[AMPS] Grounds

[Peter Chadwick]

Mauri says:

	>The differential switch is actually placed between a local ground point

	>and the neutral wire, 

Interesting. We use to have that system in the UK, but it is no longer allowed.
These were called ELCB - Earth Leakage Circuit Breaker - popularly called
'voltage trips'. These days, we have 'current trips', which work on the basis of
live and neutral currents differing by more than 30mA. These of course give
interesting problems when providing filters for screened rooms, where the
capacity is such that there's 1 or 2 amps flowing from live to the ground, but
not from neutral because neutral is at ground!

There was an approach sometime back that used a phase detector to allow large
capacitive loads from live to ground while tripping on very low resistive load
currents, but I don't know if it ever went into production.

73

Peter G3RZP


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