ACS850 Motor Control Problem


Thread Starter


We have a mixer driven by 125HP motor being controlled by ACS850 through PLC.

We encountered motor stop in the middle of our mixing operation which is not supposed to be... Its normal operation only stops when the material reaches the 110-degree celcius set value, but the motor just stop even if the temperature is still low @ 80-degree C to be specific and there's no alarm on the ACS850 drive even in our SCADA/PLC control.

Do you have any opinion about the cause? Thanks
You need to provide more information regarding your problem like what have you done to troubleshoot the problem, was the motor able to restart and run properly, did the problem occur again, has this happened before. Was the motor too hot? Did you check the temperature cutoff circuit? Do you have a VFD? Is there anything else in the motor control circuit or VFD that could cause a shutdown, etc.?

Incomplete problem statements and lack of information regarding the system and what has been done so far make it difficult for people on this forum to provide effective help and waste the time of people on this forum. Technical people should be able to provide a good problem statement, system description, and what you have done so far to troubleshoot the problem.

Here are some guesses as to some potential causes.

1. Motor tripped by overloads or a low speed trip due to agitator in a bind. Do you have a agitator speed measurement? Does it show what happened?

2. Failure of temperature cutoff circuit

3. Bad temperature measurement

4. Loss of power to the motor control circuit or to the motor

5. Variable speed drive failure.

6. Inadvertent manual shutdown.

William (Bill) L. Mostia, Jr. PE
ISA Fellow
WLM Engineering Co.
You need to narrow it down a bit.

Did it stop because the drive shut down or because the PLC told it to or removed the Run signal?

If the motor is operating near full load perhaps the overload tripped.

Does the viscosity change with temperature?