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Thread: ABB Drives

  1. #1
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    Frown ABB Drives

    I have a question about ACH 550 ABB Drive the control company that installed the Venmar rtu has been out our campus numerous times for a Earth fault hard lock out they made some adjustments to the drives programming, to no avail they have not fixed the problem ,feeling frustrated and looking for some answers ,can anybody help ?

  2. #2
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    The rep here usually disables the earth fault protection when we have intermittent issues. They don't feel it's a big deal to do so because of redundant safety devices...
    "If history repeats itself I am so getting a dinosaur"

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  4. #3
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    What type of application/ motor is it on?
    Probably not the drive's fault. You could be having winding condensation issues. ABB has a motor warming program you can put into the drive to prevent this. Also, return fans are subjected to a lot of moisture in the air passing over them if it's not a sealed-type motor.
    You can also change the level of sensitivity on the earth fault detection if you don't want to disable it completely.

    I would look at the motor/operating conditions first. I assume you megged the motor?

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  6. #4
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    Well we have not got that far yet as to get the ABB rep on site ,the control company that had installed the controls is the one that called ABB tech support and ABB said for them to turn down the sensitivity on the drives for any voltage imbalances ,so they changed it to what ABB had said to ( what ever that is ) then when it happened again a few days later with the same code the controls company said we have dirty voltage incoming from the main power source to which we called Duke Energy to have them check our incoming power grid at those times and the report showed no signs of issues at those times .The problem continues and I am just trying to educate myself on the issue to be better informed.These drives are installed on a Venmar RTU which cleans the air in the building as well as chem lab fume hoods and also does ac and heat to the structure as well and reheat capabilities with fresh air intake

  7. #5
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    OK so the type of motors are Baldor closed motors and there are two of those one for fresh air and the other for supply air ,then we have two vari speed condenser fan motors .the sensitivity has been changed according to the contractor as per ABB tech support instructions now as to whether or not the tech had megged the motor i do not know.but the lock out code does not happened to all three every time sometimes it can be just two or all three.the most recent event had all three then today it was just two and it was the exhaust and condenser.the tech had also changed the parameters for the condenser fan motors because they were not coming on on start up I hope this info helps you to help me and I appreciate any and all adive you can give on the matter .

  8. #6
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    if the power company says your power is clean, the only thing to do other than hire a 3rd party power analyzer and, if it comes out dirty, install expensive power filter banks, is to say ok it's good.
    Here is what you can do to make sure your basics are covered:
    -Make sure everything is grounded properly (at least a visual inspection of connections and wires)- motors, drives, VFD cabinet door, anything in the circuit. A true grounding analysis is expensive but could be the root of certain issues.
    Grounding is a major source of issues with drives, connected motors, even with sensitive electronics in the same building as VFD's
    -get a inverter/VFD rated and sealed motors. If not feasible, definitely check out the next thing...
    -look up "cool blue" common mode chokes. These help protect the motors attached to the drives and it will help clean up the harmonics the drive will put into the buildings power.
    -Inquire with your mechanical contractor and controls company about motor winding condensation. It is real but certain factors about the timing of the faults (which is time and date stamped on the drive) can give you clues. If it happens when it's colder in the space and the motor haven't been running (morning start-up?) is one clue. If this is suspected, contact ABB and they can give you a set of parameters you can put in the programming to keep the motor windings warm while idle.

    With these things covered and a proper megger check of the motors, you can pretty much rule out the drives, especially if you are having failure on multiple drives. At that point you may have a serious issue with grounding or power distribution at your mains.

    You can always turn the earth ground detection off but I would always vote against completely disabling a safety. There is no redundancy outside of the drive in case of a ground. If it's a small ground, the drive may fault off on over amp. If it's a catastrophic one the drive will definitely have major current runimg through it and could easily fry.
    If you decide to turn the earth fault off, definitly FUSE the incoming power TO the drive. It is not a 100% protection of the drive but it will definitely increase its odds of surviving a motor failure.

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  10. #7
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    Check your trends to see if the controls are sending a signal for 100% to the drives during their off time. In other words when your unit starts the fan motors are running at 100% and the computer starts ramping them down.
    Retired, after 43 Years

  11. #8
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    Thanks so much RezAtDorsia for that response , I checked with the contractor they said they did not meg the motor because it ohmed out fine =( , I checked the voltage with and without a load on the system no spikes or variances in the voltage to the system ,they keep saying we need a power choke maybe we do maybe we don't but they are not very receptive to the concerns for this new system I mean they did not even meg the motor as per what I understand as proper procedure but any way's I digress again thanks so much for the feed back .

  12. #9
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    The fact that you are having the earth fault on multiple drives on the same unit, with different motors tells me something systemic is going on. BUT...

    I absolutely would have megged the motors to check that off the list. You CANNOT use an ohmmeter to check in a case like this. Some grounds are hidden and only appear with the stress of running conditions. A megger helps find these by applying high voltage (500v if it's 2--V motor, 1000v for 4--V). An ohmmeter is not sufficient for this situation.
    It's not very time consuming, they could test it at the motor leads (they have to disconnect it from the drive first) in the cabinet. If they find a ground then you move to the terminal box on the motor and test the motor itself, isolated from the conductors. You could have wires that were pulled too aggressively through the unit!
    This is routine and needs to be done before you throw anymore money/hours at this problem.

    Also, as far as power analysis, you would need a good oscilloscope and a lot of know-how to find the type of power disturbances (harmonics) we are talking about.

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  14. #10
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    RezAtDorsia,I agree with you 100% and I also understand this especially with the megging topic these guys are supposed to be controls specialist's and should know this but I just wanted to get an outside third party opinion on the matter just to make sure I am not the one who is delusional or uninformed , and again thanks so much for the help in this matter ,I will follow up later once I get the contractor to tow the line on this matter

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