| On 3 phase there is no neutral. You have L1, L2, and L3
That's not what I've seen.
| On the American 110/220 0r 115/230 system there is NO neutral current | on a 220/230 volt load, and a straight 220/230 volt device will run | without any problems on only the L1 and L2 (black and red) wires.
And there is no connection to a neutral wire, either. His compressor doesn't need any neutral. It does need a ground for safety.
| Electric heating units run this way, as do 220 volt motors not | requiring a magnetic starter.
Of course.
| Some compressors will require 3 wire plus ground because they either | use 110 volt heaters on the starter switch, or use 110 volt pressure | control switches to activate the magnetic starter (contactor) to start | and stop the compressor according to tank pressure.
Then they need a "neutral".
But, IMHO, it is dumb to design it that way. If the compressor needs
240 volts, then other parts should be made for 240 volts, too. It's not like they can't design such parts for that voltage, else they'd not even have them at all in Europe.
| Most of these compressors will be larger than 20 amp, and ALL of them | will be hard wired, so are outside the realm of this discussion.
Why would the have to be hard wired?
| In the north American system the "neutral" is "bonded" at the panel, | and a separate "ground" or "bond" wire is connected to both the metal | outlet box, the frame of the receptacle, the "ground" connector, and | from there, the case or chassis of the connected device. | This is a "safety ground". The maximum voltage from any live conductor | to ground is the nominal syatem voltage of 110, 115, or 120 volts. If | either line conductor shorts to ground the breaker/fuse trips. | On a 220 volt line code requires the breakers to be "tied" so if one | trips, they both trip. On a fused panel, code requires the fuses to be | in ganged removeable fuse blocks, so it is impossible (or at least | much less likely) to accidentally remove one fuse, leaving one side of | the device live. If, as is often the case, only one fuse blows, there | is still the danger of having a device that does not function, but is | still "live" with 110 volts. | The same fuse blocks are generally also used for "split" receptacles | for the same reason, with one half of the duplex receptacle connected | to L1-N and the other L2-N
So I've seen nothing that supports your statement that 3 phase has no neutral. 208Y/120 sure does. The lights would not work if the neutral is gone. You must be thinking of corner grounded delta.