I have a VFD that controls an AC motor which compresses air. It is an 30kW motor. I have set the parameters required to drive the motor and it runs the motor but not properly. During the test the lamps in the room start to vibrate,plus we measure voltage between phase-neutral it drops by 10V(not running motor 238V when running 228V). The VFD outputs 80 amps ,however it is 3-4 times of the current required by the motor. During the motor startup sequence 0hz - 50hz we can observe huge mechanical vibration, the motor was shaking so hard, it is not normal vibration.

The VFD's type:3G3RX

I don't know what to do at this point.

  • \$\begingroup\$ Is that motor suited for VFD? I ask because a standard induction motor is built with the fewest amount of iron possible, and that means a lower AC frequency requires you to lower the AC voltage, too. Otherwise the iron gets overexcited, which leads exactly to that overcurrent you are seeing. VFD-friendly induction motors have a bigger iron core so they can run at lower frequency without requiring you to lower the voltage. \$\endgroup\$ – Janka Oct 20 '19 at 18:45
  • \$\begingroup\$ It sounds like you need help from someone with more experience. Is it possible to hire a consultant? Can you get help from the supplier of the VFD? I have only worked with smaller VFD's (5.6kW). Usually, though, if you at least get a few basic parameters correct, the motor will spin OK with no load. The other thing to double-check is if you have a bad connection on one phase. If the motor vibrates, maybe one phase is not connected. \$\endgroup\$ – mkeith Oct 20 '19 at 18:47
  • \$\begingroup\$ @Janka, A VFD will also reduce voltage when driving at reduced speed. I think the OP has programmed in the wrong nominal speed and voltage for the motor OR is using sensorless vector control with incorrect parameter values. Any three phase induction motor should be controllable. There could be issues with cooling for motors with shaft driven impellers, or insulation breakdown for non VFD motors. But this excessive vibration is something else. Bad wiring or incorrect programming. That's what I think anyway. \$\endgroup\$ – mkeith Oct 20 '19 at 19:46
  • \$\begingroup\$ I agree with mkeith. The VFD must not be configured properly for the motor or the motor may not be connected properly. The motor may be connected for 230 V line to line while the VFD is configured for 400 V. The VFD has sufficient current limiting capability that to could still run the motor. I have been working with VFDs since 1968. \$\endgroup\$ – Charles Cowie Oct 20 '19 at 20:31
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    \$\begingroup\$ Note that there should be nothing connected to the N/- terminal. That is not a neutral terminal, it is the negative side of the DC link. \$\endgroup\$ – Charles Cowie Oct 20 '19 at 22:37

I don't have enough rep to leave a comment, so this is going in the answer section, but here are a few things to consider: Do you have enough power capacity upstream? You might be trying to draw too much power from your existing upstream transformer.

Did you correctly match all parameters of your motor with your VFD? Is a winding burnt open in your motor and it's single-phasing? (Unlikely, because it wouldn't turn then.) Is the compressor mechanically binding somehow? Maybe it's flooded and trying to compress a liquid instead of a gas, and thereby creating a temporary high current condition? Disconnect the compressor from the motor to see if it runs fine with no-load. Is your shaft alignment good? Check the coupling. If someone installed the motor without checking for the shaft alignment you get problems.
Maybe it's a cheap VFD that doesn't properly check all fault conditions and tell you what's wrong. (I've seen blown windings be falsely diagnosed by the VFD as "bad incoming power") Measure the current on each phase. They should be nearly equal. Troubleshoot further from there. These are just a few things to get you started.

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    \$\begingroup\$ +1 for alignment. I've had a VDF/pump combos shake uncontrollably just because the coupler was pinched. \$\endgroup\$ – C. Lange Oct 21 '19 at 14:24

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