My bad, I did mean asynchonous and not synchronous.
I suppose another option is to get ahold of a variable frequency drive. These are used to control the speed of pumps etc..., but if a small version could be found you could easily use it as your motor speed controller. Esssentially it allows you to control the voltage frequency, and hence the motor speed.
I suppose another option is to get ahold of a variable frequency drive. These are used to control the speed of pumps etc..., but if a small version could be found you could easily use it as your motor speed controller. Esssentially it allows you to control the voltage frequency, and hence the motor speed.