U.S. 240v to Europen 220/240v conversion

joztheshark · Dec 8, 2020

Hello, I'm in the U.S and most of the information I'm finding is about 120v to 240v and vice versa. My question is about 240v to 220/240v conversion.

I bought a Chinese CNC machine (hasn't arrived yet) that works on 220/240v and it comes with an European style 2 cylindrical prongs connector. One is Live/hot and the other is Neutral. The manufacturer said it works with 60hz and it uses 12amps.

I want to connect it to a 240v U.S outlet so I was going to change the plug to an American style 240v plug but I know that the U.S. uses two 120v wires to make 240v instead of one hot 220/240v wire and one neutral. How would I rewire this?

The shop where I'm putting the machine hasn't been wired yet and an electrician is coming to install breakers and some 120v and 240v outlets. Would it be better to install a 20 or 30amp 240v outlet?(the 240v breaker would be dedicated to this machine only) Do I have to use some kind of 240v to 240v transformer to use with this machine? would it be better to use a step up transformer from a 120v outlet? do these transformers provide only one 240v connector and one neutral? I can rewire the machine from the inside and I'm attaching some pictures the manufacturer sent me where they point to the hot and neutral wire connectors inside the machine.

I need some help and thank you in advanced.

R-fur · Dec 8, 2020

You are correct to be careful here. I believe american supplies at 240V use a centre tap to earth with 2 120V outers. The rest of the world is usually 230V with one end earthed as the neutral. You would need the manufacturers drawings to decide the best way to supply it. Usually European sockets are not polarised, but I would double check anything from China.

Lucien Nunes · Dec 8, 2020

As you mention, European 2-wire 240V single-phase consists of a grounded neutral and a 240V hot, but US 2-wire 240V consists of two 120V hots. Because the voltage is correct, the machine will almost certainly function on a US 240V supply. You don't need the neutral from the outlet / panel, just the two 120V hots wired to the machine hot and neutral. If the machine is designed to operate with unspecified polarity (which it should be for Europe) then the fact that neither wire is at ground potential should not be an issue. I would definitely get that approved by the manufacturer if possible. As you also mention, it is possible to use a 240-240V transformer to create a dedicated European-style 240V supply with one wire grounded, but this would be a needless expense if the manufacturer approves of direct hookup to 120-0-120.

There might be safety or code compliance implications though, if the machine was not made for sale in the US, the approvals might not be recognised. If it is for use in a business that could be important.