I am trying to control the speed of the ceiling fan using a triac. I am using phase control method to vary the speed of the fan, I am able to control the speed of the fan using my program, but at lower speeds the fan makes a lot of noise, is there a way to avoid this noise?
When you do phase control at very low speeds, essentially most of the time the Triac is not conducting, with very narrow pulses at the end of the end of the sinewave.
That is the reason of the noise. Which by the way, is making your rotor vibrate a lot and may significantly shorten the life of the bushings.
Do avoid the noise you could used some form of higher-frequency PWM control that uses MOSFETs and not SCRs such as this, but I don't know if those are available commercially already built.
The noise is present even when i am passing 40% of half cycle of sine wave.
Is there any other method to control the speed other than phase angle method, which does not deteriorate the life of fan?