Why Single Phase Induction Motor Is Not Self Starting Like A 3-phase Induction Motor?
For a single phase motor to start there has to be a phase shift. This is because they have one set of windings. Some single phase motors have multiple windings, but they are start windings, and high or low speed windings. 3 phase motors have separate windings in them. This automatically creates a rotating field. A single phase motor has one. The field is rotating but not enough to start the rotor to spinning. There hase to be a phase shift to create this. A capicator is used to do that. In a capicative circuit current leads voltage. This shifts the sine wave and starts the rotation. Some low horsepower motors such as a shaded pole motor doesnt require this. They are a different beast all together. To learn more get a Rosenberg motor book at a book store. It is really good at explaining motors. The book can also be found on Ebay sometimes. It may cost as much as $90 though.
