RE: [CAD_CAM_EDM_DRO] Re: ELCB Issues

Just to clarify what could be ambiguous wording, The ELCB is looking for
a difference between current that flows on the live conductor and the
current that flows on the neutral conductor.
If some part of the circuit has a connection between neutral and earth,
it will not normally conduct appreciable current because neutral and
earth are theoretically at the same potential and the ELCB might not
notice. If, as the relay contacts open, the neutral contact opens
slightly faster, *all* the current will now flow through the alternate
path to earth until the live-conductor contact also opens and any arcing
is quenched, up to 1/120th (1/100th at 50Hz) of a second. The ELCB is
made to trip on only a tiny difference between the live- and
neutral-conductor current (only a few milliamps), and here you are
giving it an imbalance of several amps for a few milliseconds, probably
enough to trib the breaker.
As Lester (and perhaps others) suggested, the cure is to ensure there is
no path between the neutral supply line and earth. It does not
necessarily have to be a low-resistance DC path, even a few k-ohms (or
the equivalent capacitance at that frequency, a few microfarads) would
do it.
-Kevin Martin

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Lester Caine
[...]The ELCB is looking for a difference in current that flows between
the live and neutral.[...]