why capacitor is used in a Fan?

What is a FAN?

An electric fan runs on AC power supply using capacitor as a means of starting device to kick-start the actual rotation of the fan. 

Now, lets observe the electrical operation of a fan. A fan is an asynchronous electric induction motor and from the study of electromagnetism and machine systems. 

Asynchronous motor are electric motor that require two source of electric supply in other to get started because of the stator and rotor inside the motor.

Stator the stationary part of the motor requires AC current to generate the require electromagnetic property.

also, the Rotor which is the rotary part of this type of machine requires another source of electric current to generates its require electromagnetic property.

This thus means that two source of electric current has to be supplied to each part of the motor component (stator and rotor) and the interaction of the two field created by this two device causes the require electromotive force needed to set the fan on motion.

This thus answer my first wondering as to why the fan rotates while the capacitor is removed and me using my hand to turn it which sets it into motion. 

So, If a capacitor is removed from a ceiling fan, it will not run, but it will rotate by pushing by hand because it get direction for magnetic repulsion

For this reason, a capacitor is used to provide another phase of current that actually leads the actual face of the supply incoming current of the fan.

Conclusion 

Ceiling fan uses a single phase induction motor to run it. This motor is NOT self-starting i.e. it requires external force to run it at the time of starting.

To overcome this drawback, a capacitor is used. It is connected across a part of the winding in the fan motor. 

This creates a phase difference between the windings (one part with the capacitor connected and other part without the capacitor).

Thus, a field is produced which is resultant of the two fields. The rotor rotates according to the direction of the resultant field.

The capacitor may be connected via. a centrifugal switch to increase the efficiency of the fan. 

How to Replace a Ceiling Fan Capacitor

Most ceiling fans use a type of motor known as a “permanent split capacitor motor. 

These motors have two coils, a start and run winding. 

A capacitor is connected in series with the start winding to insert a phase shift, but once the motor is up to speed it becomes an auxiliary winding. 

In order to reverse the motor, the capacitor is applied to the run winding which then becomes the start winding. In some cases the windings may have taps to provide different speeds, in others the value of the start/run capacitor is lowered to provide different speeds. Other designs will have additional capacitors wired in series with the motor as a whole to regulate speed.  

Signs of a bad capacitor in a ceiling fan include:  

•Fan runs slowly or not at all on all speeds 

•Fan will not start but will spin if started by hand 

•Certain speeds are slow or do not work 

•The motor hums and turns freely by hand but will not spin 

procedure to replace capacitor

 Prepare by opening the case. Make sure you have the necessary tools, including a voltage tester, a screwdriver that matches the screws on the fan, wire nuts, wire cutters and wire strippers. 

Switch off the power to the room that contains the fan by opening the breakers at the electrical panel or removing the corresponding fuses. Place a stepladder under the fan and make sure it is high enough for you to reach the fan without having to stand on the top two steps.  

Replacing the actual capacitor is usually straight forward but first you need to determine the correct value. 

If the marking on the case of the original part is obliterated or unreadable you should consult with the fan manufacturer or check the schematic to determine the original value. Otherwise determine if 2 wire or 3 wire. 

Two wire capacitors are easy as they only contain one capacitance value. Capacitor values are measured in “microfarads” (uf), ex: 4uf is a 4 microfarad capacitor. 

Fans that have more than one speed will often use more than one capacitor for speed regulation. To save space quite often capacitors that contain more than one value will often be used. Three wire capacitors are a bit more difficult as they contain two different values. For example a three wire capacitor may contain a 2uf and a 4uf capacitor in the same case with one common wire. One wire goes to the 2uf side and the other goes to the 4uf side.  

The color of the wires is not always the same as the original device so in the case of a 3-wire capacitor care must be taken to determine which wire was originally connected to which value.  

For capacitors containing more than 3 wires there is usually a schematic on the inside or the original owner’s manual explaining the various values.