[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

MMC Capacitor voltage - How long will they last???



Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

Somebody IS finally doing something :O)

http://hot-streamer.com/temp/GreatCapTest-003.jpg

http://hot-streamer.com/temp/GreatCapTest-002.jpg

http://hot-streamer.com/temp/GreatCapTest-001.gif

Cheers,

        Terry




Hi,

Somehow, someday, somebody, has to do something... :-))

Probably the "last unknown" of MMCs is how long the (CD 942C20P15K) will tolerate say 60Hz at 2000Vp-p....

Maybe do a bunch of different voltages to make a nice graph of 'lifetime vs. over voltage'...

That would tell us all we still want to know...

Cheers,

        Terry



One usually overrates the cap for AC use. I suggest Erms x 2 as a correct DC rating, so with your 15 kV AC xmfr, for a near bullet proof cap bank, you want a cap bank rated at 30 kV DC.

If you are using 0.15 uF 2 kV caps in your strings then each 15 cap string would be rated .01 uF at 30 kV DC.

With a 30 mA xmfr you need approx .014 uF capacitance so you cheat a bit and use 11 caps in each string. This gives you a single string rated .0136 uF at 22 kV DC which will work fine with your 30 mA xmfr. You try to avoid a .01 uF match with the xmfr as the cap bank might resonate with the xmfr and damage the xmfr. Going a bit higher usually works very well. 1.2-1.3 x Cres.

Dr. Resonance