Hi All, I am new to ABB ACS 800 Drives. I would appreciate if you guys can help me out to understand the settings of ABB drives parameters regarding overload and over current limits.

We have a ABB ACS 800 VVVF drive to run a motor which is rated 685 A. Last night, motor current exceeded till 800 A and drive temperature rise to 90 Deg C but drive didn't trip and we stopped it from the control room. I checked the maximum current l of the drive in parameter group 20.03 which is set to 1350 A while the load current limit in 72.18 is set to 500 %. User load curve in 72.01 is set to inactive.
If you guys have any good tips to clarify why the current limit is set to 500% , should i reduce it to motor nominal current range? and if user load curve is inactive, then how the drive will function in case of overload.
Please guide. Thanks,

 

What value is the motor nominal current parameter, 99.06?

 

What value is the motor nominal current parameter, 99.06?

Hi GMcc, Thanks for your reply. Motor nominal current value in 99.06 is 685A, same as name plate data. Max current limit in parameter 20.03 is set to 1385 A. while user load curve in parameter 72.01 is inactive.

 

You’re welcome Tahoe. I have used ACH580 which have some common parameters with the ACS. What value are the parameters Motor Thermal Protection, 30.04 and Motor Therm P Mode, 30.05? Do you expect the motor to be overloaded for short periods of time due to variations in the mechanical load? The thermal protection should be set up to protect the motor, other limitation settings are generally to protect the load if required from too much torque. See ABB Tech Note attached.

 

Dear GMcc
I have checked the parameters 30.04 is set to FAULT and 30.05 is set to DTC mode. Here i would like to mention that 30.06 which is motor thermal time is set to 8000 sec which seems too high. what do you suggest about it?
Secondly thanks a lot for sharing this technical note. I would appreciate if you can share the same technical note file for ACS 800 or guide me how to access it online.
Moreover, this technical note is explaining about motor protection I2t in ACS 550. Kindly guide me how to find out this parameter in ACS 800?
As per this note, Max current limit should not be adjusted to motor name plate Amps as it would affect the motor over load protection. kindly suggest how much i should adjust it then?

 

As 30.05 is set to DTC the motor temperature is estimated by the VSD. Do you have any temperature sensors on your motor? normally the bigger and more expensive a motor is, the more you spend on protection to make sure you don't break it. 30.06 is only used if 30.05 is set to user mode, so this does not apply.
I presume you have the ACS800 manual, if you search for thermal protection you will find the relevant parameters for I2t.
The tech note applies to all ABB AC drives in general, only the examples and parameters are for the 580 series. As per tech note - The Maximum current parameter setting should be left at factory default unless the equipment requires current limit protection. This is to protect the equipment that is mechanically coupled to the motor, not the motor itself. Hopefully you have a mechanical engineer that knows about the equipment at your site and can advise you if a limit is required.

 

Thank you once again, but I am not able to find the relevant parameter of I2t. The only parameter group which i have found is group 30 which is motor thermal protection related parameters as explained above in my reply and you further elaborated about the time set in 30.06.
regarding overload settings in ACS 800, there is parameter group 72 "user load curve" but the issue is in our drives sub parameter 72.01 which describes the function of user load curve is set to "NO" which means it is not activated.

 

I2t and thermal protection are the same thing, just not mentioned by I2t in the ACS manual. With 30.05 set to DTC, the drive automatically calculates motor thermal time and motor load curves for the motor thermal model. When the model thinks the motor has reached 95% of the temperature limit a warning is generated, when it thinks it has reached 100% the drive trips on a fault. You really should have temperature sensors in the windings of a motor this big rather than just rely on the thermal model in a drive to protect the motor. From the ACS manual - User tuning is typically needed only if the ambient temperature differs from the normal operating temperature specified for the motor. You should consult the motor supplier if you think this applies.

 

Dear GMcc, As the 30.05 is set to DTC but our motor has drawn the current upto 800 AMPs or may be more as 800 AMP was the max scale limit in DCS which has recorded the drawn AMPS while the motor rated is 685 A however, the drive didn't trip because of overload. So this is the main concern for us that why drive didn't trip in this particular situation when the drawn current is more than the rated capacity of the motor. the max current limit in group 20 was set to 1300 Amps which we have set to motor rated 685 but the technical note you shared earlier is not recommending to set the max current limit to motor rated AMP. so the question is how much we should adjust it? 110% of rated 120% or rated or any other suggested value?

regarding motor winding sensors, I believe that there are PT100 sensors installed and temperature is monitored in DCS as analog signal but I am not sure if it is configured in the drive as well or not, I have to confirm this point.

 

The drive parameters you mentioned in your original post seem to be correct. Short term currents higher than the name plate current are normal for a lot of motor applications. The tripping of motor protection is based on current and time, it will not trip instantaneously when the name plate current is reached as it takes both current and time to cause damage to the motor, the higher the current the less time required to trip. The actual time all depends on the thermal model in the drive which there is little detail about in the manual. How long was the motor current draw at 800A or more? 800A is around 17% higher than 650A so not a large overload. If you wish to trip the drive earlier than the drive thermal model you should program this in the DCS. You should also check if the PT100 sensors wired to the DCS can trip the drive/motor if the motor temperature gets too high.

 

Dear GMcc, motor was running with 800 A or may be more for 1 minute approximately. I said 800 A or may be more because our DCS scale max limit is upto 800 A so it wasn't able to record any value which was above 800 A.

Anyhow it was such a healthy discussion with you and clarified many doubts for me. I appreciate you for your time and technical advise. If I have some more questions, how may i approach you?