What determines a low leakage capacitor?

[John Larkin]

On Mon, 20 May 2019 13:48:32 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

John Larkin wrote:
On Sun, 19 May 2019 22:33:00 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sun, 19 May 2019 14:01:19 -0700, John Larkin wrote:

Big oil or film metal-can energy-storage caps are usually shipped with a
bunch of bare wire shorting the screw terminals. This prevents killing
customers.
Those are typically quite low F value caps, though. Not much energy can
be stored in them. In any case, why not just send them out uncharged?
Seems the obvious thing. :-/

A serious energy storage cap can store kilojoules, or 10s of kJ. 10
joules is considered to be leathally dangerous in some places.

Discharging 100 joules is an impressive event.


There are some effects that cause capacitors to develop
bothersome charge even after having been discharged.
One is dielectric absorption, sort of like charge hiding
away in nooks and crannies for a while, before coming out
again when you least want it. Another is the slow
accumulation of stray free charge. That's probably self-
limiting.

Anyway, it's safer to ship big capacitors shorted. I've
had some nasty surprises in cases where this wasn't done.

Jeroen Belleman

General Atomics makes some impressive caps, like 50 kJ at 44 kV. What
would one use to discharge one of them?!

NIF uses 4000 film caps that store 85 kJ each.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics