Powerflex 525 Command to run not running fault?

atomsforlunch

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Hi all, I'm an intermediate maintenance tech getting familiar with VFDs. We have a Powerflex 525 that will randomly give a command to run not running fault. d007, d008, d009 show 59, 73, 59 respectively. VFD itself never actually shows a fault as far as I know. Any ideas? Where to start troubleshooting? I believe it's some kind of communication fault.
 
73 is a loss of Ethernet comms, and 59 indicates the safety circuit is open. If you're not using the safety feature there should be a jumper installed.
 
Assuming that the drive is being told to start/stop over Ethernet, I'd bet that the issue is how you are issuing the start/stop commands.

A common method people use is to use the "not start" to issue the stop command. This will occasionally causes the issue you are experiencing. The reason being, Ethernet communications is asynchronous to the PLC scan, so every once in a while, if the comms updates at the point between your start command going away and the stop command being issued, the start and stop will be true at the same time, causing the drive no start even though you see the start command on at the same time.

A good practice is to only issue the start and stop commands as long as they need to be to get the drive started and stopped. An easy was is to use the drive active bit. The start command doesn't need to be on continuously. So putting the "drive not active" in front of your start command and "drive active" in front of your stop command will ensure that the commands can't be on at the same time.
 
dmroeder said:
Assuming that the drive is being told to start/stop over Ethernet, I'd bet that the issue is how you are issuing the start/stop commands.

A common method people use is to use the "not start" to issue the stop command. This will occasionally causes the issue you are experiencing. The reason being, Ethernet communications is asynchronous to the PLC scan, so every once in a while, if the comms updates at the point between your start command going away and the stop command being issued, the start and stop will be true at the same time, causing the drive no start even though you see the start command on at the same time.

A good practice is to only issue the start and stop commands as long as they need to be to get the drive started and stopped. An easy was is to use the drive active bit. The start command doesn't need to be on continuously. So putting the "drive not active" in front of your start command and "drive active" in front of your stop command will ensure that the commands can't be on at the same time.
Click to expand...

Thanks for the thorough reply. I am skeptical of this cause because this is a large sortation facility with probably 200+ drives and this is the only drive that gives this problem. Is it possible that the logic you laid out might have been programmed only for this drive and thus could cause this issue?
 
If your drive is programmed the way I described (not start issuing the stop), I assure you that the result I described will happen, infrequently, but it will happen. Differences might depend on the RPI of the drive, scan time of the PLC, frequency of starting/stopping. For example, drives that run all the time (conveyors) will unlikely suffer from this problem for obvious reasons.

Can you screenshot your start/stop logic?

edit: Definitely be skeptical
 
Last edited:
Absolutely true. I have seen people remedy this by re-commanding the start if a start has been commanded and the frequency is 0 after 3 seconds.

Why add new lines to correct a problem when you can just... fix the problem?

Sounds like OP is experiencing a communication issue. Is the drive going back to a Stratix? Can you monitor the port for dropped packets, etc?
 

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