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Insight - How Fan Regulators work

Written By: 

Arpit Jain


Fan regulators have an important place in the electrical switch boards. Fan regulators are very similar to light dimmers.Their function is to regulate/control the speed of the fan and provide a convenient environment for the residents. 
The traditional regulators which are bulky use a resistance having taps and connected in series with the fan. When we move the knob different amount of resistance gets inserted in the circuit. Although cheap the biggest problem with such a regulator is that a considerable amount of energy is lost in form of heat through the resistance. When the fan is operating at low speed the power loss is significant.
The technologically superior electronic regulators overcome these problems by using electronic components to control the speed of the fan.
Some of the advantages of electronic fan regulators are:
1.      They provide a continuous speed control.
2.      Power saving at all the speeds.
3.      Smaller size and weight.
The heart of the electronic fan regulator is TRIAC. TRIAC is a semiconductor device belonging to the family of thyristors. 
Front and back Images of Electronic fan Regulator
Fig. 1: Front and back Images of Electronic fan Regulator
The above images show the front and back images of an electronic fan regulator. Once again it is available is a variety of shape, size, color depending on manufacturer to manufacturer.

Structure of Fan Regulator

Structure of Fan Regulator
Fig. 2: Structure of Fan Regulator
The plastic knob which is connected to potentiometer (a variable resistance) is shown in the image above. When we rotate the knob, the resistance of the circuit changes, which in turn controls the firing angle of the TRIAC.

Internal Components of Regulator

Fig. 3: Internal Components of Regulator

The arrangement of the different components can be seen on removing the front and back plastic casing. 

Role of Inductor & Capacitor & TRIAC

Circuit Arrangement of Regulator

Fig. 4: Circuit Arrangement of Regulator


An inductor along with a capacitor behaves as a radio frequency interference filter. It reduces the interference arising due to switching on and off the AC.
Role of TRIAC

TRIAC of Fan Regulator

Fig. 5: TRIAC of Fan Regulator

The TRIAC which is the heart of the circuit is shown in the image above. In simple terms TRIAC is like a semiconductor device having an input to be fed externally. The waveform of voltage is sinusoidal in nature. When the TRIAC is fired at 30 degree, it allows only the waveform after 30 degree to pass though it in both the positive and negative half cycles.  The input to the TRIAC is the angle called the firing angle.
The firing angle can be controlled by means of a variable resistor and/or capacitor to allow only certain portion of the AC cycle to pass through it, thereby reducing the average voltage over the complete cycle.  Since the voltage supplied is proportional to the speed and hence the speed of the fan can be increased or decreased.

Role of Potentiometer

Potentiometer and Capacitor of Regulator

Fig. 6: Potentiometer and Capacitor of Regulator

The potentiometer and the capacitor are shown in the image above. In this case only a variable resistor is used to vary the firing angle. The capacitor used is of fixed value.


thank you 


i want the circuit diagram of regulator

i want circuit diagrame of fan regulater using Traic

please give circuit diagram.


Hey i want Ckt diagram & also some explanation


Though advantages about electronic fan controllers are listed, I find that the speed variation between max(5) position and the next (Position 4) is very significant. Positions 3-2 show no change to 4. In Position 1 fan does not work at all. what is this functionality? How to make a perfect regulator?. Please explain

Nice question! 

Even I have observed the same behavior with smaller regulators (single module; the one shown in the pic). If you buy the double-module regulator then you'll find the speed increments to be smoother. Moreover, I was told by the dealer that these small regulators do not really save any energy. Bigger ones do. I have to check his claim though, with a power meter.