Safe-Torque-Off Reset for PF755 VFD

phuz

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Jun 2008
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We are using a safe-torque-off board on a PF755. This gets triggered when the system is E-stopped. It initiates a safety board fault in the drive, which I am unable to clear with a simple Ethernet ClearFaults command. I also don't see a way to map a reset to the safety board. So far, we've had to power cycle the PF755 in order to clear it. What is the easier method to this?
 
Hello,

I had an issue a couple of days ago where the safety relay lost its marbles and of course the drive was faulted. (Had to replace the relay)

I understand this may not be the case with you as you would have seen this long ago.

I had issues in the past with these port cards getting dirty or the pins slightly corroded due to humidity in the air and causing all sorts of problems..included blown IGBT´s.

I would suggest, if possible, getting another card and replacing it or if you can, updating the firmware of the main control card and seeing where that takes you.

Maybe before any of that try re-seating the card if you haven´t already:)

Hope this helps.

Cheers.

TM
 
This is not the case. Everytime we hit an E-stop, the drive needs to be power cycled. The safety board works as intended, but I don't know how to clear it.
 
Ok.

For what it´s worth, try connecting to the drive with Drive Executive from Rockwell.

Maybe you´ll find some more clues.
 
Havent used the Powerflex drives with STO, but I know we had some issues when replacing older ATV61s with the new process drives. The old drives only had a single input for the interlock. The new ones had an A and B channel for SIL3 rating. So the sparkie bridged STOB with 24V and put the original interlock wire to STOA.

The first time we tested it we got a fault as the drive saw a discrepancy between the two safety inputs. Had to move the bridge to A and B. ( used for fast stopping drive if motor isolator opened, not for safety circuit).

Is this possibly what's happening with your situation?
 
We have had similar problem some time ago not with PF755, but with PF525 and, probably PF753.
Each of STO channels was connected to separate relays contacts. There was subtle time difference between contacts closure time. It produced fault that could be reset only by cycling power to the drive.
I believe there is an article in knowledge base about this, do not know number.

PaulB.
 
I dont know if this works STO fault. Try this



How do I configure an explicit message in ControlLogix to perform a Reset Device on a PowerFlex 755 drive?

How do I reset the PowerFlex 755 Safe Speed Monitor option card (20-750-S1) without reseting the whole drive?

Environment
20G PowerFlex 755
Answer
An explicit message can be used to perform a Reset Device for a PowerFlex 755 drive. An example of how this message should be configured is shown in the image below. The Source tag should be a SINT data type. This Source tag needs to have a value of 3 in it to perform the reset. The drive must be inhbited from the PLC for the message to complete. An SSV instruction can be sent to inhibit the VFD (SSV, Class Name = module, Instance = drive name, Attribute = mode, 0=inhibit, 4 =not inhibit).
reset_device.jpg
 
im not sure about the parameter in the 755's but i know with the 525s you need to set t106 to 1 "FltClr Reset", then you should be able to send a clear faults command over ethernet and it will clear the fault on the drive.
 
This probably isn't helpful, but you could always use a contactor in front of the drive (old-school) that would power the drive off on an e-stop condition.

Then you wouldn't have to reset the drive!

Seriously, though, I'm not familiar with the PF755, but I know PF525 has a parameter (t105) that enables/disables a drive fault based on STO.
 
Last edited:

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