DTC

[vennivivi]

Hi,

I just installed one 1500 A ACS800 drive. It`s running on DTC control mode and the motor is drawing excessive current at half nominal speed. Another drive of different make hardly drew 60 % nominal current at that particular speed. The ACS drive drew around nominal current at that speed. I am not too familiar with the ABB drive and would like to have comments from memebers of the forum.

Thanks.

Grundig

 

[sreid]

Have you gone through whatever proceedure is required for the drive to find the motor parameters?

 

[vennivivi]

Yes, the ID Run was performed as instructed in the manual.
In any case, the drive is configured as ID Mag that is each time a start command is given, the drive will magnetise the motor to develop the model.

Grundig

 

[Skogsgurra]

And all parameters entered correctly? There's usually a mistake regarding wye or delta and name-plate reading when this kind of problem occurs. Never, repeat never, was the drive's fault. Always my mistake.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[sreid]

Since its a "Half Speed" problem, is the number of motor poles entered correct? This the drive does need to know for "Vector Control."

 

[DickDV]

I would go through the parameters in Group 99 and make sure they are all correct straight from the motor nameplate. Then rerun the ID Run using at least the Reduced motor model. If you can decouple the motor, use the Standard motor model.

When you use the ID Magn, it only builds its model on the first start. It does not redo it on every subsequent start.

This does definitely sound like a motor data error. Usually, the ID Run will not finish with wrong data but occasionally it can be fooled.

 

[ozmosis]

What is the application?
Is everything running freely with the load?
Is the ACS800 going into current limit? your description of excessive current would actually be excessive if the drive is going into current limit. Is there an alarm/warning coming up on the drive's display?

I would agree with previous posters, it is generally a parameter setting issue but it would pay to check the above as well.
Is the current 'excessive' when you go from start to half speed or when you go from full speed to half? If the latter, what is the current like at full speed?

 

[vennivivi]

Hi,

Thanks all for the inputs. The motor data are correctly entered. It is also worth mentioning that the previous drive was a variable torque one. I am in touch with the ABB people and shall keep all informed.
Thanks again.

Grundig

 

[Skogsgurra]

Yes, please do!

This may be a case that we can all learn from.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ozmosis]

So the application was variable torque( a centrifugal fan or pump) one assumes.
Seems a little odd to be using an ACS800 with DTC control.
What about setting the ACS800 to VT setting? see if this makes any difference.

 

[DickDV]

It would be interesting to switch the drive to Scalar mode in Group 99 and see what happens to motor current with that type of V/Hz control.

Another thought. In DTC mode, the Group 23 gains need to be set to make the speed loop operate correctly. I would like the OP to advise his settings in Group 23.

 

[niallnz]

Ozmosis
The OP siad it was 1500Amp drive, at 400V that's about 1000kVA, that's why ACS800.

 

[roydm]

Check the V/Hz ratio, I have had a similar problem with that. Voltage was too high at lower frequency
Roy

 

[edison123]

A few months back, my repair shop got a 40-year old GE motor which was name-plated at 220 V. On review of the winding design, we found it was actually a 440 V winding. Someone had converted the winding design in its previous rewind and didn't bother to put in the right nameplate.

May be this is the case in your case too.

 

[ozmosis]

niallnz
I just wondered why DTC setting and not V/F (scalar), not the fact the ACS800 is used.

 

[niallnz]

DTC is the default setting for an ACS800 drive. Just because DTC is good at constant torque loads, doesn't mean that it shouldn't be used on variable torque loads. In fact DTC (vector) on variable torque gives you the opportunity to optimise the flux to match the load, there by reducing the magnetizing current component. This has the benefit of reducing winding temperature and posibly electricty cost (debatable). Scalar control can't do this. The only time I have used scalar control on an ACS600 (also DTC drive) is when more than one motor was connected to the drive and to test the driver cards and IGBT when I was repairing one.