PaulKim1003

PowerFlex 755 - Static tune

22 posts in this topic

Posted (edited)

Hello guys

There are 4 VFD and they are all set up the same way (same parameters).
However, one of my VFD is having an issue with F12 (HW Overcurrent).

I don't know why only one VFD is getting that fault. 

I would like to do the "startup  wizard" in the CCW program to see if that helps.

My question is what happens to the parameters when I do the "static tune" ? 

and another question, is there a way to do only "static tune" without going thru all the steps in the startup wizard?

Thanks in advance :)

 

Edited by PaulKim1003

Share this post


Link to post
Share on other sites

My question is what happens to the parameters when I do the "static tune" ?

Autotuning introduces a drive to a new motor. It sets the best possible values for IR Voltage Drop (P73), Ixo Voltage Drop (P74), Flux Current Ref (P75), and Slip RPM (P621).

You only need to autotune when you're installing a new system or replacing a motor on an existing system. If you're replacing a drive and downloading a known good program from the previous drive, the autotune values will still be valid so long as it's the same motor. 

The Static Tune energizes the motor but does not rotate it. Rotate Tune turns the motor without load coupled, while Inertia Tune turns the motor with the load coupled.

Never autotune with process material present in the system, as this will throw the whole thing off. So if you're tuning a drive/motor where the motor is permanently coupled to a pump and the pump is cooled by the process material (and therefore can't be run empty) Static Tune might be the preferred method.

and another question, is there a way to do only "static tune" without going thru all the steps in the startup wizard?

You can access the autotune at parameter 70. From the HIM, select the type of tune you want to use, hit enter, then start. Also, if you're in the Wizard in CCW you're allowed to jump back and forth to any step you care to simply by clicking on the desired label in the Wizard Step menu.

Since you have CCW available, before you start tuning you should run the Compare tool on the suspect drive against a known good drive. This might get you to the problem quicker. 

Hope this helps and let us know how it worked out :-)

Share this post


Link to post
Share on other sites

Thank you for the reply @ElectronGuru, Since I am not changing a VFD or a motor, I guess I don't need to do static tune? 

Share this post


Link to post
Share on other sites

Is this a new installation? Is it 4 drives connected to 4 identical motors?

If it's an existing system that started showing this fault, I would look at the motor and its coupled load.

If it's a new system, the motors may not be perfectly identical enough for identical tuning parameters to work well. In that case, doing the static tune on the problem drive may sort it out.

Share this post


Link to post
Share on other sites

Hi @Joe E.No it is not a new installation. yes 4 drives are connected to 4 identical motors.

All of sudden, getting a fault 12 (Hw overcurrent), so i thought doing the static tune would help. 

 

Share this post


Link to post
Share on other sites

Gotcha. For fault 12 HW OverCurrent, the manual (Page 321) says:

Quote

The drive output current has exceeded the hardware current
limit.
Check the motor and external wiring to the drive output
terminals for a grounded condition. Check the programming.
Check for excess load, and other causes of excess current.
Insulation Resistance (IR” test the wiring to motor.

https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/750-pm001_-en-p.pdf

 

Share this post


Link to post
Share on other sites

@PaulKim1003 no, doing a tune isn't first on my list of things for this problem. If you suspect someone has played with the parameter settings, run the compare tool. Sometimes it's a quick and dirty check just to eliminate that as a possibility if you have co-workers who like to tinker.

Hardware Overcurrent means the drive is working too hard to power the motor. If it is a parameter issue it's probably because someone changed the motor nameplate data or maybe the carrier frequency. It's far more likely the problem is in the wiring between the drive and motor, or the motor itself, as suggested by @Joe E..  

Share this post


Link to post
Share on other sites

If you find differences between them, use CCW to backup the current configuration of the drive before making any changes...just in case. If the only differences are in the tuning parameters and the motors are at least nominally identical, I wouldn't change any parameters without investigating a bunch of other things first. I'd check to see if the pump/motor has been replaced recently. We have a machine here where a NEMA Design B motor was replaced with a Design D (or maybe the other way around....) and it kept tripping the overloads. The other nameplate information was identical, so it wasn't obvious at first glance what the problem was. Something like that could cause a tuning issue.

But...my first suspicion is still a mechanical issue or damage to the motor or wiring.

1 person likes this

Share this post


Link to post
Share on other sites

Assuming no parameters have changed, F12 is often cabling or the motor. Disconnect the motor at the junction box and start the drive. If it runs, the cables are good. If the issue occurs when the motor is hooked up, megger at 1500v with drive disconnected. If this occurred after replacement or commissioning then parameters are likely the issue. If settings didn’t change, likely a motor or cable issue. If F12 occurs with no leads connected then you have a drive problem. Hope this helps. Interested to hear the solution

Share this post


Link to post
Share on other sites

Posted (edited)

Megger testing at a significantly higher voltages than a motor is rated for could cause motor winding damage. Very few people will ever have a need for "proof testing" a motor, which uses higher voltages. Routine maintenance testing and troubleshooting tests should be done at as close to nameplate voltage rating as possible.

@PaulKim1003 definitely let us know how it works out. :)

Edited for a bit more clarity.

Edited by ElectronGuru
Added more detail for clarity.

Share this post


Link to post
Share on other sites

Hi guys, @ElectronGuru, @VFD Guy , @Joe E.

I did not have time to try all the stuff you guys recommended because our plant cant be down right now.

What I did was I lowered an output (speed reference) by 15% in PLC program and I stopped getting the alarm from the drive.  

Thanks you guys for the replies :-)

 

Share this post


Link to post
Share on other sites

While the drive is running, check the display parameters (I don't remember which one) for the output current and see where it is compared to the other units running at the same speed. And maybe confirm the current reading with a clamp-on meter (being aware that the readings won't match since the clamp-on meter is only looking at one phase and they aren't as accurate when reading VFD current). Reducing the speed of a pump will reduce the torque (and therefore the current). Your results make me more suspicious of a mechanical issue in the pump or motor.

I know you know this, but production also needs to know that even though it's running without faulting right now you haven't actually fixed anything. If a component (electrical or mechanical) is in the process of failing, you may have bought some time but this problem will almost certainly come back.

Share this post


Link to post
Share on other sites

I 100% agree with you @Joe E.. It will definitely come back since it is not fixed. 

I will find a day to do the things you guys mentioned. 

Thank you and have a good weekend :-2

Share this post


Link to post
Share on other sites

@ElectronGuru  yes meggering significantly higher than motor insulation can damage a motor. Many vfd rated motors are rated to 1488v. 12v higher than that won’t cause an issue. I’ve seen countless times of people meggering at only 500v and say no motor issue. A motor can see up to 2 times dc bus with ringing for short periods. So 650vdc, that’d be about 1300v and why a 500v megger would cause a false success.

@PaulKim1003  it would help if you stated when the fault occurs. On every start? Acceleration? Since lowering the speed helped, did the fault only occur above certain speeds?

Share this post


Link to post
Share on other sites

@VFD Guy yep! For a 60-second spot check, rotate the motor shaft a 1/4-turn and check again, higher voltage checks are probably OK so long as you're doing that every week. But for a longer test, such as a ten-minute polarization index, I would stick with the motor nameplate values. Either way, I think we're on the same page.

Share this post


Link to post
Share on other sites

@BobLfoot - I don't remember if it was the same VFD. I think it has a high chance it could be the same VFD.

@VFD Guy -The fault usually comes up during acceleration.

Share this post


Link to post
Share on other sites

Since this is a pump, I’m assuming no encoder and non FV mode. If those are true, I still feel my previous post applies. Since it’s failing at a higher speed, that means higher voltage and likely a cable or motor issue. Of course a scope on the output would give you the proof. F12 means 2x drive rated current was seen my CTs. What is the amperage of the drive?

Share this post


Link to post
Share on other sites

Posted (edited)

Is this a new installation? Is it 4 drives connected to 4 identical motors?

mobdro
 

vidmate
 

Edited by picheholiya

Share this post


Link to post
Share on other sites
On 5/3/2022 at 7:53 AM, picheholiya said:

Is this a new installation? Is it 4 drives connected to 4 identical motors?

mobdro
 

vidmate
 

IF you read through the thread you will find the answers to your questions. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now