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Re: [TCML] Another MMC question.
Hello Bart -
How were the "temperature rise" values determined for this chart? As a
purely calculated value, it seems like you'd need to know the dielectric
loss factor for the cap, the operating frequency, the thermal mass of the
cap, etc.
Terry Fritz' original test setup used an RF power supply to pump 3.5A at 350
KHz through the cap, and then measured the temperature rise after 15
minutes. Terry's test setup can be seen at:
http://www.hot-streamer.com/TeslaCoils/MMCInfo/GeekCaps/GeekCaps.htm
Terry's formulas for determining the power handling capability of an MMC are
at:
http://www.hot-streamer.com/TeslaCoils/MMCInfo/MMCPower4.html
I'm just curious how the temperature rise info was obtained, for use in
calculating the temp rise for other types of capacitors.
Regards,
Scott Hanson
----- Original Message -----
From: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, December 12, 2007 9:14 PM
Subject: Re: [TCML] Another MMC question.
Hi Michael, All,
I deleted that old MMC Cap Chart. I created another chart in the way "I"
would do it for the 0.15uF CD cap which is so common. The chart is good
only for that cap. I basically added Vp and Temp Rise for a given
transformer type and then added combinations to meet the value for
Resonant, Static LTR, and SRSG LTR.
Basically:
The higher the voltage rating = the better the cap.
The lower the Temp Rise = the better the cap.
For a given NST type, I stopped when the MMC met or exceeded 2.5 x Vp and
if the temperature rise per cap in degrees centigrade was below 2 (when
both conditions were met). In all cases, the temp rise is either "good" or
"excellent". It's the standoff voltage really that is of the most concern
with this particular chart.
Like I've said in the past, I don't use charts, but for those that prefer
a chart to get "as near as possible to stated LTR sizes", this one should
help (and if you can't understand if the string combo is good or bad, then
just ask the TCML). Due to the single cap value (0.15uF), the "nearest"
mmc value must be used. The old chart didn't really explain that. With
this chart, the value you see is the actual value of the mmc. Just
something I noticed while going through numbers on the old chart.
http://www.classictesla.com/download/mmc_cap_chart.pdf
This chart is 60Hz only. If there are "any" 50Hz coilers desiring the
same, just let me know. It's no big deal (but please ask while it's still
fresh in my brain).
Take care,
Bart
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