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Re: [TCML] Capacitor differences
Right, thanks. I think you're looking the minimum voltage and not the 2kV and 3kV specs.
Since I'm looking to minimize costs, would I be better off looking at something like a single Maxwell 37667 cap rated at .030uF, 35kV and 25kA peek? Seems cheaper than an MMC.
Best Regards,
Miles
Sent from my iPhone
On Apr 23, 2010, at 2:27 PM, Steve Ward <steve.ward@xxxxxxxxx> wrote:
Your peak current calculation looks right (545A), but the RMS in this case
is not just simply the Ipk * 0.707 (that only works for continuous signals),
its actually much harder to derive because it depends on break rate and the
time it takes for the primary current to ring down.
If i had to guess, the RMS current in your situation would probably not
exceed the capacitor rating to a degree that is dangerous for short runs,
but in general it will be 10's of amps for a coil like yours.
Also, maybe you grabbed the wrong Ipk values from the datasheets, i see 432
and 216A for the 942 and 940 respectively. The proposed 940C bank thus has
an Ipk rating of 648A, and Irms of 30.3A, which sounds like a pretty safe
margin to me.
Steve
On Fri, Apr 23, 2010 at 10:43 AM, Miles Mauldin <teslamiles@xxxxxxx> wrote:
Hi Steve,
My plan was to use 3 strings of 15 each of the 940C30P15K-F to get to 30nF,
at 45kV. I am using 3 NSTs of 12kV/30mA each in parallel (90mA). If I have
done my math correctly I come up with 545A peak, 385A rms using 29uH for L,
30nF for C and 16970V for Vpk.
3 Strings of 15 each 940C would be 177A pk and 8.1A rms
3 Strings of 15 each 942C would be 231A pk and 8.4A rms
Looks to me like I would be stressing the 942C series as well. Or is this
ok for short (a minute or two) runs?
http://www.cde.com/catalogs/942C.pdf
http://www.cde.com/catalogs/940C.pdf
________________________________
From: Steve Ward <steve.ward@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Fri, April 23, 2010 10:24:58 AM
Subject: Re: [TCML] Capacitor differences
I think the problem is that very few coilers actually figure out how to
spec
their capacitors, and stay within the component ratings for peak current.
I
too use the 940C series on my solid state systems, but im careful to mind
the specs that the manufacturer gives! Yes, the 942C series handles more
peak current, the datasheet says it, nothing to figure out there! Dont be
surprised when your caps break because you exceeded the current rating.
Ipk = Vpk / SQRT(L/C)
Is that so hard?
Steve
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