View Full Version : What to look for in a phase convertor?

10-26-2003, 11:17 PM
What to look for in a phase convertor? I just acquired a machine, and I need to convert single phase to three for my VMC with 15 h.p. spindle. Any suggestions or recommendations?

10-27-2003, 10:40 AM
Hi CNCPro,

It is going to cost you a bit for a convertor, and convertors are "dumb".

Consider an AC variable frequency drive. In smaller motor sizes, they do allow the frequency drive to generate the 3 phase from a single phase input. However, you need to purchase a much larger drive than 15 hp to run a 15 hp motor. This could be as much as a 30 hp drive required. Check with the manufacturers on whether this can even be done with this size of a motor. Baldor is a popular manufacturer of this type of device. A Vector drive (with encoder feedback off the motor) is the absolute best system, because the motor will always run at commanded speed. The cheaper "vectorless drives" will not be as accurate, and also are gutless at speeds less than 10% of rated rpm.

But at least, you will have the option for a variable speed on your spindle motor then, and much nicer to interface with a cnc controller.

A 15 hp load running off of a single phase electrical panel is a significant load. You should talk to an electrician about it.