Help for ABB VFD (slightly urgent)

[Isaacwjp]

Hi All,

I am currently doing a project at a site that uses ABB ACS880 VFD.

As you can see from the tracer below, the VFD Tripped at 43Hz due to the fault: Overspeed.

I am unable to identify the root cause.

-Shouldn't the fault only occur on 50Hz?
-Does the trip margin change based on the current Hz?
-For anyone using this model, do we have to set the trip margin manually?

Really need help identifying the root cause..

 

[Gr8blu]

Overspeed is a mechanical constraint (the ability to hold things that move together so no one gets hurt). It is a direct relationship to the rotating machine's operating speed - which, for a VFD has a relationship with output frequency. If the machine max operating speed is a given value, the "alarm" condition related to speed is about 1.05X, with a trip at roughly 1.10X the max speed. This allows the machine to start slowing down before it gets to the mechanical safe speed (roughly 1.25X).

So yes, an overspeed trip could be triggered at 43 Hz fairly easily, if the "running" frequency was down around 38-40 Hz.

Converting energy to motion for more than half a century

 

[TugboatEng]

Your motor nameplate appears to say that it's rated for 9.05 hz. Can you clarify this?

 

[jraef]

Yeah, if that motor is designed to go 197RPM at 9.05 (or 9.85) Hz, and you are running it at 43Hz, someone is trying to do something this motor was NOT designed to do.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

To develop 20 HP at 9.85 Hz, the motor would be the approximate physical size as a 100 HP 1440 RPM motor.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[iop95]

Too few informations...

Overspeed is related to speed limits set in VFD parameters (maximum and minimum) not with a particular frequency, even 50Hz or so.
Check these limits and all related speed error alarms also; if is not unsafe may disable some speed error alarms and check.
What kind of motor control is set on VFD? Speed/torque/other?

At 30.12 you set 197rpm maximum speed.
If at 99.8 and 99.9 values are set as motor nameplate, motor speed will be 197rpm at 9.85Hz VFD output, so overspeed error for higher output frequency.

 

[Isaacwjp]

Thank you all so much for your help.

I am trying to gather more data as well as I am a cooling tower specialist so I'm not exactly trained in electrical.

Apologies for the images, the Motor is rated 9.85.

I might not be right, but could it be that usual induction motors usually run to 50Hz on VFDs but this motor is a permanent magnet motor and they are running it based on a induction motor setting?

Possible for it to have a translating software to make 50Hz on the VFD = 9.85 Hz on the motor?

 

[edison123]

This is a 6 pole PMSM motor. Do the standard VFD's work on PMSM motors?

And you cannot run at nearly 4.5 times rated speed as others have said.

Muthu

http://www.edison.co.in

 

[waross]

Is that a minimum speed/frequency, based on cooling?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

I don’t think so. The nameplate data saying 9.85 Hz is the section with all the other full load data.

You can barely make it out, but that nameplate also says “Maximum safe speed… 600 RPM”. So if the motor is truly designed for 9.85Hz and 197RPM normal operating speed, that means the highest frequency it can run at would be 30Hz.*

But assuming this is a centrifugal fan, at
roughly times (300%) rated speed, the motor load would increase at the CUBE of that speed change, so 3[sup]3[/sup], which means the required shaft HP would need to be 27x larger than it is. Looked at it the other way, assuming 20HP was the required load at 9.85Hz, then at 30Hz, you would need 540HP. You might as well have been turning it on into a locked rotor, but because it is centrifugal, it would have actually started rotating. The Over Load would have taken a few RPM to develop.

*(If that says 9.05Hz, then it’s down to 27.65Hz max frequency.)


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

All the cooling towers that I have been near used propeller fans.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[wcaseyharman]

I’m not a VFD expert but based on the parameter list it looks like your speed feedback is AI1. If the VFD is properly limiting the output to 9.85 Hz it doesn’t seem possible to overspeed the motor on a cooling fan.
Therefore if it’s true that the speed feedback is from a separate analog input, I would investigate your speed feedback - look at scaling and feedback type - is the speed transmitter set up for the same signal type as the VfD (4-20ma, 0-10V etc)? Is it scaled properly?

 

[Gr8blu]

Nameplate data from above images: 20 HP (14.9 kW) at 197 rpm with 400 Vac, 3-phase supply operating at 9.85 Hz. Max safe speed (which means the overspeed trip should kick in BEFORE this speed) is listed as 600 rpm ... which in turn is roughly 30.0 Hz.

If the OP is actually applying a higher frequency (i.e. above 30 Hz), then the overspeed trip is doing what it is supposed to do.

And, as wcaseyharman indicated, verify that the speed feedback signal is appropriate and calibrated correctly.

Converting energy to motion for more than half a century

 

[ILikeLearning11]

Were you able to get this figured out? If not, I have a couple of contacts that could help you with these motors/drives setup.