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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
Philpem knows some people who tried this and found some capacitors are excellent but others can and will fail in this application due to inferior manufacturing. The cheap "1F" ones have too high internal resistance and you'd need to use about 20 of them in parallel to get any useful current.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
I was looking at using Super-caps in my 45v (rewound)MOT power-supply (4 MOTs, 2 parallel, 2 series on the primary, 4 series on the secondary) I have some 600f caps but the internal resistance was so high, once I had put them in series, the resistance would have caused them to dissipate an unacceptable amount of energy, saying nothing about the charging current which would have been several hundred amps, blowing fuses and rectifiers all over the place. Of course, if you have a peak voltage of less than 2.7v, the R(i) matters less, however you still get very high (and prolonged) charging currents
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
Well these 2500F maxwell capacitors i have shorted out 4 in series and made the 50mm2 wire i was holding in my hand untouchably hot while the capacitors were stone cold. so i think that they are just fine :)
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i used to make ultra/super caps in high school, back in 1997 they were way to expensive to buy. but we learned the plates and the Helmholtz layer can still be destroyed in short circuits, seeming to be fine, later revealing a failed cap.
modern ones are better, but still its a roll of the dice if its not in the datasheets.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
I calculated that in fact 18 off the shelf CCFLs with the gnd returns tied together with 2k2 balance resistors would with additional work (cough 2 stage CW inverting multiplier /cough) power a magnetron for my HTSC work. Much easier to control, and instant on/off with no overshoot.
DIY 12V microwave would be cool although 18V@9A would be pushing the diddy little 2SD965s near their thermal limit with some heatsinks this would be just as reliable as the Panasonic inverter but 1/2 the size.
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