On Fri, 8 Jul 2005 06:56:18 -0700, "Mike Fields"
wrote:

The key here is the type of motor you are trying to control.
If it is a "universal" type (ac/dc with brushes), you can
easily control it with a solid state "dimmer type" control
(although some work better than others). If the motor is
an induction motor (like many grinders etc - no brushes,
uses the rotating AC magnetic field to spin it), the only
real way to control it is with a variable frequency drive
since the speed of the motor is determined by the frequency
of the AC applied to the windings.

mikey

Got to be three phase though.
Alec