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Thread: A Few Notes On Two Speed Induction Motors

  1. #11
    Join Date
    Sep 2017
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    Poulsbo, WA
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    Here is the Data Plate from the motor
    I read it as
    5 HP, 3390 RPM, 13.2 A
    3 HP, 1710 RPN, 10.2 A

    Be_Zero_Be



  2. #12
    Join Date
    Nov 2007
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    Woodinville, WA
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    Quote Originally Posted by Noitoen View Post
    In his case, low speed 5hp high speed 3hp.
    no... other way around. Constant torque means rpm increases with speed. No quite linear, but close enough.

  3. #13
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    Jan 2004
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    Missouri
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    Quote Originally Posted by lakeside53 View Post
    no... other way around. Constant torque means POWER increases with speed. No quite linear, but close enough.
    Fixed it
    1601

    Keep eye on ball.
    Hashim Khan

  4. #14
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    lol.. thanks and it's even later for you than me!..

    ...but heck rpm does increase with speed

  5. #15
    Join Date
    Oct 2013
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    Setubal, Portugal
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    That plate is stamped out wrong (on purpose ). It's true that the motor draws more current in the high speed but the real power at the shaft is less. It draws more current due to poor efficiency. I've been in the motor rewinding business for many years and repaired a lot of these motors for construction cranes.
    Helder Ferreira
    Setúbal, Portugal

  6. #16
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    We will just disagree then.

    Were the motors you worked on were wound for constant HP and not constant torque? I can see why a crane would want a constant HP motor (same lifting capacity at different speeds). The OP motor is constant torque and very common in machine tool applications.
    Last edited by lakeside53; 06-13-2018 at 10:50 AM.

  7. #17
    Join Date
    Dec 2016
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    Helsinki, Finland, Europe
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    Quote Originally Posted by lakeside53 View Post
    We will just disagree then.

    Were the motors you worked on were wound for constant HP and not constant torque? I can see why a crane would want a constant HP motor (same lifting capacity at different speeds). The OP motor is constant torque and very common in machine tool applications.
    The 2 most common Dahlander motor windings round here are constant torque and quadratic torque.
    constant torque one would make 50% power at half speed
    quadratic torque ones are used with fans and centrifugal pumps and make only 25% of power at half speed.
    Constant HP 2-speed motors are rare beasts.

    For example:
    http://lst.fi/webshop/media/M3000_Aluminium.pdf

    Fan-drive 2-speed motors start at page 31 and constant torque ones at page 35
    Last edited by MattiJ; 06-13-2018 at 11:05 AM.

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