PowerFlex 70 & 700 Fault Resets

curlyandshemp

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Jul 2005
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I am on a startup that has several VFDs and E3 overloads on Device Net. This morning when I walked in, 5 of 8 of the VFDs, PowerFlex 70s and PowerFlex 700s, were all displaying OverVoltage Faults. Apparently a powersurge occured through the area overnight. What I don't get is why the PowerFlex's did not fault reset. I always have logic, that worked in the past, to reset a fault automatically.

Code attached along with UDT assigned to bits for the PowerFlex command work via the Comm-20 D.

I had to manually reset all the faults using the HIM module attached to each drive


pflex_reset.jpg




pfex_cmd_udt.jpg
 
PowerFlex 700 Fault Clr

Good morning:
Just a check of a few things you might look at.

Param 241 (Fault Clear Mode) should be set to Enabled.
Confirm Communication file param 271, bit 3 is set to true.
Check Diagnostics Param 226 to confirm what the DC bus voltage was at the time of the fault.

(Param 174 default = false: and ONLY enabled if you desire to attempt an autostart after the fault is cleared.)

Your PP1_VFD.CLEAR_FAULT ONS Param 240 to true?

I hope this helps.
 
Curly, is this a conditional routine or does it run continuously?

If it runs every scan, then you will constantly be trying to clear faults as they occur. What if the drive can't clear the fault? The PLC logic will not stop trying...

Might be useful to have an operator/tech push a button to trigger the fault clear logic. I usually tie drive reset logic to a master reset button somehwere...

Maybe the drive reset logic went true during the power spike, the drive could not clear the fault, then power went off and came back on with the fault logic true the whole while.

What happens if the drive powers up and the fault_clear bit is already true? The drive might need to see a false to true transition of the fault_clear bit.

Another thing you might do is add an internal bit address (that you can toggle from RSLogix)in parallel with theexisting code to reset the drive fault via devicenet rather than use the HIM module. That would at least let you test the devicenet reset logic.

Just my observations. Let us know what you find.

Paul
 
Not sure if the Powerflex is the same as the older A-B Plus II drives but I think they are, it will basically act like a one shot rising instruction. So if the fault was not clear yet, and you trigger a fault reset, it might not reset. Holding the fault reset will not keep triggering resets. Just once.

So if this is the only way you have to reset the drive, you might want to look at cycling the reset on and off periodically. That's if you want to make certain the drive will reset automatically from the program.
 

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