ABB VFD delta high leg

W

wncjefftino

Member
Location
Asheville, NC
Occupation
electrician
Hi All,

I have a system installed since 2018 that has been working without fault until recently. It is a chain disk to move grain and it has a 3 hp metric motor on a ABB ACS355 drive. The building utility is 240/120 delta high leg. There is 2 transformers on the pole. I am getting a phase loss fault. I have voltage on all 3 legs but missing current on A phase. I've replaced the breaker, the fuses, and VFD. I moved the wire on A and the no current "moved" to the new location, C. I recently checked the motor and found the 6 leads on the wrong posts. (It would only run in wye). After moving the leads it runs in delta.

Running voltage is 237, 237, 231
Running amps is 0, 9.5, 9.8

I know I could swap the drive for a bigger single phase input version or use a drive isolation transformer. I don't think it's the building supply. I checked a glycol 3 phase system and I have current on all 3 phases.

I'm not sure if I am missing something.

Thanks for your help.

Jeff
 
Had another item to add. The side of the drive has an EMC screw (this is plastic) and a VAR screw (this is metal). I think I might remove the metal VAR screw and try operating the drive.
 
What is the phase to ground on all three?

Did you replace the breaker + fuses because they tripped or just to see if that fixed the issue?
 
Did the utility do the work recently?

* Edit * Does the pole or transformers look new and are you sure it is feeding your builidng?
 
Over the last 12 years the energy company has had issues with the transformers. At least twice that I know of they've replaced transformers. It's been at least a year or two where we lost a phase. I'm confident that they indeed feed our building.
 
wncjefftino said:
Over the last 12 years the energy company has had issues with the transformers. At least twice that I know of they've replaced transformers. It's been at least a year or two where we lost a phase. I'm confident that they indeed feed our building.
Click to expand...

What I was trying to see was if their recent work caused the issue. It wouldn't appear so. Any issue from them would have taken a while to cause a problem. If they are constantly replacing transformers than they are most likely under sizing which isn't going to help. If they are causing the issues than you might need to put in some PQ monitors on the service and try to get things running with a generator to test the VFD is okay.

I would start by asking them for a power quality study at the meter/main. I would complain about harmonics causing equipment failure. Just know, if they find that the harmonics are coming from the site you are working on, they will probably require you to fix it.

Some utilities won't even start a study without you putting your own PQ meter on the main for a week and testing it.

It would seem that most posts and online forums say that the voltage imbalance from the VFD causes the issue. I would look at trying to power the motor without the VFD or putting in an isolation transformer? I would be mostly guessing on a solution from here. Maybe reach out to ABB for advice?
 
Hi,

I got to checking the system without using the VFD. Here's the following:

A phase 10.7A
B phase 8.7A
C phase 8.7A

AB phase 240V
BC phase 230V
AC phase 240V

So that voltage difference is 4.2%

I went over to 2 other 3 phase systems and measured voltage and found the same as above.

cooler outside unit
AB 238V
BC 226V
AC 238V

chiller
AB 240V
BC 230V
AC 240V

Do I need to call the POCO?

Thanks!
 
wncjefftino said:
Hi,

I got to checking the system without using the VFD. Here's the following:

A phase 10.7A
B phase 8.7A
C phase 8.7A

AB phase 240V
BC phase 230V
AC phase 240V

So that voltage difference is 4.2%

I went over to 2 other 3 phase systems and measured voltage and found the same as above.

cooler outside unit
AB 238V
BC 226V
AC 238V

chiller
AB 240V
BC 230V
AC 240V

Do I need to call the POCO?

Thanks!
Click to expand...

You could call them and ask. It wouldn't hurt.

I don't know if they will be receptive to the issue though. That might take some convincing or a notice or known issue from ABB about open deltas having a negative impact on VFDs.

They might ask you if you tested the VFD at a different location or with a tester and if it was working as intended.
 
What are your L-N and L-G voltages?
Things look fairly balanced across the phases but you might be having L-G issues.
 
Like most VFDs, the ABB drive is not looking at the voltage, it actually doesn't care. It's only looking a the DC bus RIPPLE to determine if there is a phase loss or not, and that is ALSO dependent on the load current. This is why you can over size the VFD to allow the use of single phase, because the more capacitance in the drive, the less effect the load current has on the DC bus ripple. So when the VFD says "Input Phase Loss", that is actually an ASSUMPTION as to the cause of the excessive DC bus ripple. There can be other causes, such as a winding imbalance in the motor. Seeing that you have high current on A phase to the motor, you may be having a problem in the motor that is SHOWING UP as excessive DC bus ripple, so the drive is INTERPRETING that as a phase loss. Now, you actually HAVE a phase loss, because you have zero current on one leg. But until recently, the motor load was not enough to cause that excessive ripple. NOW it is.
 
ptonsparky said:
You can rotate the phases on the existing load to balance it if you desire, but things don't look that bad from here.
Click to expand...
I swapped A and C on the VFD input, and the no current "followed" to the new location. I'm going to use the original VFD at a different location (still 240 delta system) to see if it's an ABB VFD issue.
 
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