leakage of caps... ->and madness

[Martin Czech]

I forgot:

I had to work in a high voltage lab during my university years. 1MV
and more. Now, you are not allowed to work allone (for obvious reaons).
You need a supervisor.

One thing to get the supervisor mad was to get your hands to short on
the earthing bar, ie. to near to the object to be earthed, before the
hand protector.

But you could really make them mad if you ommited the short clamps on the
high voltage caps (1m long, 20cm diameter cylinders).  Because of the
"memory effect" of the molecules in the dielectrica caps can magically
recharge hours after beeing discharged, which is a deadly danger. So a
short clamp across the  terminals is absolutely required. But this is
of course uncomfortable and after a while you'll leave it away.

No "elementi piccoli piccoli", all this gear was heavy, solid metal, about
1m long, and the connections were made by 6mm bolts and nuts minimum.
The Faraday cage arround it was at least 4mx4mx4m.

So , just fixing some capacitor and resistors could really make you
swaeat.


Especially nice was the grounding gear: Pure copper belts, 1cm thick
and 10cm wide, it felt like pulling a large rope...

But it was great fun, especially when the clouds of smoke lifted...

But not only such monster equipment can give you shocks.
Tiny stuff can also recharge, it is enough to give you a helluva shock.
For the same reasons caps don't like rapid discharge. Use always enough
resistance to limit the current. Otherwise the dielectricum could be damaged.

Do your EMI filter caps have some resistance to discharge?
If not they can teach you if you pull the plug and touch the
electrodes with your hand. Quite painfull experience.

m.c.