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Help required for Fan Dimmer-Important


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Hello ,

I require your little favor for my Fan Dimmer( Fan Speed Controller) Circuitry .

Well i have also attached an image of circuitry in which u can clearly see Transistor ( PN BT134 600D 0701) , Diode (C 502 ) , Capacitor ( 2E104K ) , Resistor color code ( Brown,Red, Orange,Golden ) & Potentiometer .

Now the problem i am facing is that Fan dimmer works fine for normal electricity . But whenever i operate that on UPS or on generator,  it burns .

Please suggest me what should i do to make this circuit more effective in terms of it's operation in UPS & in generator . Your help in this regard would be highly appreciated.

Thank you !


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As mentioned before the output from your UPS might not be a sine wave. To rectify this one could put a suitable choke in series with the fan and its electronics. The choke will round off ant squarish waves presented. The choke could be between 2 and 5mH and on the side of the fan a smallish cap of 47nf, voltage about 650. I seem my local spares provider sell a "Mains capacitor" which is a 450v unit. Remember the mains of 220v is actually the rms value, the peak value is around 330volts.

Another thing that can cause malfunction is high voltage spikes. This does not cause the fan to burn out, but will break down any weak insulation points, seeing you spoke of "burn" is is more likely a consistent unusual supply that can do this, pointing to irregular wave shapes. Experiment with a choke.

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  • 3 weeks later...

I had a problem with lightning, the spikes from a nearby flash would damage the PSU on my computers, modems and even the gate motor. I put in a choke on each leg of the mains wires, it was fitted in a box with plugs on it so that the box plugs into the socket and the other equipment plugs into the box. One also has to put in a MOV to absorb high spikes, and there is a small cap on the mains side and one on the equipment side. This protects everything.

We did not discuss the voltage of the fan, this could help if you used a MOV to protect it as well. If it is a DC fan then add a 10 ohm resistor in each leg of the supply and on the fan side put in a MOV rated slightly higher than the supply voltage. This would work for an AC fan as well.  This will only stop spikes, and will not round off the square waves from the UPS. I have used inverters giving off square waves and this did not affect equipment performance, because the AC is rectified and smoothed and the transformer will round off the square edges. In a computer power supply the AC is rectified and smoothed, with a big capacitor, then is chopped at a high frequency through a small transformer down to the required voltage. A transformer is more efficient at a higher frequency, so you can see that square waves should not have that much of an influence.

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I don't think lighting is responsible. The speed controller fails when run from the UPs because of the high voltage spike given off by the motor when the current is suddenly interrupted by the square edge of the modified sinewave. You could try a choke and smoothing capacitor but I don't think it'll help. You need to power the fan from a true sine wave, which involves upgrading the inverter.

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