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Thread: Yaskawa VFDs

  1. #1
    Join Date
    Mar 2004
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    Austin, Texas
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    Does anyone know if Yaskawa model E7U VFDs can tolerate an electrical disconnect between the VFD and the motor? Some drives will smoke the drive (catastrophic failure) if the disconnect is shut off while the drive is operating the motor. I've looked through the manual and don't find any indication that a disconnect should NOT be installed between the drive and the motor or that it is OK.

  2. #2
    Join Date
    Oct 2003
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    Call Yaskawa tech.support 1-800-972-5292

    Have model and Serial # of drive Ready

    There the one's that can say yes or no.

  3. #3
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    I got the following email response back from Yaskawa.

    "The E7 drive, as well as all other Yaskawa drives, will tolerate a disconnection between the drive and the motor while in operation. However, at no time do you want to close a contact between the drive and the motor while the drive is running."

    Hmmm, I thought it was the circuit being opened that smoked the VFD. From this answer it looks like these VFDs will tolerate the circuit being opened, but not remade. It sounds like the disconnect would have to have a sign something like "Turn off VFD in room 105 prior to switching disconnect back to ON".

    Would that make sense to you if you were on a roof working on a fan with no VFD in sight?

  4. #4
    Join Date
    Oct 2003
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    I would get rid of Disconnect and turn off and on from vfd

    Because somebody is not going to read the sign and blowup the vfd.


    Make sure you lock and tag for safety

  5. #5
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    Why the vfd would blow the motor? as far as I know vfd work by converting the ac signal into dc, then the capacitor bank stores the dc power and the inverter converts it into a variable ac output.

  6. #6
    Join Date
    Sep 2000
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    Miami, Fla. USA
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    A really great installation will have a micro switch in the service disconnect. If you pull the handle the VFD will shut down on external interlock before the knives break. A normal restart will then occur upon closure.
    But then again how many great installs are there?

    By the way, Yaskawa was right on.

  7. #7
    Join Date
    Sep 2000
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    Miami, Fla. USA
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    Originally posted by jaymax
    I would get rid of Disconnect and turn off and on from vfd

    Because somebody is not going to read the sign and blowup the vfd.


    Make sure you lock and tag for safety
    Sorry man, you cannot get rid of the disconnect. Think safety over equipment.

  8. #8
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    Mar 2004
    Location
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    Originally posted by Chomper
    A really great installation will have a micro switch in the service disconnect. If you pull the handle the VFD will shut down on external interlock before the knives break. A normal restart will then occur upon closure.
    But then again how many great installs are there?

    By the way, Yaskawa was right on.
    That would be the best solution. Second best would be to run power from the breaker to the disconnect, then back to the VFD. That way when the disconnect was opened it killed the VFD. But this is already installed so no one wants to change anything. Engineer thought he could specify that the VFD had to tolerate a disconnect anywhere. Unfortunately, there don't seem to be any of those VFDs available. If only engineers were really as good as they thought they were...

  9. #9
    Join Date
    Oct 2003
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    230

    Talking

    Valdelocc

    The VFD Blows up not the motor.

    Major damage to the Rectifier circuit inside VFD, lots of fire and smoke!



    Things never work when you let the smoke out.

  10. #10
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    Mi scusi ,Mi scusi

  11. #11
    Install a disconnect with a "late make, early break" aux. contact. Then just intterupt the "run forward" input on the VFD through that aux. contact.

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