Have you ever wondered why the speed of your ceiling fans starts to decrease after the elapse of time? And ultimately they start to rotate very slowly or stop working.
There are actually two reasons behind the slowing down of your ceiling fans.
1) The capacitance starts to lose its capacitance value.
2) Reduction in Supply voltages.
In most cases, the supply voltage is fixed, so this article will only provide insight into the decrease of the speed of a ceiling fan due to capacitive issues. I will also provide some methods which can help you to improve the speed of your fans.
A ceiling fan works on only one voltage phase (Single phase induction motor), in order to provide a torque to the blades of the fan you need a rotating magnetic field. But the problem is that in a single phase motor the torque becomes zero, the field provided by the stator winding is “Alternating magnetic field” not “Rotating magnetic field” which you need to rotate the fan. This happens because the negative and positive halves of the field coming from the stator tend to cancel each other resulting in no torque.
This is where the capacitor in the ceiling fan plays a role, there are two windings in the motor, namely “Run winding” and “Start winding” and a capacitor is connected in series with the auxiliary winding. A capacitor splits the phase such that you get the output of a multi-Phased motor. A capacitor provides a phase shift between the currents in the motor windings, by adding a capacitor to the auxiliary winding of the motor a phase shift by 90 degrees is created between both the windings. This creates a rotating magnetic field which makes the fan rotate.
The phase shift provided and the torque produced depends on the value of the capacitor when the capacitance starts to decrease it ultimately produces less torque to rotate the fan; hence the fan starts to lose its original speed.
What should you do to improve fan speed?
1) The easiest thing to do is just replace the capacitor with a new capacitor (Mostly 2.15 MF and 3.15 MF capacitors are used in ceiling fans depending on the motor winding). This is if the old capacitor has gone bad.
2) Sometimes the problem may be arising due to rusty bearings, you should clean and lubricate them.
3) Check to see if any of the fan blades are bent or are miss-shaped, the angles of the blades must all be the same.
4) There may be a problem due to overheating or an issue in the winding, so make sure to check that out or get it checked by a professional.