Knifemaker / Craftsman / Service Provider
- Oct 30, 2015
Yeah part of my problem was the pull setup I was using to bump the speed to the higher umbers. I have a small 1hp 3ph motor that I’m putting on my mill that says 1775rpm but then says max 6000rpm. It’s designed to be used on a vfd. If I could snag one of these in a larger HP rating I would be more then happy. The problem with VFD and motors is torque and hp. If you run at name plate rpm you get the nameplate hp. But as soon as you use the vfd to drop the rpm you loose HP but it try’s to keep torque. This is becaus motors have a voltage to HZ ratio. If you go over this ratio then the stator becomes saturated and does not work. So as you drop the speed which is HZ the vfd must drop voltage to keep the V/HZ ratio corect. If you go the other way and speed a motor up the vfd can’t put out more voltage then it’s given so it keeps the voltage at the 240v and just increases the HZ. What this does is increases RPM but keeps HP at the name plate rating. But this comes with a drawback and that is a drop in torque. Here is a chart that might make a little more sence.