[RFI] Off Topic Request for Info

dgsvetan@rockwellcollins.com dgsvetan@rockwellcollins.com
Thu, 2 May 2002 13:32:38 -0500


Is your office/factory fed with 3-phase power?  It is possible for one
phase to have surges and spikes while the others are minimally affected.
(With 3-phase, the standard 120 V, single phase wall receptacles are
(usually) fed by a 120/208 wye-connected transformer.)  If power is single
phase (fed via the usual 120-0-120 volt transformer, as in a house), it is
still possible that something caused big transients or arcs that affected
only one side of the transformer.  However, that "something" would likely
be directly powered by the same side of the transformer.

Assuming that you do have 3-phase power, some interesting things can happen
when 1 phase is lost and there are large 3-phase loads, such as big motors,
on the line.  I have witnessed the surge effects under such conditions,
which have, in most cases, been caused by construction activity accidents
that damage one phase of the main feeders, wreaking havoc on many of the
connected loads.  The sequential blowing is interesting - perhaps someone
else has seen that effect before.  I have only witnessed simultaneous
blow-ups.  Let us know what you learn.

73, Dale

Terry Dunlap <kk6t@joneslumber.com>@contesting.com on 05/02/2002 12:48:19

Sent by:    rfi-admin@contesting.com

To:    rfi@contesting.com

Subject:    [RFI] Off Topic Request for Info

Please excuse the off topic message but this seemed like the best
reflector for my question.

All our workstations are on UPS's.  Yesterday I watched in horror
as all the UPS's on one circuit started blowing one by one moving
down the line in sequence.  By "blowing" I mean arcing and smoking
from what I assume to be the power supply.

The power company (S.C. Edison) and the electrical contractor we
use are investigating but at this point haven't volunteered any info.

One thought was that it was a large voltage spike but that raises the
question as to why only the one circuit was affected.

I would appreciate any thoughts you folks might have as to the cause.

73 de Terry KK6T

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