Re: Looking for mini-VFD for 120VAC/1ph

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Doug Fortune <pentam@...> wrote:

>
>
> Can anyone suggest a mini-VFD variable frequency drive
> for 120VAC/single phase, suitable for varying the speed
> of (variable speed) laminate trimmers such as the Ridgid R2400?
>
> The standard $30 variable speed controls don't work at all
> on this laminate trimmer, and the built-in control on the R2400
> only varies from 20,000 rpm to 30,000 rpm, which is not slow enough.
>
> cheers
> Doug Fortune
>

Doug. VFD's only work on 3 phase motors where the frequency of the
supply directly effects the speed of the drive. Routers use
"universal motors" (most will work on AC or DC) and the speed is
roughly porportional to the applied voltage. Phase control only works
from about 50% to 100% of the max RPM. The problem with reducing the
voltage too much is that you lose torque as well. As soon as you put
the motor under load it just stalls out. Some speed control circuits
will sense back EMF (porportional to speed) and use it to do a rough
regulation of the speed so that it addds in more voltage if the RPM
starts to drop from load. Usually an external speed control will not
work on a motor that already has a speed control.

I don't know what to tell you. Might be time to look at a true
spindle with belt reduction (or a router with a real speed control)
but they still won't work to drastically drop the speed to less than
10,000.

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