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Thread: York YMC2 VSD-MOTOR CURRENT THD FAULT

  1. #1
    Join Date
    Oct 2021
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    York YMC2 VSD-MOTOR CURRENT THD FAULT

    Hi
    Working on a YMC2 and am having vsd- motor current THD fault occur. Can run the unit with no issue at 70% once it ramps to 100% it will fault. I have noticed the grid THD is sitting at 7% could this be causing the issue

  2. #2
    Join Date
    Apr 2015
    Location
    Kent, OH
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    All I have for the YMC squared chillers is the operation manual so not a lot of details. The alarm description for VSD - MOTOR CURRENT THD FAULT says “motor current (inverter output) total harmonic distortion (THD) level is exceed. The fault is based on a fixed value of measured harmonic current from the inverter.”
    I would imagine that the displayed THD going over the limit would trigger the alarm but what the limit is and what’s causing the unit to exceed that I have no idea. I have two of these units running right now with no issues one is running 25% capacity with THD values in the 3% range, the other is around 47% capacity with THD around 5%

  3. #3
    Join Date
    Oct 2021
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    Thread Starter
    When this unit was running correctly I had similar values as well, now while running it sits around 8%

  4. #4
    Join Date
    Mar 2010
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    High THD values can be caused by misfiring gate drivers on the inverter. Also, if the output LC filter components have been damaged it will fail on THD as the load increases.

  5. #5
    Join Date
    Jan 2006
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    In a land far, far away
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    You appears to be a tech, so moved to the Open Chiller's forum.

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