[Prev][Next][Index][Thread]
MMC Cap Dissipation testing...
Hi All,
I dissipation tested three more MMC caps tonight:
0.047uF 1500V Arcotronics capacitors "RS" from Richie Burnett
2.5 amps RMS 350kHz 2.2 degrees C
0.022uF 1200V Panasonic Q-E?? from Bill Noble
2.0 amps RMS 350kHz 4.8 degrees C
0.056uF 1600V Phillips 376 KP/MMKP HQ from Finn Hammer
3.5 amps RMS 350kHz 1.5 degrees C
I also retested my Panasonic with my more refined setup of today
0.056uF 1600V Panasonic ECW-H16563JV
3.5amps RMS 350kHz 3.1 degrees C
It seems like the caps with the larger packages run cooler. This is
probably due to them being a bit more insulated or perhaps they just have
more surface area to dissipate heat. I suspect a small fan blowing on MMCs
could really help especially if they seem to be getting too warm normally.
In general, I think running such caps at 10C above ambient is "safe". 15C
is getting risky. The temperature is proportional to the value and
proportional to the square of the current. Finn's caps can take almost 9
amps RMS safely which could do some NST coils on only one string! However,
my Panasonic caps at 6.3 amps RMS are not really that far behind. So it
looks like all these high power caps are fairly close to each other. This
is great because it shows that many manufacturers caps will work giving us
a great selection to choose from. I would say the important MMC cap
parameters are as follows:
1. Polypropylene is the ONLY acceptable dielectric
2. "Self healing"
3. 1500-2000 VDC rating The ~630VAC rating is immaterial
4. High-energy, pulse-discharge, high-dI/dT, high-dV/dT, or good
continuous end/lead attach is a must.
5. 0.05 to 0.10uF seems to be the best range of values-all things considered.
6. WIMA, Phillips 376, and other relatively large potted styles seem to
run a bit cooler.
Cheers,
Terry