View Full Version : 3 Phase Converter Wiring

05-08-2008, 08:47 PM

I just found this forum and I hope you guys can help me with a wiring question.

I have a 3 phase converter and I need a little bit help wiring it to my specific receptacle. I have wired a converter to a piece of machinery before but this one is a bit more difficult and I don't want to screw it up.

The outlet I have to wire is a NEMA L21-30. It's a 5 wire outlet. My 3 phase generator consists of black, red and blue (plus ground - no common). I know I can use the pre-existing ground but how about the common from the single phase (I think I can)?

Below is an image of the receptacle.


How I would wire it would be
X - Black (L1)
Y - Red (L2)
Z - Blue (L3)
W - Common
G - Ground (Existing Ground From Single Phase Power)

Would this be correct?

Thanks in advance for the help!

05-08-2008, 08:53 PM
If you intend using W as the neutral, it should not be grounded as shown, although it is connected to ground in the panel.
Also, the neutral can only be referenced (used) with respect to the two original 240v 1 phase conductors.

05-08-2008, 09:01 PM
Thanks for the quick reply. I think I understand what you are saying but I just want to clarify. I will be using the common (W) from the original 240 and that goes to the breaker panel. That's what you mean, right? Also how about X Y and Z? Does that look right?

05-08-2008, 09:09 PM
Yes, I assume that Y is the artificial phase?

05-09-2008, 05:36 PM
Thanks for the help Al!

I am not sure if Y is the artificial phase. How can I verify that? Also, I made a diagram to show what I want to do.

05-09-2008, 05:44 PM
The two conductors marked HOT go straight through to the receptacle.
How come you need a neutral that way anyway?
If you have any other equipment that uses the neutral. it should be on a circuit of its own, not off the RPC output.
Normally for typical RPC loads you do not require a neutral.
Is the convertor static or rotary?

05-09-2008, 06:34 PM
The converter is a 10HP CNC Rotary and the only reason I am concerned about the common is because that's what the specs say.

05-09-2008, 07:59 PM
I have never seen a RPC that needed or supplied a neutral, unless it was used internally for contactor switching etc.