Powerflex755 Torque control

Join Date
Apr 2003
Location
Toronto
Posts
151
Just wondering if anyone can send me a simplified Torque setup for a 40HP Allen Bradley 755 Powerflex drive. I worked all day manipulating what a previous engineer has done and it makes no sense.

The previous engineer installed 97.5 Amps as a current limit whereas the drive has a 65 Amp limit. (Par 411 ad 412) I changed these back to the maximum motor limit which is 65 Amps. My Torque min and max is 150%

I had the bright idea to Static Tune the drive and now my o speed current went from 32 Amps to 45 Amps leaving just 20 or amps before i reach my limit.

I had to change some settings on the drive to get it to become quite (during Jog the shaft would hammer)and when I started the drive the Torque accelerate the slack violently.

I am planning to reset the drive to factory default, set it into Speed mode do and autotune and then revert back to Torque control. Playing around with someone else's manipulated drive setup does not seam to work.

I am here because the customer has noted that the drive shuts off under heavy loads. The IGBT;s witll PWM from 4Khz to 2 KHz and then the current is dropped and then the drive stops due to excessive heat in the IGBT's.

I figured that telling the 65 amp drive that its a 97 Amp drive is partially to blame but I am not sure. Hence I would like a brief description of which parameters does what I have read the manual but it does not go into any other detail. Simply put I want to control the Torque on the motor nothing else nothing more.

Thank anyone who replies.

Regards

Ron:wish:
 
This sounds very familiar to a problem we are having now. Newly installed we were able to lift 30,000 pounds all day, and now it's barely able to lift 10,000 some times. Drive is going into current limit. Without a load the drive is putting out 25 amps to run the arms up.
 
Powerflex Torque Control revisited

OK A couple years later and the problem still exists. LOL
What have I learned AB Drives are great last year i started 66 of these puppies on three lines so yes the experience is getting better everyday. Fast forward another machine with a Torque Control. The winding is straight forward we have a diameter calculator that keeps the motor speed about 100 RPM above the actual feedback and the Torque starts at 22 % and goes to 44% on a 2:1 Winder build up. All with no Encoder feedback, Induction FV openloop. At speeds above 3-4% the Torque is stable and can run forever. At standstill the load oscillates until I cant stand it no more. I need to get rid of the oscillations but as usual no manual explains the proper setting for this to happen. If anyone has a proper explanation of "how to" i would love to hear from you.

I have an Idea but not sure if this can work or if it can be done.

First the motor does have an encoder that is connected through a BEI Swift wireless (Dont buy these ever as they wind up an error and then reset whenever they feel like it). The BEI application engineer told me that it maybe due to the base not being mounted on insulator type material (F'n Black magic) I had the motor in Speed mode with limited Torque and I captured the moment the motor lost its Torque, bloody nightmare wire everywhere broken parts etc. So we decided to go Open Loop Torque, this works except at zero speed. I have thought about switching the mode of operation at zerospeed, as the reference would be zero, I am also thinking about switching "in" the encoder at zero speed as the dangers of loosing the encoder would be "oscillation" So if anyone knows something that I missed please lets get it out there since Torque applications abound, anyone can do speed not to many understand adjusting openloop Torque loops. Ok enough ranting, been working on this system for 4 weeks.
 
When I tried to control a similar load at zero speed with sensorless vector control, I had similar results - worked great while moving - oscillated at zero speed. My local AB drive rep explained that the routines the drive uses to estimate the rotor position tended to fail at zero speed. Closed loop encoder feedback fixed it good.

Don't know if you can tune the drive to perform better with open loop?
 

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