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Question on converting amp / volts to watts

Discussion in 'Electronic Repair' started by Hoopster, Sep 22, 2005.

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  1. Hoopster

    Hoopster Guest

    Hello,


    I just purchased a product and the motor has 4 different speeds. The
    box says 0.7 amps / 120 volts.


    I'm assuming that you just multiply the amps x volts to get the watts
    which would be 84 watts. Is that correct? If it's correct is that the
    max on the highest setting? Meaning if you put it on the slowest
    setting would it be under 84 watts?


    Sorry for the newbie / dumb type questions, but I know nothing about
    this stuff.



    Thanks in advance for any help.



    Hoops
     
  2. Ken Weitzel

    Ken Weitzel Guest

    Hi...

    You're promoted from newbie to... to... to whatever comes next :)

    Ken
     
  3. Eric Vey

    Eric Vey Guest

    And if you want to have some real fun, get a clamp-on multimeter (these
    things don't cost as much as they used to). Then get a cheap 6' lamp
    extension cord and carefully split the wire for about a foot, taking
    care to keep both wires insulated. Plug your device in to the extension
    cord, clamp over the hot and you can see exactly how much current the
    motor is using at each speed.

    It's a gas.
     
  4. Mike Berger

    Mike Berger Guest

    Nominally, yes, you multiply amps x volts to get watts. But it's
    not completely accurate due to "power factor". But lets not
    complicate things.

    The figure on the box normally reflects the highest amount of
    current it should draw under normal operation. Depending on the
    device and how it's controlled, a lower speed doesn't necessarily
    mean lower current.
     
  5. James Sweet

    James Sweet Guest


    Power factor can be pretty significant, the amperage draw of an inductive
    load can easily be double what the actual power draw is.
     
  6. Asimov

    Asimov Guest

    "James Sweet" bravely wrote to "All" (23 Sep 05 03:18:53)
    --- on the heady topic of "Re: Question on converting amp / volts to watts"

    JS> From: "James Sweet" <>
    JS> Xref: core-easynews sci.electronics.repair:342872



    JS> Power factor can be pretty significant, the amperage draw of an
    JS> inductive load can easily be double what the actual power draw is.

    An ac motor, at the moment it starts, typically draws about 3 times
    its rated current.

    A*s*i*m*o*v

    .... The current limits placed are based on resistance
     
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