I'm using this circuit to control the speed of ceiling fan. The fan speed is divided into 8 steps. (0:off & 8:full speed) with 100us gate pulse.
This circuit works with incancescent light bulb perfectly. But having some issues with FAN.
if I increase the speed of fan step by step with 1.5 s delay of each step (12 s full speed time) fan works fine at full speed.
If I start fan at 5th step instantly fan rotate at its speed, and increase each step with required delay of1.5 s fan works fine.
If I start fan at 5th step instantly fan rotate at its speed, and instantly put fan at 8th step(full speed) fan stops with some humming sound.
If I start fan at full speed(8th step) instantly, fan does not work. It gives humming sound.
This concludes that if the fan has required torque on current step it works on next step otherwise not. But for first 5 steps it always works fine.