Another MMC cap candidate (UK)
I just tried out a string of the 0.047uF 1500V DC caps
in parellel with my existing 0.067uF cap.
The transformer is 8KV DC, 250mA
The coil frequency is 200kHZ.
I started with 8 in series no problem, went down to
6 and ran for over a minute with no apparent heating.
I then tried 5 but I stopped the run when I thought I
saw a flash from one of the caps - no apparent damage though.
The caps are film and foil polypropylene, axial construction.
pulse rated at 2000 V/uS.
Made by LCR, available from Farnell (code 106-372)
5+ 46p (70cents) 25+ 40p, 100+ 35p, 500+ 32p
I'm also using 10M equalising resistors, rated for 2500VAC (.5W)
metal glazed. 10+ 16p, 300+ 11p,
Farnell code (341-850)
I'm probably going to use 8 in series for safety, and build 2, 8 by 8 caps
I'll put off purchasing these in case any one has ideas on
how to get them cheaper.
I've got some large single sided copper clad board, is it a good idea to
build the cap on a PCB, I can have a one inch gap for each capacitor,
and give an inch and a half width of copper for the buses at each end.
I'ld also give it a couple of coats of varnish to discourage ionisation
on the edges of the copper tracks.
Alan Sharp (UK)