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Fan

Fan

(OP)
Hi,

I am commissioning one 132 Kw 400 V 50 Hz motor drivng a centrfugal fan.The motor is powered through a ABB ACS800 drive.The drive is configured for a scalar application.I am having overcurrent trippings of the drive,this happened four times during a 12 hours operation.During normal running at nominal speed,the current noted on the drive is around 130 A.
The acceleration and deceleration ramps are at 40 seconds for both.I am looking for some guidances for those very familiar with the ACS800 drive.
Would DTC mode fit my application better ?

Thanks.

Guardiano

RE: Fan

You can try also in DTC mode but, everything should be OK in Scalar also. When this trip comes. During acelerating, decelerating or normal run.

Milovan Milosevic

RE: Fan

(OP)
Thanks Milovan for your quick reply.The drive tripped during normal running at 45 Hz with a fixed frquency reference.

Guardiano

RE: Fan

You can also write:

1) Which ACS800 you are using (that we can see how much is nominal current of drive)
2) How much you put for current limit
3) How much is maximum current during acc and dec
4) Do you have some suddenly increasing of load during run at full speed.
 

Milovan Milosevic

RE: Fan

OK I write above message before I read yours.
So you dont need to answer to question 2.

Milovan Milosevic

RE: Fan

Sorry,

Not question 2. Question 3 is now not interesting.

Milovan Milosevic

RE: Fan

(OP)
Hi Milovan,
Thank you for your interest.The maximum current of the drive is 260 A,the current limit is set at 260 A,the maximum current during acc. and dec. are within the normal limit of the drive and did not exceed 200 A.There is no sudden incerease of load as the speed of the fan determines the load and the drive was running at fixed speed.

Guardiano

RE: Fan

You probably meant on maximum continuos current, not maximum current. If you write type code of drive I can see nominal ratings in catalogue. I suppose that drive is ACS800-04-0165-3 or ACS-01-0165-3 (both of them have same ratings). Theese drives have maximum continuos current 260 A. If this is true and if you correctly put parametar nominal motor current than you have some problems. I would check motor and cable on some light short circuit. I hope you dont have some power factor compensation after drive. How long is motor cable.

Milovan Milosevic

RE: Fan

Guardiano, an overcurrent trip can be caused by the input power making a sudden shift with respect to ground.  This would be possible if the three phase power is floating or if it has only high resistance to ground.

I would check what type of power supply is being used.  The least troublesome would be a solidly grounded wye (star) or a low resistance grounded wye (star) source.  Anything else can be a source of trouble.

If your power supply is one of the problem types, you must read the instruction manual carefully and follow the directions for disconnecting the CE filter networks.  You also must turn off the ground fault protection in Group 30.

While it is true that the overcurrent fault can be caused by failing motor or motor lead insulation or even failing IGBT's, that is rather uncommon on the ACS800.

And, Milovan, just a note, the Overcurrent Fault is not affected by the Overcurrent setting in Group 20.  It is a fixed value determined by the power section capacity.  The overcurrent setting in the parameters determine when the speed reference starts to be reduced to get away from overload conditions.

RE: Fan

DickDV,
I know that value of overcurrent trip doesnt have anything with current limit. I asked about current limit just to check how near is to trip.
Are you sure that problems on supply side can cause overcurrent fault (overcurrent on motor side). I think there are no current mearurments in ACS800 in line side.

Milovan Milosevic

RE: Fan

(OP)
Thanks again Milovan for your support.DickDv,you are absolutely right.Our network is a high impedance one.But the ABB supplier who sold me the drive told me that the drive was equipped with an RMI filter compatible with a high impedance grounding and that there was no grounding strap to remove as we used to do with the ACS550 one.
I don't see any grounding protection associated with group 30 protection.Thanks again for your expert advice.

Guardiano

RE: Fan

Yes you have ground fault protection in group 30. Parametar is called earth fault.

Milovan Milosevic

RE: Fan

If line fuses are never blown, and you never had overvoltage or undervoltage fault i would rather suspect on motor side then line side problems.

Milovan Milosevic

RE: Fan

Milovan, you are correct that the acs800 does not have current detection on the input side but, when a floating source makes a sudden shift in ground reference, it can cause significant currents to flow momentarily in the output.  The drive catches these and reports them as overcurrent faults.  Depending on how the shift is made, it can also be reported as a ground fault.

I would turn off the ground (earth) fault in Group 30 and see if the nuisance faults go away.

If the floating input is the problem, your solution is a drive isolation transformer with a grounded wye secondary.  I know!  It's not pretty but floating AC sources are so hazardous and troublesome that they should be outlawed, in my opinion.

RE: Fan

(OP)
DickDV,the solution of an isolation transformer is not an easy one for me mostly because a transformer of this size is not available on site.I will disable the ground fault and see if the fault persists.


Guardiano

RE: Fan

(OP)
DickDV,the EMI filter on the drive is a E210 one,which should not cause any trouble on an isolated network.

Guardiano

RE: Fan

I see nothing in my spec sheets that says the +E210 CE filter is ok on unbalanced power supplies but it may well be.  I don't think that would be a factor with the faulting anyway.

Yes, let's see what happens with the ground fault turned off.

RE: Fan

DickDV,
Why you think that you will get anything by switching off ground fault protection. There was no any ground fault only overcurrent fault if i undestood well.
According to your messages i have a feeling that you had very bad expirience with floating networks.
I am still thinking that problem is on motor side, but we will see.
I hope that Guardiano will tell us what was problem at the end.

Milovan Milosevic

RE: Fan

Unbalanced and floating networks are nothing but trouble for VFD's.  I am quite confident that Guardiano's problems are due to that.

In addition, floating networks are potential hazardous beyond the hazards of a balanced grounded wye-star system.  This is worse at 480 and 600V than at 230 and 400V but still bad.  The problem is that, if one phase is grounded, the remaining two phases go up to the system voltage.  In wet, condensing, or conductive dust conditions, the higher voltage tends to ionize thru the dust and will effectively leak around switches, contactors, and disconnects.  The result is system voltage on conductors that were thought to be locked out and dead.  I was nearly killed by this phenomenon 15 years ago.

My advice to technicians working on floating or high impedance grounded systems is to always jumper to ground the downstream conductors from a disconnect.  This protects you even if there is leakage on two of the phases.  In fact, in North America, that is standard procedure with the electric utilities who use floating systems for power distribution.

As to VFD's, my experience is that often a drive isolation transformer is the only solution to nuisance faulting in ungrounded systems.

We will see how Guardiano does with his.

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