This motor turns the platter in a microwave. Periodically the direction of rotation reverses.
How is this accomplished?

 

The direction randomly reverses on startup.
Every time ac power is applied the motor has 50/50 chance of turning clock ways.

 

Thanks for the response. A "normal" ac motor doesn't do that - how does this motor differ?

 

"normal" motor has something to help it choose rotation direction, more phases, or capacitor, or shaded pole, or external starter, or rectifier ...

 

For a microwave oven, the motor does not have any mechanism to select the direction, so it can start in either direction. To select an "always" direction would usually require a shaded pole or a rachet scheme. The "shaded pole" consists of a one-turn copper coil around part of one pole piece, which creates a phase shift thatthen always starts in one direction.

 

I see. Thanks for the responses.