It was the winner of the dsPIC design contest 2007 of Circuit Cellar.
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.