What will happen if we don't use capacitor in a ceiling fan?

If a capacitor is not used in a ceiling fan, the fan will either not start at all or will struggle to rotate properly, especially from a standstill. Ceiling fans use single-phase induction motors, which are inherently not self-starting. The capacitor creates a phase difference between the main and auxiliary (starting) winding, simulating a two-phase power supply. This phase shift is crucial because it helps generate a rotating magnetic field that starts the rotor spinning.

Without a capacitor, this phase shift does not occur. As a result, the rotor receives no directional torque to begin rotation. You might hear a humming sound, and if you manually spin the blades, the fan may start running slowly in either direction, but it won’t perform efficiently. Additionally, running the fan without a capacitor can cause overheating of the windings, reduce motor lifespan, and in some cases, lead to permanent motor damage due to stalled operation.

Here's a more detailed explanation:

Single-phase motors and the need for a phase shift:

Ceiling fans typically use single-phase induction motors. These motors require a rotating magnetic field to start and operate, but single-phase power doesn't inherently create this rotation. 

Capacitor's role:

The capacitor acts as a phase-shifting device. It stores electrical energy and then releases it to one of the motor's windings (the starting winding), creating a slight time delay in the current flow compared to the other winding (the running winding). 

Rotating magnetic field:

This time delay (phase shift) is what allows the magnetic fields generated by the two windings to interact and create a rotating magnetic field, which then pulls the rotor (and blades) of the fan along with it, causing the fan to spin. 

Consequences of no capacitor:

Without the capacitor, the magnetic fields would be in phase, and they would oppose each other, preventing the motor from starting. Even if the fan were to be manually pushed to start, it would likely run weakly, overheat, and potentially burn out due to the lack of torque and the continuous high current draw.

Summary:

If you don't use a capacitor in a ceiling fan, it won’t start on its own because the motor needs the capacitor to create the phase difference for rotation. Without it, the fan may just hum or not spin, and trying to run it this way can damage the motor over time.