3ph motor jumpy

  1. Kram

    Kram Member

    Messages:
    840
    Location:
    Sussex
    I've been noticing my motor getting less smooth and sometimes jumpy changing speeds. I assumed this was the belt, today I tried without belt and it is very obviously the motor, or the inverter in someway being out of sync! This was before I recently changed pulleys.

    Any ideas? Tried to get video but doesnt show up.

    TEC 1.5kw 6 pole, Invertek 2.2kw E3
     
  2. WorkshopChris

    WorkshopChris Forum Supporter

    Messages:
    4,723
    Location:
    South East Essex
    Have you checked all the terminals are tight and no broken cores in cable, can happen if a phase is powered intermittently?
     
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  3. daleyd

    daleyd Member

    Messages:
    6,188
    Location:
    Wrexham, North Wales
    You say it’s jumpy as you change speed - Are you changing speeds with an external pot or the one on the front of the drive - if it’s jumpy as you turn the pot it could be on its way out?

    Is there any ramp up/down setting on the drive?
     
    Kram likes this.
  4. timgunn1962 Member

    Messages:
    81
    Location:
    Lancashire UK
    What is the pot? and what is the speed range over which it is jumpy?

    If the pot is at all dodgy, that may cause a problem. Carbon track pots have given me problems in the past and the issue has been overcome by changing to wirewound.

    If running in V/F mode (probably parameter 51) there is a tendency for the motor to become "coggy" at low frequencies. Running in Sensorless Vector mode normally fixes this. I found 7 Hz was the point at which cogginess started to affect the finish when I played with some drives on my lathe a few years ago. SV drives were fine to less than 2 Hz.

    Is the drive new and set up (by you?) specifically for the job? It's unlikely, but if it was from something else, there may be skip frequencies from the original application.
     
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  5. Kram

    Kram Member

    Messages:
    840
    Location:
    Sussex
    Thanks for replies, I will get motor out and check terminals and at vfd later.

    The pot is relatively now, although the first in the bag was bad and replaced already. I'll try another.

    Problem speed is around 700-900rpm which is rough guess 45-48hz?

    Min speed is set 250rpm, 12.5hz?

    It was all new setup in November
     
  6. timgunn1962 Member

    Messages:
    81
    Location:
    Lancashire UK
    I'd check the pot first. With it disconnected, you can stick an Ohmmeter on it and check that the resistance between the wiper and an end changes progressively as you turn the pot. Check it both ways and from the wiper to each end.
     
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  7. Anguz

    Anguz Forum Supporter

    Messages:
    485
    bedfordshire
    try setting the drive speed range as just 50hz... it will ignore the pot then. i have seen drives partially lose 1 phase output and they do sound as you describe
     
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  8. Kram

    Kram Member

    Messages:
    840
    Location:
    Sussex
    All connections appear good, which is annoying. There are some speeds where it does not sound good and a bad phase connection would explain all.

    Sadly the pot is a bad one and Ive lost the packet of them, dont have any better ones. So for now Im stuck with it. My own fault for buying cheap on ebay.

    Where can I buy a decent quality 5k pot?

    Cheers
     
  9. Gragson

    Gragson Forum Supporter

    Messages:
    502
    Location:
    Bucks
    RS components on line is where I used to get my pots, always had a good range in stock
     
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