ATV 930

https://www.se.com/uk/en/work/support/customer-care/contact-schneider-electric.jsp

Perhaps the <...we...> needs to discuss the problem with the crane manufacturer. That's what the telephone is for.

https://www.motioncontroltips.com/what-are-methods-for-vfd-control-of-ac-motors/

https://www.machinedesign.com/motors-drives/article/21833844/how-to-choose-the-right-control-method-for-vfds

This is not an unusual problem, where mechanical conditions will upset the typical vector control parameters programmed into a VFD. Bad coupling, sticky or bent shaft, any unusual torque/speed curve can make vector control unstable. A 4 motor drive seems to be ripe for this sort of non-linear torque behavior.

You could try tuning the vector control loop to be really sluggish, which I have tried and abandoned really quickly, but the best solution is to revert to really stable V/Hz operation, as you figured out for the original install.

Your drive does have the V/Hz operation, it should show up as Custom V/Hz operation and an option on Regulator. You can’t see it because you need to enable the next layer of configuration parameters they keep hidden to prevent confusion for the typical user.

I’ve used Altivar drives, they have the same basic configuration options as all VFDs, and I have yet to see a sensorless vector drive that didn’t have V/Hz mode, provided for exactly the reason you are looking for it.

Hopefully the dynamic response is good enough to achieve your control objectives, patience with ramp times up and down will usually solve your control problems.