Dear Larry, I think those are two different things (splitting phase, which is an advantage for an AC synchronous motor controller, vs electrically switching speed, which can be done by either controlling voltage or AC frequency or both, depending upon the type of motor). The only issue would be for an induction motor where there is kind of a plateau for voltage, below which the torque falls to zilch. Please anyone correct me if I'm wrong in this; motors are a complex subject that I hardly can claim to study on a daily basis. I am going on my fading memory of Mark Kelly's teachings.
Also, it's not "two separate power lines" strictly speaking. It's taking the sinusoidal AC wave form and generating a second one that is 90 degrees away from the first, so the motor is driven in quadrature. As I understand it, the more perfectly that is achieved, the smoother the motor will run. That's what a capacitor tries to do but does not do nearly as well.
Roscoeii and Redglobe, perhaps you can contact me by email. I cannot seem to find your respective email addresses. Let me know if you cannot find mine. I may be able to help, in any case.
