Questions about Powerflex 40 auto restart

[Ncg249]

Hello everyone, I'm new here.

First of all I just want to say that you guys are very knowledgeable and reading your posts on here has saved my butt a couple times. I'm a young guy, new to the industry, and basically the only person in my facility with any controls experience at all on my shift. I'm by no means helpless but I do have a question for you all.

I have a powerflex 40 VFD that kept giving us an "FO4" fault. Undervoltage. The root cause for this in my opinion, is the fact that the contactor connected to the safety circuit for this machine is on the line side of the VFD. Whenever an operator opens the safety doors, the contactor opens and the VFD loses power. Sometimes they don't have the door open for very long though, and the bus capacitor drains just enough to give us our "FO4" fault. Then maintnence has to be called out to manually reset it.

Anyway, I was tasked with fixing it. The cabinet is a mess and there's no prints for it anywhere. After talking to a controls tech on another shift, we decided to change the auto restart tries to 3, and the auto restart timer to 0. This way the fault has been clearing on its own, and we haven't had to send anyone out to clear it manually. BUT, a controls tech on another shift has recommended that we set the restart timer back to 1.0. When I try that, instead of restarting the VFD it simply gives me an "F33" fault which appears to be the auto restart failing. I have tried this from .1 to 1.0. It only works when the timer is set to 0. Do any of you experienced guys have an explanation for this? I am not quite understanding why it is behaving this way.

Thanks, and happy to be here. Hope to become an active member of this community.

 

[5618]

Setting the tries to non-zero and the delay to zero is a built in workaround to ignore three specific faults: undervoltage, overvoltage, and some heat sink alarm I don't recall ever encountering. We have done this to all our drives to save the hassle of resetting after a power blip. Any "real" fault still requires manual intervention to reset and we want it that way. By adding a delay time, the drive will attempt to reset any fault.

Another workaround I'll mention we have done for PF70 ,750, and 525 with a line side contactor is to add an auxiliary from the contactor to an input setup for precharge enable. This forces the drive to a precharge state where undervoltage is not an alarm. It's gentler on the drive too. Unfortunately, that's not available on the PF4/40.

 

[Ncg249]

Setting the tries to non-zero and the delay to zero is a built in workaround to ignore three specific faults: undervoltage, overvoltage, and some heat sink alarm I don't recall ever encountering. We have done this to all our drives to save the hassle of resetting after a power blip. Any "real" fault still requires manual intervention to reset and we want it that way. By adding a delay time, the drive will attempt to reset any fault.

Another workaround I'll mention we have done for PF70 ,750, and 525 with a line side contactor is to add an auxiliary from the contactor to an input setup for precharge enable. This forces the drive to a precharge state where undervoltage is not an alarm. It's gentler on the drive too. Unfortunately, that's not available on the PF4/40.

Alright, gotcha. I wasn't aware that setting the parameters like that targeted those 3 specific faults. Thank you for your help!

 

[James Mcquade]

The contactor should be on the line side of the vfd as described.
your issue as i know it is this.
when you open the doors, the safety circuit kills the contactor power to the vfd.
the vfd detects the power loss and begins to power down as it is supposed to.
the issue comes when the power is restored before the vfd is completely shut down.
it is doing what it is supposed to do which is shut down, but; you tell it to run and it really gets confused.
i don't know your process so here are a few suggestions.
1. when the safety doors are opened, kill the power to the vfd contactor(s) and start a tof timer that prevents you from resetting the safety circuit
until the drive(s) have completely shut down. see the mfg. recommended time before starting back up)
2. do a threat assessment and see if you can kill the power to the vfd controls and not the vfd.
as i said, i do not know your process. so a safety assessment must be done on item #2.
james

 

[robertmee]

Killing power on the line side of a pf40 will significantly degrade its life. I have a plant that will be upgrading to 525s with proper STO safety because they lose a pf40 about once a month because of line side power cycling. You end up with safety 'engineers' that aren't really engineers dictating line side power removal without understanding the ramifications. Seen it far too often.