What causes fan to run in reverse?

Answer 1

(1)What happens when polarity of the fan is reversed?

It depends upon your definitions of reversal of capacitor,in a series circuit reversing a capacitor in the actual sense means not a mechanical reversal by changing its metal leads,its just reversing the current direction in the capacitor.

(2)Now next question is does fan capacitor have a polarity?

Ofcourse it has,all capacitors have polarity,but fans capacitor is not electrolytic capacitor,so it doesnt have inbuilt polarity.

(3)How we recognize the polarity of capacitor of a ceiling fan?

Since it doesnt have inbulid polarity,the direction of the current entering the mesh determines positive polarity and current leaving is assumed as negative polarity.while doing mathematical analysis we can take any convention it will not affects the magnitude since we are taking modulus in calculations.

(4)Final Assumption reveling the facts about fans reverse rotation

If we connect the fan in such a way that currrent is leaving or reversing the direction of current,the capacitor polarity changes and fan will rotate in reverse(since it is a single phase induction motor{note: rotating magnetic field and working of fan}),need of the capacitor is it gives the initial torque and technically improves the power factor,capacitor charges and discharges with respect to the frequency of the ac and gives the stability to the system,its efficiency will be lower and speed reduces if we remove the capacitor theoratically,so finally you can say the fan rotates reverse if we change the polarity of the capacitor(indirect meaning of changing direction of current).if you want any simple mathematical analysis of the detailed explanation,mail me at "ellipsis047@gmail.com" or call me 07259434969 "Sreenath SM(India)".i can make you understand the basis of all analog and electrical circuits.