>
>
> On Sat, May 16, 2015 at 1:39 PM, Harold Hallikainen
> <harold@hallikainen.org> wrote:
>


> >
> Opto
> couplers are one way to get the isolation, but then you have to power the
> > LEDs with an isolated supply. Ideas?
>

I'll probably write this up in more detail sometime, but I had a recent
experience where about 25 VDC managed to cross

a barrier rated at 2000 + or VDC.

When the primary side catches fire so that the isolated IC is incinerated
and an arc forms across the broken primary circuit and then finds a nice
carbon char path into the primary side 'fun things can happen'.  And did.

In my case the isolation device was a hall sensor and had high overcurrent
flowing in it, "which didn't help", but fire anywhere near either side of
such an isolator may bypass the isolation.

Quick precomment: If a Hall sensor is rated at 20A DC and claims tolerance
of up to 5x overcurrent, if a fault current higher than that happens and
the seemed to be correctly current rated, DC operation rated double pole
breaker doesn't trip, what happens next? :-). (A 100A DC arc is fun to see.
Afterwards).



               Russell
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