single phase motor

[SAMER]

I would like know why rotor continue rotating after the starting winding is disconnected so there is no rotating field just an alternating field.

[marke]

Hello Samer

 

Welcome to the forum.

 

The single phase single winding situation does create and alternating magnetic field, but this is the equivilent of two equal and counter rotating fields. Have a look at http://www.lmphotonics.com/single_phase_m.htm and have a look at the rotating vectors. The blue vector rotates in one direction and the red in the opposite.

The rotor will synchronise on the field that is closest to its own speed. You can start the single phase motor on the run winding only, but you need to give it a spin to set the direction, otherwise it will sit and vibrate.

 

Best regards,

[Guest]

In some cases the single phase induction motor rotate in the reverse direction that is due to a weak capacitor or start winding itself. I think that weakness change the phase and this cause to change polarity of stator, this why rotor turn in the reverse direction. Is that correct?