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Re: NST and GFI ?
Hi Ed, Chris, all,
> Original Poster: Esondrmn-at-aol-dot-com
>> << Original Poster: CTCDW-at-aol-dot-com
>> GFI protection is generally NOT considered a good
>> thing for coils..I have actually been able to run my coil
>>(15/60) from a GFI outlet, but I think that is the
>>exception, rather than the rule.
> Chirs,
> That's good. Heck, I have an old refrigerator out in the
>garage that won't even run off of a GFI outlet. Too much
>leakage current I guess.
Having posted this before, I still CANNOT find a single reason
why a coil canīt be powered off a GFI outlet. I run my coil off
a GFI outlet, too, and have never set the GFI off due to coiling.
Using a NST that encorperates a GFI internally is another thing,
esp. if the GFI checks the secondary side of the NST (as some
German units, that I have seen, do). This wonīt work, but on the
low (mains) side, I see no way that a normally operating TC will
trigger a GFI.
A GFI does nothing more than to check that voltage *coming* from
Ph is returned properly via the N line (and not via Grnd). It does
NOT measure the voltage ON the ground line in any true way.
I have a 3 phase 380V/40A/30mA GFI in my shop and basement
house wiring. I always power my TC from this part of the house
and my GFI has never tripped because of a running coil. It really
shouldnīt either. Why? Well the GFI is designed to trip under two
circumstances:
a.) fault current from N to Grnd.
Although usually residing at the same potential, it is possible
(doesnīt hold true for U.S. residential wiring, as there is no
three phase wiring) that N may actually float above "zero"
volts, esp. if R-S-T (3 ph.) arenīt loaded equally, which is
why you donīt want a short between N and ground.
b.) fault current from Ph to Grnd.
Quite obviously, you donīt want to "raise" the potential of
the ground line and this isnīt the way the current should
(the GFI thinks, ooops, some has his fingers on the wiring
and trips) flow. Like when some gal insists on using a
hairdryer IN the bathtub and then drops it into the
water ;o)
It should NEVER trip, when the current flows from Ph-N,
which is exactly what we have in a TC circuit. There (should)
NEVER be any current flowing from Ph to Ground in a TC,
as there is NO direct connection bewtween Ph and Grnd. In
other words, the secondary is (AND should be) completely
isolated from the mains wiring. Once via the primary and
secondary and once via the HV xformer. The fact that you
are (esp. if you donīt use a dedicated ground) "nailing" a few
hundred kV into the ground canīt trip a GFI, because there is
no relation to the mains phase and this is the only thing that
the GFI really tests.
Personally, I feel a little *safer* with a GFI, because it CAN
and SHOULD trip under the following circumstance:
a.) As I coil outside, it enhances the safety, if I ever should
get *caught* in the primary (i.e: mains) wiring of the HV
circuit. Of course, it wouldnīt help me on the HV side of the
power circuit, as this is, once again, isolated from the mains
part via the xformer.
A GFI COULD trip under the following circumstance:
a.) You get an arc from the secondary to the primary (not the
strike ring) and this overvolts the HV secondary of the
transformer, which in turn arcs to the primary winding of the
xformer (aka back to the mains). However this is highly
unlikely and IF it does happen, youīll need to worry about
more than just a tripped circuit breaker or GFI ;o(((.
Coiler greets from Germany,
Reinhard