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  • Category: Technology

    Do electric fans consume the same amount of electricity when operated at different speeds?

    Interested in knowing about electricity consumption of fans? Find response from experts on this page.

    The electric fans come with a regulator to increase or decrease its speed. Many people say that the electric fans consume the same amount of electricity whether operated at a slow speed or at the full speed as the resistance element provided inside the regulator consumes the electricity when operated at a slower speed. Do electric fans consume the same amount of electricity when operated at different speeds?
    Experts: do respond.
  • #138677
    The regulator, which comes to regulate the speed of fan is of different types. One type, which uses potentiometer kind of thing and regulate the speed by dropping the voltage across resistances kept in series of fan.
    For different speeds, different sets of registers are used in series with fan. Thus for more resistors in series, more voltage will drop in resistors and lesser voltage will drop across fan. This lesser voltage across fan (say 150 V in place of standard 230V) will reduce the fan speed.
    In such type of regulator electricity consumption will be equal at all speeds, as same power loss will be there in all cases. Voltage drop across resistors will generate heat inside regulator. These types of regulators were rarely used now.
    Now a days different type of regulator is used which uses triac as regulator. It controls the flow of current by changing the firing angle. Here current is reduced, therefore power consumption is less. Changing of firing angle is basically limiting or chopping off the waveform by limiter or zero detector and thus reducing the average voltage to the fan and reducing its speed. Power is the product of current and voltage. Thus by reducing current and voltage we reduce the consumption of electricity.
    Therefore, we can conclude that the consumption of electricity does not change at different speed of fan if we use old resistor type of regulator. But by using triac type of regulator electricity consumed at different speed is different and for lesser speed we have to spend less electricity.

  • #138696
    Earlier days, the regulators used in electric fans were resistors. The regulators used to resist flow of electric current causing less speed, when the regulators functioned at higher level. There was no change in flow of electricity. So, in case of electric fans where old type of regulators are used, the consumption of electricity is always same irrespective of the speed of the fan.

    However, nowadays a new type of regulators is being used in electric fans. It controls the flow of current. In case of electric fans where these new regulators are being used, consumption of electricity is different at different speed.

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  • #138710
    Earlier, the function of the resistor was to restrict the flow the electric - current. More is the resistance employed, lesser will be voltage and hence less will be the current flow. But in that way, the power - consumption could not be reduced since because of higher resistors, there was wastage of energy in the form of heat. In case of employment of less resistance, the entire current offered the maximum power to operate the fan in full speed.
    So, we could conclude that speed - variation by applying different resistors provided the variable speed but the power consumption was constant in all the cases.
    With the advent of new type of regulator in the market, the consumption of current is directly proportional to the speed of the fan and hence, lesser is the speed, lesser is the power - consumption.

  • #138805
    The five stage voltage regulator regulate the speed of fan by dropping the voltage across registers kept in series inside the regulator. For different speeds, different sets of registers are used in series with fan. If more value of a resistor in series, the more voltage will drop across the resistor. If less value of register, less voltage drop across register. This less voltage across the registers will reduce the fan speed.The electricity consumption will be equal at all the speeds because voltage drop across resistors will generate heat inside regulator.
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  • #140371
    A typical AC powered multispeed fan will use more power at higher speed positions. The work being done is moving air and at higher speed, more air is moved using more work from the motor. Keeping it at as low a speed as possible will save more energy.
    Rheostats have a huge coil inside. When you choose low speed options, you are actually choosing higher circuit resistance, leading to a lower current (as voltage is fixed), lower voltage a power to the fan, making fan slower. Hence, rheostats can make the fans slower or faster and overall power consumed will be lower at lower speed but you don't save as much as you expect. Power not used by fan is dissipated in form of heat in regulator (this wastage is higher in fraction at lower speeds). That is why they have a small vent at the top and also a black trail above them on the wall in long term.
    Capacitive regulators are more energy efficient and do consume less power at low speeds and vice versa.

  • #142826
    No, the fan consumes the same amount of current operated at different speeds. As when you control the speed of your fan you are actually controlling the voltage drop. This voltage drop actually generates heat inside the regulator, which does not affect the current flow or the current consumption at all.

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