Re: Need a variable-speed 2hp or greater AC motor for serious

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 07:50 08/06/03 -0600, you wrote:
>Original poster: "Jeremy Scott by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <supertux1-at-yahoo-dot-com>
>
>If you don't mind DC, www.sciplus-dot-com has a 2HP 120V
>4800 RPM DC motor (from a treadmill I think.) Tricky
>part there is getting the thing to spin at the right
>speed and phase adjustment. I bought one and am
>currently designing a digital IGBT/MOSFET drive for
>it. Speaking of which, I'm looking for something
>(chip/circuit) that provides at least 10 (preferably
>16) bit PWM. The BS2p's PWM command is sorely lacking
>the resolution for accurate speed control.

Some of the Microchip PICs have a 10-bit timer onboard. I've used these to 
run a PWM controller for a Peltier cooler. You may find (like I did) that 
you can get by with less resolution than you think. If the controller has a 
fast update rate, the output will dither rapidly between adjacent values 
and the inductance/inertia of the motor will smooth it out to the right 
speed. That was what my design did, anyway. It updated 12 times a second 
and was stable to within 0.1 degree C. Of course my new employers want 
0.001 degree :(

Steve C.