Re: [CAD_CAM_EDM_DRO] Re: VFD Selection

george_barr wrote:

>Leslie,
> It seems to me a Variac only limits the voltage going out. I
>already tried a variable router speed controller found at:
>http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=43584
>
>This router speed controller does not work since my rouers normal
>speed range is 8k - 20k rpm and I need to have a speed of about 1k
>rpm. The speed controller cannot slow this router below 8k it
>seems.
>
>Are you saying that a VFD cannot work with my router?
>
>

No VFD will work on a series-wound brush motor. You are trying to get
appreciable power delivered to a cutting tool at 1/8th of the lowest
operating speed of the motor? Good luck, and I hope you can
afford to replace it once you burn up the motor. At 1000 RPM, it
will only have the torque available for the 8 - 20K RPM range, but
at 1/8th the speed, the power produced will be miniscule. The cooling
airflow through the motor will likely be something like 1/64th of normal,
too!

Jon