Originally Posted By: pca
Altering the speed of a single phase motor is a right sod, and often almost impossible.


Have you explored the idea of putting a suitable capacitor in series with one leg the the AC supply? This works extremely well for me here with smaller motors (15uF for a 0.7amp motor). Near 100% efficient, so one just needs suitable non-polarized metal/poly film capacitors rated for 450V.