50Hz PWM frequency for controlling speed of single phase ceiling fan?


Joined Jun 4, 2014
It would probably be better, as a ceiling fan has a large momentum and speeds up or slows down fairly slowly, to use a much lower pwm speed such as 1Hz, switching the AC voltage at the zero crossing point to avoid generating interference. It should always be fed with a whole number of AC cycles which means only using alternate zero crossing points to avoid any DC component, particularly at high mark-space ratios when the power is connected most of the time.


Joined Jul 18, 2013
IMO if you want to PM an AC 1ph motor you would need to also re-create the 50Hz AC exactly the same way a 3 phase VFD does, in order to PWM it, not with a Triac.
Otherwise you would have to synchronize each PWM pulse signal to the zero crossing point and just vary the width but this will only give you phase angle control the same or similar way shown in Fairchild AN-3006.