My Norcold DE-704 with the swing compressor has an input of 12 vdc or 120vac.
The 12 volts runs an oscillator ar 60 hz. and has a transformer shared with the 120 vac with an output from the DC oscillator or the 120VAC of about 24 VAC at 60Hz.
The swing compressor is very sensitive to the frequency of the power going to it.
Many of these fridges don't work correctly because the oscillator has drifted off that 60 hz.
Some of these wont work on 12 vdc or don't work on 120vac.
The advantage of these units is that they don't have a current surge on starting.
The dorm fridges will work on an inverter, but it has to be a fairly large on to start.
I had a 300 watt inverter that would not start a 40 watt dorm fridge
A cigarette plug in inverter about maybe 100 watt or less will run the Norcold on 12 volt easily, but the the thing will run on 12 VDC all by itself.
My long term test on power showed that it averaged about 17 watts over several weeks.
Also the fridge
runs fine on power from the tow car and when stopped the trailer battery
will also keep up easily.
Personally I prefer this to the propane/12/120 unit I had in a 1980 VW Westfalia camper years ago.