AB PF525 strange behaviour

alexbeatle said:

Cables aren't shielded. I'd prefer they would be. But all of the VFD's are inside the MCP and the Ethernet are running only there - min 10cm away from the VFD power\motor cables.


Noted. Disabled since not the application and hasn't helped to solve anyways.


Will perform. Fro the Manual it only sets the A496 value. Is it safe to say that I can do it on one motor and set the same value for all of the others, since all motors are the same?


Changed the StopMode=Ramp,CF with the decel 2-4s. Will observe.

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Changed the StopMode=Ramp,CF with decel=4s and the fault has gone away. Timed when the StopMode=Coast,CF it was stopping in under 1s on its own.

alexbeatle said:

Changed the StopMode=Ramp,CF with decel=4s and the fault has gone away. Timed when the StopMode=Coast,CF it was stopping in under 1s on its own.

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The only way (in my mind at least) that setting the stop mode to coast would cause an overvoltage fault and ramp mode NOT cause that fault is if your program is commanding the drive to restart while the motor was still coasting down. So you've "solved" the issue but your program may still have a glitch that you've put a bandaid on. Maybe it's normal behavior in the process for a conveyor to stop and be restarted in less than a second, but I'd question that.

rupej said:

The only way (in my mind at least) that setting the stop mode to coast would cause an overvoltage fault and ramp mode NOT cause that fault is if your program is commanding the drive to restart while the motor was still coasting down. So you've "solved" the issue but your program may still have a glitch that you've put a bandaid on. Maybe it's normal behavior in the process for a conveyor to stop and be restarted in less than a second, but I'd question that.

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I agree. But having no feedback from the rotor itself (which is my case) it's not possible to predict the start command.

alexbeatle said:

Will perform. Fro the Manual it only sets the A496 value. Is it safe to say that I can do it on one motor and set the same value for all of the others, since all motors are the same?

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No, they are not. You can do it on 2 and compare the parameters, then you'll see the difference. It is recommended to do it after each motor replacement(even in case of identical motors). It will do a couple of things more, can check p.259 of the manual.

You say the last conveyor is the one that gives you most trouble. Is also a decline conveyor that meand the conveyor is holding the load back.
First as I have said before your drives are undersized for the job. The reason you are getting the overvoltage fault is because when the load on the conveyor goes down the decline the motor tries to maintain the commanded speed so the load is in regenerative mode load pushing the breaking energy back into the DC Buss, Buss voltage goes up. A buss loader will help this.
Some on here have said to set the vfd for coast to stop and use flying start on restart. That a very bad idea the vfd needs to stay in control of the motor if you want to restart it before it has come to a complete stop. With an overhauling load like you have you will never know when it is fully stopped. The flying start function is designed to loads like a fan where after it is stopped the natural flow air moving through the fan will cause it to rotate the load would be very light when the motor starts. When the vfd starts it sends a small current to the motor to find the armature position. Depending on the manufacture they stop the motor before accelerating it others If you try to restart while you have the conveyor moving with a heavy load it would be like an across the line starter with a rotating motor. I have seen motor shafts shear off, motors blow up. Starter contacts weld together under this type of conditions. You could blow up the vfd. If the vfd has a DC injection at start mode it may help but again they are designed for light loads.
The under voltage fault may be just power down but, I would look at the load a heavy load on the vfd with the vfd trying to accelerate to quickly could give you a low buss voltage.