PowerFlex 700S Stopping Intermittently

[ControlsGuyy 0]

Hello,

I am having an issue with a PowerFlex 700S. This drive controls a travel motor for an overhead hoist. It is periodically not starting after stopping at a programmed point and sometimes stops while traveling to the next station. It does not give any faults or alarms. It is controlled remotely from a CompactLogix through a wireless router to an N-Tron unmanaged switch to the 20-COMM-E adapter. There are some limited manual controls, but the normal operation is a start, stop and speeds all sent from the controller. We have the DI6 set to enable and that does not seem to ever be lost. When this happens the only thing that I can find is the start inhibit parameter shows a bit 8 set high which is a start request present. I can see the PLC has already sent the start signal. I can put the machine in manual mode then cycle back to auto and the drive takes off. The only thing I can see changing while doing this is the start command is dropped and then sent again. I have changed the comm adapter as originally I had thought this was an issue with comms, but now I am skeptical as I have it set to fault and stop if a comms loss is detected. I am also able to connect to this drive and others on the same hoist through the wireless comms, so I feel better about the comms path. What causes this start inhibit bit 8 to become active? Does this seem to be a communication issue or a potentially a bad drive?

[pturmel 135]

Sounds like a programming error.  For most such cases, the start command should be pulsed and only the not-stop command kept on.

FWIW, wifi is extremely fickle if regular TCP/IP traffic is sharing the channel with UDP or bare Ethernet frame for I/O devices.  A brief surge in TCP traffic can drop a few UDP packets on the floor, and suddenly your drive is misbehaving.  UDP I/O on wifi when the channel is dedicated to the purpose is highly reliable.

[ControlsGuyy 0]

Thank you for the help!

I have edited the program to separate these signals better, but it is looking just as you had stated about the traffic. I am not showing too many errors or lost packets but the retries are excessive and I believe this is causing the unreliability. We are replacing the antenna next. 

Thank you again!