Lou said:
>If both phases A&B are carrying X amps of current, there is no current flow on
>the neutral. <
Only if the two loads have identical power factors. If one is capacitive and
one is inductive, the currents in the neutral won't cancel.
>in which case it would be a dead short which will throw the breaker in a
>fraction of a second<
OK. We have to consider the possible fault current during the time that the
breaker takes to open (or not, sometimes!) Interestingly, there was a Boeing
747-400 had a bit of a problem 10 years ago because Boeing mistakenly fitted a
25 amp breaker instead of 2.5Amp breaker, and the wiring couldn't handle the
fault current. So the fuses in out mains plugs have something like a 60kAmp
fault breaking capability i.e. they can break a fault current of 60kA. They
don't get long to do it, obviously!
73
Peter G3RZP
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