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induction motor speed

Discussion in 'Misc Electronics' started by exxos, Jan 6, 2005.

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  1. exxos

    exxos Guest

    Hi all,

    I don't think its possible to alter the speed of a induction motor ?, so
    just checking......

    cheers
    chris
     
  2. Yes and no. There are variable frequency drives that allow this but not all
    induction motors lend themselves to this service. The mechanical load and
    the speed range must be considered. Motors can get very hot very fast!
     
  3. You're wrong.

    petrus bitbyter
     
  4. exxos

    exxos Guest

    I suspected altering the frequency was the key, Voltage changes nothing,
    probably not so much of a easy task to alter frequency of the motor, unless
    you work for a large power company and alter the mains down to around 25hz
    :)

    Chris
     
  5. I suspected altering the frequency was the key, Voltage changes nothing,
    This is accomplished with an inverter. The problem is that a 60 Hz (or 50
    Hz) motor does not have enough iron in it to allow efficient 25 Hz
    operation. The motor will run hot due to not having enough inductive
    reactance at the reduced frequency. Dropping down to 10 Hz would make it
    even worse. A motor designed for variable frequency drive has more iron.
    Also, it might use a different iron/steel alloy to allow efficient operation
    at higher frequencies (say 400 Hz).

    With a light mechanical load and a good motor, it's sometimes possible to
    get a reasonable speed range using a variable frequency inverter.
     
  6. A good one controls both frequency and voltage. The better ones even take
    into account that at very low speeds the resistance of the coils cannot be
    negelected.

    petrus bitbyter
     
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