AC Servo Motor Repair: Encoder Re-Alignment- The Final Step

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The expert technicians at RepairZone have a standard process they work through with every repair.  While there are multiple steps in the process of an AC Servo Motor repair, one of the final steps are one of the most crucial. This step is the encoder re-alignment.

  • If correct alignment data of a servo motor is unknown it must be gathered prior to disassembling the motor  in order to correctly realign during the assembly process.
  • When the motor has been disassembled, the encoder must be lined up again so it’s properly aligned with the magnets on the rotor and the windings of the stator.
  • If the encoder has been replaced, adjustment of the assembly is necessary.
  • Dynamic alignment (setting while under rotation) of commutation is accomplished by back driving the motor in the forward direction and using an oscilloscope to compare output of generated voltage of the stator/rotor to the corresponding commutation channel.
  • Oscilloscope traces from the line to line stator voltage and square waveform from the corresponding  hall switch represents one phase to phase voltage and one rotor position feedback signal.
  • Most units will have three position feedback signals that will match up to three line to line voltage outputs.
  • When feedback outputs are correctly matched with their voltage outputs, then adjusting one set of outputs will also adjust the remaining two.

The RepairZone technicians use manufacturer software and align the encoder to factory specifications.  Encoders differ greatly from brand to brand.  They are also very fragile and can be quite finicky.  After successful alignment, the motor is run-tested for 2-3 hours with a model specific drive or amplifier.   Without proper re-alignment, an AC servo motor simply will not work properly.

If you have any questions or need assistance, please call 989-922-0043.  To view our Servo Motor Repair capabilities  or Servo Motors in Stock at RepairZone, click the appropriate button below:

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5 Comments

  1. Nice information.
    Keep Posting information like this & it is really useful.
    I am working as service engineer in CNC Machine tool industry.

    with regards
    senthil kumar

  2. Dear cammy,

    I have recently aligned an incremental Encoder with AC servo motor whose “U” phase is ending along with the index pulse of encoder in oscilloscope. But before alignment motor was starting with high torque and high speed with oscillation after alignment there was no problem in starting and stopping as per the command but i am getting motor heating up complaint with continuous operation.

    Will encoder misalignment will create excess heat in motor?

    • Thank you for your response and question.

      Encoder misalignment will most definitely cause the motor to heat up. It would be like rotating the distributor in a car then trying to drive it. I hope this helps. Please feel free to visit us again with future questions. Good day.

      Jade York

  3. Hello
    We face 2074 encoder position disturbed alarm in servo motor , resulting in breakdown of machine. can you please suggest what precaution need to take to eliminate such problem in future, as well as what is reason of this alarm.

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