I've messed with hundreds of different types of drives over the years. I've probably seen more of them than most people that sell drives for a living.
Most of the common modern 3-phase drives have a full wave rectifier bridge that feeds onto a really big high voltage capacitor bank, then a control circuit fires IGBTs or other types of thyristors to turn that DC into an approximated sign wave in the form of a pulse width modulated output. Most of those drives can be single phased on the input because everything goes to DC before being turned back into approximated AC, but as I mentioned, there are a few exceptions. In these drives, your DC buss voltage normally runs around 1.4 times your RMS primary input voltage. As long as your DC buss stays close to that level under load, you can usually bet that your input stage is still good. If the drive dies but the buss voltage is still good, it's usually an output stage repair. If the DC buss is very low or dead, and there are no blown fuses, then it's usually a cheap repair. That's usually a popped rectifier. If a big high-speed electronic fuse is blown (like on a Saftronics or Yascowa drive) then the output stage is usually shorted. Digging deeper than that usually gets complicated.
Some other basic drive designs don't use the DC buss capacitor bank. They just have control circuits that fire thyristors (often SCRs) in time with input phasing to give spurts of direct connection to the motor outputs. These drives tend to not work at all on single phase. I also consider them to be dangerous. My pet name for these "bussless" or "across the line" drives is - suicide drives. When they fail, the failure is often pretty spectacular. Loud noises are often present & pieces of the output stage often go flying. It's kind of like what happens when you connect primary power to the motor side of a regular drive. (yep, I've seen that plenty of times on warranty claims that got denied)
I'm curious where you got your background in drives. You seem to be pretty much on equal footing with modern elevator mechanics & guys that troubleshoot automated manufacturing equipment. ...That's a compliment by the way.
