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  1. #1
    Join Date
    Jun 2012
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    VFD casuing motor issues

    I have a relatively new Danfoss VFD on a brand new 3 phase, 240 volt motor. It ran fine for a few days, but now, when the VFD gets up to around 60 hertz, the motor slows down to an idle speed. The amp draw doesn't exceed the motors ratings, and no error is indicated on the display of the drive. If I open the door to the AHU with the drive around 55 hertz, I get the same thing where the motor slows down with no indicated fault on the drive. I have to kill the disconnect to bring the motor back under control. When I bypass the drive, the motor runs fine. Where should I look next?

  2. #2
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Does the drive still have a ref signal coming in showing the sped it should be commanded to?
    UA Local 32

  3. #3
    Join Date
    Jan 2003
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    USA
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    Or put it in hand and see if anything changes.
    Propagating the formula. http://www.noagendashow.com/

  4. #4
    Join Date
    Jun 2012
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    Quote Originally Posted by orion242 View Post
    Or put it in hand and see if anything changes.
    Does the same thing when put into hand.

    Quote Originally Posted by buford View Post
    Does the drive still have a ref signal coming in showing the sped it should be commanded to?
    Yes, reference shows 100%. The drive still indicates 60 hertz.

  5. #5
    Join Date
    Sep 2007
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    edmonds wa
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    Output volts to motor?
    UA Local 32

  6. #6
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    Jan 2003
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    Nothing wrong with the controls then. Motor within limits and no alarm on the vfd, I would reset the drive to factory and set things up again before claiming the vfd is toast.
    Propagating the formula. http://www.noagendashow.com/

  7. #7
    Join Date
    Aug 2016
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    I have had a danfoss drive do something very similar in the past.
    It ran for about a month then would shut down to idle, around 15z from memory.
    Danfoss couldn't help me out, we couldn't find anything in the parameters to lock it to that speed, so they replaced it.

    I won't use the Danfoss drives anymore after we had a few issues, well not their basic model away, the 102 model seems good but expensive.
    ABB and sinamics/siemens are my only choice now.

  8. #8
    Join Date
    Jul 2013
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    Was the drive properly setup to match the motor on startup. A VFD can be configured to reduce motor speed in the event of over ramping causing higher motor amp draw.

    Sent from my XT1254 using Tapatalk

  9. #9
    Join Date
    May 2013
    Location
    Luxembourg
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    About 15 years ago I had an event like the told one when I hooked a Danfoss VFD drive to a screw compressor motor with 37 kW: The motor started up but it fell down some seconds later with speed 0 at nominal intensity. The solution has been to set the VFD drive to a constant couple of the motor.

  10. #10
    Join Date
    Mar 2005
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    840
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    sounds like torque parameters or similar
    Keep it simple to keep it cool!

  11. #11
    Join Date
    May 2013
    Location
    Luxembourg
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    Exact. As my professional life is running in french I've used the french expression. I apologize for the inconvenience.

  12. Likes stanbyyourword liked this post
  13. #12
    Join Date
    Mar 2005
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    Quote Originally Posted by stability View Post
    Exact. As my professional life is running in french I've used the french expression. I apologize for the inconvenience.
    santee
    Keep it simple to keep it cool!

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