Noise in the ceiling fan when speed controlled by triac

[gowtham velusamy]

Hi,
I have controlled the fan speed by TRIAC,I can regulate the ceiling fan step by step with phase angle control method.but i got little bit of noise from fan.So how can i regulate the fan speed smoothly without noise. I have attached my circuit diagram and waveform.

 

[jiripolivka]

Hi,
I have controlled the fan speed by TRIAC,I can regulate the ceiling fan step by step with phase angle control method.but i got little bit of noise from fan.So how can i regulate the fan speed smoothly without noise. I have attached my circuit diagram and waveform.

Using a triac changes the waveform from sine to pulse with sharp edges, therefore harmonics are generated. This is the noise you can hear.
Find a power regulator using zero-crossing method, it will reduce noise.

 

[gowtham velusamy]

Using a triac changes the waveform from sine to pulse with sharp edges, therefore harmonics are generated. This is the noise you can hear.

Hi,
Can i use any harmonic trap filter to reduce the noise?.

 

[FvM]

Not exactly harmonic trap. Try a simple LC low pass filter. Quality triac dimmers used to include it already.

 

[c_mitra]

Fans are not a "regular" inductive load, they have a capacitor to help start and that makes it (somehow) a "tank" load. The triac based dimmer is basically a variable duty cycle regulator that works on the line frequency (50/60Hz). You say that you have identified the source of the noise as the fan but it should be dependent on the fan speed. Instead of receiving smooth force over time, the fan simply receives "kicks" periodically. It will be tricky to filter off but the problem will be worse only at low speed.

 

[FvM]

Usually the noise is generated by magnetostriction of the stator core. Low pass filtering can be expected to reduce it.

 

[gowtham velusamy]

Hi,
How to calculate exact inductance and capacitance value for LC filter.

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Not exactly harmonic trap. Try a simple LC low pass filter.

Hi,
I have used 22uH/3A inductance series to the load,but there is no change in noise.

 

[c_mitra]

You can stop the fan with your hand (take great care!!) and if the noise persists, then the source is magnetostriction- as pointed out #6. If not, then the source of noise is mechanical and difficult to predict.