[Amps] *** SPAM *** Re: Safety grounding - was Mains Isolation Transformer

[Peter Chadwick]

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