While all the small home shops are dying to get 3-phase, instead of using
converters and VFDs, you have it.
If you have 3-phase, then you already have single-phase.
If it's delta, pick any two power pins (NOT ground!), and get 240 single-
phase. If its Wye, pick any two power pins (NOT ground!), and get 208
You don't get 240V single phase from Wye service without a boost
You need to know which service you have, but it's easy to determine with
a resistive load (like a 240V incandescent bulb, or two 120V bulbs of the
same wattage in series) and a voltmeter. Just apply the load across any
two power pins, and check the voltage.
If it's 240, you have delta service, if 208, you have Wye service.
Does your machine need to have a neutral lead to run 120VAC
subsystems (like coolant pumps or lamps), or is it a pure 240VAC load?
If it is a pure 240 VAC load, then pick any two of the three
phase leads and you will have 240 VAC between them. (Of course, be sure
to have the safety ground connected, too.) If your three phase is
open-delta then two of the phases are real, and the third phase is
virtual, so be sure to pick one of those two phases. Usually, I think,
you will find that one end of the two real phases is grounded, but if
there is also a setup to give you 120 VAC as well, then not so.
If you need a true 120 VAC neutral, you probably have problems,
unless you have a step-down transformer to run the 120 VAC loads.
For three phase, you could have either of two different
connectors, BTW. One (with only safety ground and no three-phase
neutral) will typically have four pins arranged in a circle (for
twist-lock connectors). But if there is a three phase neutral *and* a
safety ground, there are connectors which have the four pins in a circle
and a single round pin in the center. In that case, the round pin will
be the ground, and one of the four will be the neutral.
First -- get a connector to plug into the existing outlet which
you have, and open it up. One of the screws should be painted green
(this is the ground, and should get a green wire from the machine you
are connecting. Then two of the wires from the machine should be black
and red. (White, if present, is usually neutral, but is sometimes used
as a phase when there is no neutral) Usually, you will find letters
stamped near where the wires go in in the plug. "X", "Y", and "Z".
Probably you should use the "X" and "Y" as your 240 VAC. But *always*
remember that you need a green from the green screw on the connector to
the frame of your machine. tool.
Or -- you *could* hire an electrician to run a 240 VAC feed from
your breaker box to where you want your new machine to plug in. If you
feel uncomfortable working with this, an electrician is good piece of
There are Tooo many IFs in the US power system for someone who has to
ask to be told enough to save his life.
The only answer is GET AN ELECTRICIAN :/
In the 240volt world it is generally a no/no to do anything of that
nature without a license ( I would do it but I have survived 80 years
and been fixing things electric for about 65 of those.) :-?
I rest my case. There are so many possibilities in the US.
In Aus the domestic supply is nominally 230/400 volts wherever but many
old installations are still at 240/415 which is not much of a problem.
Any suburban house will have 4 wire three phase 230/400 at the street,
Only those wanting it, Air Con etc will have all three phases
connected, but thats the way it is anywhere.
Of course there are industires with higher voltages and special
On Sunday, October 19, 2014 11:22:35 PM UTC-4, John G wrote:
> I rest my case. There are so many possibilities in the US.
Right, get an electrician to at least look over the job that you did and ca
ll the device/appliance manufacturer to make sure (though they've usually a
llowed for more or less than nameplate voltage input).
Here in the US the NEC (National Electric Code) says to describe voltage at
120V, 208V, 240V, 277v. But manufacturers sometimes round up or down to th
eir specs. Additionally you have peak and off and other factors that result
in getting more or less than the 120v or the 240v that you think you are g
etting. (involving non-North American systems)
Electrically it's pretty simple, but if you're calling a receptacle
(what's on the wall) a plug (what's on the cord), you probably should
get an electrician, particularly if this is a commercial shop where you
have liability issues if you fry an employee.
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