21 Jun
2005
21 Jun
'05
10:09 a.m.
On 21 Jun, 2005, at 12:35, Ethan Dicks wrote:
On 6/21/05, Paul Koning <pkoning at
equallogic.com> wrote:
In Norway, you will not get mains-powered devices approved unless the
chassis is isolated. Our AC wiring does not have any concept of
"neutral", since both wires are supposed to be at the same potential
relative to ground. That way, everybody learns to be careful.
I can see the economics of using four-wire Y-connected three-phase
transformers instead of three wire plus earth delta-connected, but I
have also seen the frying potential when some genius takes for granted
that one of the power wires is supposed to be at ground potential.
The isolation transformer is your friend. Especially when it is also
cleaning spikes and flywheeling over dips.
--
-bv
If your boxes are plugged into grounded outlets,
as they should be,
then there should NOT be large currents flowing through frame ground
cables. If you do observe that, track down the fault before someone
gets hurt.
The key word is "should"... If you get some ya-hoo who decides they
can save a few $$$ and wire up an outlet... well... let's just say
that the first homeowner's tool I bought was an outlet tester, and I
found two outlets that had hot and neutral reversed...
I worked at a place where the owner plugged a serial cable in between
his PC and his Mac, and he roached the Mac serial port because of the
same problem. He had all the outlets tested and fixed, but he also
made a proclaimation - no computers were to be connected via serial
cables unless they pulled their power from the same wall outlet. A
bit inflexible, but guaranteed not to have a mismatch.