VF drives are inherently phase converters. They take 60Hz AC (or 50Hz) and convert into DC. They then turn around and convert that back to AC. Since the inverter is computer controlled and starting with DC, it doesn't care what was coming into the rectifier, and can precisely output whatever phases, frequency and voltage you want.
There is a certain economy of scale when it comes to this; VFDs are already mass produced, so it's often cheaper to adapt. Another common source are big UPS systems, which work the same way- only difference with a UPS is that there's a big battery bank attached to the DC bus. Which you'd just not install if you didn't need it.
The advantage here (using the UPS as an example) is that regardless of what's happening on the input- 45Hz 300V or 65Hz 600V (and I know one place where the line voltage DOES vary like this... grr...) that UPS will be pumping out pure, clean, 480V 60Hz.
I mention total harmonic distortion, because the rectifier is a switched power supply, and a big one, which is non-linear; the input power to the 3-phase rectifier looks more like a rectified 180Hz stepped wave than a 60Hz sine wave. As such, the current profile tends to be highly harmonic (EG, a lot of 60Hz, 300Hz, 420Hz, etc). The harmonics on a 1-phase input will have different harmonic frequencies, but the result is much the same. If the current draw is small, it matters little, but if that rectifier represents a large portion of the building load, voltage drop will cause the voltage to fluctuate the same way, and this can cause issues. It's even worse if you're coming off a generator, as the generator isn't as capable of coping with these frequencies as the utility is. So, if you have a model with a high THD (13-33%, sometimes higher), you can put on an input filter to reduce this to 5-7%, which is generally OK.
Also be aware that if you ever use this on a 3-phase wye circuit, you'll need a 200% neutral due to the triplen harmonics. Normally, the neutral just carries the imbalance, and the worst-case is a 100% imbalance, at 100% RMS load. For switched power supplies, though, it's not a sine wave, but a stepped wave- the current never drops to 0, it simply goes from high current one way, to high current the other, with harmonic current on top of that. IIRC, it works out to a theoretical max of 166% or so, but the cables don't deal with higher frequencies as well as with 60Hz (more skin effect), so a derating factor applies. 200% neutral is common.
Rotary phase converters are simple motor generators- quite literally an electric motor driving a 3-phase generator. There are pros and cons (moving equipment to break and maintain) but they're quite effective as well.
