The best choice you can make when it comes to HV filter caps
are the MP types. These are made from either metalized paper (old types)
or some sort of metalized plastic foil stacked or rolled up to proper size.
These units are not small ! But they are (most of them ) self repairing !
This means that if you get an internal breakdown/flashthrough they will just
burn away part of the metalization around the burnt hole in the foil on the next
restart. The result is a capacitor with a very slight capacity reduction.
To do this you need a transformer/ rectifier combination with a low internal
resistance to be abble to supply the necessary "burn" current. Most good
PSU designs will handle this. (disengage soft start in this case..)
In service the stored energy in the cap is usually sufficient to do the "burn"
immediately
on fault...and all you will notice is a little power " glitch" unless you have
very fast
protection circuits.
I have two of these units marked "Bosch MP " in an old homebrew amp i made here
a long time ago.
They are 4500V 8uF units. Cylindrical metal cans abt. 12 inces long and 4
inches in dia !!!
Fitted with HV ceramic connectors. Also marked "tropenfest" ---meaning rated
for
tropical conditions in temp and humidity.... They are virtually indestructible !
If you ever come across something like this : Grab them and keep them !! They
are pure gold for
any HV PSU builder !
Peter
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|