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  1. #1
    Join Date
    Apr 2010
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    Ontario
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    464

    Motor with VFD runs hot, 170*f

    Motor with VFD runs hot, 170*f.
    Cutler hammer AFM15100B. 575 volt, 3ph, 10hp
    10.4 amp motor, 10 hp motor.
    Measured input voltage at 592, output voltage at 650, running at full speed, 60 hz, 10.6 amps.
    When speed drops to 56 hz, amps are 9.6, output volt are 643.
    Blows one fuse, the same fuse after some 3 hours of run time.

    Volt to hertz ratio set to high? Customer says no one has touched anything.
    I'll need to go back with a manual.

    Any thoughts?
    ENJOY THE RIDE

  2. #2
    Join Date
    Oct 2001
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    6,853
    is the motor and VFD new items since install.is the VFD rated for that motor in Volts and HP maximum off tag?the motor is 170F or the VFD cabinet is?if the motor is old and the VFD was installed as add on?are the fuses before the VFD or between the VFD and motor?if the motor is older having run 60Hz since install now the windings are seeing voltages above tagged nameplate as the amps drop in inversion ramping....is it just a soft start or are you doing VAV static supply air to setpoint.how far is the VFD from the motor...is the VFD vented or cooled in anyway besides just the MER
    "when in doubt...jump it out" http://www.youtube.com/watch?v=Px5YcOeQB4I

  3. #3
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    Apr 2010
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    Ontario
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    Motor and vfd have been there for years.

    Motor is 170*f.

    Power goes through starter before the vfd. Power goes through the contactor part, then to the vfd, back to the starter into the overloads and to the motor.

    Vfd and motor are 15 feet apart.

    Vfd responds to static pressure.
    ENJOY THE RIDE

  4. #4
    Join Date
    Jul 2007
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    Mount Airy, MD
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    Moved to Tech to Tech

  5. #5
    Join Date
    Feb 2012
    Location
    Upstate SC
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    84
    Not saying that your problem is here, but I have never seen a VFD that also required a starter and heater.

  6. #6
    Join Date
    Oct 2005
    Location
    B.C. Canada
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    826
    Quote Originally Posted by jburchstead View Post
    Not saying that your problem is here, but I have never seen a VFD that also required a starter and heater.
    I am agree.. sounds like a weird configuration.. may not be the problem, but how does the contactor look??

  7. #7
    Join Date
    Nov 2011
    Location
    British Columbia
    Posts
    48
    I would recommission the drive, no doubt about it.

    Who knows maybe someone was curious and changed a parameter by mistake and doesn't want to say.

    Make sure the switching frequency is not se too high on the VFD.

    Also, get rid of the starter and its OLs, the VFD already handles those duties. They aren't rated for VFD voltages anyway - not good!
    Last edited by RuralSpaceman; 03-29-2012 at 12:06 AM. Reason: thought of something else.

  8. #8
    Join Date
    Feb 2009
    Location
    good old Europe
    Posts
    160
    If the motor is rated 575VAC @ 60Hz, the drive should provide 575VAC @ 60Hz. Usually a motor accepts a +/- 10% variation in input voltage which would be 632VAC. You measured 650VAC. If you apply slightly higher voltages to a motor the amps decrease. Your motor read the maximum amps with higher voltage. This could be an indication of increased mechanical load on the shaft (controlled pressure above design?). I think it is worth to check the motor settings in the drive (Depending on them the drive sets the V/f ratio which do not really fit in your case.) and whatever is attached to this motor.
    "Quality exists, when the price is long forgotten."

    Henry Royce

  9. #9
    Join Date
    Oct 2001
    Posts
    6,853
    you mentioned blowing a fuse but you have a starter?maybe somebody can kick in here are you pulling inverted voltages thru a starter?the VFD itself is an overload protection.i have seen slow-blow fuses and a 3 phase contactor supply a VFD and called a power contactor with Trane units.the 3 phase out of the VFD should go to the load not an overload device!
    "when in doubt...jump it out" http://www.youtube.com/watch?v=Px5YcOeQB4I

  10. #10
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,278
    FLA 10.4 "or" SFA 10.4 ?

    and the drive is programmed for which?

  11. #11
    Join Date
    Apr 2010
    Location
    Ontario
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    464
    Customer had me replace the motor. He had no interest in checking out the vfd or removing the starter. He said no one has touched the vfd and the starter has been there for years. So it has to be the motor. New motor is still to hot to touch. Everything else was the same when I left. So now he'll call to say it broke again, never call me again in embarrasment, or it actually works. Either way I had him sign off to say he accepts all outcomes, good or bad.
    ENJOY THE RIDE

  12. #12
    Join Date
    Nov 2011
    Location
    British Columbia
    Posts
    48
    You can lead a horse to water...

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