[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Voltage - Gap
That is fantastic,
Does anyone else run their Maxwells in this way? I would love to collect some data on the usage!
Thanks,
John "Jay" Howson IV
"Why thank you, I will be happy to take those electrons off your hands."
----- Original Message -----
From: "drieben" <drieben@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, January 31, 2012 7:48:08 PM
Subject: Re: [TCML] Voltage - Gap
Jay,
I have a cat # 31885, .1 ufd, 75 kV rated Maxwell
that I believe is also rated at a "mere" 25 amps RMS,
but I run my Green Monster coil (10 kVA pig fed
and overdriven up to 20 kVA) with it as the sole
primary cap and I have never been able to notice
any external warmth on it above ambient temp,
even after several minutes of non-stop 15 kVA +
running.
David Rieben
----- Original Message -----
From: <jhowson4@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, January 31, 2012 3:50 PM
Subject: Re: [TCML] Voltage - Gap
> Hmm alright, I shall poke the archives and see what useful information i
> can obtain. =)
>
> what you describe is pretty much what I have been doing, playing with the
> data for just the .15 2Kv caps in an excel spread sheet to nail all the
> formulas down. once i am done that i will expand it to the other cases in
> an actual programming sense.
>
>
> I have made several poly caps previously, and to date none of them have
> failed. Two open air units and one under oil.
> I got around the need for thick Aluminium sheeting by tapping each turn of
> the roll with a nice long strip of aluminium and tying them all together,
> this allows many paths for the charge to escape. Minimizing the over all
> current flowing threw any given junction.Thus minimizing heating and the
> like. This also means for a pretty low inductance.
> I have run these guys for very long runs, and they get only lightly warm
> to the touch and while being over driven for what I designed them for as
> well. Work for me.
> Thus far solely in terms of cost analysis, the poly caps are by far the
> cheapest route to go for me. Due to maxwells being so bloody expensive ,
> and the sheer quantity of MMC caps i need to get the RMS currents to work
> out. That's with my RMS current equation thought, which I am trying to
> improve upon. Best case scenario is as I make my equation more accurate,
> the RMS current drops and I need less capacitors. or I stumble upon some
> very useful information regarding the ratios of actual RMS current to
> rated RMS current. Which from what I found last night, is information that
> does exist somewhere, I just need to dig it up again.
>
> 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?
>
>
>
> Thanks,
> John "Jay" Howson IV
>
>
> "Why thank you, I will be happy to take those electrons off your hands."
>
> ----- Original Message -----
> From: "Jim Lux" <jimlux@xxxxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Sent: Tuesday, January 31, 2012 9:36:42 AM
> Subject: Re: [TCML] Voltage - Gap
>
> On 1/31/12 12:06 AM, jhowson4@xxxxxxxxxxx wrote:
>> Ah yes I see the posts you are talking about back in the archives.
>>
>> I am going to spend a little bit of time reading threw this
>> material!
>>
>> So for the 2000Vdc cap, and the heat dissipated for the standard .15
>> 2Kv would be .9W, seems reasonable. I don't really see how this is
>> all that useful to me yet, but i am sure after reading thew the
>> material you helped me find, I will learn what to do with it.
>>
>
> Actually, dissipating almost a watt in something made mostly of plastic
> might be pushing a bit. I guess they're quite a bit bigger than, say, a
> 2W resistor, but thinking in terms of stuff you have around the house
> that dissipates a watt in a small area.
>
> One way to estimate the power dissipating capability of the capacitor is
> to look and see if there is a derating curve for the case temperature.
>
>
>> Going back to what you said earlier, with before you work too hard
>> modeling fine details, do a simple subset and see if it makes a
>> significant difference. You might find that in an RMS current,
>> heating sense that it doesn't make much difference between one big
>> pulse at Imax and 3 successive pulses at Imax/3, because the duty
>> factor is lower at the former. (Yes, heating goes as the square of
>> current, so that's clearly not true in this specific example, but
>> it's what I was able to come up with before my coffee as a direction
>> to look)
>>
>> Its definitely something I need to consider, does this really
>> matter? Well I am having a good time learning about all this stuff in
>> the process, so why not try and figure it all out. Plus if i do i
>> might be able to correlate some interesting things and add to the
>> general knowledge base for everyone to learn from.
>
>
> You make a good point. However, I find that it's nice to do a couple
> cases by hand that sort of bracket what you're interested in. Not only
> does that make sure you have the conceptual understanding, but it also
> lets you spend your time effectively. You might be trying to model
> something where there isn't any good data to model from and you wind up
> chasing what is essentially experimental uncertainty in the raw data.
>
> Maybe another term is to do a sensitivity analysis.
>
>>
>> another interesting thing about my coil in particular, Because I am
>> basing it on Steves DC design, but optimizing the parameters, I can
>> pretty much assume that the tank cap will be fully charged on what
>> ever time scale I want it to be charged on. meaning that I can pick
>> my BPS to be what ever I want and still achieve the maximum bang
>> energy, assuming I have the current to push the system of course. I
>> am designing for 600bps because that's the maximum my gap will be
>> able to push. Hence my heavy interest in the RMS current, because
>> that means a huge difference in price of the MMC. Its will all be too
>> expensive for me anyway and I will be making my own poly caps in the
>> end. But its been an interesting and knowledgeable exercise thus far,
>> so I might as well keep going. FOR SCIENCEEEEEE!!
>>
>
>
> I don't know how much you consider your time is worth, but it's unlikely
> that making your own poly caps will work as well as either surplus pulse
> caps or a MMC. Making the rolled poly cap isn't all that hard, it is
> somewhat time consuming. Although, scrounging appropriate materials is
> harder than it seems. It's not like you go down to the supermarket and
> buy aluminum foil and cling wrap. The archives are full of stories
> about where to get the right plastic in the right thicknesses, and where
> to find aluminum sheet.
>
> And then there's the whole "how do you attach a wire to the aluminum"
> question. After all, you don't want a nice low impedance, low ESR cap,
> with high AC resistance wiring connecting it.
>
> And the oil fill and pumpout/degassing process. Did I mention the
> inevitable leaking oil?
>
> This all said, making your own capacitors is a satisfying project: you
> DO get to say "I did it myself", and some 15-20 years later you can
> write this post<grin>
>
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla