Induction motor starting direction

[John94N]

I have a question on induction motor starting direction. I understand the phase delay between the running winding and starting winding, but I don’t see why an induction motor should start in the same direction each time. Is there a directional bias on the stator or rotor coils that ensures the torque is always in one direction?

 

[Phrak]

The bias is obtained from the start winding used in conjunction with the run winding to start the motor.

Let's say the start winding induces a magnetic field in the armature so the north pole is at 12:00 o'clock. After a delay, the run winding peaks with it's south pole at 3:00 o'clock and north pole at 9:00. This will induce the armature to rotate clockwise.

 

[John94N]

That's makes sense. Thanks.

 

[Phrak]

You're welcome. Glad to help.