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Power consumption of 1/10 HP motor.

Discussion in 'Electrical Engineering' started by RFI-EMI-GUY, Jun 18, 2008.

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  1. RFI-EMI-GUY

    RFI-EMI-GUY Guest

    Can anyone comment the power consumption of this motor? Is this at all
    typical. The application is a 800 CFM attic fan.

    "1.2.2 Motor: 1/10th HP, thermally protected shaded pole type, 1100 RPM,
    3.4 AMPS." - used at 115 VAC - 391 VA

    My concern is not with peak load, but typical consumption when running
    in that application. By comparison I measured my 1/2 HP rated air
    handler motor at 3.0 Amps 230 VAC. 690 VA

    Given that this is 1/5 the motor as the one used in my airhandler I
    would expect it to consume only about 138 VA or 1.2 A at 115 VAC.

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"©

    "Treason doth never prosper: what's the reason?
    For if it prosper, none dare call it treason."

    "Follow The Money" ;-P
     
  2. James Sweet

    James Sweet Guest


    You need to know the power factor in order to get a meaningful number
    here, it may only be around 0.5. One of those $20 Kill A Watt devices is
    perfectly adequate for measuring the true power consumption.

    Shaded pole motors are not very efficient, you'll notice they tend to
    run very hot. Still, without knowing the actual load or the power factor
    you're flying blind and anything is just a guess, but it's easy to measure.
     
  3. RFI-EMI-GUY

    RFI-EMI-GUY Guest

    True but I have neither the motor or a Kill A Watt meter on hand.



    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"©

    "Treason doth never prosper: what's the reason?
    For if it prosper, none dare call it treason."

    "Follow The Money" ;-P
     
  4. RFI-EMI-GUY

    RFI-EMI-GUY Guest

    The 3.4 amp specs are typical for attic exhaust fans. Should I assume
    that the nameplate current draw is "locked rotor" value provided in case
    someone decides to install 5 of these on one 15 amp circuit?

    I am only interested in what the motor normally draws while running. If
    two of these fans require nearly 800 watts to exhaust and cool my attic,
    I am concerned. If its only 300 watts I am less concerned. Does anyone
    have a ballpark on this?

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"©

    "Treason doth never prosper: what's the reason?
    For if it prosper, none dare call it treason."

    "Follow The Money" ;-P
     
  5. James Sweet

    James Sweet Guest


    I would guess about 140W, but that's only a guess. The power factor if
    uncorrected is probably only about 0.5, so the VA will be around double
    what the wattage is, and the label is for worst case conditions. In the
    real world, the fan is probably not pushing the motor to produce its max
    rated horsepower.
     
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