burst,
> spewing oil and smoke while the coil continued happily arcing away.
>
> Again, I exceeded the designed pulse rate of the cap. My wife was
> standing next to me when it happened and had the iPhone out taking
> pics. They're posted somewhere, maybe on my Flickr site.
>
> However - in stark contrast to those two failures, I have successfully
> run parallel combinations of three of those 37667s, and have had no
> detonations even with my pig driven coil running at 10kva or so for as
> long as I felt like running. I don't have the ability to go much higher
> than that, so I couldn't say how happy I would have been at higher input
> powers.
>
> Cheers,
>
> Joe
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