Originally Posted by brightspark
Why would anyone want to?
I doubt if the components required could be sourced any cheaper than buying a complete unit (nevermind the time involved in assembly).
If anyone wanted to build it as a project, I would expect that they would already have such an understanding of electronics that they would be able to design the inverter themselves.
It can be done without electronics, a 3 phase motor is used with L & N to 2 of the phase connections on the motor and the 3rd phase is generated by the motor itself on the 3rd phase connection. A capacitor is needed to initially start it, and so there is 230v 3 phase produced between the L-N-3rd motor connection. I put one of them in a workshop before, and it also had a step up transformer from 230v to 400v. Different size capacitors were needed between the L and produced phase and also between the N and produced phase to balance the phase angle, this part was done by the commissioning fella who supplied the invertor.
To run a small 3 phase motor from single phase it can also be done by connecting L and N to 2 phases of the motor and the 3rd phase is produced for the motor operation by connecting the right size capacitors from the Live to the unconnected phase, and the Neutral to the unconnected phase. A 230v line voltage motor would be needed connected in delta for a 230v single phase supply.