[Phil Allison[_4_]]

John Williamson wrote:

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For the curious - it involves fitting a 25amp bridge in series
with the safety ground conductor. This allow the item to float up
to a volt or so above ground with NO current flow.

The bridge is wired as pairs of inverse parallel diodes and can
cope with a massive fault current if need be until a fuse blows
or a supply breaker trips.

My workbench scope has this scheme fitted inside, for example.



Similar items are sold as galvanic isolators for boats connected to a
shore supply. The diodes in the one I use are rated at 2000Amps for long
enough for the fuse to blow.


** Typical mag thermal breakers trip in under 1mS.

The diodes in a 25A bridge are rated for 300amps for a half cycle or 8ms.

AFAIK, power supply on a wharf is normally 3 phase for medium and large boats.

I guess a single phase outlet is also available with it own breaker.

In any case, diodes fail short, so safely in this case.



...... Phil