# VFD won't stop completely, but button still works



## oliquir (Jan 13, 2011)

bad programming of the vfd


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## John Valdes (May 17, 2007)

Please take a few minutes and fill out your required profile.

Check min speed in parameters.


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## Funkadelicfred (Jan 30, 2019)

That was my thought too but they all run on the same programming(there's 4 of the same augers) with only the node/ip address different so that shouldn't be it.


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## gpop (May 14, 2018)

Funkadelicfred said:


> The problem, have a VFD for an auger that when you press stop on the computer screen, it will stop running but won't completely stop and will drop to 6 Hz or so and then just stay there and continue to rotate. Has to be shut off with breaker. Any ideas?


Bad programming or bad wiring.

6hrts is either min speed limit, digital input speed control or a bit set in the logic telling the drive to run at set speed. 
(big clue......look in the program to see where 6hrts is listed)

If you want a real answer post the make and model of the vfd, list all the control wiring and where its landed and if you have the post count post a picture of it.


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## Funkadelicfred (Jan 30, 2019)

It's a Flex 40. I will check the parameters for something around 6 Hz but I didn't see that when I was in there last time. Wiring hasn't changed on it ever so I figure it's something with the programming but I'm also a bit confused because no one has access to it and they match the drive files that were saved and downloaded a while ago. I will check min speed and the other settings when I go back there next and I will update for the future. Thank you for the replies.


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## Cow (Jan 16, 2008)

It sounds like you're not giving it a stop command, but instead, just taking away the speed reference.


At that point, the drive just slows down to a pre-programmed min. speed of 6hz.


That's my wild guess based on limited info....


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## John Valdes (May 17, 2007)

Welcome Funk.
Thanks for taking the time to fill out your profile.

Check min speed


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## frenchelectrican (Mar 15, 2007)

there is two spots you will have to check it out is min speed setting it should be at 0 HZ 

second thing check the stop command setting to see what it react to the setting and when you hit the stop command it should shut off the load connection.


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## paulengr (Oct 8, 2017)

Is run-forward jumpered or a digital input? If it’s an input check the analog input signal and the digital signal.


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## gpop (May 14, 2018)

My understanding you are using a network to control the drive if so....
Its not easy on a powerflex but you can access what the plc is telling the drive. It in bit level so you have to read it as 1 and zeros then decode it. 

Sometimes a plc will glitch and a 1 will get written into a table and nothing turns it off so its stuck unless you reboot or manually remove it. (Glitch may be the wrong word as its basically bad programming that has nothing to do with the drive but something else being written to the wrong place)


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## Funkadelicfred (Jan 30, 2019)

Yes it is controlled by network, stop and go and such are performed by PC buttons


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## JRaef (Mar 23, 2009)

There is a potential issue with using what is called the "Bus Regulation Mode" on a Powerflex 4 class drive and where there is a long distance between the drive and motor. Bus regulation is intended to help avoid DC bus over voltage tripping by automatically overriding and extending out the programmed Decel ramp time when it detects a build-up of voltage on the DC bus that is higher than necessary. When there is a significant amount of cable capacitive charging taking place, as in when there is a long distance from drive to motor and VFD cable was not used, that capacitive charge can fool the DC Bus Regulation feature into extending the Decel out so long that it appears to keep running. EVENTUALLY it will likely stop, or trip on "Stall Fault", but that may be far longer than is safe for the application. So there are two things you can do:
1) Unless you know that you NEED this DC Bus Regulation feature, you can just disable it using Parameter A117. The factory default is Enabled.
2) If controlled Decel is not important, turn that off, i.e. set the drive to Coast to a stop using P037 set to a 1 (the default setting is 0 for Ramp). Bus regulation will become irrelevant.


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## Funkadelicfred (Jan 30, 2019)

JRaef said:


> There is a potential issue with using what is called the "Bus Regulation Mode" on a Powerflex 4 class drive and where there is a long distance between the drive and motor. Bus regulation is intended to help avoid DC bus over voltage tripping by automatically overriding and extending out the programmed Decel ramp time when it detects a build-up of voltage on the DC bus that is higher than necessary. When there is a significant amount of cable capacitive charging taking place, as in when there is a long distance from drive to motor and VFD cable was not used, that capacitive charge can fool the DC Bus Regulation feature into extending the Decel out so long that it appears to keep running. EVENTUALLY it will likely stop, or trip on "Stall Fault", but that may be far longer than is safe for the application. So there are two things you can do:
> 1) Unless you know that you NEED this DC Bus Regulation feature, you can just disable it using Parameter A117. The factory default is Enabled.
> 2) If controlled Decel is not important, turn that off, i.e. set the drive to Coast to a stop using P037 set to a 1 (the default setting is 0 for Ramp). Bus regulation will become irrelevant.


I will be back to the plant Monday and I will see if this is the issue. No matter the issue, I will post an update and see where we are with this. The previous drive that was swapped out kept reading Undervoltage so we switched it out to this one. No idea why it was saying that either as it's all on the same bus and the other drives work fine. Don't know if this helps at all though.


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## oliquir (Jan 13, 2011)

anyway controlling start-stop of a vfd only by comms is a bad practice, it should always be controlled by digitals inputs (via a plc (plc can shutdown vfd if comms are bad) or relays,) and other parameter can be controlled by comms (speed,...)


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## Funkadelicfred (Jan 30, 2019)

Ok went back today, none of the parameters were off (min speed/frequency) and all the other augers (there are 4 in total with the exact same settings, just different comm mapping) are on Ramp but when I switched this one to Coast, it now shuts down completely and the issue seems to be fixed. 
I should mention that I am just the apprentice and I wasn't there when it was built, my boss is just an old timer with very little electronics knowledge so I get stuck trying to figure it out so my knowledge on the system isn't great either but I'm trying to learn.


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## JRaef (Mar 23, 2009)

Funkadelicfred said:


> Ok went back today, none of the parameters were off (min speed/frequency) and all the other augers (there are 4 in total with the exact same settings, just different comm mapping) are on Ramp but when I switched this one to Coast, it now shuts down completely and the issue seems to be fixed.
> I should mention that I am just the apprentice and I wasn't there when it was built, my boss is just an old timer with very little electronics knowledge so I get stuck trying to figure it out so my knowledge on the system isn't great either but I'm trying to learn.


:thumbsup:


When people ask me how I learned all the stuff I know, my answer is always the same...


"One mistake at a time, hopefully not the same one twice..."


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## glen1971 (Oct 10, 2012)

oliquir said:


> anyway controlling start-stop of a vfd only by comms is a bad practice, it should always be controlled by digitals inputs (via a plc (plc can shutdown vfd if comms are bad) or relays,) and other parameter can be controlled by comms (speed,...)


In our area we've got 6 left that use comms to start and stop them and I've been after them for 10 years to switch that, but no go. I told them that the HOA's by the fans don't necessarily shut the motors down and that they keep running or start at random when the switches are off.. They said it was ok.. I tell all the operators and mechanics that the switches don't work and they need to open the breakers to be sure.. (Yes we open the breakers and lock the fans out when we're working on them).


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## Peewee0413 (Oct 18, 2012)

JRaef said:


> [emoji106]
> 
> 
> When people ask me how I learned all the stuff I know, my answer is always the same...
> ...


Did you just Kung Fu that one J?

Sent from my SM-G965U using Tapatalk


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## Funkadelicfred (Jan 30, 2019)

Allright, just adding this in case someone comes through here in the future. Turns out the maintenance guy was messing with the motor box and the ground was touching across one of the leads. Why it didn't show up as a fault or nothing is beyond me but once we removed that, it worked again just fine.


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## AK_sparky (Aug 13, 2013)

Funkadelicfred said:


> Allright, just adding this in case someone comes through here in the future. Turns out the maintenance guy was messing with the motor box and the ground was touching across one of the leads. Why it didn't show up as a fault or nothing is beyond me but once we removed that, it worked again just fine.


Interesting. Thanks for coming back to follow up. I find some of these threads get ignored after the problem is found, but the solution is never shared with the rest of us.

Whereabouts in Ontario are you?


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## PSmitty (Aug 19, 2019)

Funkadelicfred said:


> The problem, have a VFD for an auger that when you press stop on the computer screen, it will stop running but won't completely stop and will drop to 6 Hz or so and then just stay there and continue to rotate. Has to be shut off with breaker. Any ideas?


I initially would of said programming of min speed on VFD was most likely your culprit. But if you have identical VFD's working fine it makes me think your speed control to drive has a problem.

ie. If speed control is 4-20ma check that signal. This may be easy where it's an augur application and if you can safely try this: Swap it 4-20ma signal with an adjacent VFD/auger. Turn them both on then stop them see if problem carries to different VFD?


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## glen1971 (Oct 10, 2012)

Funkadelicfred said:


> Allright, just adding this in case someone comes through here in the future. Turns out the maintenance guy was messing with the motor box and the ground was touching across one of the leads. Why it didn't show up as a fault or nothing is beyond me but once we removed that, it worked again just fine.





PSmitty said:


> I initially would of said programming of min speed on VFD was most likely your culprit. But if you have identical VFD's working fine it makes me think your speed control to drive has a problem.
> 
> ie. If speed control is 4-20ma check that signal. This may be easy where it's an augur application and if you can safely try this: Swap it 4-20ma signal with an adjacent VFD/auger. Turn them both on then stop them see if problem carries to different VFD?


Why would the OP continue to troubleshoot when they found the solution 4 months ago and posted what they found? See Post#20, copied and pasted above...


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