Hugh,
Having worked on a seasonal farm with large power demands and five back up generators, I have yet to see a pto generator that outputs modified sine wave power. Also the stator and rotor windings are all spread equally through out the machine, so even if one 120 volt leg is loaded a little more, the bearings carry the same load all the time. – Solar Guy
Hugh Replies: I would have to agree with this statement. I like my pto generator because it simply means one less gas/diesel engine that I have to maintain, and it produces a true sine wave. Most generators that have rotating hardware and rotate at 1800 or 3600 rpm will produce true sine waves. Where this breaks down is when the manufacture tries to save money by developing a generator that can run at various speeds for changing loads. These generally produce three phase AC (like your car alternator) at a variable frequency. This is then rectified to DC and electronically altered into modified sine wave or even square wave generators. That allows manufacturers to save money, bringing you a lower price, but you pay for it by not having true Sine wave.
In our case, we keep a small 2KW generator to power the normal things, like the refrigerator and lighting. When needed, the 15kw pto generator comes out, and we run everything that needs power at once– freezers, deep well irrigation pump, et cetera. This concept allows us to power the high usage items (usually for about 4 hours per day) and yet keep the wear and tear on the tractor to a minimum.