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Re: Crowbar installation

Subject: Re: Crowbar installation
From: M.J. Gregory <m.j.gregory@talk21.com>
Date: Fri, 17 Jan 2003 16:10:30
A further thought is that it might have been old stock.  Electrolytic
capacitors that have been on the shelf for a long time (say more than two
years without power being applied) should be "re-formed" before use to
reduce the chance of their blowing up.

While there are re-forming rigs, the process essentially consists of putting
a resistor in series with the capacitor to limit the current and applying
the working voltage.  I do not have any specific values to hand, but I would
expect 100 to 500 ohms to be sufficient.  There will be an initial rush of
current to charge the capacitor, but this should rapidly drop to zero --
continued flow of current indicates leakage that should reduce as the
capacitor plates re-form.  It may be necessary to leave the voltage applied
for some miles to make sure that re-forming is complete.

Failing that, ensure that the capacity you have is from new stock.

Fly safely

Mike
Europa Club Safety Officer
m.j.gregory@cranfield.ac.uk

-----Original Message-----
From: forum-owner@europaclub.org.uk
Subject: Re:  Crowbar installation


Hi,
 Just a thought, you may just check that the capacitor is connected in the
correct polarity..when I studied electronics we had great fun blowing these
up simply by connecting the polarities the wrong way and applying a little
current.

Regards

Simon



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