AC Drive

VFDs convert the line AC voltage to DC, then fire the DC to recreate an AC output. But the DC voltage it creates from the line cannot be any higher than the Peak voltage of the line. Then because of that limit, the AC output voltage can never be higher than what you can create from that Peak DC voltage. So in general, output voltage cannot be higher than input voltage. The way to deal with it is to use a transformer ahead of the VFD to increase the line input. Simple and clean.

But there are minor exceptions. "Line Regenerative" VFDs, those that have a PWM input instead of a diode bridge, can use their line interactive ability to over charge the bus capacitors just a little bit, maybe 5%. But 400V to 480V is 20%, so even that isn't going to work. Besides, a Line Regen version of a VFD that would have this capability is typically 2X the price of a VFD without it, so a transformer on the input side is always cheaper if you don't need the line regen for some other reason.

Another exception is that in very small drives, as in under 3HP, mfrs can install a "Voltage Doubler" which is a system of caps and diodes that can convert and double the DC voltage ahead of the VFD's own rectifier. I have only seen this in the US market where you want to feed a VFD with 120V single phase and run a 230V 3 phase motor. But as HP goes up, the size of the caps to do this gets ridiculous and a transformer becomes a better option. I have also never seen this done for higher voltages, the capacitor voltage would get extreme.

Thirdly, if you are using a low-harmonic drive such as a 12, 18 or 24 pulse version where you have a phase shifting transformer ahead of the drive, you can use that feature to increase the line input to the drive.