A ceiling fan is one of the most common electrical appliances. And there always is a fan regulator with every ceiling fan to control its speed. You might have noticed that older fan regulators (still being used in some homes) are a lot bulkier than electronic regulators we see today. Below are the both types of fan regulators (conventional and electronic) explained.
Conventional fan regulator (Resistive type)
Old ceiling fan regulators look like a big rectangular box having a circular knob on it, popping out of the switchboard. These are also known as resistive regulators. The box consists a wire wound resistor with different taps which is connected in series with the motor of the fan. Basic circuit diagram of a conventional fan regulator is as shown in the figure below.
The circuit diagram shown above explains very well about working of a conventional fan regulator. When the knob is at position 1, the maximum resistance is added in series with the single-phase AC motor of the fan. Thus, the voltage drop across this resistance of the regulator will be maximum and hence, a reduced voltage will be applied to the motor of the fan.(See – speed control methods of induction motor.) When we move the knob to position 2, resistance R12 will be dropped out, and only the resistance from point 2 to point 5 will be in the circuit. Hence, in this case, the voltage applied to the motor will be slightly greater than that of the previous case. Similarly, as we move knob towards towards right, the series resistance will decrease. When the knob is at position 5, full voltage will be applied to the motor as there is no external resistance in the circuit and hence, the speed of the fan will be maximum. This was the basic working principle of a conventional ceiling fan regulator.
Electronic fan regulator
Nowadays, fan regulators have become a lot more compact than conventional regulators. These Electronic fan regulators come in sizes as small as a regular electric switch. According to size, electronic regulators are classified as (i) switch type and (ii) socket type. Further, there are two common types of electronic fan regulators: (i) TRAIC based fan regulator and (ii) Capacitive type fan regulator.
TRAIC based (dimmer or stepless type) regulator
A general circuit diagram of electronic TRIAC based fan regulator is shown in the figure below.
Resistor R1 is a variable resistor (potentiometer) which is attached to a knob. This knob controls the gate current of the TRIAC, through a circuit consisting of a DIAC and a capacitor (called as firing circuit). This gate current controls the current flowing through the TRIAC, consequently controlling the power fed to the motor of the fan. Thus, the speed of the motor (fan) is controlled.
This type of regulator offers stepless speed control. They are expensive than resistive type regulators. One main drawback of this type of regulator is harmonic distortion, which causes fan motor to heat up and produce a humming noise. Also, active devices such as DIAC and TRIAC being susceptible to power supply transients, these regulators have high failure rate.
Capacitive type (stepped) regulator
In a capacitive type fan regulator, various combinations of capacitors is used to control the speed of the fan. Following is the basic block diagram of a capacitive type fan regulator.
The basic principle – voltage across a capacitor is given as Vc = Q/C where Q is the charge and C is the capacitance. According to this formula C ∝ 1/Vc (or voltage across capacitor is inversely proportional to the capacitance). Hence, if capacitance is increased then the voltage across the capacitor decreases allowing more voltage across the fan motor. Hence, if capacitance is increased, speed of the fan motor also increases. Capacitance is increased or decreased in a capacitive type regulator by connecting capacitors in different configurations.
For example, consider a regulator that consists 3 capacitors of 1 μF, 2.2 μF and 3.1 μF. When the knob position is at 1, then only 2.2 μF capacitor gets connected into the circuit. For knob position 2, only 3.1 μF capacitor gets connected. When the knob is at position 3, capacitors of 3.1 μF and 1 μF in parallel configuration is connected so that equivalent capacitance becomes 3.1+1=4.1 μF. For position 4, parallel configuration of 3.1 μF and 2.2 μF is connected. And for the maximum speed, no capacitor is connected in the circuit.
Which one is energy efficient?
- In conventional regulator, voltage drop in the resistance is converted into heat energy, which means the loss of energy. This loss is maximum, when the fan is running at minimum speed (as more resistance is connected in series more energy is lost into heat).
- In electronic regulators, TRIAC based circuit is used to control the output voltage which causes very less power loss as compared to that of conventional regulators. Similarly, power loss will also be lower in case of capacitve type regulator as capacitors do not dissipate much of energy in the form of heat.
Conclusion: An electronic regulator is more energy efficient than a conventional (resistance type) regulator. However, a stepless electronic regulator may not be good for the life of fan. A stepped capacitive type fan regulator is energy efficient as well as more reliable.
Learn here how to wire a ceiling fan.