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The display on the drive shows 26 amps with little variation at all speeds.

  • At 176.14 RPM it shows -9.2% motor torque, 25.63 amps.
  • At 977 RPM it shows 26.04 amps and 2.4% torque.

The motor spec shows a max of 178 ft-lbs torque, 460 VAC at 1182 RPM, 53.5 amps, 6 poles. The table jitters at speeds less than 300 RPM.

I am trying to determine if this is a problem with the parameter torque settings in the ABB drive or some kind of mechanical problem.

Additional informetion:

ABB ACS880-11-065A-5 37KW 50HP DRIVE, Motor is a Marathon Blue Max model WD 364THFS8391FU W 40HP 230/460 VAC 3 PHASE. Had other techs set it up but are still mystified as to the jitter. This planer has a combo chain drive thru a two speed transmission setup where it uses this drive and can be disengaged to use a 75hp dc direct drive for high speed planing. Has two 20' 10,000lbs tables bolted together. Runs fine with one table but attach the other and there is jitter, so torque, inertia etc could be a factor

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    \$\begingroup\$ Without measuring current ripple, accelerometer table vibration and rotor balance, bearing slack etc it’s a big unknown \$\endgroup\$ May 26 at 18:09
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    \$\begingroup\$ It might help to know the drive model number. Do you have experience setting up that model drive? \$\endgroup\$ May 26 at 18:09
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    \$\begingroup\$ Just a SWAG but it sounds like your loop gain is to high. Without knowing what motor and controller etc that is about all I can do. \$\endgroup\$
    – Gil
    May 26 at 18:10
  • \$\begingroup\$ Correlation of certain speeds with fixture resonance can be measured by a modal impact network analyzer for resonance < 5 Hz \$\endgroup\$ May 26 at 18:12
  • \$\begingroup\$ ABB ACS880-11-065A-5 37KW 50HP DRIVE, Motor is a Marathon Blue Max model WD 364THFS8391FU W 40HP 230/460 VAC 3 PHASE. Had other techs set it up but are still mystified as to the jitter. This planer has a combo chain drive thru a two speed transmission setup where it uses this drive \$\endgroup\$ May 26 at 19:24
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I would expect speed stability problems at lower speeds ( below 60% rated motor speed).

From your description the VFD is running open loop with no encoder feedback. You can try different drive modes such as Constant Torque or Vector control - but without encoder speed feedback on the motor the speed and frequency control is open loop and low speed stability is limited.

It’s also likely that you are having vibration issues unrelated to the VFD and motor.

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You could try the scalar mode instead of DTC. However, I am inclined to think the problem may be mechanical resonance or an interaction between the feed drive and the mill drive if those are driven by separate drives. Note that it may be difficult to get full torque at low speeds with scalar mode. Starting could be difficult, but not feeding material until the mill is at operating speed would mostly avoid that problem. If there are some specific speeds that are problematic, you could program the drive to avoid those speeds if there are not too many of them and they are not wide ranges.

From another source, I received advice that likely the gain is too high on the speed regulator. Testing operation in scalar mode might confirm that.

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