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# fan direction and torque?

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#### gauthamtechie

##### Member level 1
About the rotation of a ceiling fan:

A single-phase capacitor start induction motor uses a capacitor during starting and while running gets disconnected after providing that starting torque. Now my doubt is whether if i remove the capacitor(i.e. no starting winding now) and then switch on the fan, and rotate it manually in direction, will it produce the starting torque required and continue running - question being whether it'll run in any direction i rotate it?

#### srizbf

##### Advanced Member level 5
About the rotation of a ceiling fan:

A single-phase capacitor start induction motor uses a capacitor during starting and while running gets disconnected after providing that starting torque. Now my doubt is whether if i remove the capacitor(i.e. no starting winding now) and then switch on the fan, and rotate it manually in direction, will it produce the starting torque required and continue running - question being whether it'll run in any direction i rotate it?

it will run in the direction you rotated without capacitor.

note:
move this post to suitable section.(may be hobby circuits? )

##### Super Moderator
Staff member
There are ceiling fans which have a switch for reversing direction. I don't know if this has something to do with the starting capacitor. I don't know if it will or won't work without the capacitor.

#### gauthamtechie

##### Member level 1
thank u! so i see that without 'Starting' capacitor it DOES assume the direction we rotate it ..

Also building upon this doubt, pls clarify this: the starting element mentioned was a capaitor. To reverse direction, i know the conventional explanation is reversing the polarity of either start or run winding. Now if replace capacitor with a good inductor, then again the direction would reverse right ?

#### milind.a.kulkarni

##### Advanced Member level 3
Actually As i know the current in the running and starting winding are phase shifted by means of capacitor....so running winding current lags the in phase with respect to current in the starting winding but more importantly ....it used to create the rotating magnetic filed ....now when it comes to concept of rotating magnetic field it is the direction of current that really matter and the motor rotates in the direction of rotation of magnetic field ....so even if you add an inductor as a replacement for capacitor....it dose not change the direction of magnetic filed ....so even you add the inductor in the filed it will rotates in the same direction if you don't reverse polarity....

Good Luck

- - - Updated - - -

Actually As i know the current in the running and starting winding are phase shifted by means of capacitor....so running winding current lags the in phase with respect to current in the starting winding but more importantly ....it used to create the rotating magnetic filed ....now when it comes to concept of rotating magnetic field it is the direction of current that really matter and the motor rotates in the direction of rotation of magnetic field ....so even if you add an inductor as a replacement for capacitor....it dose not change the direction of magnetic filed ....so even you add the inductor in the filed it will rotates in the same direction if you don't reverse polarity....

Good Luck

#### gauthamtechie

##### Member level 1
thanks milind! but i felt so because as you mentioned, running winding current lags behind starting winding current because of the capacitor. Hence by replacing with inductor, the running current would lead right? So it would produce a rotating magnetic field in the opposite direction and hence rotate in the reverse direction?? Am i wrong?

#### milind.a.kulkarni

##### Advanced Member level 3
I think Gautham .... One need to do this experiment...bcz I some how fell your thought is write....

#### FvM

##### Super Moderator
Staff member
A series inductor will only generate a small phase shift compared to direct connected winding, because the motor impedance is already inductive. The torque may be sufficient to start a fan, though.

#### gauthamtechie

##### Member level 1
in the direction opposite to what it would, if i had a start capacitor?

#### gauthamtechie

##### Member level 1
So finally..will the fan roatate in the opposite direction with a starting "inductor" as it would with the usual capapcitor? Because the starting current would lead while using a capacitor and lag while using an inductor.. So does that have to do with direction of rotation?

#### FvM

##### Super Moderator
Staff member
Yes, in the opposite direction, if at all.

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