Re: [CAD_CAM_EDM_DRO] another VFD question

Joe Vicars wrote:

> Jon,
> Is the speed proportional in the 1-60 Hz range then? If not is there
> a standard curve that I can use to make a speed chart that will
> correlate motor RPM to the Hz readout on the box?

It is nearly proportional. There is the slip of the induced field in
the rotor, which is proportional to load, and inversely proportional
to stator over-excitation. Not easy to compute, but fairly small.
This is the difference between synchronous speed and the
normal motor ratings like 1725 RPM or 3425 RPM.

The belt reduction ratios are also hard to predict better than 10% or
so, so it might be best to measure spindle speed. IF you change belts,
the speed can change, as the belt may sit at a slightly different radius
in the groove.

Jon