Single Phase PS to 3-Phase System

Thread Starter


Joined Oct 14, 2011
I'm just curious, but what exactly would happen if you were to connect a single phase input power supply to a 3-phase source? I suspect the single phase power supply, being rated for a smaller voltage (V rather than V*1.732), would simply overheat and ultimately fail. Does anyone know exactly? Thanks!


Joined Dec 28, 2011
That would depend on the voltage requirements of your single phase power supply and which 3 phase system you are attempting to connect it to.

120/240 single phase with neutral
120/208 3 phase with neutral
277/480 3 phase with neutral
120/240 3 phase ungrounded

There are a couple more out there still in use in the US. If you were to connect a power supply that was 240VAC single phase to a 208VAC 3 phase system, the power supply may still work, though it would be derated some. However, if you connected it to the 480VAC system it would immediately fail, BIG!