Does anyone know a design for a single-phase induction motor controller?

[Magnox]

I have a belt grinder that I use for knife sharpening/making that has a single phase 600W induction motor. It would be very useful to control the speed but the only off-the-shelf controllers I can find are all three-phase. Likewise, all the circuits I find are aimed at three phase control.

I understand the principles of designing a single-phase controller for it, but wondered if anyone knows of an existing circuit for this? I don't want to reinvent the wheel, and probably end up with an oval one that needs tweaking.

Thanks,
Rick.

[mris99]

Hello,

Check this:
http://www.circuitcellar.com/microchip2007/winners/first.html
It was the winner of the dsPIC design contest 2007 of Circuit Cellar.

Summay:
Variable Speed Induction Motor Controller

Variable-speed drives for AC induction motors are readily available on the market. But what if you need one for a single-phase motor that operates in the 2-HP range? This innovative controller is the solution. Designed for use with a capacitor-start/capacitor-run motor, it includes active power factor correction (PFC) and inrush current limiting. The motor drive hardware is built around a dsPIC30F2020 DSC. The drive communicates via an optoisolated serial port to a PIC16F687-based interface unit.

Regards,
Mris