DC fans

petertearai
petertearai Solar Expert Posts: 471 ✭✭✭✭
in General Solar Power Topics #1
Bought a DC desk fan uses 10 watts . Similar AC ones are around 30 watts.
Was telling my neighbor about the energy saving ..they asked WHY  is a dc fan more energy efficient.
Didn't have an answer ... anyone know?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    DC fans have permanent magnets and the brushless ones have a very power saving control circuit.
     Efficiency measures have not been applied to AC fans in the same manner.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    The 12VDC fans  use brushless dc motors BLDC, which do not suffer magnetizing losses as do asynchronous AC induction motors, thereby making them inherently more efficient  The torque required to move air would offset efficiency gained, so the use of multiple blade usually 5 shallow pitch, as opposed to 3 deep pitch for AC fans where energy is of less concern. The volume of air moved has to be factored into the equation to make an accurate comparison, as well, the quality of the AC motor used in fans is probably not the best so perhaps ~75-80% efficient, whereas BLDC are in the mid 90% region. 
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #4
    Thanks for your replys . Should have said it is supplied with AC  but then must be rectified.AC to DC conversion must also be efficient .
    Seems to have a good airflow .... but not specs on that. Indeed it has 5 blades .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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