Re: VFD Positioning?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "C.S. Mo" <cs@v...> wrote:

> Assuming you put an encoder w/Index on your spindle, what kind of
> positional accuracy can you get controlling the spindle with a 'typical'
> VFD (not one of the super accurate ones - but a standard FM50 or

FM100 as

> example)?
>
> As in, is it possible to have the spindle turn x degrees? Or can you

only

> control RPM?

Pretty much just RPM. There are vector drive type AC servo controllers
out there, but they are frighteningly expensive. "Regular" vector
drives were developed to allow much better control of an induction
motor's torque at very low RPMs, but this is not the same as a servo
control. If you need degree accuracy, DC servos are still the king.