text: <s>[INST] CONVEYOR BELT DRIVE GEARBOXES JERKING Summary: CONVEYOR BELT DRIVE GEARBOXES JERKINGHello, I have a set of 4x250kW flange motors coupled to gearboxes (two motors are sharing a shaft to turn a pulley) which will drive a 1.5km conveyor belt that carries 3000t/h of coal. Now my problem is that the gearboxes has just developed a jerking up and down movement should we run at +45Hz but all along it has been stable. What could be the problems,encoder or parameters on the POWERFLEX 700S? Note; I used LEINE LINDE XHI 861108956 Part number 750729-12 on a POWERFLEX 700s 355kW [/INST] Why do you think the problem lies with the encoder or the drive parameters if the system has been stable until now? If the system WAS stable at 45 Hz but is not now, that sounds like the load has changed and is causing a resonance at that frequency. I would look for a mechanical problem, something that has increased friction along the conveyor length. If NOTHING else has changed, there should be no reason to look at drive parameters. It's possible the encoder could be giving problems, but you would encounter it at more than just one specific frequency. \\n </s>