View Full Version : Still more VFD questions

Buzzer John
01-25-2008, 08:09 PM
Can a single phase motor be run from a 3 phase VFD? I bought a 3 Phase 220 V output, 240 v single phase input unit at Cabin Fever last weekend. I wanted it for my mill, which has 3 phase motors. My lathe has a single phase motor and it would be nice to run it from the VFD also. I can only operate one machine at a time anyway. If I had a true 3 phase line input, it would be no problem. However, I don't know it these units have to have their outputs balanced. If so, could a resistive load be used to balance it?
Thanks, John

01-25-2008, 09:08 PM
Short answer: no. The starting circuit of a single-phase motor gets confused if the motor is slowed down significantly.

01-26-2008, 03:20 AM
What SGW said... NO. A single phase motor has a start circuit which almost always has a centrifugal (speed) switch which MUST be activated or the motor start windings and/or capacitor will fail. Also, the VFD may not like an unbalanced load and resistors will not balance it. It has to do with phase angle in windings VS resistor. What I would do is buy a cheap 3 phase motor for the lathe and then use the VFD for both:D . You will love the VFD on your lathe.