Speed Control of a A.C motor , single phase

Hello Sir(s)
I am Samkit from India.
I am working on a project in which i want to regulate the speed of an A.C motor digitally.
Can you please help me , how can i do this?
Thank You
Samkit

You say AC machine?

What type:
Induction machine
Syncrounous machine

If it is a syncronous machine the speed of the rotor is directly influenced by the frequency of the stator field (ie the frequecy of the voltage applied to the winding terminals)

If it is a syncrouns machine then it isnt to hard. So some info abt the machine will be helpful

Type (Induction/Sycronous)
Number of poles
Power output
method used to "sense" rotor speed

Without critique , the most accepted way to control an AC motor is by controlling Frequency.
However what Styx said is true all the parameters matter and the more the information the better to solve your question.

I found this circuit.

Ya that's called a chopper circuit, not good for exact control or the lifetime of the motor , but it will work.

If you put a NP 30-100uf @330 Vac cap across the AC socket, the motor woulnt get as angry( hot)as the inductive properties of the moters windings and the cap become a smoothing filter.

As you have told you are from INDIA, so i think you can easily get a copy of "Electronics For You" magazine. refer the November'2003 issue, it's having construction project : "Proportional Load control using PC", pg52.

Amit Garg