[rashid11]

the troubles continue. My KB Electronics KBAC 27D 2HP VFD controller
causes really bad vibrations in 2 different motors: 2 HP 3600 RPM
Emerson and 1.5 HP 1750 RPM Dayton. Both are Invertor duty, brand new motors from Grainger. So is the controller. 220V in , 3 phase 208 out.


While it is not that bad with 2HP , as it is used in belt grinder, the
other motor was supposed to become VFD drive for my 9x20 lathe. With it shaking like this (NOTHING on the shaft, firmly bolted down to a massive bench, it shakes it badly, throughout whole range of speeds) there's no way it is going to work on a lathe. Vibrations only disappears at the max RPM.

To load it some, I removed a chuck from a lathe and chucked it right
onto the shaft of 1.5 HP. No effect.


What gives ? Is it typical for VFD contoller to induce this type of
vibrations ? I reckon not, as so many people use VFD drives on their mills and lathes ... I am @ loss.


Will call KB electronics, now that I know it is not a problem with a
motor.


If I spin both motors to high RPM, and then turn off the controller,
the vibrations instantly disappers and motors become smooth as silk and coast down to stop.

[Al_The_Man]

Sounds like VFD problem (fault), Off load especially, a motor should be silent and smooth throughout the speed ranges.
All the VFD's I have installed have fired up smooth out of the box with the default parameters, even before tuning etc.
Al.

[JPMach]

Check the carrier frequency, if this is to low the motors will be jerky. This is not the variable frequency you use for speed, this is the frequency at which the dc pulses are sent to the motor to mimic the sine wave. I don't remember exactly but I think this should be around 400 + cycles.

JP

[titchener]

When the VFD is new they typically ship with default parameters set so that it should fire up and run the motors without requiring any adjustments and the motors should run very smoothly. The fact that 2 different motors aren't running right is making it likely that either the VFD is defective or somehow one or more of its parameters got set to bad values. I'd get a guy for KB on the phone, have him go through the setup of the unit to make sure its set right and if the motors still don't run smooth they should exchange the unit.

Paul T.