There is a lot to say about the old motors and a lot of that is good. Three phase are slightly more efficient and less maintenance intensive than single phase.
I would consider keeping the old motor and drive it off a VFD intended to take a 230 VAC single phase supply. This may be less expensive than replacing the motor.
There are a couple provisos on this though
1. Check the nameplate - if motor is a dual voltage ie 230/460 then at 230 you should have no problem with the higher voltages imposed by VFD.
2. I would ensure the motor shaft is grounded to prevent bearing erosion cause by current imposed in shaft. Need not be complicated use a brush holder out of a starter motor. If possible best to ground both shaft ends.
3. Find a good distributor who really knows VFDs. In this case I do not recommend Grainger. Take a photo of the nameplate to them so they know what kind of motor they are dealing with.
4. Unless you have an unloader I would not get a V/F type VFD but would recommend a vector type - better starting capability.
Whichever way you go do NOT scrimp on the conductors feeding this unit. If mine I would go up one and probably two wire sizes to ensure it has minimal volt drop when starting.
Dan Bentler
