Why Capacitor is Used in Ceiling Fan?


Some of us have a question, why electric ceiling fan has a capacitor? Maybe for saving charge? Is this a real fact? Let us know about the real facts behind it. Today we will discuss why capacitor is used in ceiling fan?

If we say in simple words, when we press the switch to turn on the fan, the capacitor is used for the torque of the rotation. You should have a clear idea of induction motors to understand the use of capacitors. Because this motor is used in ceiling fan. This understanding will help you the concept of why capacitor is used in ceiling fan?

why capacitor is used in ceiling fan
Ceiling Fan

So we will start with the work process of the induction motor. By understanding the work process it will be easy for you to understand why capacitor is used in ceiling fan?

Work Process of Induction Motor 

Take a magnet bar. Then hang it in the air. Which direction it is facing? The answer is north-south. Because it wants to stay in the same direction as the magnetic field of the earth. It is a general characteristic of the magnet. Every magnet wants to align with an external magnetic field.

If we rotate the magnetic field, the magnet will also rotate with it. It’s the main process of the motor. It means the motor works with two magnetic fields. Rotating magnetic field and still magnetic field, which follows the moving magnetic field. 

How Rotating Magnetic Field is Made?

  • We can obviously do it by rotating the magnet. It can also be done by the electric flow. You must have heard of the electromagnet. 
  • We all know that, if electricity flows in a coil it creates a magnetic field. 
  • By giving the wire solenoid shape and flow of DC current, the created magnetic field is as same as the magnet bar’s magnetic field. Because the coil will act as a short circuit for DC current. As DC current has no up-down, the frequency is zero. So there will be no changing magnetic field. 
  • But it’s not rotating. There is an interesting way to create an electromagnetic field. The way is supplying 3 phase current. Because it has up-down or frequency. 
  • You can see three live wires in the transmission and distribution line. If the same amount of current flows through the wires there still be some difference. Current flow in each wire is 120° away from each other.
  • They have no other difference except this. But this exception has brought a big advantage in motor design. When we fold this 3 phase current and because of it’s flow, there will be an acquisition magnetic field that is rotating.
  • And if we put a magnet in the middle, it will follow this magnetic field and keep rotating. And this is our motors working process. Because same pole of magnetic field attracts and opposite pole distracts each other. This motor is not induction motor. It is called synchronous motor. Because it’s rotation speed is the same as rotating magnetic fields speed. 
3 phase signal
3 Phase Signal

In an induction motor, there is no magnet, a loop of wire is in the middle of it. Michael Faraday has shown that, if the changeable magnetic field is used in a wire loop, current flow will be induced. This is electromagnetic induction.

Most of the house has one phase connection. Then how does the induction motor of the ceiling fan work? Or, you can say why capacitor is used in ceiling fan?

A rotating magnetic field is not created by any one-phase current flow. Because two equal but the opposite rotating magnetic field can create equal and opposite torque in the motor loop. As a result, the motor stays still.

But if you move the fan in any direction, the torque value will increase on that side. Then torque is not zero and the motor gets activated or the fan turns on. It is called the manual starting of ceiling fan.

Sometimes, if the fan doesn’t get started and you move it to any side it continues the rotation. And that’s the reason why capacitor is used in ceiling fan.

That’s all for today’s article ‘why capacitor is used in ceiling fan?’

Hope it was helpful for you to understand why capacitor is used in ceiling fan?

You can also read: Discussion about Load Break Switch