Hi Sebi!
It's really quite simple, and though not really suitalble for running high end CNC machines, it will run other 3 phase motors perfectly.
The thing is, a 3 phase motor will RUN on single phase, but will not start
with single phase alone. Put simply, what happens in mine is, because the motor is one of the old heavy types (not new aluminium frame) and because of it's size (10hp) it needs a star/delta start. So, what you can do is, start the motor in star, using the live + neutral and with say 200uf starting capacitor between live and the 3rd leg on the motor. when the motor is up, switch into delta - simultaneously switching out the 200uf cap and switching in smaller ones, say 20/30uf to keep the motor currents balanced. YOu can do all this switching with 3 x 4 pole contactors, and a timer.
You mentioned you dont like processors - well my converter does'nt have any, but I do have plans to fit a PIC to control the star/delta switch over point instead of a timer, the reason for that is, sometimes the motor needs a little longer in star to come up to speed, this usually happens on very cold mornings, or if you're doing alot of stop/starting of the converter it usually does'nt need as long in star before it's up.
With the PIC, and using an optical sensor, my plan is (if it works ha!) is to fit the sensor with a flag on the shaft of the motor, and make the PIC monitor the RPM of the motor shaft and control switch over point on that basis instead of time, which is a bit too rigid.
There's lots on good info about converters on the web, I just figured out all this as I went along, I had many failures before I had success, I also nearly got killed by it! but that was my fault really - long story!
Hope this helps!
Dougal