Re: caps reversed

Andrew,

Reversing the polarity on an aluminum electrolytic capacitor
depolarizes it. That means the ultra-thin coating of oxide (isulator
or dielectric) is de-plated and its insulating property disappears. A
large DC current begins to flow between the foil capacitor plates and
heats the electrolyte between them. The electrolyte fluid begins to
boil, and that creates a pressure inside the aluminum can sufficient
to explosively rupture it should the safety vent not work.

Or: Look at the size of the capacitor. It will explode like a similar
sized firecracker. There will be aluminum foil confetti all over the
place along with a really good spray of corrosive electrolyte all
over the surrounding electronic circuitry. It is a mess to clean up
but the "bang" is fun if you aren't expecting it. Hopefully the can
will miss your face as it flies by at a few hundred feet per second.
Other than that, it's not a problem.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "andrewyslee" <andrewlee@s...> wrote:
> Hi,
>
> Just to remind those using G201 to check that the capacitors they
put
> on terminal 1 and 2. I may have blown 2 3Amp fuses because I had
the
> polarity on the z-axis reversed.
>
> When I switched on the driver, I noticed the LED on the z-axis was
> unlit. Thinking it might be the fuse, I switch fuses on the y-axis
> and the z-axis. Sure enough, the y-axis now is unlit, and the z-
axis
> LED light came on. But the joy was brief, as was the light. It went
> out after approx. 1-2 sec. On closer examination, I noticed that
the
> polarity of the 470uF was reversed.
>
> What is the effect of having the 470uF capacitor reversed?
>
> andrew