Hopkins wrote:
> What is the best way to control the speed of a single phase induction
> motor.

you need a variable frequency drive to control the speed of an induction
motor.

> Can a light dimmer triac circuit be used?

no. The speed of an induction motor is proportional to the line frequency
and number of poles (minus slip, of course)

> Some type of H Bridge with PWM?

that's sort of the concept for variable frequency drive. The motor might
not like being driven by alternating square waves, so there are variations
on this scheme that make the square waves look more like sinusoidal
waves. Ideally you should also vary the amplitude. The ratio of voltage
to frequency should be constant to avoid saturation. 

hope that helps get you started in the much-needed research you
need to do :)
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist