Re: [CAD_CAM_EDM_DRO] Re: 3 phase motor math

rainnea wrote:

>Can you run a larger motor than a VFD is rated for, ie. run a 5HP
>motor from a 1.5kw VFD ?
>ie. can you limit the voltage / current output from the VFD ?
>
>

Generally, no, or at least not recommended. I popped an early and crude
VFD this way. The reason is larger motors have lower inductance.
The VFD is designed to take that into account. The PWM waveforms
are not designed for the lower inductance motors, and may cause magnetic
saturation. You could put inductors in series with each motor wire to
bring the inductance up to the right range. I had to do this to run some
air bearing high speed spindle motors from a standard VFD.

>Could a VFD be used to run an AC servo ?
>
>

Generally, no, because they do not excite the rotor flux at zero speed, and
they respond way too slow to dynamic changes in the speed command. If
you could live with dynamic response of about 1 Hz, then it would mostly
work,
except for some jitter when sitting still.

Jon