ABB ACS 550 VSD OVER Current Repeated fault 4

[Mohamed haggag]

I have Electric Motor 30kw operates with ABB ACS 550 VSD .. I Face Repeated over current fault when i increased frequency to 40hz ..which equals 1150 RPM ..where rated speed of motor 1500 RPM
THE MOTOR used to drive supplu air fan for AHU system ...when we operate the motor in low speed 900 RPM ..no problem happens and No fault appears ..Any one has explanation for this issue ?

 

[jraef]

Was it working fine before and just began doing this? Or is this a new installation?


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

 

[Mohamed haggag]

it was working well, motor was changed over year

 

[waross]

When the motor was changed, were the VFD parameters checked and upgraded for the new motor?
The first things that I would look at when problems develop after a motor change is to compare the specs of the new motor with the old motor and check that the VFD programming matches the characteristics of the new motor.
If the full load current of the new motor is greater than the FLC of the old motor, the VFD parameters should be changed.

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

 

[Gr8blu]

Unless your motor is a synchronous machine of some type, the rated speed is NOT going to be 1500 rpm at line frequency. It will be something less (due to slip). Chances are reasonably good that the old motor and the new motor don't have quite the same slip - and, as waross mentioned, probably not the same full load current draw at nameplate shaft power (due to efficiency, power factor, and basic materials and geometry differences). Time to tune up the drive to the new motor parameters.

One other possibility is that at the specified shaft speed, the fan curve requires more power than the drive will let the motor deliver (variable torque application). Again - the limits are probably based on the original motor speed and current data - so check parameters.

Converting energy to motion for more than half a century

 

[waross]

The main cause of an over current fault on a motor is, surprise surprise, overloading.
As for the speed, the difference between the rated speed and the synchronous speed is the slip.
Eg: a motor rated for 1460 RPM will have a slip of 40 RPM (1500 RPM - 1460 RPM = 40 RPM slip.
At your calculated speed of 1150 RPM,the actual speed will be 1110 RPM at full load. (1150 RPM - 40 RPM = 1110 RPM)
Have there been any changes to the drive belt and pulleys?
One possibility is an adjustable pitch pulley used to tighten the belt.
As the belt wears and the pitch is increased to compensate, the drive ratio is reduced, so that the fan runs faster for the same motor speed.
Have you checked the actual fan speed, rather than guessing based on the supply frequency?
Do you realize that the Fan Laws predict that a change from 900 RPM to 1150 RPM results in double the HP required?

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

 

[jraef]

In the drive, when you change the motor, you must do an "autotune" to the new motor, even if it is exactly the same. Every motor has slightly different properties, so if the VFD is using the motor properties from the old motor, that may have effects when applied to the new one.

In ABB's parlance, they refer to this as an "I.D. Run" procedure. Look for that term in the manual and perform that on this motor.


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

 

[Mohamed haggag]

I checked all parameters all were good
increased acceleration and deceleration times
performed ID RUN ...
the drive only worked well to values under 35 HZ
When I increased the value over 35 HZ ..over current fault appears
also ..mechanical team checked belts ..all is t=well
checked bearing and rotate fan freely...No problem
what makes me mad ..that over current appears with out actual over current and this was confirmed after put the drive on Data Logger ..current stable but over current appears

 

[iop95]

Old motor up to what frequency worked without overcurrent?

What control mode (scalar, vector, etc.) is used? If scalar what is slip compensation?
Open-loop or closed loop?
Overcurrent error apear total aleatory or at short time after start (or increase setpoint above 30Hz)?

Seems that a 6 pole motor was changed with a 4 poles, same power but lower torque in speed range used.

 

[Mohamed haggag]

NEW MOTOR WORKED WEEL FOR OVER YEAR WITHOUT ANY PROBLEMS TILL LAST WEEK
CONTROL MODE IS SCALER CONTROL MODE
OPEN LOOP CONTROL SYSTEM WITHOUT FEEDBACK
OVER CURRENT APPEATS AFTER 3 OR 4 MINUTES FROM STSRTING SPEED WITH FREQUENCY OVER 30 HZ

 

[jraef]

If there is no over current as confirmed externally, then I would suspect a bad transducer inside of the drive. Many drives use Hall Effect transducers to sense current, a few years ago Honeywell produced a bad batch of them that caught a number of drive manufacturers unawares, costing them a lot of money with recalls and field retrofits. A few units slipped through the net because the transducers didn’t fail right away. Yours may be one of those. Or, it may just be a “normal” field failure if the transducer.

I’ve also seen where an A to D converter fails and when they do, they often fail “high”, so the digital value of current jumps to 65536 (all 1s in a 16 bit register). Look at the memory of the drive to see if it stored the current that it tripped on. If it is done ridiculously high number like that, it could be this issue.

This likely needs attention from ABB Services.


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

 

[moa1]

Motor nameplate details. Motor changed. Why? Rewound? One year? What occurred last week? Ducting? Control rpm (low speed) how? Good luck

 

[edison123]

I would check out the motor for any ground and interturn faults.

Muthu

http://www.edison.co.in

 

[wcaseyharman]

I didn’t see this in the discussion, so if it’s already been discussed I apologize.
I would put a clamp-on amp-meter or a CT to an oscilloscope and run the motor up to verify the current output and compare it to the VFD LCD read-out. Is the current actually exceeding load current or is the VFD measuring incorrectly? The outcome of this exercise would determine whether it’s a VfD measuring problem or a motor/load problem. Check all three phases if possible to rule out an imbalance issue. If it’s a VFD issue I’d probably call ABB or just get a new drive if the issue isn’t obvious.
There’s of course a host of issues possible in the motor/load situation, many of which others would be better to discuss. A couple thoughts come to mind - failed component in the motor (rotor bars, bearings) or a characteristic change in the load (things like dampers being open/closed for a fan, fan is misalign and rubbing on the fan shroud, failing bearings, etc).
Just some thoughts that may help.

 

[Mohamed haggag]

Hi Lads

just to let you know , after several trails and many attempts were taken

we changed the drive and adjusted parameters like old drive and motor is working well

thanks for your support

 

[waross]

Thank you for the closure.
Much appreciated.

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