"PrecisionMachinisT" wrote in message
...

"Chris Lewis" wrote in message
...
According to PrecisionMachinisT :

"volts500" wrote in message
om...

"Joshua" wrote in message
om...
How do I wire up a 480v Single Phase circuit? I'm familiar with
480V
3P but not single. The machine has a preinstalled 3-wire cord, one
of
which is a ground so I'd only be using twom wires.

Also what exactly does poles mean? Like a circuit breaker is
either
1-2-3 poles, is that the same as phase? Thanks.

480 volt single phase is any two phases line-to-line of a 3 phase
480
volt
system. If you had to ask a simple question like that, it would be
in
your
best interests (and possibly others) NOT to be messing with it.
Call
a
qualified Commercial/Industrial electrician.

Poor description--two phases ???

Not really. "Two phases from a 3 phase circuit" is a perfectly
reasonable way of saying it. Doesn't make the resulting circuit two
phase tho. It's single phase. Hint: if you were to scope one hot
relative to the other, it's still a simple sine wave.

Yes, really....

"Two phases from a three phase circuit" would better describe a circuit
connected to a three phase supply through three wires but having no load
across one of the phases.

Hint: our shop has a single phase service at 400 amps, we buss 170 amps of
this to generate our own three phase power via rotary transformer in order
to supply the machinery.

At any rate, a better description IMO would have been something like " a
two wire service, usually one phase of a three phase supply"

One phase to neutral of a 480 volt 3 phase supply is single-phase but the
voltage is only 277 volt. The OP wanted to know what single-phase 480 volt
was. Chris was absolutely right, whenever 2 phases of a 3 phase system are
combined, the resultant sine-wave is single-phase. (It's called
single-phase because _that's_ what it is.)

On a 277/480 volt 3 phase Wye connected system (which is VERY common and
most likely what the OP has):
Single-phase 277 volt is one phase to neutral.
Single-phase 480 volt is any two phases, line-to-line.

The same is true for the also so very common 120/208 volt 3 phase Wye
connected system:
Single-phase 120 volt is one phase to neutral.
Single-phase 208 volt is any two phases, line-to-line.

Like Turtle said, a single-phase 480 volt load is very uncommon. Usually
you'll see single-phase 277 volt loads (one phase to neutral, very common
for Commercial lighting) sharing the neutral on 3 phase branch-circuits, or
3 phase 480 volt (with no neutral) for motor loads.

One example of a single-phase 480 volt load, though, is Commercial parking
lot lighting. While 277 volt for parking lot lighting is more common, in
somes cases the light ballasts are sometimes connected single-phase 480 volt
(any two phases line-to-line), when the runs are very long. A 3 phase 480
volt feeder is provided and the load is balanced accordingly. That is, the
first light pole is connected phase A to phase B. The second light pole is
connected phase A to phase C, the third light pole is connected phase B to
phase C, then repeat for each additional light pole.

Another example of a 480 volt single-phase load is a control transformer for
a motor controller. Usually the motor circuit is 3 phase 480 volts, but the
desired control voltage is 120 volts. In that case, a single-phase 480 volt
(line-to-line) control transformer is connected across any two phases of the
feeder (properly fused, etc) and steps it down to the 120 volts.

Like others have stated, I'd like to know what the 480 volt single-phase
load is that the OP is talking about. If I were to guess, I'd say something
with a heating element. That's why I told the OP to call a qualified
COMMERCIAL or industrial electrician, because if the load is really
single-phase 277 and he slaps 480 single-phase on it, it's toast. Plus
there are other, mostly safety issues, that he probably isn't aware of.