Improved - MMC Capacitor Power Calculations
I was helping Chip design a MMC cap for his coil and I discovered that my
power calculations had two problems.
The first was that the temperature was proportional to BPS^2 instead of
The second is that a non sync gap only delivers half the power of a sync
gap due to the "beating" effect. That is actually a pretty significant
thought!!. Since a non sync gap spends a lot of time firing at less than
optimal voltage, the system power is cut in half!!
Since Chip wants to run at 1000 BPS(!) these problems showed up right away.
I have reworked and somewhat simplified the calculations. I now find the
energy in each cap and find how much of that goes into cap heating. This
requires that one know the primary circuit resistance (which few do) but
just use three ohms and you will be pretty close. The improved
calculations are at:
At 08:40 PM 7/1/99 +0200, you wrote:
>Hey, that was nice, I was just about to ask you, how to calculate RMS
>I arrive at 6.97 degrees, with 300 BPS.
>I can see now, why it is *bad* to get smaller than standard housed
>The standard 22 nF /1600 VDC 376 cap is 27,5 mm leadbase, but mine which
>came out of a special cased order for another company, is 22,5 mm
>spaced. So otherwise the temp rize could have been only 4,16 degrees,
>earning an "excellent" in reliability.
>But I don`t think my cap rises that much in real life tesling, will
>measure it this weekend.
>I don`t worry, couse I think that electrical things that don`t blow up
>within the first minute, or so, will probably last forever :-)
>Thank you for this great post!
>Tesla List skrev:
>> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>> Hi All,
>> I have posted a draft set of formulas and calculations describing
>> design MMC caps for various power conditions. This shows how to calculate
>> how hot MMC caps will get given various parameters. I would like anyone
>> interested to check this over and make any suggestions. The Irms
>> calculation and tables may need some adjustment. I took the data from WIMA
>> but they should hold true for most similar types of poly caps.