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Re: MMC WIMA caps -- good or bad?
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To: tesla-at-pupman-dot-com
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Subject: Re: MMC WIMA caps -- good or bad?
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From: Terry Fritz <twftesla-at-uswest-dot-net>
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Date: Sun, 12 Mar 2000 17:39:10 -0700
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Approved: twftesla-at-uswest-dot-net
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Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme
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In-Reply-To: <20000312175121.36876.qmail-at-hotmail-dot-com>
Hi David,
Be sure to see the following if you haven't already:
http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCPower4.html
http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCCALC2.ZIP
The first are the equations to use for designing the MMC so it won't burn up.
The second is a simple BASIC program which helps in selecting the rows and
strings. You will have to change the lines 300 to 330 for your particular
caps.
I have the WIMA book here... The "lead spacing" is 37.5mm on your caps so they
heat at 33.3 degrees C per watt of internal dissipation. Line 305 in my
program should be changed from 40 to 33.3 for these caps.
They are rated at 5000v/uS dV/dT.
My program gave the following for your 0.047uF caps, 15kV transformer, 180mA,
120BPS... I changed lines 2100 and 2110 to "1 to 30" to get more cap
selections.
Break rate = 120
Cap value = 4.7E-08
Strings Caps/Str Capacitance Voltage Temp C Cost
2 3 31.33 6000 71.17 6.00 :-(( :-((
4 6 31.33 12000 17.79 24.00 :-(( :-(
6 9 31.33 18000 7.91 54.00 :-| :-)
7 11 29.91 22000 5.29 77.00 :-)) :-)
--------------------------------------------------------------------
8 12 31.33 24000 4.45 96.00 :-)) :-))
9 13 32.54 26000 3.79 117.00 :-)) :-))
9 14 30.21 28000 3.27 126.00 :-)) :-))
10 15 31.33 30000 2.85 150.00 :-)) :-))
11 16 32.31 32000 2.50 176.00 :-)) :-))
11 17 30.41 34000 2.22 187.00 :-)) :-))
12 18 31.33 36000 1.98 216.00 :-)) :-))
12 19 29.68 38000 1.77 228.00 :-)) :-))
13 19 32.16 38000 1.77 247.00 :-)) :-))
13 20 30.55 40000 1.60 260.00 :-)) :-))
14 21 31.33 42000 1.45 294.00 :-)) :-))
====================================================================
14 22 29.91 44000 1.32 308.00 :-)) :-))
15 22 32.05 44000 1.32 330.00 :-)) :-))
15 23 30.65 46000 1.21 345.00 :-)) :-))
16 24 31.33 48000 1.11 384.00 :-)) :-))
16 25 30.08 50000 1.02 400.00 :-)) :-))
The program recommends 7x11. I set the cost at a dollar each so your 14x21
array will cost 3.8 times as much as the recommended size. Your 14x21 array my
be too over designed but to each their own. I use the DC voltage rating for
the peak Tesla coil voltage rating and anything above a 5C temperature rise is
getting risky.
Cheers,
Terry
At 12:46 PM 03/12/2000 -0500, you wrote:
>
> I am planning to build an MMC array for my TC, I just have to find the
> right caps. So far, I have been eyeing the WIMA FKP1 2000 VDC/700 VAC at
> 0.047 uF capacitors and the WIMA FKP 2000 VDC/ 700 VAC 0.068 uF Snubber
> capacitors at <http://www.wima-dot-com>http://www.wima-dot-com Does anybody know
> anything about these caps? including price, current rating; I plan to buy
> around 500 - 600 of them with one of my friends.
> My setup will be run with 15000V at 180 mA and a regular 120 bps on an 8"
> coil. The cap bank will have 14 strings of 21 caps using the FKP1's for
> .0313 uF, or 10strings of 22 caps using the FKP Snubbers for .0309 uF, both
> rated around 15000VAC. You do think that the current will be divided enough,
> right? I know, I know, I probably don't need that many for my power setup,
> but I'm a perfectionist-- better safe than sorry--, or something.
> Any pointers or info about these caps or any others that are good will be
> appreciated- happy coiling, thanks a million
>
> BTW- anybody know anything about Elecrocube 950 series?
> <http://www.electrocube-dot-com>http://www.electrocube-dot-com