Input Phase Loss on VFDs

Discussion in 'General Electronics Chat' started by Xavier Pacheco Paulino, Oct 11, 2017.

  1. Xavier Pacheco Paulino

    Thread Starter Member

    Oct 21, 2015
    38
    0
    Hi,

    I have a VFD (Variable Frequency Drive) which throws an error indicanting Input Phase Loss. I have others VFDs connected to the same grid, but they work. Just that one is showing that error, so my power source is okay. What could be the cause of this error? Faulty capacitors?

    Just in case:
    Model: DELTA VFD-B
    The error says: PHL
    According to the datasheet it means: Phase Loss.
    As corrective action it says: Check Power Source Input

    But my Power Source is okay.
     
  2. tsan

    Member

    Sep 6, 2014
    53
    6
    So you have all three phases (I assume a three phase VFD) at the VFD input terminals? If so, then the VFD itself is faulty. There is no description of the phase loss supervision, but it could be based on high DC voltage fluctuation caused by loss of one of the supply phase. For example if a rectifier diode fails to a short circuit, an internal or external fuse/breaker should stop short circuit current flow.
     
  3. BR-549

    Distinguished Member

    Sep 22, 2013
    3,047
    742
    Verify the input phases with your meter at unit. Reset drive. Does error appear before trying to energize motor.....or after? Can you safely measure the DC bus? This is dangerous!
     
  4. Xavier Pacheco Paulino

    Thread Starter Member

    Oct 21, 2015
    38
    0
    Yes, I have all three phases at the VFD input terminals.
     
  5. Xavier Pacheco Paulino

    Thread Starter Member

    Oct 21, 2015
    38
    0
    The VFD starts working normally. After 5-10 min, the error appears.
     
  6. BR-549

    Distinguished Member

    Sep 22, 2013
    3,047
    742
    Measure the input voltages as soon as you get error.

    Something's fishy......it has low and high bus error alarms.....which you are not getting.

    Can you reset and restart unit right after shutdown error? And motor works ok?
     
  7. Xavier Pacheco Paulino

    Thread Starter Member

    Oct 21, 2015
    38
    0
    Okay. I will measure input voltages as soon as I get the error. And yes, I can reset unit after the error.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    13,145
    3,625
    I agree with your possible assumption it could be the input capacitors, in most VFD's, the input supply goes directly to a 3ph rectifier then capacitor bank, so most do not monitor the actual 3ph supply, other than the resultant DC.
    Max.
     
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,715
    2,585
    Check tight connections in wiring going to the VFD.
     
  10. BR-549

    Distinguished Member

    Sep 22, 2013
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    According to the manual.....the bus voltage is ok. Diode and caps should be fine. I was thinking like Max....loss of bus...loss of phase. But this unit must be sensing each input phase. This means troubleshooting must be immediate.

    If all terminal connections are tight.......check motor relay thermal overloads.

    I had this problem once......an electrician had stole the thermal and replaced it with an oddball spec.

    You must put salt on my comments......been 20 years since I been in a drive.
     
  11. Xavier Pacheco Paulino

    Thread Starter Member

    Oct 21, 2015
    38
    0
    Hi all.

    Certainly the problem was the motor because I tried the VFD using another motor and it did not show any error. Why is the motor causing that kind of fault?
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    13,145
    3,625
    Try the motor on direct 3ph and monitor each phase current, it could be motor failure, this is why it is prudent to use a 3ph choke before the motor, for both VFD and motor pretection, particularly if the motor is not vector rated.
    Max.
     
  13. tsan

    Member

    Sep 6, 2014
    53
    6
    Was the load on the another motor at least as high as on the original motor? DC voltage ripple/fluctuation increases with increasing load. If another motor works with load, then there is problem with original motor like unbalanced phase currents.
     
  14. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,715
    2,585
    I don't recall ever seeing a bad motor cause phase loss faults. But stranger things have happened. I suppose if the motor had a shorted phase, it could be pulling the DC bus down on the same input cycle every time, (if the ouput is 60hz) which would appear as a loss of input phase. But I would expect an output current fault to occur first.
     
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