I am having an issue with a 10HP Powerflex40 Drive. I randomly get a F081 fault on the VFD, it will automatically re-establish communication and I am then able to start/control the pump from the HMI screen. When this fault happens it seems to confuse the PLC program and when the communication comes back sometimes the program wont control it any more. We have been having this issue for awhile now and have replaced the Com card on the VFD and the Ethernet cable from the Ethernet switch to the VFD. We are running a program from a 1769-L35E Controller.
Could there be anything in the PLC program or anything else that could be causing this random F081 fault?
First off, the Ethernet cards for PF40 drives are known to be VERY sensitive to heat and even if in an air conditioned enclosure, they can get over heated because of air flow issues. A lot of people cram the drives into a box and ASSume that slotted wire duct is going to allow air flow, so they don't count it as an "obstruction" when deciding how far away to mount it from the drives. The MINIMUM distance is
4" above and below the VFD, less than that and air current eddies will cause those Ethernet add-on cards to cook themselves. Again, this is a KNOWN issue of PF40s because the Ethernet card were something that came along long after the VFD was released, so as an afterthought, it had to have it's own power supply on the card, and that power supply is what over heats if there isn't proper air flow across it.
As a gross general rule though once you have eliminated the possibility of a bad comm card (by replacing it with a NEW one, not another old one), the problem usually points to noise on the Ethernet cable. If you used cheap "office grade" Ethernet patch cords, that's a DEFINITE point of noise entry, if you made up your own cable ends, that is another typical source for noise, or if you have a bad ground connection somewhere, that too can cause it. I had a huge project where the PF40 Ethernet cards would not reliably communicate, it turned out that one of the managed switches was not grounded (terminal was crimped to the insulation, not the copper).
The other thing you could do, depending on how you operate the drive via the comms, is to possibly change how it reacts to a comm loss. So IF for example the Ethernet is not being used for Stop functionality, you can change A115 to say "Continue running at last commanded speed in RAM memory" if the comms are lost. But if you are using the Ethernet to Stop the drive and there is no E-Stop hard wired to it, that's potentially a dangerous thing to do, so think that through.
