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question : about a DC-motor

Discussion in 'Electronic Basics' started by bamse, Jan 21, 2004.

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  1. bamse

    bamse Guest

    I have a chart that shows the correlation between torque and rotational
    speed for a DC-motor:

    The chart can be viewed here:

    The motor is inside an actuator, which is used to control the pitchangle of
    a rotor blad on a wind turbine.

    For those who do not know what "pitchangle" is, I can inform that pitching
    of a wing just means rotation of
    a wing around its length-axis.

    My question is:

    What is the chart used for? What can you deduce from this chart? And what
    relevant information can be deduced when the motors purpose is taken into
  2. I don't have any information about the torque and speed requirements
    of your application, especially, how the motor will be geared, so I
    can't tell you how fast the motor will turn, or its efficiency or its
    current and power requirements. You need to produce a system curve
    that relates torque to speed for your load. In other words, if you
    had a way to measure the load's torque as you applied different speeds
    of rotation to it, a graph of that relationship would be the system
    curve. When you add a trace of that curve over the motor torque speed
    line (in red) the point where they cross will show approximately what
    speed the motor will operate at, and what torque it will be
    producing. Then you draw a vertical line through that common point
    through the other curves, to find out what the power requirements and
    efficiency of the motor will be, operating at that speed and load.

    If that speed is not acceptable, you have several choices. Either you
    change the applied voltage (which result in a different set of motor
    curves, that are fairly extrapolatable from this set) and repeat the
    process, or you change the gear ratio to change the system curve, or
    you select a different motor.
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