Dear all,

I have 60amp 6ra70 installed in a plant, Extruder application. Its an old installation and now I am getting A31 alarm. I did optimisations, checked P171 and change it to 125 from 100. But still same condition, just happening on higher current. Then I checked R40. It is showing 9. Field current is limiting the speed. Why motor draws more field current? How can I prevent it?

What can I do now? Can there be any problem with drive hardware?

Kbv.

Dear experts,

Please share your thoughts on my problem.

Also one basic question:

All values are shown in % in drive monitor. What is reference for this %. I mean if I am getting 4 V in analog input then setpoint will show 40%. But how do I know 40% corresponds to which speed? There is no reference speed parameter as in sinamics?

Similarly, what is the reference for currents and voltages. I mean if I am seeing 95% current then is it 95% of rated current as in P100 or any other value.

Please help.

Kbv.

Kbv

Dear all,

I have 60amp 6ra70 installed in a plant, Extruder application. Its an old installation and now I am getting A31 alarm. I did optimisations, checked P171 and change it to 125 from 100. But still same condition, just happening on higher current. Then I checked R40. It is showing 9. Field current is limiting the speed. Why motor draws more field current? How can I prevent it?

What can I do now? Can there be any problem with drive hardware?

Kbv.

 Hello,

A031 = Speed controller monitoring i.e. difference between set speed (P590) & acual speed (P591) exceeds the limit set in P390. Is your drive goes in current limit mode? Please check your speed feedback device e.g. tacho or encoder, its coupling. In case of analog tacho check out put voltage & ripple contains in it.

HTH.

Kbv

Dear experts,

Please share your thoughts on my problem.

Also one basic question:

All values are shown in % in drive monitor. What is reference for this %. I mean if I am getting 4 V in analog input then setpoint will show 40%. But how do I know 40% corresponds to which speed? There is no reference speed parameter as in sinamics?

Similarly, what is the reference for currents and voltages. I mean if I am seeing 95% current then is it 95% of rated current as in P100 or any other value.

Please help.

Kbv.

 For speed if speed feed back is by analog tacho i.e. p083=1  - P741 = Tacho voltage at maximum speed = 100% speed correpsondence to 100% set point ( i.e. if 0-10 V DC is reference then 10V DC is 100% set point = maximum speed p741 value)

If p83=2, actual speedby pulse encoder then P143 = setting maximum speed for pulse encoder (p141=number of pulse encoder pulses/rev)

For current - Motor current limits are related to P100 value i.e. in % p100) r019 = display of actual armature current = % of P100

HTH

Dear Piscean2010,

Thanks for reply. Your answer helped me a lot.

Yes my drive goes in current limit mode, as I mentioned r40 shows 9. which means, Positive current limit (field) reached (K0273).

where can I change this limits?

Can I change response from speed limit to trip? In my application, speed drop is more unbearable, then trip.

I changed tachometer and also tried running drive in open loop with P83=3. But it is even worse.

Kbv.

Could you please attach your motor name plate details? Is your application is speed controlled or torque controlled? Have you checked no load & load currents? Is really motor getting loaded? Please check AC input current of drive (if possible,please measure motor DC armature & field current) & inform the values here.

HTH.

Thanks for reply.

Please find attached parameter list with all information.

Application is extruder motor, so it is speed control but variable torque application.

kbv.

Hello,

All parameter set values are OK. Are you facing motor overloading, or speed controller problem frequently or at specific loads? Do you face such problems when load on extruder is specific? Please observe those points.

One point I observed is, as per motor data, motor armature rated DC voltage is 460 volt, drive MLFB is 6RA7025-6DV62-0, so rated DC output voltage available will be 420V only. As such your motor rated output power will not available. In order to overcome this problem, I suggset you to installed 45 KVA SCVS or transformer (3 phase 400 / 460V delta/star configuration) at AC input side of drive, so that 460 Volt  DC will be available at drive output which will make sure that motor rated power will be available to meet designed load. This could be one of the problem of speed droping when load increses & instead of drive tripping on overcurrent, it trips/alarms on speed monitoring. Please check r019 value when your motor speed drops or A031 pops up which will help you to understand loading of motor. I also suggest you to reduce P390 value from 3 to 1.5 so that drive will trip much early as the speed drops. or you can set 

HTH.

Hello,

Seems like it was a mechanical issue. After mechanical servicing and realignment motor is taking normal current. And as for the tripping requirement, I found that F031 is disable by default in factory setting so I have to remove 31 from disabled fault list P820.

Thanks for support.

kbv.