Original poster: Sparktron01@xxxxxxxxxxx
Dan
(Terry: OT shield UP)
I must disagree with your contention about neutral not being a 60Hz AC
return path. With single phase AC power, neutral is the "grounded
conductor" (current return path), and the ground bond (bare or green wire)
the "grounding conductor" (Definitions courtesy of National Electric Code).
The neutral current in a _balanced_ three phase feeder (Y connection
assumed) will tend to zero with a balanced load, however, if there
are any odd order harmonics, the triplen frequency currents will
vectorially ADD.
There have several cases in the literature of data processing centers
catching fire due to overloaded three phase neutrals from harmonic
current content.
I am aware of one case in a manufacturing location I supported; that a
120-208Y lighting feeder nearly caught fire, due to harmonic content from
florescent lighting on the entire floor of the factory. Aluminum conduit
was at least 140 deg F (caused minor 1st degree burn to a unsuspecting
employee).
(OT shield DOWN) :^)
Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA