The short answer is no. At least on some of the newer Dell PowerEdge servers. There are some places online where it sounds like it may work with certain servers.
If you are running on 120v and then plug in a 240v line on the second PSU, the PSU light flashes 3 times and then stays off.
From the iDRAC we can see that one PSU Input Line Type is Low line (120v) and the other is High line (240v)
As a side note, the Input Wattage is different because we can pull more watts from a 240v line. Watts are Amps X Voltage, so halving our voltage, halves our total wattage.
Looking through the Lifecycle Log we see the following saying that the PSU is disabled because of a input voltage mismatch.
Being able to turn a server power supply on without having it plugged into the server can be super beneficial. You can use it to power electronics like GPU’s and they are usually really cheap.
The Instructions are for an A930P 930W server power supply. More detailed information is available at the following couple of links.
To power on the PSU, wire the pins highlighted with Blue and Green
The two pins highlighted Orange will slow the fan down.
Or by using the numbering from the picture below.
Wire pins A1 to B1 and Pins B6 to D6.
Fan is pin B2 and can be wired to B3 to decrees the fan speed to make it quieter.
You can now run stuff off of the 12 volt output.