Page 3 of 3 FirstFirst 123
Results 21 to 30 of 30

Thread: VFD Ground fault

  1. #21
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055
    In a way I was hoping to find all sorts of dust to clean up. If there was, it’s deeper than I wanted to go.
    Tom
    TBLO

  2. #22
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,930
    Quote Originally Posted by Besoeker View Post
    I don't know if it's the same product that we have here called Air Duster. If so, a word of caution. It is flammable. My daughter got a bit of a fright when she got flames coming out of her laptop. The lesson is don't use it on live equipment. I just thought ptonsparky ought to made aware of that.
    many of the air dusters are either just air or nitrogen. i don't see how either could ignite. I think some of them use propane as a propellant though.
    Bob

  3. #23
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055
    Welll, newly wound motor ran for about 2.5 days before it started tripping on ground fault. Basically the same as the loaner motor that was on for a while. An area motor shop indicates I will not find a pin hole fault with my Fluke 1507, but the VFDs will. I would have to agree just from personal experience.

    Local AB sales rep suggest we install heaters in the windings of the motors. Little late for that now and a motor that has run FLA for 60 hours is certainly not damp by then.

    Will circulating ground currents affect the VFDs ability to determine a ground fault?

    AFAIK we do have some but have yet to figure out how to get rid of them.

    Wouldn't the GF detection actually require a fault to ground? is it measuring a change of current in an amount of time that would ignore the basic smell test?
    Tom
    TBLO

  4. #24
    Join Date
    Dec 2015
    Location
    Yakima, WA
    Posts
    181
    Quote Originally Posted by ptonsparky View Post
    Wouldn't the GF detection actually require a fault to ground? is it measuring a change of current in an amount of time that would ignore the basic smell test?
    jraef will have the answer but I'd guess the ground has some type of current monitor to detect a fault. A motor on a VFD can be grounded but still run. Sounds impossible but I've seen it myself

  5. #25
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,113
    GF is a percent of non-returning current using the RCD method, in the PowerFlex drives its 25%, so that can be a lot of current and it is generally not going to be noise or circulating currents.

    At this point I'd be suspecting leakage in the cables. I've seen it where if you do a 1000V megger test and everything is dry, it passes. But there are pin holes in the cables going phase-to-phase that leak only under standing wave situations when the voltage spikes are high, but don't show as a GF so long as it never goes to ground. Then when enough moisture builds up in the conduit, it does leak to ground and becomes a GF trip.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  6. #26
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055
    That's are next step. Replace everything from the load reactor to the Motor and clean up the termination method if we can find what we need. I'd use VFD cable if someone had 15' on hand for a 200 HP motor. Plus the connectors. Plus it will be outside. Don't forget those rodents.
    Tom
    TBLO

  7. #27
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055
    Owner made some phone calls & he got a quicker response then I did. I wasn't forcing the issue yet until after we replace the conductors from vfd to motor. (You guys don't know how lucky you are sometimes to live in more populated areas. Finding parts in stock is a nightmare. I had more than 5 of my suppliers. I had 3 2/0 crimp lugs, they had 0.)

    Depending on mfg date there is an issue with the frame size we have. The drive ran for about a day and half again before it faulted this morning. Owner was going to disconnect the load side conductors and turn the drive back On. If it faults, new drive. At the moment it's running with no load.
    Tom
    TBLO

  8. #28
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,113
    Quote Originally Posted by ptonsparky View Post
    Owner made some phone calls & he got a quicker response then I did. I wasn't forcing the issue yet until after we replace the conductors from vfd to motor. (You guys don't know how lucky you are sometimes to live in more populated areas. Finding parts in stock is a nightmare. I had more than 5 of my suppliers. I had 3 2/0 crimp lugs, they had 0.)

    Depending on mfg date there is an issue with the frame size we have. The drive ran for about a day and half again before it faulted this morning. Owner was going to disconnect the load side conductors and turn the drive back On. If it faults, new drive. At the moment it's running with no load.
    Yeah, this was true on that size of drive; it was a batch of CTs on the output that were made by Honeywell and they are bad in that they fail prematurely. If it does fall into that date code, A-B will rebuild the drive for free, but if it outlasted the warranty (which it would have by now because this was 2-3 years ago), they will have to pay the freight costs. Running without a load on it by the way is not a valid test, but they could put ANY load on it, i.e. a small little motor.

    Go to the A-B Knowledgebase and look at articles 900207 and 60178
    Last edited by Jraef; 07-27-18 at 03:00 PM.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  9. #29
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055
    Quote Originally Posted by Jraef View Post
    Yeah, this was true on that size of drive; it was a batch of CTs on the output that were made by Honeywell and they are bad in that they fail prematurely. If it does fall into that date code, A-B will rebuild the drive for free, but if it outlasted the warranty (which it would have by now because this was 2-3 years ago), they will have to pay the freight costs. Running without a load on it by the way is not a valid test, but they could put ANY load on it, i.e. a small little motor.
    IDK...I do have a small motor. its only two hours one way.

    https://rockwellautomation.custhelp....ail/a_id/60178
    Tom
    TBLO

  10. #30
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    10,055

    Good news!

    The drive is no longer intermittent!

    New is on on the way.
    Tom
    TBLO

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •