VFD 220v single phase to 380v three phase.

[Voicecoil]

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I have looked longingly at these Ecogoo devices, and I wonder if they actually use a switching voltage boost on the input rather than a simple passive doubler. Also wondered about just putting a chunky transformer plus bridge rectifier in front of my existing VFD but haven't stumbled across anything cheap enough to play with yet.

They ought to if they want to have any chance of meeting the relevant regulations! The circuit in question is a thing called a PFC boost converter, these are used on the front end of most high power switch mode power supplies, but are normally wired to generate 350...400V DC output which is then either regulated down to a lower voltage or turned into 3 phase 220V AC. It's not a lot of work to make one that outputs 550...600V or so which you can make 380/415V 3 phase from.